Atmospheric Environment (v.89, #C)
Editorial board (i).
Modeling direct and indirect effect of long range transport on atmospheric PM2.5 levels by Tu-Fu Chen; Ken-Hui Chang; Chang-You Tsai (1-9).
The adverse effect of long range transport (LRT) of pollutants on local air quality has been long recognized. Previous studies only cover LRT effect without distinguishing direct and indirect effect, that is LRT of precursors directly forming PM2.5 in local areas (direct effect) and/or transported precursors interacting with local precursors in forming PM2.5 (indirect effect). The present study aims to simulate effects of East Asia emissions in PM2.5 levels in Taiwan by quantifying the direct and indirect effects. The modeling system included simulations of 4 cases: (A) Base: consider emission from both Taiwan and East Asia; (B) Zero Emission from East Asia: consider Taiwan emission only without considering emission from East Asia; (C) Zero Emission from Taiwan: consider East Asia emission only without emission from Taiwan; and (D) Zero Emission (background). The results of the CMAQ v4.6 model (with Mesoscale Model ver. 5) indicate that the contributions to annual PM2.5 average of 30 μg m−3 in Taiwan are 60, 27, 9, 3%, respectively, from Taiwan's own contribution, direct LRT, indirect LRT and background. The primary PM2.5 is almost from Taiwan's contribution whereas only 45% secondary PM2.5 (SPM2.5) is from Taiwan and the majority (53%) from LRT contribution (direct LRT 35% with indirect LRT 19%). As for composition in SPM2.5, SO 4 2 − accounts for 43% with the major contribution from direct LRT (57%), followed by NH 4 + (32%). NO 3 − is mostly from Taiwan's contribution (57%) with indirect LRT contribution of 36%. Indirect contribution of NH 4 + is 24% in the form of NH4NO3. Clearly Taiwan cannot control direct contribution ( SO 4 2 − ), but control of NO 3 − and NH 4 + may reduce PM2.5 levels. To meet the proposed annual average of 15 μg m−3, it is certainly a challenging task in that 30% emission should be reduced in Taiwan, preferably the reduction of NO X and primary PM.Display Omitted
Keywords: East Asia contribution; Direct long range transport (LRT); Indirect LRT; Emission control strategy; CMAQ v4.6 model;
A study on high ozone formation mechanism associated with change of NO x /VOCs ratio at a rural area in the Korean Peninsula by Won-Bae Jeon; Soon-Hwan Lee; Hwawoon Lee; Changhyoun Park; Dong-Hyuk Kim; Soon-Young Park (10-21).
We present an analysis of high surface ozone (O3) episodes occurring in the rural area of Chuncheon, which is situated 70 km to the prevailing westerly downwind direction of Seoul Metropolitan Area. During the episode days, the daily maximum O3 concentration exceeded 120 ppb and an O3 warning was issued in Chuncheon. Although Chuncheon has much lower emission levels than Seoul, the daily mean and maximum O3 levels were higher in Chuncheon than those in Seoul during the episode days. In addition, the high O3 concentrations in Chuncheon were not dependent on the meteorological condition being generally favorable for O3 production. The inverse trajectory analysis using HYSPLIT clearly shows the features of pollutant transport from Seoul to Chuncheon. For further investigation, we conducted numerical experiments using the atmospheric dynamic Weather Research and Forecasting (WRF) model and the air quality Community Multi-scale Air Quality (CMAQ) model to examine the detail process of these high O3 episodes with the Decoupled Direct Method (DDM-3D) and Integrated Process Rate (IPR) analyses. The DDM-3D analysis results demonstrate that the O3 concentration in the air mass moving from Seoul to Chuncheon was very sensitive to the concentration of nitrogen oxide (NO x ) because of abundant biogenic volatile organic compounds (BVOCs). The IPR results also show that the NO x emitted from Seoul strongly affected the high O3 levels over its downwind area, mainly with local BVOC emissions. The produced O3 was gradually accumulated during its transport downwind, leading to an O3 concentration maximum at Chuncheon.
Keywords: Precursors; Ozone formation; WRF; CMAQ; Chemical process analysis;
Application of air quality combination forecasting to Bogota by Joakim Westerlund; Jean-Pierre Urbain; Jorge Bonilla (22-28).
The bulk of existing work on the statistical forecasting of air quality is based on either neural networks or linear regressions, which are both subject to important drawbacks. In particular, while neural networks are complicated and prone to in-sample overfitting, linear regressions are highly dependent on the specification of the regression function. The present paper shows how combining linear regression forecasts can be used to circumvent all of these problems. The usefulness of the proposed combination approach is verified using both Monte Carlo simulation and an extensive application to air quality in Bogota, one of the largest and most polluted cities in Latin America.
Keywords: Air quality forecasting; Bogota; Forecast combination; Neural networks;
Impact of HVAC filter on indoor air quality in terms of ozone removal and carbonyls generation by Chi-Chi Lin; Hsuan-Yu Chen (29-34).
This study aims at detecting ozone removal rates and corresponding carbonyls generated by ozone reaction with HVAC filters from various building, i.e., shopping mall, school, and office building. Studies were conducted in a small-scale environmental chamber. By examining dust properties including organic carbon proportion and specific surface area of dusts adsorbed on filters along with ozone removal rates and carbonyls generation rate, the relationship among dust properties, ozone removal rates, and carbonyls generation was identified. The results indicate a well-defined positive correlation between ozone removal efficiency and carbonyls generation on filters, as well as a positive correlation among the mass of organic carbon on filters, ozone removal efficiency and carbonyls generations.Display Omitted
Keywords: Chamber experiments; HVAC filters; Ozone; Carbonyl; Formaldehyde; Organic carbon;
Measurement of ammonia emissions from tropical seabird colonies by S.N. Riddick; T.D. Blackall; U. Dragosits; F. Daunt; C.F. Braban; Y.S. Tang; W. MacFarlane; S. Taylor; S. Wanless; M.A. Sutton (35-42).
The excreta (guano) of seabirds at their breeding colonies represents a notable source of ammonia (NH3) emission to the atmosphere, with effects on surrounding ecosystems through nitrogen compounds being thereby transported from sea to land. Previous measurements in temperate UK conditions quantified emission hotspots and allowed preliminary global upscaling. However, thermodynamic processes and water availability limit NH3 formation from guano, which suggests that the proportion of excreted nitrogen that volatilizes as NH3 may potentially be higher at tropical seabird colonies than similar colonies in temperate or sub-polar regions. To investigate such differences, we measured NH3 concentrations and environmental conditions at two tropical seabird colonies during the breeding season: a colony of 20,000 tern spp. and noddies on Michaelmas Cay, Great Barrier Reef, and a colony of 200,000 Sooty terns on Ascension Island, Atlantic Ocean. At both sites time-integrated NH3 concentrations and meteorological parameters were measured. In addition, at Ascension Island, semi-continuous hourly NH3 concentrations and micrometeorological parameters were measured throughout the campaign. Ammonia emissions, quantified using a backwards Lagrangian atmospheric dispersion model, were estimated at 21.8 μg m−2 s−1 and 18.9 μg m−2 s−1 from Michaelmas Cay and Ascension Island, respectively. High temporal resolution NH3 data at Ascension Island estimated peak hourly emissions up to 377 μg NH3 m2 s−1. The estimated percentage fraction of total guano nitrogen volatilized was 67% at Michaelmas Cay and 32% at Ascension Island, with the larger value at the former site attributed to higher water availability. These values are much larger than published data for sub-polar locations, pointing to a substantial climatic dependence on emission of atmospheric NH3 from seabird colonies.
Keywords: Coastal nitrogen; Seabirds; NH3 measurement; Atmospheric dispersion modelling;
Diurnal and seasonal trends of carbonyl compounds in roadside, urban, and suburban environment of Hong Kong by Y. Cheng; S.C. Lee; Y. Huang; K.F. Ho; S.S.H. Ho; P.S. Yau; P.K.K. Louie; R.J. Zhang (43-51).
Seasonal and diurnal variations of carbonyl compounds were investigated in roadside (MK), urban (TW), and suburban (UST) environments in Hong Kong. Thirteen carbonyls (C1–C6) were identified and quantified in the samples. The average total quantified carbonyl concentrations decreased in the order of roadside (12.16 ± 3.52 μg m−3), urban (10.45 ± 4.82 μg m−3), and suburban (5.14 ± 3.35 μg m−3). Formaldehyde was the most abundant species, accounting for ∼52%, ∼52%, and ∼46% of total measured carbonyls at MK, TW, and UST, respectively. At MK, the summer/winter ratios of most carbonyls were below one. The diurnal variations were associated with traffic flows, with high concentrations in daytime but low in nighttime. Good correlations were found between most carbonyls and carbon monoxide (CO), showing primary vehicular emission was the major source at the roadside location. In contrast, the summer/winter ratios of most carbonyls were larger than one at the urban site of TW and their carbonyls correlated well with secondary pollutant of ozone (O3), indicating photochemical reactions contributed significantly in the formation of carbonyls, especially in summer. Distinct diurnal variations of carbonyls were observed at TW on a hazy winter day of 28 Jan 2012. Most carbonyl concentrations reached the first peak at noontime and had the second peak in the evening. The first peak was ascribed to be the products of photochemical reactions as maximum concentrations of nitrogen monoxide (NO) and O3 occurred just before and after the carbonyl peak, respectively. The correlations among the carbonyl species were strong in summer but fair in winter at UST. Natural sources (e.g. biogenic) were usually the major source at the suburban, as far as its surrounding environment is concerned.
Keywords: Carbonyls; Diurnal variations; Seasonal variations;
Development and evaluation of the unified tropospheric–stratospheric chemistry extension (UCX) for the global chemistry-transport model GEOS-Chem by Sebastian D. Eastham; Debra K. Weisenstein; Steven R.H. Barrett (52-63).
Global chemistry-transport models (CTMs) typically use simplified parameterizations or relaxation to climatology to estimate the chemical behavior of the stratosphere only in the context of its impact on tropospheric chemistry. This limits investigation of stratospheric chemistry and interactions between tropospheric and stratospheric chemistry-transport processes. We incorporate stratospheric chemical and physical processes into the model GEOS-Chem in the form of a unified chemistry extension (UCX). The stratospheric chemistry framework from NASA's Global Modeling Initiative (GMI) is updated in accordance with JPL 10-06 and combined with GEOS-Chem's existing widely applied and validated tropospheric chemistry to form a single, unified gas-phase chemistry scheme. Aerosol calculations are extended to include heterogeneous halogen chemistry and the formation, sedimentation and evaporation of polar stratospheric clouds (PSCs) as well as background liquid binary sulfate (LBS) aerosols. The Fast-JX v7.0a photolysis scheme replaces a hybrid of Fast-J and Fast-JX v6.2, allowing photolytic destruction at frequencies relevant to the stratosphere and of species not previously modeled. Finally, new boundary conditions are implemented to cover both surface emissions of new species and mesospheric behavior. Results for four simulation years (2004–2007) are compared to those from the original, tropospheric model and to in situ and satellite-based measurements. We use these comparisons to show that the extended model is capable of modeling stratospheric chemistry efficiently without compromising the accuracy of the model at lower altitudes, perturbing mean OH below 250 hPa by less than 5% while successfully capturing stratospheric behavior not previously captured in GEOS-Chem such as formation and collapse of the Antarctic ozone hole. These extensions (with supporting validation and intercomparison) enable an existing and extensively validated tropospheric CTM to be used to investigate a broader set of atmospheric chemistry problems and leverages GEOS-Chem's existing tropospheric treatment.
Keywords: GEOS-Chem; Stratospheric chemistry; Ozone hole; Model development; Model validation;
Overview of the impact of wood burning emissions on carbonaceous aerosols and PM in large parts of the Alpine region by H. Herich; M.F.D. Gianini; C. Piot; G. Močnik; J.-L. Jaffrezo; J.-L. Besombes; A.S.H. Prévôt; C. Hueglin (64-75).
During the past years, actions implemented for the reduction of particulate matter emissions have in many European countries focused on road traffic emissions. Much less attention was paid to emissions from domestic wood combustion though the importance of residential wood burning as a source of atmospheric particulate matter (PM) in the Alpine region has been shown in many studies.Here we review the current knowledge about the contribution of wood burning emissions to ambient concentrations of elemental carbon (EC), organic carbon (OC) and PM in the Alpine region. The published results obtained by different approaches (e.g. macro-tracer method, multivariate receptor modeling, chemical mass balance modelling, and so-called Aethalometer modeling) are used in an ambient mono-tracer approach to estimate representative relationships between wood burning tracers (levoglucosan and mannosan) and EC, OC and PM from wood burning. The relationships found are applied to available ambient measurements of levoglucosan and mannosan at Alpine sites for estimation of the contributions of wood burning emissions to average levels of carbonaceous aerosols and PM at these sites. Our results imply that PM from wood burning alone adds often up to 50% and more of the EU daily limit value for PM10 in several alpine valleys during days in winter. Concentrations of carbonaceous aerosols in these valleys are often up to six times higher than in urban or rural sites at the foothills of the Alps.
Keywords: Wood burning; Alpine region; Levoglucosan; Source apportionment;
Experimental method development for estimating solid-phase diffusion coefficients and material/air partition coefficients of SVOCs by Xiaoyu Liu; Zhishi Guo; Nancy F. Roache (76-84).
The solid-phase diffusion coefficient (D m) and material/air partition coefficient (K ma) are key parameters for characterizing the sources and transport of semivolatile organic compounds (SVOCs) in the indoor environment. In this work, a new experimental method was developed to estimate parameters D m and K ma. The SVOCs chosen for study were polychlorinated biphenyl (PCB) congeners, including PCB-52, PCB-66, PCB-101, PCB-110, and PCB-118. The test materials included polypropylene, high density polyethylene, low density polyethylene, polytetrafluoroethylene, polyether ether ketone, glass, stainless steel and concrete. Two 53-L environmental chambers were connected in series, with the relatively stable SVOCs source in the source chamber and the test materials, made as small “buttons”, in the test chamber. Prior to loading the test chamber with the test materials, the test chamber had been dosed with SVOCs for 12 days to “coat” the chamber walls. During the tests, the material buttons were removed from the test chamber at different exposure times to determine the amount of SVOC absorbed by the buttons. SVOC concentrations at the inlet and outlet of the test chamber were also monitored. The data were used to estimate the partition and diffusion coefficients by fitting a sink model to the experimental data. The parameters obtained were employed to predict the accumulation of SVOCs in the sink materials using an existing mass transfer model. The model prediction agreed reasonably well with the experimental data.
Keywords: Semivolatile organic compounds; Polychlorinated biphenyls; Solid-phase diffusion coefficient; Material/air partition coefficient; Chamber testing; Mass transfer modeling;
Atmospheric PM and volatile organic compounds released from Mediterranean shrubland wildfires by Elisa Garcia-Hurtado; Jorge Pey; Esther Borrás; Pilar Sánchez; Teresa Vera; Adoración Carratalá; Andrés Alastuey; Xavier Querol; V. Ramon Vallejo (85-92).
Wildfires produce a significant release of gases and particles affecting climate and air quality. In the Mediterranean region, shrublands significantly contribute to burned areas and may show specific emission profiles. Our objective was to depict and quantify the primary-derived aerosols and precursors of secondary particulate species released during shrubland experimental fires, in which fire-line intensity values were equivalent to those of moderate shrubland wildfires, by using a number of different methodologies for the characterization of organic and inorganic compounds in both gas-phase and particulate-phase. Emissions of PM mass, particle number concentrations and organic and inorganic PM x components during flaming and smouldering phases were characterized in a field shrubland fire experiment. Our results revealed a clear prevalence of K+ and SO4 2− as inorganic ions released during the flaming–smouldering processes, accounting for 68–80% of the inorganic soluble fraction. During the residual-smouldering phases, in addition to K+ and SO4 2−, Ca2+ was found in significant amounts probably due the predominance of re-suspension processes (ashes and soil dust) over other emission sources during this stage. Concerning organic markers, the chromatograms were dominated by phenols, n-alkanals and n-alkanones, as well as by alcohol biomarkers in all the PM x fractions investigated. Levoglucosan was the most abundant degradation compound with maximum emission factors between 182 and 261 mg kg−1 in PM2.5 and PM10 respectively. However, levoglucosan was also observed in significant amounts in the gas-phase. The most representative organic volatile constituents in the smoke samples were alcohols, carbonyls, acids, monocyclic and bicyclic arenes, isoprenoids and alkanes compounds. The emission factors obtained in this study may contribute to the validation and improvement of national and international emission inventories of this intricate and diffuse emission source.
Keywords: Biomass burning; Mediterranean shrubland; Water soluble ions; Trace elements; Organic compounds; VOCs;
Estimation of the long-range transport contribution from secondary inorganic components to urban background PM10 concentrations in south-western Sweden during 1986–2010 by Lin Tang; Marie Haeger-Eugensson; Karin Sjöberg; Janine Wichmann; Peter Molnár; Gerd Sallsten (93-101).
The contribution of long-range transported (LRT) to urban background PM10 concentrations was investigated from a long-term view from 1986 to 2010. Regional air concentrations of sulphate (SO4 2−), nitrate (NO3 −), and ammonium (NH4 +) were used as a sum (C ion) to investigate the contribution from these ions to the LRT PM10 concentrations at an urban background site in Gothenburg, Sweden. Utilizing backwards trajectory analysis, the LRT contribution from C ion to the urban background PM10 concentrations ( LRT C ion ) was estimated for six unique transport pathways and related source areas. Air masses transported over eastern Europe, UK/North Sea/Denmark and the vicinity of Scandinavia were associated with high C ion concentrations observed in Gothenburg. For each pathway, multiple linear models based on the C ion concentrations were used to estimate LRT C ion and PM10 at the urban background site. The performances of the multiple linear models were satisfying with R 2 between estimated and observed annual mean PM10 concentrations of 0.81 during the monitoring years 1990–2010. The models were able to describe the main features of the day-to-day average PM10 concentrations, but underestimated high level values. The annual estimated LRT C ion contribution decreased from 7 ± 2 μg/m3 for 1986–2000 to 5 ± 1 μg/m3 for 2001–2010. The higher LRT C ion contribution was related to the transport cluster from eastern Europe, UK/North Sea/Denmark and the vicinity of South Scandinavia.
Keywords: Long-range transport; Local contribution; Secondary inorganic aerosols; PM10; Transport clusters; South-western Sweden;
Atmospheric wet deposition of nitrogen and sulfur in the agroecosystem in developing and developed areas of Southeastern China by Jian Cui; Jing Zhou; Ying Peng; Yuanqiu He; Hao Yang; Jingdong Mao; Mingli Zhang; Yanhua Wang; Shuwei Wang (102-108).
Atmospheric nitrogen (N) and sulfur (S) deposition is a significant and growing issue for ecological environment in many parts of the world such as China. However, the study on atmospheric deposition, especially N deposition, is still at the initial stage and usually neglected in agro-ecosystems. To assess the characteristics of N and S wet deposition in agro-ecosystems, we selected Yingtan Station (YTS) located in the developing area and Changshu Station (CSS) in the developed area as typical, agricultural study sites in Southeastern China during 2010–2011. In the two areas, the total N and S wet deposition were in ranges of 30.49–37.37 kg ha−1 year−1 N and 56.02–59.06 kg ha−1 year−1 S, respectively, surpassing their corresponding critical loads in China. The annual means of NH4 +–N, NO3 −–N and dissolved organic N (DON) deposition contributed 49.6%, 26.4% and 24.0% of the total deposition, respectively. Similar total N and S deposition data were observed in the two sites, but their N species, especially DON, were different due to different numbers of slaughter pigs and types of N fertilizers applied. In conclusion, DON was identified as an important contributor to the total N deposition and should also be monitored in the future. Such high N and S deposition would deteriorate agroecosystems in Southeastern China. Related political measures on livestock industries, managements of motor vehicles and technologies of coal and oil combustion should be improved timely and implemented effectively for reducing the regional N emission and deposition in the future.
Keywords: N and S wet deposition; Agroecosystem; The developing area; The developed area; Southeastern China;
Effect of aerosols on evapo-transpiration by B.S. Murthy; R. Latha; Manoj Kumar; N.C. Mahanti (109-118).
Aerosol direct radiative forcing (ARF) at surface is estimated from instantaneous, simultaneous observations of global radiation and aerosol optical depth (AOD) during winter, pre-monsoon and monsoon seasons over a tropical Indian station at the south-eastern end of Indo Gangetic basin. A comparison of observed and model derived ARFs is made and possible reasons for mismatch are discussed. Aerosol-induced reduction in solar visible (0.4–0.7 μm) spectrum energy (SWvis), contributing 44% to total broad band (0.3–3.0 μm) energy (SW), and its effect on surface energy fluxes are discussed in this study. Aerosols on an average reduce SWvis at surface by ∼27%. SWvis reduces by 14.5 W m−2 for a 0.1 increase in AOD when single scattering albedo (SSA) is 0.979 where as it reduces by 67.5 W m−2 when SSA is 0.867 indicating the significant effect of absorbing aerosols. Effect of ARF on net radiation, Rn, sensible heat flux, H and latent heat flux/evapo-transpiration, LE are estimated using the observed ratios of Rn/SW, H/Rn and LE/Rn, having reasonably good correlation. Observed Rn/SW varies between 0.59 and 0.75 with a correlation of 0.99 between them. LE, calculated by energy balance method, varies from 56% to 74% of Rn but with a lesser correlation, the possible reasons are discussed. For a given ARF, LE decreases by ∼14% and Rn by ∼15% with respect to observed LE and Rn respectively. The reduction in LE increases from 37% to 54% of ARF when LE increases from 220 W m−2 to 440 W m−2, suggesting that wet soil induces relatively larger reduction in evaporation. The results agree with earlier model sensitivity studies that Rn reduces more with increase in aerosol absorption which is compensated by proportionate reductions in H and LE depending on soil and atmospheric conditions.
Keywords: Shortwave radiation; Aerosol radiative forcing; Radiation budget; Evapo-transpiration;
Source apportionment of airborne particles in commercial aircraft cabin environment: Contributions from outside and inside of cabin by Zheng Li; Jun Guan; Xudong Yang; Chao-Hsin Lin (119-128).
Airborne particles are an important type of air pollutants in aircraft cabin. Finding sources of particles is conducive to taking appropriate measures to remove them. In this study, measurements of concentration and size distribution of particles larger than 0.3 μm (PM>0.3) were made on nine short haul flights from September 2012 to March 2013. Particle counts in supply air and breathing zone air were both obtained. Results indicate that the number concentrations of particles ranged from 3.6 × 102 counts L−1 to 1.2 × 105 counts L−1 in supply air and breathing zone air, and they first decreased and then increased in general during the flight duration. Peaks of particle concentration were found at climbing, descending, and cruising phases in several flights. Percentages of particle concentration in breathing zone contributed by the bleed air (originated from outside) and cabin interior sources were calculated. The bleed air ratios, outside airflow rates and total airflow rates were calculated by using carbon dioxide as a ventilation tracer in five of the nine flights. The calculated results indicate that PM>0.3 in breathing zone mainly came from unfiltered bleed air, especially for particle sizes from 0.3 to 2.0 μm. And for particles larger than 2.0 μm, contributions from the bleed air and cabin interior were both important. The results would be useful for developing better cabin air quality control strategies.
Keywords: Aircraft cabin; Particle concentration; Size distribution; Airflow rate; Source apportionment;
Reducing transit bus emissions: Alternative fuels or traffic operations? by Ahsan Alam; Marianne Hatzopoulou (129-139).
In this study, we simulated the operations and greenhouse gas (GHG) emissions of transit buses along a busy corridor and quantified the effects of two different fuels (conventional diesel and compressed natural gas) as well as a set of driving conditions on emissions. Results indicate that compressed natural gas (CNG) reduces GHG emissions by 8–12% compared to conventional diesel, this reduction could increase to 16% with high levels of traffic congestion. However, the benefits of switching from conventional diesel to CNG are less apparent when the road network is uncongested. We also investigated the effects of bus operations on emissions by applying several strategies such as transit signal priority (TSP), queue jumper lanes, and relocation of bus stops. Results show that in congested conditions, TSP alone can reduce GHG emissions by 14% and when combined with improved technology; a reduction of 23% is achieved. The reduction benefits are even more apparent when other transit operational improvements are combined with TSP. Finally a sensitivity analysis was performed to investigate the effect of operational improvements on emissions under varying levels of network congestion. We observe that under “extreme congestion”, the benefits of TSP decrease.
Keywords: Transit bus emissions; Emission modeling; MOVES; Compressed natural gas; Transit signal priority; Queue jumper lane;
Measurement of the stable carbon isotope ratio of atmospheric volatile organic compounds using chromatography, combustion, and isotope ratio mass spectrometry coupled with thermal desorption by Hiroto Kawashima; Mai Murakami (140-147).
The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular of their stable carbon isotope ratio (δ 13C), could potentially be used as an effective tool for identifying the sources of VOCs. However, to date, there have been very few such analyses. In this work, we analyze the δ 13C values of VOCs using thermal desorption coupled with chromatography, combustion, and isotope ratio mass spectrometry (TD–GC/C/IRMS). The measured peak shapes were of high quality and 36 compounds in a standard gas containing 58 VOCs (C5–C11) were detected. The measured δ 13C varied widely, from −49.7‰ to −22.9‰, while the standard deviation of the δ 13C values varied from 0.07‰ to 0.85‰ (n = 5). We then measured samples from two passenger cars in hot and cold modes, three gas stations, roadside air, and ambient air. In comparison with existing studies, the analytical precision for the 36 compounds in this study was reasonable. By comparing the δ 13C values obtained from the cars and gas stations, we could identify some degree of the sources of VOCs in the roadside and ambient air samples.
Keywords: Volatile organic compounds; Stable carbon isotope ratio; Vehicle emissions; Source apportionment; Thermal desorption; TD–GC/C/IRMS;
Development of a fluctuating plume model for odour dispersion around buildings by Harerton Dourado; Jane Meri Santos; Neyval C. Reis; Ilias Mavroidis (148-157).
This paper presents a fluctuating plume model, which incorporates the PRIME algorithm in order to include the effect of plume elevation and downwash due to buoyancy and the presence of obstacles. The Gaussian fluctuating plume model has the ability to predict both mean concentrations and concentration fluctuations. Therefore, it is useful for modelling dispersion in cases where concentration fluctuations are important for environmental impact assessment, such as for odorous compounds. The model is validated using two different experimental datasets, one involving dispersion around a complex building in a wind tunnel and the other involving dispersion around an isolated cube in the field. The results suggest that the model in general predicts adequately mean concentrations and concentration fluctuation statistics, such as concentration peaks and intermittency, downwind of the near-wake. However, mainly due to the formulation of the PRIME algorithm, it underestimates concentrations in the near-wake recirculation region of the obstacle and although it can adequately predict the maximum intermittency value, it does not predict accurately its location. In general, the model appears to over-predict dispersion if compared to the wind tunnel data. This can be partly attributed to the larger scales of turbulence not reproduced in the wind tunnel as also suggested from the comparison of the model results with field data. Finally, due to the assumptions incorporated in PRIME, the model cannot capture the effect of the complex shape of a building on near-field dispersion.
Keywords: Atmospheric dispersion; Concentration fluctuations; Odours; PRIME algorithm; Intermittency;
The role of temporal evolution in modeling atmospheric emissions from tropical fires by Miriam E. Marlier; Apostolos Voulgarakis; Drew T. Shindell; Greg Faluvegi; Candise L. Henry; James T. Randerson (158-168).
Fire emissions associated with tropical land use change and maintenance influence atmospheric composition, air quality, and climate. In this study, we explore the effects of representing fire emissions at daily versus monthly resolution in a global composition-climate model. We find that simulations of aerosols are impacted more by the temporal resolution of fire emissions than trace gases such as carbon monoxide or ozone. Daily-resolved datasets concentrate emissions from fire events over shorter time periods and allow them to more realistically interact with model meteorology, reducing how often emissions are concurrently released with precipitation events and in turn increasing peak aerosol concentrations. The magnitude of this effect varies across tropical ecosystem types, ranging from smaller changes in modeling the low intensity, frequent burning typical of savanna ecosystems to larger differences when modeling the short-term, intense fires that characterize deforestation events. The utility of modeling fire emissions at a daily resolution also depends on the application, such as modeling exceedances of particulate matter concentrations over air quality guidelines or simulating regional atmospheric heating patterns.
Keywords: Fire emissions; Atmospheric modeling; Air quality;
Sensitivity of predicted pollutant levels to anthropogenic heat emissions in Beijing by Man Yu; Gregory R. Carmichael; Tong Zhu; Yafang Cheng (169-178).
A new parameterization method for anthropogenic heat (AH) parameterization (called NewLUCY) is developed in the WRF-Chem model, which estimates hourly heat fluxes with a single-peak diurnal variation pattern and utilizes updated urban built-up land use data. The impacts of accounting for anthropogenic heat (AH) fluxes on the meteorology and air quality of the Greater Beijing area are studied using this upgraded WRF-Chem model system. Including AH is shown to increase the surface temperature by 0.8°C in daytime and 1.2 °C at nighttime. The Planetary Boundary Layer (PBL) heights are also increased, with a maximum incrementation exceeding 320 m during daytime and 160 m at night. Spatial and vertical distributions of the simulated pollutants are also impacted by the AH. Surface ozone concentrations increase in the urban areas (4ppb for daytime and 18 ppb for nighttime) when AH is included in the analyses. Moreover, the impacts of AH are not limited to the urban centers, but extend regionally. For example, the simulated PM2.5 concentrations increase in the rural areas as well, due to a decrease in rural precipitation rates when AH is included. In general, incorporation of AH increases the accuracy of the predictions comparing to the observations. At the Peking University site (PKU), the mean error (ME) of the 2-m temperature prediction is reduced from 1.55 °C to 0.61 °C. The predictions of the high ozone episodes are also improved.
Keywords: Anthropogenic heat; Air quality model; WRF/Chem; Ozone;
Revisiting haboobs in the southwestern United States: An observational case study of the 5 July 2011 Phoenix dust storm by Aishwarya Raman; Avelino F. Arellano; John J. Brost (179-188).
Convectively-driven dust storms (or haboobs) are common phenomena in the southwestern United States. However, studies about haboobs in this region are limited. Here, we investigate the state and fate of a massive haboob that hit Phoenix, Arizona on 5 July 2011 using satellite, radar, and ground-based observations. This haboob was a result of strong outflow boundaries (with peak wind gusts of 29 m s−1) from storms that were initiated in the southeast of Tucson. In particular, we find three major outflow systems (based on radar data) that were generated by forward propagating storms, ultimately merging near Phoenix. This resulted in peak hourly PM10 and PM2.5 concentrations of 1974 μg m−3 and 907 μg m−3 at US EPA stations near Phoenix. The high PM concentration is consistent in space and time with the dust wall movement based on our analysis of radar data on hydrometeor classification. Enhanced aerosol loadings over metropolitan Phoenix were also observed on 6 July from NASA Terra/Aqua MODIS aerosol optical depth (AOD) retrievals (AOD > 0.8). We infer from CALIOP vertical feature masks and HYSPLIT back trajectories that remnants of the haboob were transported to northwest of Phoenix on 6 July at 2–4 km above ground level. Ratios of PM2.5 to PM10 from IMPROVE stations also imply low-level transport to the east of Phoenix on 8 July. Finally, we find that this haboob, which had local and regional impacts, is atypical of other dust events in this region. We note from this analysis that extreme events such as this haboob require an integrated air quality observing system to provide a more comprehensive assessment of these events.
Keywords: Southwest US; Storm outflow; Haboob; Air quality; Extreme event;
Fine particulate matter predictions using high resolution Aerosol Optical Depth (AOD) retrievals by Alexandra A. Chudnovsky; Petros Koutrakis; Itai Kloog; Steven Melly; Francesco Nordio; Alexei Lyapustin; Yujie Wang; Joel Schwartz (189-198).
To date, spatial-temporal patterns of particulate matter (PM) within urban areas have primarily been examined using models. On the other hand, satellites extend spatial coverage but their spatial resolution is too coarse. In order to address this issue, here we report on spatial variability in PM levels derived from high 1 km resolution AOD product of Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm developed for MODIS satellite. We apply day-specific calibrations of AOD data to predict PM2.5 concentrations within the New England area of the United States. To improve the accuracy of our model, land use and meteorological variables were incorporated. We used inverse probability weighting (IPW) to account for nonrandom missingness of AOD and nested regions within days to capture spatial variation. With this approach we can control for the inherent day-to-day variability in the AOD-PM2.5 relationship, which depends on time-varying parameters such as particle optical properties, vertical and diurnal concentration profiles and ground surface reflectance among others. Out-of-sample “ten-fold” cross-validation was used to quantify the accuracy of model predictions. Our results show that the model-predicted PM2.5 mass concentrations are highly correlated with the actual observations, with out-of-sample R 2 of 0.89. Furthermore, our study shows that the model captures the pollution levels along highways and many urban locations thereby extending our ability to investigate the spatial patterns of urban air quality, such as examining exposures in areas with high traffic. Our results also show high accuracy within the cities of Boston and New Haven thereby indicating that MAIAC data can be used to examine intra-urban exposure contrasts in PM2.5 levels.
Keywords: Particulate matter; PM2.5; Aerosol Optical Depth (AOD); High resolution aerosol retrieval; MAIAC; Intra-urban pollution; Variability in PM2.5 levels; Scales of pollution;
Comparison between Lagrangian and Eulerian approaches in predicting motion of micron-sized particles in laminar flows by M.S. Saidi; M. Rismanian; M. Monjezi; M. Zendehbad; S. Fatehiboroujeni (199-206).
Modeling the behavior of suspended particles in gaseous phase is important for diverse reasons; e.g. aerosol is usually the main subject of CFD simulations in clean rooms. Additionally, to determine the rate and sites of deposition of particles suspended in inhaled air, the motion of the particles should be predicted in lung airways. Meanwhile there are two basically different approaches to simulate the behavior of particles suspension, Lagrangian and Eulerian approaches. This study compares the results of these two approaches on simulating the same problem. An in-house particle tracking code was developed to simulate the motion of particles with Lagrangian approach. In order to simulate the same problem with Eulerian approach, the solution to the transport equation with appropriate initial and boundary conditions was used. In the first case study, diffusion of particles, initially positioned homogeneously on an infinite plane was modeled with both approaches and the results were compared and the mismatch between Lagrangian and Eulerian approaches was analyzed for different concentrations. In the second case study, airflow with parabolic velocity profile moving between two parallel plates was modeled with two approaches. The airflow initially contained a homogeneous suspension of particles and the plates were maintained at zero concentration. The concentration along the plates was compared between the two approaches and the differences in the performance of each approach were investigated, again for different initial concentrations. The overall results confirm that as particle concentration falls below a minimum amount, approximately 105 m−2, the results of the two approaches deviate considerably from each other and hence the Eulerian approach cannot be taken as an alternative for Lagrangian approach for low concentrations. For the third problem, we investigated the 3D particle flow in an expanding lung alveolus. It is shown that when the number of total released particles increases, the results of Eulerian approach can be used as an alternative to Lagrangian simulation. Since the number of particles existing in the lung alveolus in normal condition is much lower than this value, we concluded that Eulerian method cannot be applied to problems involving low concentration of particles. Although, the results of the Lagrangian problem may converge to the Eulerian one by increasing simulation time, but it is a hypothetical situation which not really exist in short time scale problems such as third case study in this paper.
Keywords: Lagrangian approach; Eulerian approach; Aerosol; Particle deposition;
Polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matters in Nanjing, China: Distributions, sources and meteorological influences by Jiabao He; Shuxian Fan; Qingzi Meng; Yu Sun; Jian Zhang; Fan Zu (207-215).
A study of 16 polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matters at suburban and urban sites in Nanjing was carried out each season from November 2009 to July 2010. At the suburban and urban sites, the concentrations of total PAHs (T-PAHs) were in the ranges of 30.76–102.26 ng/m3 and 25.92–90.80 ng/m3, respectively. This paper elucidates the distributions, sources of PAHs and meteorological influences: 1) PAHs concentrations at the two sites were close to each other and similarity between PAHs profiles of the two sites indicated they had common sources, which were attributed to the combined effect of regional transport and local emission. 2) At both sites, the profiles displayed obvious seasonal variations, as a result of the seasonality of sources and meteorological influences. The T-PAHs concentrations were in the order of winter > spring > autumn > summer. 3) Source apportionment showed vehicle exhaust (72.93–87.24%) was the greatest contributor in all seasons. The coal combustion and coke production (coal/coke) (10.02–18.63%) were identified in all but summer seasons, because of the low collection efficiency of PAHs markers of coal/coke under high temperature. For autumn, biomass burning (10.58%) was an extra contributor. 4) Regarding meteorological parameters, a negative effect of temperature over PAHs was confirmed, with a correlation coefficient of −0.51 (p < 0.05). Precipitation could remove PAHs to some extent. Both positive and negative correlations between PAHs concentration and wind speed in each season were analyzed in combination with air mass back-trajectories so as to evaluate the effects of regional air transport. The results showed that polluted air from ENE-S and NNW-NE brought in outside sources to the study area and played a major role in the accumulation of fine-particulate PAHs in spring and winter respectively, while clean air from southwest contributed to the dilution in summer.
Keywords: Polycyclic aromatic hydrocarbons; PM2.1; Source; Meteorological influence; Regional transport;
Historic and future trends of vehicle emissions in Beijing, 1998–2020: A policy assessment for the most stringent vehicle emission control program in China by Shaojun Zhang; Ye Wu; Xiaomeng Wu; Mengliang Li; Yunshan Ge; Bin Liang; Yueyun Xu; Yu Zhou; Huan Liu; Lixin Fu; Jiming Hao (216-229).
As a pioneer in controlling vehicle emissions within China, Beijing released the Clean Air Action Plan 2013–2017 document in August 2013 to improve its urban air quality. It has put forward this plan containing the most stringent emission control policies and strategies to be adopted for on-road vehicles of Beijing. This paper estimates the historic and future trends and uncertainties in vehicle emissions of Beijing from 1998 to 2020 by applying a new emission factor model for the Beijing vehicle fleet (EMBEV). Our updated results show that total emissions of CO, THC, NO x and PM2.5 from the Beijing vehicle fleet are 507 (395–819) kt, 59.1 (41.2–90.5) kt, 74.7 (54.9–103.9) kt and 2.69 (1.91–4.17) kt, respectively, at a 95% confidence level. This represents significant reductions of 58%, 59%, 31% and 62%, respectively, relative to the total vehicle emissions in 1998. The past trends clearly posed a challenge to NOx emission mitigation for the Beijing vehicle fleet, especially in light of those increasing NO x emissions from heavy-duty diesel vehicles (HDDVs) which have partly offset the reduction benefit from light-duty gasoline vehicles (LDGVs). Because of recently announced vehicle emission controls to be adopted in Beijing, including tighter emissions standards, limitations on vehicle growth by more stringent license control, promotion of alternative fuel technologies (e.g., natural gas) and the scrappage of older vehicles, estimated vehicle emissions in Beijing will continue to be mitigated by 74% of CO, 68% of THC, 56% of NO x and 72% of PM2.5 in 2020 compared to 2010 levels. Considering that many of the megacities in China are facing tremendous pressures to mitigate emissions from on-road vehicles, our assessment will provide a timely case study of significance for policy-makers in China.
Keywords: Vehicle; Air pollutant; Beijing; Emission control; The EMBEV model;
Indoor air pollution in slum neighbourhoods of Addis Ababa, Ethiopia by Habtamu Sanbata; Araya Asfaw; Abera Kumie (230-234).
An estimated 95% of the population of Ethiopia uses traditional biomass fuels, such as wood, dung, charcoal, or crop residues, to meet household energy needs. As a result of the harmful smoke emitted from the combustion of biomass fuels, indoor air pollution is responsible for more than 50,000 deaths annually and causes nearly 5% of the burden of disease in Ethiopia. Very limited research on indoor air pollution and its health impacts exists in Ethiopia. This study was, therefore, undertaken to assess the magnitude of indoor air pollution from household fuel use in Addis Ababa, the capital city of Ethiopia. During January and February, 2012, the concentration of fine particulate matter (PM2.5) in 59 households was measured using the University of California at Berkeley Particle Monitor (UCB PM). The raw data was analysed using Statistical Package of Social Science (SPSS version 20.0) software to determine variance between groups and descriptive statistics. The geometric mean of 24-h indoor PM2.5 concentration is approximately 818 μg m−3 (Standard deviation (SD = 3.61)). The highest 24-h geometric mean of PM2.5 concentration observed were 1134 μg m−3 (SD = 3.36), 637 μg m−3 (SD = 4.44), and 335 μg m−3 (SD = 2.51), respectively, in households using predominantly solid fuel, kerosene, and clean fuel. Although 24-h mean PM2.5 concentration between fuel types differed statistically (P < 0.05), post hoc pairwise comparison indicated no significant difference in mean concentration of PM2.5 between improved biomass stoves and traditional stoves (P > 0.05). The study revealed indoor air pollution is a major environmental and health hazard from home using biomass fuel in Addis Ababa. The use of clean fuels and efficient cooking stoves is recommended.
Keywords: Indoor air pollution; PM2.5; Solid fuel; Stove type; Addis Ababa;
A yearlong study of water-soluble organic carbon in Beijing II: Light absorption properties by Zhenyu Du; Kebin He; Yuan Cheng; Fengkui Duan; Yongliang Ma; Jiumeng Liu; Xiaolu Zhang; Mei Zheng; Rodney Weber (235-241).
Light absorption properties of water-soluble organic carbon (WSOC) in Beijing were investigated by 24 h-averaged fine particulate matter (PM2.5) samples collected from October 2010 to November 2011. The light absorption spectra of WSOC exhibited strong wavelength dependence such that the absorption Ångstrom exponent was approximately 7.5. The light absorption at 365 nm (Abs365), which is typically used as a proxy of water-soluble brown carbon, was found to correlate strongly with WSOC (R 2 > 0.75, p < 0.01). Moreover, the correlation between Abs365 and levoglucosan (especially in fall and winter) indicated that biomass burning could contribute significantly to water-soluble brown carbon. Source apportionment with Positive Matrix Factorization (PMF) model showed that biomass burning and mixed sources contributed 58.0% and 20.8% to total Abs365, compared with 21.2% from WSOC associated with sulfate and oxalate. The mass absorption efficiency (MAE) of WSOC in Beijing showed distinct temporal variations (averaging 1.26 m2/g and 0.51 m2/g during winter and summer, respectively), and was approximately 2–3 times the values of that observed in the southeastern United States, but was substantially lower than the summertime results from Los Angeles. Influence factors responsible for the temporal and spatial variations of MAE were investigated. MAE were calculated for each PMF factor. It was found that the MAE for WSOC from biomass burning (1.19 m2/g) and mixed primary sources (2.89 m2/g) was much higher than that of WSOC associated with sulfate or oxalate (0.32–0.33 m2/g) in Beijing. In addition, it was concluded that differences in the precursors of WSOC might also be responsible for the observed variation of MAE such that WSOC associated with anthropogenic precursors are more light-absorbing compared with WSOC biogenic sources.
Keywords: WSOC; Brown carbon; Light absorption; Biomass burning;
Nitrated polycyclic aromatic hydrocarbon pollution during the Shanghai World Expo 2010 by W. Wang; L. Jing; J. Zhan; B. Wang; D.P. Zhang; H.W. Zhang; D.Q. Wang; Y. Yang; J. Zhao; Y.F. Sun; X.H. Bi; X.T. Wang; J.L. Feng (242-248).
Atmospheric particulate matter with aerodynamic diameter <2.5 μm (PM2.5) was collected at Xujiahui and Baoshan in Shanghai, China in 2010 when the World Expo took place. Eight nitrated polycyclic aromatic hydrocarbons (NPAHs) were analyzed. Significant reductions in individual NPAH (69–324%) and the mean ΣNPAH (about 140%) concentrations were measured during the Expo period. In order to minimize the influence from the meteorological condition, individual NPAH concentrations of 2010 Expo period were compared with those in the same time period from 2008. Significant effects from the source control measures were revealed, i.e., the individual NPAH concentration reductions ranged between 31% and 477% at the mixed residential and industrial Baoshan site, and only 0–88% at the urban Xujiahui site. The relatively high 2-nitrofluoranthene/1-nitropyrene ratio values (11–31) suggested a predominance of photochemical formation of NPAHs in the atmosphere during the Expo period. It could be concluded that the air quality during the Shanghai World Expo 2010 was benefited from the following three factors; (1) source control measures during the Expo period, i.e., prohibition of open field biomass burning in surrounding areas, (2) the three-year plan implemented from October 1, 2009, including construction sites shut-down, flue-gas desulfurization/denitrification and the vehicle upgradation and (3) the Asian monsoon which brings in clean air from the ocean during spring and summer into Shanghai.
Keywords: PM2.5; Nitrated polycyclic aromatic hydrocarbons; Shanghai World Expo 2010;
The spatial and temporal relationships between CO2 and CH4 exchange in a temperate ombrotrophic bog by Derrick Y.F. Lai; Nigel T. Roulet; Tim R. Moore (249-259).
We investigate the relationships between CO2 and CH4 fluxes across space and time at a temperate ombrotrophic bog in Canada to assess the coupling between plant production and CH4 emissions. Based on periodic manual chamber measurements, we show that maximum net ecosystem CO2 exchange (NEEmax) was a good predictor of the spatial variations in CH4 flux among the wetter Eriophorum and lawn sites (r 2 = 0.61–0.88), but not the drier hummock sites (r 2 = 0.04–0.49). Also, we observed large interannual variability in the NEEmax-CH4 relationship at the Eriophorum and lawn sites, with a smaller regression slope in 2010 that had a seasonal mean water table 8 cm lower than in 2009. Results of cross-correlation of instantaneous gross ecosystem production (GEP) and CH4 flux from autochambers show a moderate relationship (σ = −0.31) in the Eriophorum community at a lag of 9–12 h, suggesting a rapid turnover of recent photosynthate for methanogenesis. On the other hand, we found in two Maianthemum-dominated chambers that the temperature-independent residuals of daily mean CH4 flux lagged behind GEP by 18–26 days at the seasonal scale. The lagged correlations between GEP and CH4 flux by month were particularly strong in the late growing season in the Eriophorum and Maianthemum/Ledum communities. Our results suggest the presence of spatial and temporal coupling of plant production and CH4 emissions in this bog, whose strength varies with species composition, water table position, and plant phenology.Display Omitted
Keywords: Carbon dioxide; Cross-correlation; Methane; Ombrotrophic peatland;
Surface tensions of solutions containing dicarboxylic acid mixtures by Jae Young Lee; Lynn M. Hildemann (260-267).
Organic solutes tend to lower the surface tension of cloud condensation nuclei, allowing them to more readily activate. The surface tension of various dicarboxylic acid aerosol mixtures was measured at 20 °C using the Wilhelmy plate method. At lower concentrations, the surface tension of a solution with equi-molar mixtures of dicarboxylic acids closely followed that of a solution with the most surface-active organic component alone. Measurements of surface tension for these mixtures were lower than predictions using Henning's model and the modified Szyszkowski equation, by ∼1–2%. The calculated maximum surface excess (Γmax) and inverse Langmuir adsorption coefficient (β) from the modified Szyszkowski equation were both larger than measured values for 6 of the 7 mixtures tested. Accounting for the reduction in surface tension in the Köhler equation reduced the critical saturation ratio for these multi-component mixtures – changes were negligible for dry diameters of 0.1 and 0.5 μm, but a reduction from 1.0068 to 1.0063 was seen for the 4-dicarboxylic acid mixture with a dry diameter of 0.05 μm.
Keywords: Aerosol; Organic aerosol; Cloud condensation nuclei; Climate change; Surface tension; Dicarboxylic acid;
Spatial variability of trace elements and sources for improved exposure assessment in Barcelona by María Cruz Minguillón; Marta Cirach; Gerard Hoek; Bert Brunekreef; Ming Tsai; Kees de Hoogh; Aleksandra Jedynska; Ingeborg M. Kooter; Mark Nieuwenhuijsen; Xavier Querol (268-281).
Trace and major elements concentrations in PM10 and PM2.5 were measured at 20 sites spread in the Barcelona metropolitan area (1 rural background, 6 urban background, 13 road traffic sites) and at 1 reference site. Three 2-week samples per site and size fraction were collected during 2009 using low volume samplers, adding a total of 120 samples. Collected samples were analysed for elemental composition using Energy Dispersive X-ray fluorescence (XRF). EC, OC, and hopanes and steranes concentrations in PM2.5 were determined. Positive Matrix Factorisation (PMF) model was used for a source apportionment analysis. The work was performed as part of the ESCAPE project.Elements were found in concentrations within the usual range in Spanish urban areas. Mineral elements were measured in higher concentrations during the warm season, due to enhanced resuspension; concentrations of fueloil combustion elements were also higher in summer. Elements in higher concentration at the traffic sites were: Ba, Cr, Cu, Fe, Mn, Mo, Pb, Sn, Zn and Zr. Spatial variations related to non-traffic sources were observed for concentrations of Br, Cl, K, and Na (sea salt origin) and Ni, V and S (shipping emissions), which were higher at the coastal sites, as well as for Zn and Pb, higher at sites closer to industrial facilities.Five common sources for PM10 and PM2.5 were identified by PMF: road traffic (with tracers Ba, Cr, Cu, Fe, Mo and Zn); fueloil combustion (Ni and V); secondary sulphate; industry (Pb and Zn); and mineral source (Al, Ca, Mg, Si, Sr and Ti). A marine aerosol source, a mixture of sea salt with aged anthropogenic aerosols, was found only in PM10. EC, hopanes and steranes concentrations correlate strongly with the PM10 road traffic source contributions, being hence all attributed to the same source. OC may arise from other sources in addition to road traffic and have a high contribution of secondary OC.Significant spatial and temporal variation in the PM2.5 and PM10 elemental composition was found. Spatial patterns differed per element, related to the main source. The identified source contributions can be used in health studies of source-specific particles.
Keywords: PM; Metals; Source apportionment; Urban; PMF;
Characterizing metal(loid) solubility in airborne PM10, PM2.5 and PM1 in Frankfurt, Germany using simulated lung fluids by Clare L.S. Wiseman; Fathi Zereini (282-289).
The purpose of this study is to assess the solubility of traffic-related metal(loid)s associated with airborne PM of human health concern, employing a physiologically-based extraction test with simulated lung fluids (artificial lysosomal fluid (ALF) and Gamble's solution). Airborne PM (PM10, PM2.5 and PM1) samples were collected in Frankfurt am Main, Germany, using a high volume sampler. Following extraction of the soluble metal(loid) fractions, sample filters were digested with a high pressure asher. Metal(loid) concentrations (As, Ce, Co, Cr, Cu, Mn, Ni, Pb, Sb, Ti and V) were determined in extracts and digests per ICP-Q-MS.All metal(loid)s occurred at detectable concentrations in the three airborne PM fractions. Copper was the most abundant element in mass terms, with mean concentrations of 105 and 53 ng/m3 in PM10 and PM2.5, respectively. Many of the metal(loid)s were observed to be soluble in simulated lung fluids, with Cu, As, V and Sb demonstrating the highest overall mobility in airborne PM. For instance, all four elements associated with PM10 had a solubility of >80% in ALF (24 h). Clearly, solubility is strongly pH dependent, as reflected by the higher relative mobility of samples extracted with the acidic ALF.Given their demonstrated solubility, this study provides indirect evidence that a number of toxic metal(loid)s are likely to possess an enhanced pulmonary toxic potential upon their inhalation. The co-presence of many toxic elements of concern in airborne PM suggests an assessment of health risk must consider the possible interactive impacts of multi-element exposures.V, Pb, Cu, As & Sb solubility (%) in PM10, PM2.5 and PM1 extracted with artificial lysosomal fluid (ALF) and Gamble's solution (24 h) (n = 36).Display Omitted
Keywords: Airborne PM; Metal bioaccessibility; Metal solubility; Simulated lung fluids; Artificial lysosomal fluid; Gamble's solution;
A statistical modeling framework for projecting future ambient ozone and its health impact due to climate change by Howard H. Chang; Hua Hao; Stefanie Ebelt Sarnat (290-297).
The adverse health effects of ambient ozone are well established. Given the high sensitivity of ambient ozone concentrations to meteorological conditions, the impacts of future climate change on ozone concentrations and its associated health effects are of concern. We describe a statistical modeling framework for projecting future ozone levels and its health impacts under a changing climate. This is motivated by the continual effort to evaluate projection uncertainties to inform public health risk assessment. The proposed approach was applied to the 20-county Atlanta metropolitan area using regional climate model (RCM) simulations from the North American Regional Climate Change Assessment Program. Future ozone levels and ozone-related excesses in asthma emergency department (ED) visits were examined for the period 2041–2070. The computationally efficient approach allowed us to consider 8 sets of climate model outputs based on different combinations of 4 RCMs and 4 general circulation models. Compared to the historical period of 1999–2004, we found consistent projections across climate models of an average 11.5% higher ozone levels (range: 4.8%, 16.2%), and an average 8.3% (range: −7%–24%) higher number of ozone exceedance days. Assuming no change in the at-risk population, this corresponds to excess ozone-related ED visits ranging from 267 to 466 visits per year. Health impact projection uncertainty was driven predominantly by uncertainty in the health effect association and climate model variability. Calibrating climate simulations with historical observations reduced differences in projections across climate models.
Keywords: Air pollution; Climate change; Emergency department visit; Health impact; Ozone; Statistical model; Uncertainty quantification;
An unconventional adaptation of a classical Gaussian plume dispersion scheme for the fast assessment of external irradiation from a radioactive cloud by Petr Pecha; Emilie Pechova (298-308).
This article focuses on derivation of an effective algorithm for the fast estimation of cloudshine doses/dose rates induced by a large mixture of radionuclides discharged into the atmosphere. A certain special modification of the classical Gaussian plume approach is proposed for approximation of the near-field dispersion problem. Specifically, the accidental radioactivity release is subdivided into consecutive one-hour Gaussian segments, each driven by a short-term meteorological forecast for the respective hours. Determination of the physical quantity of photon fluence rate from an ambient cloud irradiation is coupled to a special decomposition of the Gaussian plume shape into the equivalent virtual elliptic disks. It facilitates solution of the formerly used time-consuming 3-D integration and provides advantages with regard to acceleration of the computational process on a local scale. An optimal choice of integration limit is adopted on the basis of the mean free path of γ-photons in the air. An efficient approach is introduced for treatment of a wide range of energetic spectrum of the emitted photons when the usual multi-nuclide approach is replaced by a new multi-group scheme. The algorithm is capable of generating the radiological responses in a large net of spatial nodes. It predetermines the proposed procedure such as a proper tool for online data assimilation analysis in the near-field areas. A specific technique for numerical integration is verified on the basis of comparison with a partial analytical solution. Convergence of the finite cloud approximation to the tabulated semi-infinite cloud values for dose conversion factors was validated.
Keywords: Photon fluence; Atmospheric dispersion; Cloudshine dose;
Effect of Asian dust storms on mortality in three Asian cities by Hyewon Lee; Yasushi Honda; Youn-Hee Lim; Yue Leon Guo; Masahiro Hashizume; Ho Kim (309-317).
Asian dust storms (ADS) have affected several Asian countries and have been a major concern due to adverse effects on public health. The occurrence of ADS differs in each country based on geographical features and distance from the storms' origin. Many studies have reported significant associations between ADS and morbidity. However, regarding the association between ADS and mortality, only a few studies have found statistically significant ADS effects in Korea, Taiwan and Japan. Accordingly, this study aimed to examine the effects of ADS on daily mortality in three Asian cities (Seoul, South Korea; Taipei, Taiwan; and Kitakyushu, Japan) and to explore the differences in the extent of effects in each city. We performed time-series analyses using a generalized additive model (GAM) with Quasi-Poisson regressions. Deaths due to accidents or external causes were excluded. We used a dummy variable as an indicator of ADS and considered lag effects of ADS. Stratified analyses by disease and age and sensitivity analyses controlling for NO2, SO2, and PM10 were also conducted respectively. Additionally, influenza epidemics were adjusted for considering seasonal patterns, and a meta-analysis was performed. We reported results as excess mortality by percentage due to Asian dust storms. We found significant excess mortality in Seoul and Kitakyushu as follows. In Seoul, ADS showed adverse effects on mortality under 65 years old (lag 2: 4.44%, lag 3: 5%, lag 4: 4.39%). In Kitakyushu, ADS had adverse effects on respiratory mortality (lag 2: 18.82%). Contradictory to results in Seoul and Kitakyushu, ADS seemed to have a protective effect in Taipei: total non-accidental mortality (lag 0: −2.77%, lag 1: −3.24%), mortality over 65 years old (lag 0: −3.35%, lag 1: −3.29%) and respiratory mortality (lag 0: −10.62%, lag 1: −9.67%). Sensitivity analyses showed similar findings as the main results. Our findings suggest that ADS may affect mortality in several Asian cities, and that a dust storm warning system could help protect people from dust storms.Display Omitted
Keywords: Asian dust storms; Mortality; Lag effect; Multi-city study; Dust storm warning;
Gauging intraurban variability of ambient particulate matter arsenic and other air toxic metals from a network of monitoring sites by Varun Yadav; Jay Turner (318-328).
A four site monitoring network was established in the Missouri portion of Metropolitan St. Louis during 2008 to characterize spatiotemporal patterns in PM10 arsenic. Arsenic measured at two urban sites in the City of St. Louis was typically higher than arsenic at two suburban sites. Spatiotemporal variability in arsenic is examined by plotting the Pearson correlation coefficient (PCC) against the coefficient of divergence (COD) for each site-pair to merge the temporal tracking ability of PCC with COD's ability to gauge spatial homogeneity. Arsenic measured across the network is apportioned into a network-wide baseline and site-specific excess concentrations to semi-quantitatively differentiate local-scale emission source contributions from sources exerting influence over larger spatial scales. Comparing measured concentrations at each site against the network-wide baseline concentration using a scattergram of PCC and COD emphasizes the impact of local sources on intraurban variability. Conditional probability function (CPF) plots constructed using site-specific measured arsenic and surface winds identify a broad emission source region towards the east, but mask the bearings of local sources in the urban core. CPF plots using site-specific arsenic in excess of the baseline concentrations provide better resolution of local emission source bearings and are triangulated to identify a likely arsenic emission source zone along the industrialized Mississippi Riverfront. Additional air toxic metals measured in this study (selenium, manganese and lead) are also investigated to examine the efficacy of this methodology to characterize intraurban variability.
Keywords: Air toxic metals; Spatial variability; Temporal variability; Correlation coefficient; Coefficient of divergence; Local source identification;
A visibility and total suspended dust relationship by M.C. Baddock; C.L. Strong; J.F. Leys; S.K. Heidenreich; E.K. Tews; G.H. McTainsh (329-336).
This study reports findings on observed visibility reductions and associated concentrations of mineral dust from a detailed Australian case study. An understanding of the relationship between visibility and dust concentration is of considerable utility for wind erosion and aeolian dust research because it allows visibility data, which are available from thousands of weather observation stations worldwide, to be converted into dust concentrations. Until now, this application of visibility data for wind erosion/dust studies has been constrained by the scarcity of direct measurements of co-incident dust concentration and visibility measurements. While dust concentrations are available from high volume air samplers, these time-averaged data cannot be directly correlated with instantaneous visibility records from meteorological observations. This study presents a new method for deriving instantaneous values of total suspended dust from time averaged (filter-based) samples, through reference to high resolution PM10 data. The development and testing of the model is presented here as well as a discussion of the derived expression in relation to other visibility-dust concentration predictive curves. The current study is significant because the visibility-dust concentration relationship produced is based on visibility observations made 10–100 km from the dust sources. This distance from source makes the derived relationship appropriate for a greater number of visibility recording stations than widely-used previous relationships based on observations made directly at eroding sources. Testing of the new formula performance against observed total suspended dust concentrations demonstrates that the model predicts dust concentration relatively well (r 2 = 0.6) from visibility. When considered alongside previous studies, the new relationship fits into the continuum of visibility-dust concentration outcomes existing for increasing distance-from-source. This highlights the important influence that distance to source has on the visibility-dust concentration relationship.
Keywords: Duststorm; Sandstorm; Air quality; PM10; Aerosols; TSP;
Comparison of carbonaceous particulate matter emission factors among different solid fuels burned in residential stoves by Guofeng Shen; Miao Xue; Yuanchen Chen; Chunli Yang; Wei Li; Huizhong Shen; Ye Huang; Yanyan Zhang; Han Chen; Ying Zhu; Haisuo Wu; Aijun Ding; Shu Tao (337-345).
Uncertainty in the emission factor (EF) usually contributes largely to the overall uncertainty in the emission inventory. In the present study, the locally measured EFs of particulate matter (PM), organic carbon (OC), and elemental carbon (EC) for solid fuels burned in the residential sector are compiled and compared. These fuels are classified into seven sub-groups of anthracite briquette, anthracite chunk, bituminous briquette, bituminous chunk, crop residue, fuel wood log, and brushwood/branches. The EFs of carbonaceous particles for these fuels vary significantly, generally in the order of anthracite (briquette and chunk) < wood log < brushwood/branches < crop residue < bituminous (briquette and chunk), with an exception that the brushwood/branches have a relatively high EF of EC. The ratio of EC/OC varies significantly among different fuels, and is generally higher for biomass fuel than that for coal because of the intense flaming conditions formed during the biomass burning process in improved stoves. Distinct ratios calls for a future study on the potential health and climate impacts of carbonaceous PM from the residential combustions of different fuels. A narrow classification of these fuels significantly reduces the variations in the EFs of PM, OC, and EC, and the temporal and geographical distributions of the emissions could be better characterized.Display Omitted
Keywords: Carbonaceous particulate matter; Residential solid fuels; Fuel comparison; Reduced variations; Narrowing fuel classification;
A uniform classification of aerosol signature size distributions based on regression-guided and observational cluster analysis by Clemens von Bismarck-Osten; Stephan Weber (346-357).
Fine and ultrafine particles affect human health, especially in urban areas with a large number of emission sources and significant particle number concentrations. The mixture of different aerosol sources, their temporal evolution over the diurnal course and the impact of naturally occurring processes, e.g. particle nucleation, all contribute to the spatio-temporal exposure variability across a city and its suburban areas. A differentiation between different aerosol source types is of importance for the assessment of urban aerosol pollution and exposure in a city at a certain point in time. Therefore three years of particle number size distribution (NSD) measurements from three European cities were analysed by using cluster analysis in order to identify characteristic size distributions (signatures) which are associated to specific meteorological and spatio-temporal properties. A ‘triple-site’ approach was established with data from roadside, urban background and rural sites measured over a diameter size range of 8 < D p < 700 nm. After applying two different clustering approaches – a ‘regression guided’ and an ‘observational’ K-Means clustering – a number of 7 clusters were best representing the occurring individual aerosol “signature types”: two ‘low pollution’ clusters that showed the highest relative occurrence of around 40% on average, an ‘aged combustion’ type (∼20%), a ‘traffic’ (∼13%), a ‘remote transport’ cluster (∼10%), a cluster consisting of various unspecified local emission sources (∼10%) and a ‘particle formation’ cluster (∼7%). The cluster size distributions were distinguishable by their total number concentration, peak mode diameters and shape of the size distribution. A specific signature was assigned to each of these cluster types based on the temporal and seasonal occurrence and the prevailing meteorological conditions. The ‘regression guided’ approach was able to slightly better differentiate between homogeneous data whereas the weakness mainly lies in the time-intensive data preparation.
Keywords: Particle number size distribution; Classification; K-Means; Multiple regression; Source identification;
Characteristics of volatile organic compounds (VOCs) emitted from a petroleum refinery in Beijing, China by Wei Wei; Shuiyuan Cheng; Guohao Li; Gang Wang; Haiyan Wang (358-366).
This study made a field VOCs (volatile organic compounds) measurement for a petroleum refinery in Beijing by determining 56 PAMS VOCs, which are demanded for photochemical assessment in US, and obtained the characteristics of VOCs emitted from the whole refinery and from its inner main devices. During the monitoring period, this refinery brought about an average increase of 61 ppbv in the ambient TVOCs (sum of the PAMS VOCs) at the refinery surrounding area, while the background of TVOCs there was only 10–30 ppbv. In chemical profile, the VOCs emitted from the whole refinery was characteristic by isobutane (8.7%), n-butane (7.9%), isopentane (6.3%), n-pentane (4.9%%), n-hexane (7.6%), C6 branched alkanes (6.0%), propene (12.7%), 1-butene (4.1%), benzene (7.8%), and toluene (5.9%). On the other hand, the measurement for the inner 5 devices, catalytic cracking units (CCU2 and CCU3), catalytic reforming unit (CRU), tank farm (TF), and wastewater treatment(WT), revealed the higher level of VOCs pollutions (about several hundred ppbv of TVOCs), and the individual differences in VOCs chemical profiles. Based on the measured speciated VOCs data at the surrounding downwind area, PMF receptor model was applied to identify the VOCs sources in the refinery. Then, coupling with the VOCs chemical profiles measured at the device areas, we concluded that CCU1/3 contributes to 25.9% of the TVOCs at the surrounding downwind area by volume, followed by CCU2 (24.7%), CRU (18.9%), TF (18.3%) and WT (12.0%), which was accordant with the research of US EPA (2008). Finally, ozone formation potentials of the 5 devices were also calculated by MIR technique, which showed that catalytic cracking units, accounting for about 55.6% to photochemical ozone formation, should be given the consideration of VOCs control firstly.
Keywords: Volatile organic compounds; Petroleum refinery; Source apportionment; Ozone formation potential;
A simple and rapid analysis for gas-phase polycyclic aromatic hydrocarbons using an organic-solvent-based method by Guangzhu Jin; Linlin Cong; Hao Wang; Miao He; Junlin Li; Xiangfan Piao; Weihong Zhu; Donghao Li (367-372).
Monitoring of atmospheric organic pollutants is usually conducted by means of active or passive air samplers. In this study, we developed a simple, conventional, economic and fast sampling method for volatile and semivolatile compounds that is based on a liquid-phase organic solvent. Laboratory tests showed the feasibility of the method, and the major parameters of the method, such as temperature, organic solvent, carrier gas and air flow rate, were preliminarily optimized. For 16 kinds of polycyclic aromatic hydrocarbons (PAHs), the recovery, relative standard deviation and detection limit were ranged from 87.0 to 104.4%, 2.6 to 15.6% and 0.08 to 0.45 ng mL−1, respectively. Field application of the new method also showed good sampling efficiency for PAHs in real air samples, comparable to the results with an XAD-2 resin-based method. The similarity was closed to 1, suggesting that the new method is suitable for sampling of volatile and semivolatile organic pollutants in air and has great potential for air-pollution monitoring.
Keywords: Atmosphere; Sampling device; Organic pollutants; Monitoring;
Concentrations and source insights for trace elements in fine and coarse particulate matter by Nicholas Clements; Jenny Eav; Mingjie Xie; Michael P. Hannigan; Shelly L. Miller; William Navidi; Jennifer L. Peel; James J. Schauer; Martin M. Shafer; Jana B. Milford (373-381).
The Colorado Coarse Rural–Urban Sources and Health (CCRUSH) study is a multi-year study focused on characterizing the mass, composition and sources of coarse particulate matter (PM10−2.5) in Denver and Greeley, CO. Between the two cities, Denver is expected to have greater influence of industry and motor vehicles as sources of PM10–2.5. Greeley is a smaller city with greater expected influence of agricultural activity. As part of the CCRUSH study, we collected integrated 24-h samples of PM from four sites in Denver and Greeley at six day intervals from February 2010 to March 2011. Dichotomous samplers with Teflon filters were used to obtain samples for gravimetric and elemental analysis. Magnetic Sector Inductively Coupled Plasma-Mass Spectroscopy (SF-ICP-MS) was used to analyze digests of monthly composited filter samples for 49 elements. Thirty-nine elements were retained for statistical analysis after excluding those with low signal-to-noise ratios. The elements Sb, Cd, Zn, Mo, As, B, Cu, Pb, and W had crustal enrichment factors greater than 10 in the PM2.5 and PM10–2.5 size ranges in both Denver and Greeley. Using positive matrix factorization (PMF) with bootstrap uncertainty estimation, we identified five factors influencing the element concentrations: a crustal factor contributing to both PM2.5 and PM10–2.5; a sodium-dominated PM10–2.5 factor likely associated with road salt; a vehicle abrasion factor contributing in both size ranges; a regional sulfur factor contributing mainly to PM2.5 and likely associated with coal combustion; and a local catalyst factor identified with high Ce and La enrichment in PM2.5 at one of the sites in Denver.
Keywords: Coarse particles; PM10–2.5; Elemental composition; Factor analysis; Northeastern Colorado;
Spatial and temporal variability of air pollution in Birmingham, Alabama by C.L. Blanchard; S. Tanenbaum; G.M. Hidy (382-391).
Quantification of the spatial and temporal variations of outdoor air pollutant concentrations provides important information for epidemiological and other air-pollution studies, many of which have relied in the past on data from a single, centrally-located air pollution monitoring site. A method is developed for combining air pollution measurements from multiple monitors and monitoring networks to generate daily air pollution concentration fields representing spatial variations over distances of approximately 1–10 km. Meteorological and co-pollutant data are used to estimate missing site measurements, yielding more realistic concentration fields as the number of monitoring locations with available data increases. Monitoring data are interpolated with weights computed from intersite pollutant correlations, which decay with distance, so distances between interpolation points and monitoring sites are factored into the interpolation weights. The approach minimizes the influence of source-oriented sites that represent limited areas, because data from such sites exhibit low intersite correlations and yield interpolation weights that decay rapidly to zero. Interpolated values represent pollutant concentrations averaged over spatial scales that depend on intersite distances and the interpolation grid, and do not delineate sharp spatial gradients associated with roadside or near-source conditions. The approach yields quantified interpolation errors the values of which depend on measurement uncertainties, intersite distances, and the representativeness of monitoring site locations. The method is illustrated using an 11-year period of measurements of ozone, PM2.5, and PM10 concentrations from Jefferson County, Alabama. The principal city is Birmingham, which is influenced by regional-scale air pollution and by local emissions from mobile sources, industrial facilities, and residential communities. Emission sources are not distributed uniformly throughout Birmingham, the ridge-and-valley topography complicates dispersion of local emissions, and monitoring data indicate that air pollutant concentrations vary spatially as well as temporally. No single monitor represents air quality across the entire study area.
Keywords: Particulate matter; Ozone; Spatial interpolation; Epidemiology; Birmingham; Jefferson County; Alabama;
Size and mass distributions of ground-level sub-micrometer biomass burning aerosol from small wildfires by Rintaro Okoshi; Abdur Rasheed; Greeshma Chen Reddy; Clinton J. McCrowey; Daniel B. Curtis (392-402).
Biomass burning emits large amounts of aerosol particles globally, influencing human health and climate, but the number and size of the particles is highly variable depending on fuel type, burning and meteorological conditions, and secondary reactions in the atmosphere. Ambient measurements of aerosol during wildfire events can therefore improve our understanding of particulate matter produced from biomass burning. In this study, time-resolved sub-micrometer ambient aerosol size and mass distributions of freshly emitted aerosol were measured for three biomass burning wildfire events near Northridge, California, located in the highly populated San Fernando Valley area of Los Angeles. One fire (Marek) was observed during the dry Santa Ana conditions that are typically present during large Southern California wildfires, but two smaller fires (Getty and Camarillo) were observed during the more predominant non-Santa Ana weather conditions. Although the fires were generally small and extinguished quickly, they produced particle number concentrations as high as 50,000 cm−3 and mass concentrations as large as 150 μg cm−3, well above background measurements and among the highest values observed for fires in Southern California. Therefore, small wildfires can have a large impact on air quality if they occur near urban areas. Particle number distributions were lognormal, with peak diameters in the accumulation mode at approximately 100 nm. However, significant Aitken mode and nucleation mode particles were observed in bimodal distributions for one fire. Significant variations in the median diameter were observed over time, as particles generally became smaller as the fires were contained. The results indicate that it is likely that performing mass measurements alone could systematically miss detection of the smaller particles and size measurements may be better suited for studies of ambient biomass burning events. Parameters of representative unimodal and bimodal lognormal fits to the distributions are provided for reproduction of distributions in aerosol and climate models.
Keywords: Biomass burning aerosol; Particulates; Air quality; Southern California;
Assessment of carbon monoxide (CO) adjusted non-methane hydrocarbon (NMHC) emissions of a motor fleet – A long tunnel study by Wen-Tzu Liu; Sheng-Po Chen; Chih-Chung Chang; Chang-Feng Ou-Yang; Wei-Cheng Liao; Yuan-Chang Su; Yue-Chuen Wu; Chieh-Heng Wang; Jia-Lin Wang (403-414).
Speciated hydrocarbons (NMHCs) and CO were simultaneously measured by evenly distributed samples along the entire length (12.9 km) of the tunnel in different traffic conditions. Four passes (two round-trips) were made at four different fleet speeds (i.e., 45, 65, 75 and 85 km h−1). Individual NMHC and CO mixing ratios were observed to be sensitive to the fleet speed, which is compounded by driving conditions and traffic volumes. We propose using ratios of NMHCs to CO to cancel out the factor of traffic volumes to determine CO-normalized NMHC emissions, such that a less biased comparison can be made between different fleet speeds in this study and even between different studies. Moreover, to obtain robust CO-normalized NMHC emissions which are sufficiently representative of the fleet speeds, only samples collected deep inside the long-tunnels between 8 and 12 km were used.Of the 61 target NMHCs, isomers of butane, pentane, ethylene, acetylene and toluene were the most abundant species regardless of the driving conditions. We observed that different driving conditions not only affected the emission strengths but also altered the compositions of the NMHCs. To simplify the data analysis, the target NMHCs were classified into four chemical groups, i.e., alkanes, alkenes, aromatics and alkynes. For the slower and more congested driving condition (fleet speed = 45 km h−1), the CO-normalized NMHC emissions were the highest, with alkanes contributing to approximately 60% of the total NMHC levels, suggesting poorer fuel utilization at slower driving conditions. In terms of the CO-normalized ozone forming potentials (OFPs), the contribution of the alkanes diminished dramatically to approximately 9–22% despite their high weight percentage, whereas the contribution of the alkenes was enhanced significantly to 50–60% from their weight percent of only approximately 26%.Our total NMHC to CO ratios of 0.06–0.20 for the four fleet speeds generally fall within the range constrained by many other tunnel or chassis dynamometer studies; however, the sensitivity to the driving conditions and the robustness with the long-tunnel data are better demonstrated in this study.
Keywords: Tunnel study; NMHC; CO; NMHC/CO ratio; OFP;
Continuous measurement of black carbon aerosol in urban Nanjing of Yangtze River Delta, China by B.L. Zhuang; T.J. Wang; J. Liu; S. Li; M. Xie; X.Q. Yang; C.B. Fu; J.N. Sun; C.Q. Yin; J.B. Liao; J.L. Zhu; Y. Zhang (415-424).
As a short-lived climate forcing agent, black carbon (BC) aerosol plays an important role in climate change, atmospheric environment, and human health. In this study, continuous measurements of BC and trace gases were made at an urban site in Nanjing, Yangtze River Delta (YRD) of China in 2012. The annual mean BC concentration in Nanjing was found to be 4157 ± 2626 ng/m3, with a range of 221–24,686 ng/m3. The value was much lower than that in most megacities of China and also lower than that in LinAn, a rural site in YRD. BC concentrations in Nanjing showed strong seasonality, high in spring and autumn and low in summer. The concentrations also varied diurnally, high at rush hours and low in the afternoon. The diurnal cycles of BC loadings in winter to spring 2012 were similar to those in 2011 in magnitude and shape. BC concentrations followed a typical lognormal pattern, with over 75% of data samples between 1000 and 6000 ng/m3. The maximum frequency occurred in low BC concentrations in summer and high BC concentrations in other seasons. In Nanjing, high levels of BC were mainly caused by local and regional emissions. Low levels of BC were mostly associated with winds from northern and eastern directions of Nanjing. BC and CO varied similarly with season, having a correlation coefficient over 0.7 in most seasons. Annual mean ΔBC/ΔCO was about 7 ng/m3/ppb, implying that the sources of the BC likely came from combustions of bio-fuel, industry-coal, and vehicle-gasoline. Serious pollution episodes with high levels of BC were detected in early June at the site. Analysis suggested that the episodes were due to biomass burning in northwestern region of Nanjing. During this period, ΔBC/ΔCO reached about 9.7 ng/m3/ppb and much higher BC levels were found at mid-night.
Keywords: Black carbon aerosol; Concentration; Temporal variations; Pollution episode; Yangtze River Delta;
Organic characterisation of PM10 in Cape Verde under Saharan dust influxes by C. Gonçalves; C. Alves; T. Nunes; S. Rocha; J. Cardoso; M. Cerqueira; C. Pio; S.M. Almeida; R. Hillamo; K. Teinilä (425-432).
The current study presents, for the first time, a long-term organic speciation of aerosol at the Cape Verde archipelago. The Cape Verde location, in the Atlantic Ocean, provides a unique laboratory to study background aerosol, long-range transport, aerosol mixing with mineral dust, biomass burning and sea surface components. In order to contribute to a better understanding of this environment, a one-year long measurement campaign was performed in Praia City, Santiago Island. PM10 concentrations (20.5–370 μg/m3) and the organic composition of PM10 were influenced by the African dust influxes. The carbonaceous content of PM10 was very low, suggesting that most of the mass has mineral origin. The PM10 composition was essentially characterised by a large variety of organic compounds, which can be grouped into general compound classes, such as n-alkanes, n-alkanols, n-acids and sugars. The n-alkane total concentrations varied from 3.77 to 53.2 ng/m3. The n-alkanols distribution showed a significant biogenic contribution whether from microbial origin or from epicuticular plants during African dust outbreaks. The total concentrations of n-alkanoic acids varied from 0.011 to 4.51 ng/m3. The lower n-alkenoic acids content, obtained during the periods of long-range transport from Africa, indicated a more aged aerosol. The monosaccharide anhydrides were detected in all samples with a range of concentrations from 2.06 to 12.7 ng/m3.
Keywords: PM10; Organic compounds; GC–MS; Cape Verde archipelago; Sahara dust;
Characterization of chemical composition and concentration of fine particulate matter during a transit strike in Ottawa, Canada by Luyi Ding; Tak Wai Chan; Fu Ke; Daniel K.W. Wang (433-442).
From December 10, 2008 to February 9, 2009, a strike stopped the public transit services in Ottawa, Ontario, Canada. To understand the changes in air quality associated with the transit strike, the chemical composition and concentration of the fine particulate matter with diameters less than 2.5 microns (PM2.5), collected before, during, and after the transit strike period, were evaluated. The collected PM2.5 samples were analyzed to determine the particulate matter mass, the levels of organic carbon (OC) and elemental carbon (EC), as well as the particulate non-polar semi-volatiles, e.g., polycyclic aromatic hydrocarbons (PAHs), hopanes, and steranes. Particle number size distributions measured during and after the transit strike period were also compared. Results indicated that during transit strike months, particle number size distributions were entirely dominated by nucleation mode particles leading to an increase in total particle number concentration by about 79%. In addition, particulate matter, organic carbon, and elemental carbon mass concentrations also increased by over 100%. The average total PAH levels during the strike months were higher by a factor of about 7. Elevated concentrations of high molecular weight PAHs (i.e., PAH with 5 and 6 rings) observed during the strike months suggested that there were more gasoline-powered vehicles on the roads over that period. The level of carcinogenic benzo[a]pyrene was higher by a factor of 5. Mass concentrations of hopanes and steranes were 30–98% higher during the strike months than non-strike months and exhibited strong correlations with EC suggesting the primary origin of these compounds. These results indicated that the increased traffic volume due to the passenger vehicles and the change in driving pattern during the transit strike period reduced the local air quality.
Keywords: Organic carbon; Elemental carbon; Polycyclic aromatic hydrocarbon; Hopanes; Steranes; Number size distribution;
Composition of key offensive odorants released from fresh food materials by Ki-Hyun Kim; Yong-Hyun Kim (443-452).
A refrigerator loaded with a variety of foods without sealed packaging can create quite an olfactory nuisance, and it may come as a surprise that fresh foods emit unpleasant odorants just as those that are decaying. To learn more about nuisance sources in our daily lives, we measured a list of 22 compounds designated as the key offensive odorants (e.g., reduced sulfur, nitrogenous, volatile fatty acid (VFA), and carbonyls) from nine types of common food items consumed in S. Korea: raw beef, raw fish, spam, yolks and albumin of boiled eggs (analyzed separately), milk, cheese, onions, and strawberries. The odor intensity (OI) of each food item was computed initially with the aid of previously used empirical equations. This indicates that the malodor properties of target foods tend to be governed by a few key odorants such as VFA, S, and N compounds. The extent of odorant mixing of a given food was then evaluated by exploring the correlation between the human olfaction (e.g., dilution-to-threshold (D/T) ratio) and the odor potential determined indirectly (instrumentally) such as odor activity value (OAV) or sum of odor intensity (SOI). The overall results of our study confirm the existence of malodorant compounds released from common food items and their contribution to their odor characteristics to a certain degree.
Keywords: Food; Odor; VOCs; RSCs; Aldehydes; Ammonia; Volatile fatty acids; Masking effect;
Using total OH reactivity to assess isoprene photooxidation via measurement and model by A.C. Nölscher; T. Butler; J. Auld; P. Veres; A. Muñoz; D. Taraborrelli; L. Vereecken; J. Lelieveld; J. Williams (453-463).
The Tropics provide a reactive atmospheric environment with high levels of biogenic emissions, rapidly growing anthropogenic influence, high solar radiation and temperature levels. The major reactive biogenic emission is isoprene which reacts rapidly with the primary daytime oxidant OH, the hydroxyl radical. This key photooxidation process has recently been the focus of several experimental and computational studies. A novel isoprene degradation mechanism was recently proposed (MIME) supplementing the commonly used MCM 3.2 scheme.This study examined the photooxidation of isoprene in the controlled conditions of the Valencia atmospheric reaction chamber, EUPHORE (EUropean PHOtoREactor). Besides the detection of isoprene and its major oxidation products formaldehyde, methyl vinyl ketone (MVK) and methacrolein (MACR), the total loss rate of OH (total OH reactivity) was measured. The total OH reactivity was compared to the individual measurements of isoprene and its oxidation products to assess the significant contributors to the overall OH loss rate. Measured total OH reactivity showed excellent agreement to the calculation based on individual compounds detected by a Proton-Transfer-Reaction-Time-Of-Flight-Mass-Spectrometer (PTR-TOF-MS). On average 97% of the measured total OH reactivity could be explained by isoprene and its major oxidation products.Total OH reactivity was also compared to various isoprene degradation schemes to evaluate known mechanisms. The MCM 3.2 isoprene mechanism reproduced the temporal degradation of total OH reactivity (and isoprene) reasonably well with a 57% (and 95%) agreement within the model uncertainties and a linear curve fit slope of 0.69 (and 1.02) for a model to measurement correlation. Large discrepancies between modeled values and all observed compounds were found for the recent isoprene oxidation scheme in MIME. Possible mechanistic reasons are discussed and improvements proposed. The subsequently modified version of MIME differed from the measured total OH reactivity only about 12% at the end of the experiment and represented best the overall temporal profile (linear curve fit slope of correlation: 0.95).
Keywords: Total OH reactivity; Isoprene photooxidation; Hydroxyl radical; Master Chemical Mechanism MCM 3.2; Mainz Isoprene Mechanism Extended MIME;
Walking-induced particle resuspension in indoor environments by Jing Qian; Jordan Peccia; Andrea R. Ferro (464-481).
Resuspension of particles indoors increases the risk of consequent exposure through inhalation and non-dietary ingestion. Studies have been conducted to characterize indoor particle resuspension but results do not always agree, and there are still many open questions in this field. This paper reviews the recent research of indoor resuspension and summarizes findings to answer six critical questions: 1) How does the resuspension sources compared to other indoor sources; 2) How is resuspension determined and how does the resuspension measure change as a function of particle size; 3) What are the primary resuspension mechanisms; 4) What are the factors affecting resuspension; 5) What are the knowledge gaps and future research directions in this area; and 6) How can what we know about resuspension guide better exposure mitigation strategies? From synthesized results, we conclude that resuspension is an important source for indoor particulate matter, compared with other indoor sources. Among all existing quantification terms of resuspension, resuspension fraction has the least variation in its estimates by explicitly defining surface loading and walking frequency, and thus is recommended to be adopted in future research over other terms. Resuspension increases with particle size in the range of 0.7–10 μm, although differences exist in resuspension estimates by orders of magnitude. The primary mechanism of particle resuspension involves rolling detachment, and the adhesive forces can be greatly reduced by microscopic surface roughness. Particle resuspension is by nature complicated, affected by various factors and their interactions. There are still many open questions to be answered to achieve an understanding of resuspension fundamentals. Given the complex and multidisciplinary nature of resuspension, understanding indoor particle resuspension behavior requires cross-disciplinary participation from experts in aerosol science, textile science, surface chemistry, electrostatics, and fluid mechanics.
Keywords: Indoor air; Inhalation exposure; Particle detachment; Biological particle; Review;
Effects of teleconnection patterns on the atmospheric routes, precipitation and deposition amounts in the north-eastern Iberian Peninsula by Rebeca Izquierdo; Marta Alarcón; Laura Aguillaume; Anna Àvila (482-490).
The North Atlantic Oscillation (NAO) has been identified as one of the atmospheric patterns which mostly influence the temporal evolution of precipitation and temperature in the Mediterranean area. Recently, the Western Mediterranean Oscillation (WeMO) has also been proposed to describe the precipitation variability in the eastern Iberian Peninsula. This paper examines whether the chemical signature and/or the chemical deposition amounts recorded over NE Iberian Peninsula are influenced by these climatic variability patterns. Results show a more relevant role of the WeMO compared to NAO in the deposition of either marine (Cl−, Na+, Mg2+) or anthropogenic pollutants (H+, NH4 +, NO3 − and SO4 2−). A cluster classification of provenances indicated that in winter (December to March) fast Atlantic air flows correspond to positive WeMO indices, while negative WeMOi are associated to Northeastern and Southwestern circulations. The negative phase of WeMO causes the entry of air masses from the Mediterranean into the Iberian Peninsula, that are enriched with marine ions and ions of anthropogenic origin (NH4 +, NO3 − and SO4 2−). For these later, this suggests the advection over the Mediterranean of polluted air masses from southern Europe and the scavenging and deposition of this pollution by precipitation during the WeMO negative phases. This will carry transboundary pollutants to the NE Iberian Peninsula. However, local pollutants may also contribute, as precipitation events from the Mediterranean and the Atlantic (associated to both WeMO phases) may incorporate emissions that accumulate locally during the winter anticyclonic episodes typical of the region.
Keywords: West Mediterranean; Precipitation chemistry; Deposition; Back-trajectories; NAO; WeMO;
Rapid formation of molecular bromine from deliquesced NaBr aerosol in the presence of ozone and UV light by Paul Nissenson; Lisa M. Wingen; Sherri W. Hunt; Barbara J. Finlayson-Pitts; Donald Dabdub (491-506).
The formation of gas-phase bromine from aqueous sodium bromide aerosols is investigated through a combination of chamber experiments and chemical kinetics modeling. Experiments show that Br2(g) is produced rapidly from deliquesced NaBr aerosols in the presence of OH radicals produced by ozone irradiated by UV light. The mechanisms responsible for the “bromine explosion” are examined using a comprehensive chemical kinetics Model of Aqueous, Gaseous, and Interfacial Chemistry (MAGIC). A sensitivity analysis on the model confirms that a complex mechanism involving gas-phase chemistry, aqueous-phase chemistry, and mass transfer is responsible for most of the observed bromine. However, the rate-limiting steps in the bromine explosion pathway vary, depending on the availability of ozone and bromide in the system. Interface reactions, an important source of bromine production under dark conditions, account for only a small fraction of total bromine under irradiation. Simulations performed with gaseous ozone and aerosol bromide concentrations typical of the marine boundary layer also show Br2(g) production, with BrO(g) and HOBr(g) as the dominant Br-containing products through this mechanism. Aerosol bromide is depleted after several hours of daylight, with photolysis of BrO(g) and HOBr(g) becoming major sources of Br atoms that continue generating Br2(g) after aerosol bromide is depleted.Display Omitted
Keywords: Bromide oxidation; Sensitivity analysis; Sea-salt aerosol; Aerosol modeling; Interface chemistry;
Carbonaceous aerosols in the air masses transported from Indochina to Taiwan: Long-term observation at Mt. Lulin by Ming-Tung Chuang; Chung-Te Lee; Charles C.-K. Chou; Neng-Huei Lin; Guey-Rong Sheu; Jia-Lin Wang; Shuenn-Chin Chang; Sheng-Hsiang Wang; Kai Hsien Chi; Chea-Yuan Young; Hill Huang; Horng-Wen Chen; Guo-Hau Weng; Sin-Yu Lai; Shao-Peng Hsu; Yu-Jia Chang; Jia-Hon Chang; Xyue-Chang Wu (507-516).
Eight carbonaceous fractions from aerosols were resolved using the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol (Chow et al., 1993). The aerosols were collected at the Mountain Lulin Atmospheric Background Station (Mt. Lulin, 2862 m a.s.l.) in Central Taiwan from April 2003 to April 2012. The monthly and yearly levels of organic carbon (OC) and elemental carbon (EC) varied consistently with PM2.5 mass concentrations during biomass burning (BB) period. The highest monthly carbonaceous content was observed in March and the highest yearly carbonaceous concentration was observed in 2007. This finding is consistent with the BB activity in Indochina and indicates that carbonaceous content is a major component of BB aerosols. Lee et al. (2011) classified four trajectory groups from the air masses transported to Mt. Lulin during the aerosol collection period. For the air masses transported from the BB area (the BB group) in Indochina, the carbonaceous content was greater than the water-soluble ions in PM2.5, and the OC/EC ratio (4.8 ± 1.5) was high. With EC as the indicator of primary emission sources, the air masses of the BB group were found to contain more primary than secondary OC. The Anthropogenic group (from the local and free troposphere below the 700-hPa pressure level over the Asian continent) probably contained more secondary than primary OC or the sources of OC and EC could be quite diverse. The average char-EC/soot-EC (low-temperature EC/high-temperature EC) ratios were 3.9 ± 3.5, 0.4 ± 0.4, 0.9 ± 0.8, and 0.3 ± 0.4 for the trajectory groups BB, SNBB (from BB source areas during the non-BB period), Anthropogenic, and FT (from the oceanic area and the free troposphere above the 700-hPa pressure level over the Asian continent), respectively. The presence of a high char-EC/soot-EC ratio confirmed the correct classification of the BB group, whereas the low ratios from the other groups indicated the strong influence of vehicle exhaust. It is noted that higher OC and EC levels were obtained at Mt. Lulin as compared with those obtained at other high-elevation sites. This difference suggested that the Indochina BB plume exhibited a more serious climatic impact on the background air in East Asia than in other places in Asia and Europe. On the basis of the carbonaceous levels of the SNBB and FT groups, the background OC and EC levels of approximately 3000 m in the West Pacific are around 1.33 μg m−3 and 0.35 μg m−3, respectively.
Keywords: Biomass burning; High-elevation aerosol; Carbons from biomass burning; Background carbonaceous content;
A study on the sensitivities of simulated aerosol optical properties to composition and size distribution using airborne measurements by A.R. Esteve; E.J. Highwood; W.T. Morgan; G. Allen; H. Coe; R.G. Grainger; P. Brown; K. Szpek (517-524).
We present a flexible framework to calculate the optical properties of atmospheric aerosols at a given relative humidity based on their composition and size distribution. The similarity of this framework to climate model parameterisations allows rapid and extensive sensitivity tests of the impact of uncertainties in data or of new measurements on climate relevant aerosol properties. The data collected by the FAAM BAe-146 aircraft during the EUCAARI-LONGREX and VOCALS-REx campaigns have been used in a closure study to analyse the agreement between calculated and measured aerosol optical properties for two very different aerosol types. The agreement achieved for the EUCAARI-LONGREX flights is within the measurement uncertainties for both scattering and absorption. However, there is poor agreement between the calculated and the measured scattering for the VOCALS-REx flights. The high concentration of sulphate, which is a scattering aerosol with no absorption in the visible spectrum, made the absorption measurements during VOCALS-REx unreliable, and thus no closure study was possible for the absorption. The calculated hygroscopic scattering growth factor overestimates the measured values during EUCAARI-LONGREX and VOCALS-REx by ∼30% and ∼20%, respectively. We have also tested the sensitivity of the calculated aerosol optical properties to the uncertainties in the refractive indices, the hygroscopic growth factors and the aerosol size distribution. The largest source of uncertainty in the calculated scattering is the aerosol size distribution (∼35%), followed by the assumed hygroscopic growth factor for organic aerosol (∼15%), while the predominant source of uncertainty in the calculated absorption is the refractive index of organic aerosol (28–60%), although we would expect the refractive index of black carbon to be important for aerosol with a higher black carbon fraction.
Keywords: Anthropogenic aerosols; Optical properties; Aircraft measurements; Hygroscopicity; Aerosol composition; Aerosol modelling;
Effects of anthropogenic emissions on the molecular composition of urban organic aerosols: An ultrahigh resolution mass spectrometry study by I. Kourtchev; I.P. O'Connor; C. Giorio; S.J. Fuller; K. Kristensen; W. Maenhaut; J.C. Wenger; J.R. Sodeau; M. Glasius; M. Kalberer (525-532).
Identification of the organic composition of atmospheric aerosols is necessary to develop effective air pollution mitigation strategies. However, the majority of the organic aerosol mass is poorly characterized and its detailed analysis is a major analytical challenge. In this study, we applied state-of-the-art direct infusion nano-electrospray (nanoESI) ultrahigh resolution mass spectrometry (UHRMS) and liquid chromatography ESI Quadrupole Time-of-Flight (Q-TOF) MS for the analysis of the organic fraction of fine particulate matter (PM2.5) collected at an urban location in Cork, Ireland. Comprehensive mass spectral data evaluation methods (e.g., Kendrick Mass Defect and Van Krevelen) were used to identify compound classes and mass distributions of the detected species. Up to 850 elemental formulae were identified in negative mode nanoESI-UHR-MS. Nitrogen and/or sulphur containing organic species contributed up to 40% of the total identified formulae and exhibited strong diurnal variations suggesting the importance of night-time NO3 chemistry at the site. The presence of a large number of oxidised aromatic and nitroaromatic compounds in the samples indicated a strong anthropogenic influence, i.e., from traffic emissions and domestic solid fuel (DSF) burning. Most of the identified biogenic secondary organic aerosol (SOA) compounds are later-generation nitrogen- and sulphur-containing products, indicating that SOA composition is strongly affected by anthropogenic species such as NO x and SO2. Unsaturated and saturated C12–C20 fatty acids were found to be the most abundant homologs with a composition reflecting a primary marine origin. The results of this work demonstrate that the studied site is a very complex environment affected by a variety of anthropogenic activities and natural sources.
Keywords: nanoESI; Organic aerosol; Organosulfates; Organonitrates; Nitroaromatic;
Impacts of future climate and emission changes on U.S. air quality by Ashley Penrod; Yang Zhang; Kai Wang; Shiang-Yuh Wu; L. Ruby Leung (533-547).
Changes in climate and emissions will affect future air quality. In this work, simulations of regional air quality during current (2001–2005) and future (2026–2030) winter and summer are conducted with the newly released CMAQ version 5.0 to examine the impacts of simulated future climate and anthropogenic emission projections on air quality over the U.S. Current meteorological and chemical predictions are evaluated against observations to assess the model's capability in reproducing the seasonal differences. WRF and CMAQ capture the overall observational spatial patterns and seasonal differences. Biases in model predictions are attributed to uncertainties in emissions, boundary conditions, and limitations in model physical and chemical treatments as well as the use of a coarse grid resolution. Increased temperatures (up to 3.18 °C) and decreased ventilation (up to 157 m in planetary boundary layer height) are found in both future winter and summer, with more prominent changes in winter. Increases in future temperatures result in increased isoprene and terpene emissions in winter and summer, driving the increase in maximum 8-h average O3 (up to 5.0 ppb) over the eastern U.S. in winter while decreases in NO x emissions drive the decrease in O3 over most of the U.S. in summer. Future PM2.5 concentrations in winter and summer and many of its components decrease due to decreases in primary anthropogenic emissions and the concentrations of secondary anthropogenic pollutants as well as increased precipitation in winter. Future winter and summer dry and wet deposition fluxes are spatially variable and increase with decreasing surface resistance and precipitation, respectively. They decrease with a decrease in ambient particulate concentrations. Anthropogenic emissions play a more important role in summer than in winter for future O3 and PM2.5 levels, with a dominance of the effects of significant emission reductions over those of climate change on future PM2.5 levels.
Keywords: Future climate change; Emissions; Air quality; CMAQ; WRF; Model evaluation;
The effect of boundary layer dynamics on aerosol properties at the Indo-Gangetic plains and at the foothills of the Himalayas by T. Raatikainen; A.-P. Hyvärinen; J. Hatakka; T.S. Panwar; R.K. Hooda; V.P. Sharma; H. Lihavainen (548-555).
Previous studies have noted that aerosols originating from the polluted Indo-Gangetic plains can reach high altitudes at the Indian Himalayas and thereby have an effect on the south Asian monsoon. Here we examine the transport of pollutions by comparing aerosol properties from a Himalayan foothill measurement site and a site at the Indo-Gangetic plains. Gual Pahari is a polluted semi-urban background measurement site at the Indo-Gangetic plains close to New Delhi and Mukteshwar is a relatively clean background measurement site at the foothills of the Himalayas about 270 km NE from Gual Pahari and about 2 km above the nearby plains. The data set has more than two years of simultaneous measurements including meteorological parameters and aerosol mass concentrations. Modeled backward trajectories and Planetary Boundary Layer (PBL) heights are also used to examine the origin or air masses and the extent of the vertical mixing. The comparison shows that aerosol concentrations at the foothill site are correlated with the average PBL height. Together with the favorable synoptic scale circulation, this suggests a contribution of air mass transport from the plains.
Keywords: Aerosol; India; Himalayas; Brown cloud;
Uncertainty and variability in satellite-based water vapor column, aerosol optical depth and Angström exponent, and its effect on radiative transfer simulations in the Iberian Peninsula by Roberto Román; Julia Bilbao; Argimiro de Miguel (556-569).
The water vapor column product from the MODIS instrument onboard the Terra satellite is compared with ground-based measurements at six Spanish locations (AERONET stations) in the Iberian Peninsula. In addition, aerosol optical depth (AOD) at 443 nm and at 675 nm retrievals from the MISR instrument onboard the Terra satellite is also compared with ground-based measurements at the same locations to determine their uncertainties. Remote sensing data of water vapor and aerosol optical properties are averaged each month to obtain climatology tables and to characterize atmospheric properties at nine locations in the Iberian Peninsula. These tables are used as input in a radiative transfer model to calculate total shortwave (SW) and ultraviolet erythemal (UVER) irradiance at the nine locations. SW and UVER simulations are recalculated considering the uncertainties and the climatological variability of the input datasets. AOD uncertainty provides changes lower than 6% in most cases for both SW and UVER simulations. The propagation of water vapor uncertainty causes variations in SW simulations less than 4% for solar zenith angles below 75°.
Keywords: Radiative transfer; Erythemal irradiance; Solar radiation; Aerosol; Water vapor column; Remote sensing uncertainty;
Impact of emissions from shipping, land, and the ocean on stratocumulus cloud water elemental composition during the 2011 E-PEACE field campaign by Z. Wang; A. Sorooshian; G. Prabhakar; M.M. Coggon; H.H. Jonsson (570-580).
This study reports on cloud water chemical and pH measurements off the California coast during the July–August 2011 Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE). Eighty two cloud water samples were collected by a slotted-rod cloud water collector protruding above the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter in boundary layer stratocumulus clouds impacted to varying degrees by ocean-derived emissions, ship exhaust, and land emissions. Cloud water pH ranged between 2.92 and 7.58, with an average of 4.46. Peak pH values were observed north of San Francisco, simultaneous with the highest concentrations of Si, B, and Cs, and air masses originating over land. The lowest pH values were observed south of San Francisco due to ship emissions resulting in the highest concentrations of sulfate, nitrate, V, Fe, Al, P, Cd, Ti, Sb, P, and Mn. Many of these species act as important agents in aqueous-phase reactions in cloud drops and are critical ocean micronutrients after subsequent wet deposition in an ocean system that can be nutrient-limited. E-PEACE measurements suggest that conditions in the California coastal zone region can promote the conversion of micronutrients to more soluble forms, if they are not already, due to acidic cloud water conditions, the ubiquity of important organic agents such as oxalic acid, and the persistence of stratocumulus clouds to allow for continuous cloud processing.Display Omitted
Keywords: Cloud water; Shipping; Marine; Metals; Iron; Ocean; Cloud processing; Nutrients; Coastal region;
Near-term projection of anthropogenic emission trends using neural networks by Alessia Paola Balsamà; Lucia De Biase; Greet Janssens-Maenhout; Valerio Pagliari (581-592).
This study is the first ever analysis of the global time series 1970–2008 of the Emissions Database for Global Atmospheric Research (EDGAR) for 10 chemical species and more than 3000 subsectors with neural networks, which tries to find non-linear behaviours that several species have in common.The application of the different neural network types, suggests that General Regression Neural Networks (GRNNs) are the most suitable to train a typical Gaussian trend with a very low error level. As such, GRNNs are very suitable for filling the data points missing from the EDGAR time-series, but they are not so good at a making projections outside the time period of the database. Instead Multi Layers Perceptron (MLP) is very suitable for projecting a subsequent year to the database time period of several decades, even though MLP is characterised by a slightly higher absolute mean error than the GRNN.By means of the Principal Component Analysis (PCA), we identified which chemical substances are driven similarly by the activity data over the almost 40 years time period. In all the geographic aggregations, we observed that the emission trends of CO2, SO2 and NO x can be grouped into one cluster, and the emission trends of CH4 and the particulates into another. The best time interval for the prediction proved to be eleven years, and projections seemed to be reliable for three consecutive years following the last year of the database time-series.
Keywords: Neural networks; Prediction; Projection;
Identification of fine (PM1) and coarse (PM10-1) sources of particulate matter in an urban environment by G. Titos; H. Lyamani; M. Pandolfi; A. Alastuey; L. Alados-Arboledas (593-602).
PM10 and PM1 samples were collected at an urban site in southeastern Spain during 2006–2010. The chemical composition of all samples has been determined and analyzed by Positive Matrix Factorization (PMF) technique for fine and coarse source identification. The PMF results have been analyzed for working and non-working days in order to evaluate the change in PM sources contribution and possible future abatement strategies. A decreasing trend in PM10 levels and in its constituents has been observed, being partly associated to a reduction in anthropogenic activities due to the economic crisis. The use of fine and coarse PM in the PMF analysis allowed us for the identification of additional sources that could not be identified using only one size fraction. The mineral dust source was identified in both fractions and comprised 36 and 22% of the total mass in the coarse and fine fractions, respectively. This high contribution of the mineral source to the fine fraction may be ascribed to contamination of the source profile. The regional re-circulation source was traced by secondary sulfate, V and Ni. It was the most important source concerning PM1 mass concentration (41% of the total mass in this fraction). Although V and Ni are commonly associated to fuel oil combustion the seasonality of this source with higher concentrations in summer compared with winter suggest that the most important part of this source can be ascribed to regional pollution episodes. A traffic exhaust source was identified but only in the fine fraction, comprising 29% of the fine mass. The celestite mines source associated with nearby open-pit mines was typified by strontium, sulfate and mineral matter. PM10-1 levels were higher in working days, whereas PM1 levels remained fairly constant throughout the whole week. As a conclusion, traffic seems to be the main source to target in Granada.
Keywords: PMF; Source apportionment; PM1; PM10; Urban aerosols;
H2SO4 formation from the gas-phase reaction of stabilized Criegee Intermediates with SO2: Influence of water vapour content and temperature by Torsten Berndt; Tuija Jokinen; Mikko Sipilä; Roy L. Mauldin; Hartmut Herrmann; Frank Stratmann; Heikki Junninen; Markku Kulmala (603-612).
The importance of gas-phase products from alkene ozonolysis other than OH radicals, most likely stabilized Criegee Intermediates (sCI), for the process of atmospheric SO2 oxidation to H2SO4 has been recently discovered. Subjects of this work are investigations on H2SO4 formation as a function of water vapour content (RH = 2–65%) and temperature (278–343 K) starting from the ozonolysis of trans-2-butene and 2,3-dimethyl-2-butene (TME). H2SO4 production other than via the OH radical reaction was attributed to the reaction of SO2 with sCI, i.e. acetaldehyde oxide arising from trans-2-butene ozonolysis and acetone oxide from TME. Measurements have been conducted in an atmospheric pressure flow tube using NO3 −–CI-APi-TOF mass spectrometry for H2SO4 detection. The sCI yields derived from H2SO4 measurements at 293 K were 0.49 ± 0.22 for acetaldehyde oxide and 0.45 ± 0.20 for acetone oxide. Our findings indicate a H2SO4 yield from sCI + SO2 of unity or close to unity. The deduced rate coefficient ratio for the reaction of sCI with H2O and SO2, k(sCI + H2O)/k(sCI + SO2), was found to be strongly dependent on the structure of the Criegee Intermediate, for acetaldehyde oxide at 293 K: (8.8 ± 0.4)·10−5 (syn- and anti-conformer in total) and for acetone oxide: <4·10−6. H2SO4 formation from sCI was pushed back with rising temperature in both reaction systems most probably due to an enhancement of sCI decomposition. The ratio k(dec)/k(sCI + SO2) increased by a factor of 34 (acetone oxide) increasing the temperature from 278 to 343 K. In the case of acetaldehyde oxide the temperature effect is less pronounced. The relevance of atmospheric H2SO4 formation via sCI + SO2 is discussed in view of its dependence on the structure of the Criegee Intermediate.
Keywords: Gas-phase ozonolysis; Criegee Intermediate; Stabilization; Atmospheric H2SO4 formation; CI-APi-TOF mass spectrometry;
Characteristics of atmospheric carbon monoxide at a high-mountain background station in East Asia by Chang-Feng Ou-Yang; Neng-Huei Lin; Chia-Ching Lin; Sheng-Hsiang Wang; Guey-Rong Sheu; Chung-Te Lee; Russell C. Schnell; Patricia M. Lang; Taro Kawasato; Jia-Lin Wang (613-622).
Atmospheric CO were monitored at the Lulin Atmospheric Background Station (LABS) with an elevation of 2862 m AMSL from April 2006 to April 2011 by the in-situ non-dispersive infrared (NDIR) spectrometer and weekly flask sample collections via collaboration with NOAA/ESRL/GMD. In general very coherent results were observed between the two datasets, despite a slight difference between the two. A distinct seasonal pattern of CO was noticed at the LABS with a springtime maximum and a summertime minimum, which was predominately shaped by the long-range transport of biomass burning air masses from Southeast Asia and oceanic influences from the Pacific, respectively. Diurnal cycles were also observed at the LABS, with a maximum in late afternoon and a minimum in early morning. The daytime CO maximum was most likely caused by the up-slope transport of lower elevation air. After filtering out the possibly polluted data points from the entire dataset with a mathematic procedure, the mean background CO level at the LABS was assessed as 129.3 ± 46.6 ppb, compared to 149.0 ± 72.2 ppb prior to the filtering.The cluster analysis of the backward trajectories revealed six possible source regions, which shows that air masses originating from the Westerly Wind Zone were dominated in spring and winter resulting in higher CO concentrations. As a contrast, the oceanic influences from the Pacific were found mostly in summer, contributing a lower seasonal CO concentration throughout a year.
Keywords: CO; Lulin atmospheric background station (LABS); Biomass burning; Background values;
Different toxic mechanisms are activated by emission PM depending on combustion efficiency by O. Uski; P.I. Jalava; M.S. Happo; J. Leskinen; O. Sippula; J. Tissari; J. Mäki-Paakkanen; J. Jokiniemi; M.-R. Hirvonen (623-632).
Ambient air levels of fine particulate matter (PM ≤ 2.5 μm) are associated with mortality and morbidity. In addition to traffic, large quantities of fine and ultrafine particles (UFPs ≤ 100 nm) are emitted by residential wood combustion. Polycyclic aromatic hydrocarbon (PAH) and soot-rich emissions from small scale heating appliances have been linked with a plethora of toxicological effects. Recently, new technology appliances have been introduced into use although there are several uncertainties related to the toxicological properties of those emissions. In this study, PM1 (PM ≤ 1 μm) emissions from three different biomass combustion situations were compared. PM samples were produced in a novel adjustable biomass combustion reactor to avoid the problems encountered if one uses different appliances to generate the desired combustion conditions. The combustion conditions represented efficient, intermediate and smoldering situations. The concentration related effects of the particles (15, 50,150 and 300 μg ml−1) were investigated in a RAW264.7 macrophage cell line after 24 h' exposure. We analyzed cellular metabolic activity, cell cycle, and indicators of genotoxicty, oxidative stress and proinflammatory responses. Interestingly, the particles collected from smoldering and intermediate combustion conditions decreased cellular metabolic activity less than those from efficient combustion (10-fold difference). However, the samples from intermediate and smoldering combustion evoked greater DNA damage in the comet assay (2.5-fold difference). In contrast, only the particulate samples from efficient combustion triggered G2-cell cycle arrest and oxidative stress in the macrophages. These results indicate that ash rich PM emissions from appliances with almost complete combustion may still exert health impacts. However, particulate emissions from efficient combustion were small when compared to the two other situations. Thus, even with their faults and the obvious need for development, consumers should be encouraged to purchase efficient combustion devices in order to reduce exposure to PM induced adverse health effects.
Keywords: Biomass combustion; Health effects of aerosols; Chemical composition; Combustion particles;
The influence of future non-mitigated road transport emissions on regional ozone exceedences at global scale by J.E. Williams; Ø. Hodnebrog; P.F.J. van Velthoven; T.K. Berntsen; O. Dessens; M. Gauss; V. Grewe; I.S.A. Isaksen; D. Olivié; M.J. Prather; Q. Tang (633-641).
Road Transport emissions (RTE) are a significant anthropogenic global NO x source responsible for enhancing the chemical production of tropospheric ozone (O3) in the lower troposphere. Here we analyse a multi-model ensemble which adopts the realistic SRES A1B emission scenario and a “policy-failure” scenario for RTE (A1B_HIGH) for the years 2000, 2025 and 2050. Analysing the regional trends in RTE NO x estimates shows by 2025 that differences of 0.2–0.3 Tg N yr−1 occur for most of the world regions between the A1B and A1B_HIGH estimates, except for Asia where there is a larger difference of ∼1.4 Tg N yr−1. For 2050 these differences fall to ∼0.1 Tg N yr−1, with shipping emissions becoming as important as RTE. Analysing the seasonality in near-surface O3 from the multi-model ensemble monthly mean values shows a large variability in the projected changes between different regions. For Western Europe and the Eastern US although the peak O3 mixing ratios decrease by ∼10% in 2050, there is an associated degradation during wintertime due to less direct titration from nitric oxide. For regions such as Eastern China, although total anthropogenic NO x emissions are reduced from 2025 to 2050, there is no real improvement in peak O3 levels. By normalizing the seasonal ensemble means of near-surface O3 (0–500 m) with the recommended European Commission (EC) exposure limit to derive an exceedence ratio (ER), we show that ER values greater than 1.0 occur across a wide area in the Northern Hemisphere for boreal summer using the year 2000 emissions. When adopting the future A1B_HIGH estimates, the Middle East exhibits the worst regional air quality, closely followed by Asia. For these regions the area of exceedence (ER > 1.0) for 2025 is ∼40% and ∼25% of the total area of each region, respectively. Comparing simulations employing the various scenarios shows that unmitigated RTE increases the area of exceedence in the Middle East by ∼6% and, for Asia, by ∼2% of the total regional areas. For the USA the area of exceedence approximately doubles in 2025 as a result of unmitigated RTE, with the most exceedences occurring in the southern USA. The effects across the various regions implies that unmitigated RTE would have a detrimental effect on regional health for 2025, and potentially offset the benefits introduced by mitigating e.g. international shipping emissions. By 2050 the further mitigation of non-transport emissions results in much cleaner air meaning that mitigation of RTE is not critical for achieving the defined limits in many world regions.
Keywords: Air quality; Road traffic emissions; 3D global chemistry modelling; Future trends;
Quantitative determination of the biomass-burning contribution to atmospheric carbonaceous aerosols in Daejeon, Korea, during the rice-harvest period by Jinsang Jung; Sangil Lee; Hyosun Kim; Doyeon Kim; Hyoeun Lee; Sanghyup Oh (642-650).
To investigate the impact of biomass-burning emissions on atmospheric carbonaceous aerosols, the biomass burning tracers; levoglucosan, mannonsan, galactosan, and K+ were measured at a suburban site in Daejeon, Korea, during the rice-harvest period, during the fall, 2012. The emissions of K+ from biomass burning (K+ _BB) were estimated by subtracting sea-salt K+ and soil K+ concentrations from measured K+ concentrations. Regression analysis of levoglucosan and K+ _BB reveals that K+ _BB alone is not suitable as a biomass-burning tracer in the Daejeon atmosphere, especially when the biomass-burning contribution is low. Levoglucosan to K+ _BB ratios during the study period ranged from 0.40 to 1.39, with an average of 0.89 ± 0.30, whereas levoglucosan to mannosan ratios ranged from 4.61 to 15.45, with an average of 6.70 ± 2.69. The ratios of levoglucosan to mannosan, K+, organic carbon (OC), and elemental carbon (EC) show that biomass-burning aerosols in the Daejeon atmosphere during the rice-harvest period are emitted mainly from crop residue, grass, and leaf burnings. The contributions of biomass-burning emissions to OC and EC concentrations were 45% ± 12% and 12% ± 7.3%, respectively, indicating that a large fraction of OC was emitted from biomass burning.Display Omitted
Keywords: Biomass burning; Levoglucosan; Mannosan; Galactosan; Potassium; Organic carbon; Elemental carbon;
Analytical solution for transient partitioning and reaction of a condensing vapor species in a droplet by Albert Tianxiang Liu; Rahul A. Zaveri; John H. Seinfeld (651-654).
We present the exact analytical solution of the transient equation of gas-phase diffusion of a condensing vapor to, and diffusion and reaction in, an aqueous droplet. Droplet-phase reaction is represented by first-order chemistry. The solution facilitates study of the dynamic nature of the vapor uptake process as a function of droplet size, Henry's law coefficient, and first-order reaction rate constant for conversion in the droplet phase.
Keywords: Droplet; Diffusion and reaction; Henry's law constant;
Primary and secondary aerosols from an urban site (Kanpur) in the Indo-Gangetic Plain: Impact on CCN, CN concentrations and optical properties by Kirpa Ram; S.N. Tripathi; M.M. Sarin; D. Bhattu (655-663).
The number concentrations of cloud condensation nuclei (CCN) and submicron aerosols (CN), along with their chemical composition and optical properties, have been studied during October 2008, October–November 2009 and November 2010 from an urban (Kanpur) site in the Indo-Gangetic Plain (IGP). The concentrations of CCN and CN and their optical properties vary with primary emission and secondary aerosol formation. The CCN (at 0.38% super-saturation) and CN concentrations varied from ∼3900 to 15,000 cm−3 and ∼23,000 to 99,000 cm−3, respectively. The diurnal variability of CCN and CN show peak concentrations during early morning hours (6:00–9:00 AM) and nighttime (7:00–10:00 PM), attributable to variability in source strength of carbonaceous aerosols and secondary aerosol formation. The CCN and CN concentrations are ∼50% higher during nighttime with simultaneous increase in organic carbon (OC), elemental carbon (EC) and NO3 – mass concentrations. However, CCN/CN ratios are similar during day and nighttime suggesting their co-variability with primary and secondary aerosol formation. The CCN/CN ratios are relatively lower (range: 0.11–0.33) than global average value and those over urban areas (with similar chemical composition in China and around the world) suggesting suppressed activation and hygroscopic growth in highly polluted environment of the IGP. The average mass absorption efficiency of EC during daytime (11.7 ± 2.5 m2 g−1) is about factor of two higher than that during nighttime (5.7 ± 1.3 m2 g−1). These results have implications to study morphological features, mixing state and microphysical properties of aerosols under high acidic environment over northern India.
Keywords: CCN and CN concentrations; EC; OC; Indo-Gangetic Plain; Mixing state;
Quantifying spatiotemporal variability of fine particles in an urban environment using combined fixed and mobile measurements by R.C. Sullivan; S.C. Pryor (664-671).
Spatiotemporal variability of fine particle concentrations in Indianapolis, Indiana is quantified using a combination of high temporal resolution measurements at four fixed sites and mobile measurements with instruments attached to bicycles during transects of the city. Average urban PM2.5 concentrations are an average of ∼3.9–5.1 μg m−3 above the regional background. The influence of atmospheric conditions on ambient PM2.5 concentrations is evident with the greatest temporal variability occurring at periods of one day and 5–10 days corresponding to diurnal and synoptic meteorological processes, and lower mean wind speeds are associated with episodes of high PM2.5 concentrations. An anthropogenic signal is also evident. Higher PM2.5 concentrations coincide with morning rush hour, the frequencies of PM2.5 variability co-occur with those for carbon monoxide, and higher extreme concentrations were observed mid-week compared to weekends. On shorter time scales (<one day), spatial variability is 2–3 times greater than temporal variability. Spatial variability along the transect (within 10 km of the fixed measurement sites) was within ±3.6 μg m−3 of the stationary measurements (once the temporal variability is removed). Localized extreme values of PM2.5 concentrations ranged in the spatial dimension from a few hundred meters up to 2 km, and contributed an average of 4.4 μg m−3 to ambient concentrations.
Keywords: Indianapolis; Pollution; Hebdomadal (day of the week); Extreme concentrations; Anthropogenic;
Snow and rain chemistry around the “Severonikel” industrial complex, NW Russia: Current status and retrospective analysis by Galina Kashulina; Patrice de Caritat; Clemens Reimann (672-682).
The current (2005–2011) status of the chemical composition of snow cover and rain collected at a height of 1.5 m above ground was studied within 11 km around the Severonikel industrial complex, one of the largest SO2 and metal contamination sources in N Europe. In spite of a significant decrease in emissions during the past 20 years, Ni and Cu concentrations in snow remain extremely high near the source (2500 and 1500 times background values, respectively). Although showing a five- to six-fold decrease in Ni and Cu concentrations since 1994, rain water currently still has concentrations 150 and 80 times background, respectively. Differences in the chemical composition of snow pack and rain collected at a height of 1.5 m above ground in this case are not caused by seasonal effects, but rather by the height of precipitation sampling relative to the ground.Snow cover and rain collected at a height of 1.5 m above ground have different pathways and composition of contamination from the Severonikel industrial complex, NW Russia.
Keywords: Precipitation; Acidity; Copper (Cu); Nickel (Ni); Kola Peninsula;
Recent increase in Ba concentrations as recorded in a South Pole ice core by Elena V. Korotkikh; Paul A. Mayewski; Daniel Dixon; Andrei V. Kurbatov; Michael J. Handley (683-687).
Here we present high-resolution (∼9.4 samples/year) records of Ba concentrations for the period from 1541 to 1999 A.D. obtained from an ice core recovered at the South Pole (US ITASE-02-6) site. We note a significant increase in Ba concentration (by a factor of ∼23) since 1980 A.D. The Ba crustal enrichment factor (EFc) values rise from ∼3 before 1980 A.D. to ∼32 after 1980 A.D. None of the other measured major and trace elements reveal such significant increases in concentrations and EFc values. Comparison with previously reported Antarctic Ba records suggests that significant increases in Ba concentrations at South Pole since 1980 A.D. are most likely caused by local source pollution. The core was collected in close proximity to Amundsen–Scott South Pole Station; therefore activities at the station, such as diesel fuel burning and intense aircraft activity, most likely caused the observed increase in Ba concentrations and its EFc values in the South Pole ice core record.
Keywords: Barium; Pollution; Antarctica;
Using mobile monitoring to characterize roadway and aircraft contributions to ultrafine particle concentrations near a mid-sized airport by Hsiao-Hsien Hsu; Gary Adamkiewicz; E. Andres Houseman; John D. Spengler; Jonathan I. Levy (688-695).
Ultrafine particles (UFP) have complex spatial and temporal patterns that can be difficult to characterize, especially in areas with multiple source types. In this study, we utilized mobile monitoring and statistical modeling techniques to determine the contributions of both roadways and aircraft to spatial and temporal patterns of UFP in the communities surrounding an airport. A mobile monitoring campaign was conducted in five residential areas surrounding T.F. Green International Airport (Warwick, RI, USA) for one week in both spring and summer of 2008. Monitoring equipment and geographical positioning system (GPS) instruments were carried following scripted walking routes created to provide broad spatial coverage while recognizing the complexities of simultaneous spatial and temporal heterogeneity. Autoregressive integrated moving average models (ARIMA) were used to predict UFP concentrations as a function of distance from roadway, landing and take-off (LTO) activity, and meteorology. We found that distance to the nearest Class 2 roadway (highways and connector roads) was inversely associated with UFP concentrations in all neighborhoods. Departures and arrivals on a major runway had a significant influence on UFP concentrations in a neighborhood proximate to the end of the runway, with a limited influence elsewhere. Spatial patterns of regression model residuals indicate that spatial heterogeneity was partially explained by traffic and LTO terms, but with evidence that other factors may be contributing to elevated UFP close to the airport grounds. Regression model estimates indicate that mean traffic contributions exceed mean LTO contributions, but LTO activity can dominate the contribution during some minutes. Our combination of monitoring and statistical modeling techniques demonstrated contributions from major surrounding runways and LTO activity to UFP concentrations near a mid-sized airport, providing a methodology for source attribution within a community with multiple distinct sources.
Keywords: Air quality; Aircraft; Ground measurements; Regression; Source attribution; Ultrafine particulate matter;
Atmospheric dry plus wet deposition and wet-only deposition of dicarboxylic acids and inorganic compounds in a coastal suburban environment by Ying I. Tsai; Su-Ching Kuo; Li-Hao Young; Li-Ying Hsieh; Pei-Ti Chen (696-706).
This study investigated the chemical properties and composition sources of dicarboxylic organic acids and inorganic salts in dry plus wet deposition (DWD) and wet-only deposition at a coastal suburban area in southern Taiwan in 2008. DWD is the accumulation of dry deposition and wet deposition from the beginning of each new rain event, while wet-only deposition is the wet deposition from the beginning of each new rain event only. A total of 60 samples were collected during the period of study. The wet-only deposition samples were slightly more acidic (pH 5.01–5.50) than the DWD samples (pH 5.51–6.00). The total volume-weighted mean (VWM) equivalent ionic concentration of 784.3 ± 431.1 μeq L−1 in DWD was higher than that of 682.2 ± 392.4 μeq L−1 in wet-only deposition. In both types of deposition the major cation species were Ca2+, Na+ and NH 4 + , and the major anion species were HCO 3 − , Cl− and non-sea salt (nss) nss- SO 4 2 − . Total dicarboxylic acids contributed only 0.60% and 0.45% of the total ionic equivalent concentration in DWD and wet-only deposition, respectively, and oxalic and malonic acids were the major dicarboxylic acid species. DWD to wet-only deposition species concentration ratios (DWD/W ratios) were always higher than 1.0. DWD contained more water-soluble inorganic salts and dicarboxylic acids than wet-only deposition, with DWD/W ratios of the dust-bound species K+, Mg2+ and Ca2+ as large as 1.6–1.8 and those from photochemical species nss- SO 4 2 − and NH 4 + of 1.36 and 1.29, respectively. These ratios show that the dry deposition flux of dust is greater than that of photochemical particles. In addition, the 1.81 ratio for oxalic acid shows that oxalic acid is easier to remove from the atmosphere via dry deposition than malonic and succinic acids. Probable deposition composition sources for both DWD and wet-only deposition, investigated using principal component analysis, were marine spray, photochemical inorganic products, and terrestrial origin and photochemical organic products. As the study site is close to the coast, marine spray deposits as dry deposition, and the anthropogenic dicarboxylic acids deposit together with resuspended crustal materials.
Keywords: Rainwater; Dry deposition; Wet deposition; Dicarboxylic acids; Ion balance; Neutralization;
Performance evaluation of AERMOD, CALPUFF, and legacy air dispersion models using the Winter Validation Tracer Study dataset by Arthur S. Rood (707-720).
The performance of the steady-state air dispersion models AERMOD and Industrial Source Complex 2 (ISC2), and Lagrangian puff models CALPUFF and RATCHET were evaluated using the Winter Validation Tracer Study dataset. The Winter Validation Tracer Study was performed in February 1991 at the former Rocky Flats Environmental Technology Site near Denver, Colorado. Twelve, 11-h tests were conducted where a conservative tracer was released and measured hourly at 140 samplers in concentric rings 8 km and 16 km from the release point. Performance objectives were unpaired maximum one- and nine-hour average concentration, location of plume maximum, plume impact area, arc-integrated concentration, unpaired nine-hour average concentration, and paired ensemble means. Performance objectives were aimed at addressing regulatory compliance, and dose reconstruction assessment questions. The objective of regulatory compliance is not to underestimate maximum concentrations whereas for dose reconstruction, the objective is an unbiased estimate of concentration in space and time. Performance measures included the fractional bias, normalized mean square error, geometric mean, geometric mean variance, correlation coefficient, and fraction of observations within a factor of two. The Lagrangian puff models tended to exhibit the smallest variance, highest correlation, and highest number of predictions within a factor of two compared to the steady-state models at both the 8-km and 16-km distance. Maximum one- and nine-hour average concentrations were less likely to be under-predicted by the steady-state models compared to the Lagrangian puff models. The characteristic of the steady-state models not to under-predict maximum concentrations make them well suited for regulatory compliance demonstration, whereas the Lagrangian puff models are better suited for dose reconstruction and long range transport.
Keywords: Air dispersion models; CALPUFF; AERMOD; Validation; Tracer;
Signature of tropospheric ozone and nitrogen dioxide from space: A case study for Athens, Greece by C. Varotsos; J. Christodoulakis; C. Tzanis; A.P. Cracknell (721-730).
The aim of the present study is to investigate the variability of the tropospheric ozone and nitrogen dioxide (NO2) columns over mainland Greece, by using observations carried out by satellite-borne instrumentation and Multi Sensor Reanalysis. The results obtained show that the tropospheric ozone residual (TOR) dispersed farther away than the tropospheric NO2 column (TNO), due to the longer TOR's lifetime in respect to that of TNO. This results in the influence of the air quality of the nearby southern islands from the air pollution of the greater Athens basin. Furthermore, the TOR and TNO columns over Athens, for the period October 2004 to December 2011 were found to be negatively correlated with a correlation coefficient −0.85, in contrast to recent findings which suggested strong positive correlation. Interestingly, this strong negative correlation into a slight positive correlation when the TNO concentration becomes higher than around 4 × 1015 molec cm−2, thus being best fitted by a quadratic relationship. In addition, the temporal evolution of TOR during 1979–1993 showed a decline of 0.2% per decade and just after 1993 it seems to obey a positive trend of 0.1% per decade, thus recovering during the period 1993–2011 almost 63% of the lost TOR amounts through the years 1979–1993. Finally, the association between TOR, the total ozone column (TOZ), the tropopause height and the outgoing longwave radiation (OLR) is presented by analysing observations during 1979–2011. An unexpected positive correlation between OLR and TOR was found, which may probably be attributed to the fact that enhanced abundance in tropospheric water vapor reduces the summertime TOR maximum by destructing ozone in the lower and middle troposphere through uptake mechanisms, thus emitting higher amounts of longwave radiation upwards.
Keywords: Tropospheric ozone; Nitrogen dioxide; Tropopause height; Oxidation capacity; Athens; Greece;
Ionic strength dependence of the oxidation of SO2 by H2O2 in sodium chloride particles by H.M. Ali; M. Iedema; X.-Y. Yu; J.P. Cowin (731-738).
The reaction of sulfur dioxide and hydrogen peroxide in the presence of deliquesced (>75% RH) sodium chloride (brine) particles was studied by utilizing a cross flow mini-reactor. The reaction kinetics were followed by observing chloride depletion in particles by computer-controlled scanning electron microscope with energy dispersive X-ray analysis, namely CCSEM/EDX. The reactions take place in concentrated mixed salt brine aerosols, for which no complete kinetic equilibrium data previously existed. We measured the Henry's law solubility of H2O2 in brine solutions to close that gap. We also calculated the reaction rate as the particle transforms continuously from concentrated NaCl brine to, eventually, a mixed NaHSO4 plus H2SO4 brine solution. The reaction rate of the SO2 oxidation by H2O2 was found to be influenced by the change in ionic strength as the particle undergoes compositional transformation, following closely the dependence of the third order rate constant on ionic strength as predicted using established rate equations. This is the first study that has measured the ionic strength dependence of sulfate formation (in non-aqueous media) from oxidation of mixed salt brine aerosols in the presence of H2O2. It also gives the first report of the dependence of the Henry's law constant of H2O2 on ionic strength.
Keywords: Sulfate; Oxidation; Brine; Sodium chloride; H2O2; Ionic strength;
Determination of multiple organic matter sources in aerosol PM10 from Wrocław, Poland using molecular and stable carbon isotope compositions by Maciej Górka; Maciej Rybicki; Bernd R.T. Simoneit; Leszek Marynowski (739-748).
The natural and anthropogenic contributions of hydrocarbon groups (aliphatic and aromatic), as well as total organic carbon, in atmospheric PM10 dust (particulate matter <10 μm) collected from Wrocław (SW Poland) were assessed using combined molecular (gas chromatography–mass spectrometry – GC–MS) and stable carbon isotopic (isotope-ratio mass spectrometry – IR-MS) analyses. The PM10 samples were taken in the seasonal sampling program in 2007, and represent air pollution from all months of the year. The δ13C values of the total carbon varied seasonally from −27.6 to −25.3‰. The isotopic mass balance calculations confirmed greater coal burning input, reaching 70.5%, in the heating season and dominant transported sources 47.5% in the vegetative season. The data obtained for the aliphatic fractions: carbon preference index (CPI), carbon number maximum (C max), wax n-alkane contents (%WNA), and δ13C values of the aliphatic fractions (−36.6 to −29.4‰), indicated a dominant anthropogenic origin (gasoline/diesel/coal combustion) and a lesser biogenic input (biomass burning and natural organic matter). Petroleum and coal combustion emissions were confirmed by the presence of hopanes and moretanes. The molecular analysis of the concentrations and diagnostic ratios of the polycyclic aromatic hydrocarbons (PAHs) and the δ13C values of the aromatic fractions (−35.4 to −26.8‰) indicated that the main PAH sources were also collectively from combustion of liquid fuels and coal. Based on PAH discrimination diagrams it is also clear that the main organic carbon source is derived from coal, biomass and petroleum combustion in both seasons. However, taking into account the PAH concentrations during the vegetative and heating seasons, coal and biomass burning seem to be their major source. Additionally, the polar organic compounds (mainly levoglucosan) confirmed a significant contribution from biomass burning to the total anthropogenic input. The general conclusion derived from coupling of organic tracer analysis and carbon isotopic data of PM10 was that the total carbon (including insoluble soot) is likely derived from fossil fuel combustion, while the extractable organic matter is a mixture from different sources with significant inputs of biomass burning. We have also shown that dominant organic tracers do not always represent the major input source in aerosol PM and the unresolved part of the organic matter (soot) is important in the carbon budget.
Keywords: PM10; Stable carbon isotopes; Urban atmosphere; PAHs; Hydrocarbons; Levoglucosan;
Gas-phase reactive nitrogen near Grand Teton National Park: Impacts of transport, anthropogenic emissions, and biomass burning by A.J. Prenni; E.J.T. Levin; K.B. Benedict; A.P. Sullivan; M.I. Schurman; K.A. Gebhart; D.E. Day; C.M. Carrico; W.C. Malm; B.A. Schichtel; J.L. Collett; S.M. Kreidenweis (749-756).
Excess inputs of reactive nitrogen can adversely affect terrestrial and aquatic ecosystems, particularly in sensitive ecosystems found at high elevations. Grand Teton National Park is home to such sensitive natural areas and is in proximity to potentially large reactive nitrogen sources. The Grand Teton Reactive Nitrogen Deposition Study (GrandTReNDS) was conducted in spring–summer 2011, with the aim of better understanding sources of reactive nitrogen influencing the region, spatial and temporal variability of reactive nitrogen in the atmosphere, and current levels of nitrogen deposition. Overall, NO y was determined to be the most abundant class of ambient gas phase reactive nitrogen compounds, and ammonia was determined to be the most abundant individual nitrogen species. NO x , NO y and NH3 concentrations all showed a diel cycle, with maximum concentrations during the day and minimum concentrations at night. This pattern appeared to be driven, in part, by mountain-valley circulation as well as long range transport, which brought air to the site from anthropogenic sources in the Snake River Valley and northern Utah. In addition to the nitrogen sources noted above, we found elevated concentrations of all measured nitrogen species during periods impacted by biomass burning.
Keywords: Grand Teton National Park; Reactive nitrogen; Biomass burning; Ammonia; NO x ; NO y ;
Investigating the sensitivity of surface-level nitrate seasonality in Antarctica to primary sources using a global model by Hyung-Min Lee; Daven K. Henze; Becky Alexander; Lee T. Murray (757-767).
Determining the sources of total nitrate (TNIT ≡ NO 3 − + HNO3) reaching Antarctica is a long-standing challenge. Here we analyze the monthly sensitivity of surface-level TNIT in Antarctica to primary sources using a global 3-D chemical transport model, GEOS-Chem, and its adjoint. Modeled seasonal variation of TNIT concentrations shows good agreement with several measurement studies, given that the lack of post-depositional processing in the model leads to an expected underestimate of maximum values in November through January. Remote NO x sources have the greatest impact May–July, during when the model background concentrations are sensitive to NO x emissions from fossil fuel combustion, soil, and lightning originating from 25°S to 65°S. In this season, NO x is transported to Antarctica as TNIT, which is formed above continental source regions at an altitude of 5–11 km. In other seasons, more NO x is transported as a reservoir species (e.g., peroxyacetyl nitrate, PAN) through the free troposphere, transforming into TNIT within a cone of influence that extends to 35°S and above 4 km altitude. Photolysis of PAN over Antarctica is the main driver of modeled NO x seasonality. Stratospheric production and loss of tracers are relatively unimportant in monthly sensitivities in GEOS-Chem, driving only a few percent of surface level variability of TNIT. A small peak concentration in August is captured by the model, although some measured values in August fall outside the range of simulated concentrations. Modifications to the model to represent sedimentation of polar stratospheric clouds (PSCs) lead to increased surface level August TNIT concentrations. However, this simple representation does not explicitly account for PSC particle deposition or disappearance of the tropopause in the middle of winter, and thus the influence of stratospheric nitrate sources estimated in this study is likely a lower bound.
Keywords: Adjoint based sensitivity analysis; Antarctica; GEOS-Chem model; Total nitrate seasonality;
NO2, PM10 and O3 urban concentrations and its association with circulation weather types in Portugal by Ana Russo; Ricardo M. Trigo; Helena Martins; Manuel T. Mendes (768-785).
High levels of atmospheric pollutants are frequently measured in Portugal, a country which has been affected by several pollution episodes, exceeding PM10, O3 and NO2 legal limits repeatedly during the last decade. The occurrence of these episodes is often related to either local-scale conditions or regional-scale transport. In order to better understand the atmospheric factors responsible for poor air quality, the relationships between air pollution and meteorological variables or atmospheric synoptic patterns represent an important research area.Here an objective classification scheme of the atmospheric circulation affecting Portugal, between 2002 and 2010, is presented, where daily circulation is characterized through the use of a set of indices associated with the direction and vorticity of the geostrophic flow in the lower atmosphere. The synoptic characteristics and the frequency of ten basic circulation weather types (CWTs) are discussed and a framework that permits the identification of the main characteristics associated to the occurrence of pollution episodes is mapped based on the identified patterns. The relationship between CWTs and poor air quality allowed distinguishing between which types are most frequently associated to pollution episodes. It is shown that the anticyclonic and north types, although being the most frequent classes during the majority of the year, do not prevail during pollution episodes that are dominated by easterly types. In general, higher concentration of all three pollutants and the two extreme events analysed occur associated predominantly with synoptic circulation characterized by an eastern component and advection of dry air masses. Moreover, results on the link between CWTs and air quality for Lisbon and Porto urban areas suggest that air quality regimes are generally similar for the northern and southern regions considered with the exception of spring and autumn PM10. Results obtained highlight the existence of strong links between the interannual variability of daily air quality and interannual variability of CWTs.
Keywords: Air quality; Objective classification; Weather types; Air pollution episodes;
Health risk assessment of exposure to polybrominated diphenyl ethers (PBDEs) contained in residential air particulate and dust in Guangzhou and Hong Kong by Wei Wang; Jinshu Zheng; Chuen-Yu Chan; Min-juan Huang; Kwai Chung Cheung; Ming Hung Wong (786-796).
Polybrominated diphenyl ethers (PBDEs) were measured in air particulate PM2.5 (less than 2.5 μm), TSP (Total Suspend Particle) and dust samples from different households of two major urban centers of Pearl River Delta (PRD). ∑PBDEs in PM2.5 of households in Guangzhou (GZ) (52.9–2.03 × 103 pg m−3 mean 239 pg m−3) were significantly higher than Hong Kong (HK) (0.25–160 pg m−3, mean 43.8 pg m−3). Higher ∑PBDEs occurred in indoor TSP, ranging between 117 and 1.14 × 103 pg m−3, with a median of 333 pg m−3. BDE-209 was the largest contributor to PBDEs contained in household dust, PM2.5 and TSP samples of GZ. Among the particles in household environment, PM2.5 accumulated the highest PBDEs, especially BDE-209. The constant Cparticle/Cdust values suggested that sorption is the dominant mechanism through which PBDEs are associated with settled dust and airborne particles. PBDEs were fairly uniform from urban sites to suburban sites, indicating the predominant indoor sources of PBDEs. Compared with indoor PM2.5, indoor dust ingestion made an important contribution of particle associated PBDEs exposure for adults (25 years old) and toddlers (1–2 years old). Non-dietary exposure dominated total PBDEs exposure, accounting for 91.8–99.0% exposure dose for toddlers and 45.1–82.2% for adults. Dust ingestion (69.3–96.1%) was the predominant PBDEs exposure route for toddlers.
Keywords: PBDEs; PM2.5; Household dust; Urban-to-suburban change; Particle fraction; Non-dietary exposure;
Evaluation of MM5, WRF and TRAMPER meteorology over the complex terrain of the Po Valley, Italy by A. Gsella; A. de Meij; A. Kerschbaumer; E. Reimer; P. Thunis; C. Cuvelier (797-806).
The objective of this study was to evaluate three meteorological models (MM5, WRF and TRAMPER) by comparing the calculated meteorological parameters with observations over the Po Valley area (Italy) for 2005. The analysis shows that MM5 and WRF perform with similar quality, with advantages of WRF at following high resolution time patterns and better scores of MM5 at reproducing annual averages, noticed for precipitation and relative humidity calculations. Results from the TRAMPER model also reflect very well surface meteorological measurements, they may be however driven by data assimilation applied in this modelling system and thus strongly influenced by very local effects. This feature of TRAMPER may lead as well to large uncertainties in reproducing other parameters important for air quality modelling such as planetary boundary layer (PBL) heights, friction velocity (u*) values or stability conditions.
Keywords: Meteorological models; Numerical modelling; Po Valley; MM5; WRF; TRAMPER;
A multisource observation study of the severe prolonged regional haze episode over eastern China in January 2013 by Hong Wang; Sai-Chun Tan; Yu Wang; Chao Jiang; Guang-yu Shi; Meng-Xiang Zhang; Hui-Zheng Che (807-815).
By employing visibility observation, PM10, SO2 and NO2 concentration, MODIS AOD at 550 nm, CARSNET AOD at 440 nm, CALIPSO extinction coefficient at 532 nm, we studied the air pollution condition of a severe haze episode occurred on 6–16 January 2013 over eastern China. The study found that this severe pollution episode of large area haze was accompanied with low visibility, high PM10 and AOD in eastern China. The most polluted regions is the Jing-Jin-Ji and its near southern neighboring region including central and south Hebei, west Shandong and north Henan province in the whole China Mainland. The haze pollutants were spread to the offshore area of 125°E to the east of China, and even affected to the west of 140°E. The PM10 variation trend shows a strong linkage among the big cities in Jing-Jin-Ji and their near surrounding cities, indicating the possible inter-transport and influence among them. The suburb area of megacity suffered the similar serious pollution with urban region during this kind of severe haze episode. Most aerosol pollutants concentrated in boundary layer below 1500 m vertical height, in particular, the vertical heights of 100–800 m above the ground are peaks of the aerosol pollutants.
Keywords: East China; Haze episode; Visibility; AOD; PM10; Extinction coefficient;
Estimating halocarbon emissions using measured ratio relative to tracers in China by Chen Wang; Min Shao; Daikuan Huang; Sihua Lu; Limin Zeng; Min Hu; Qiang Zhang (816-826).
China is one of the most important halocarbons emitters in the world. However, differences exist in the compiled national emissions inventories (bottom-up) with those derived from ambient measurements (top-down). In this study, CO and 15 halocarbon species including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), CCl4, CH3CCl3 and other halogenated solvents were measured in 47 cities and using aircraft over Shandong Peninsula during 2010–2011 for China. Halocarbon species with concentrations 20% higher than that of global background levels were considered to have their local emissions; these species were chosen for developing emissions estimates using tracer ratios method. Three tracers namely CO, HCFC-22 and benzene were used to examine correlations with halocarbons in this work; HCFC-22 combined with benzene as multi-tracers showed better correlations than CO did. Halocarbon emissions were estimated using tracer emission multiplied by Halo/Tracer obtained from measured data. The calculated results revealed that HCFC-22 emission based on CO tracer was the largest ozone depletion substance (ODS) at 129.3 Gg/year; Solvent halocarbon species such as CH3Cl, CHCl3, CH2Cl2, C2HCl3, C2Cl4, etc., mainly used as solvents but not under control accounted for 79% in total halocarbon emissions. Comparisons of the tracer ratio emission estimates have been made with other emissions inventories. Results from this study showed our emission estimates for CFC-11 and CFC-12 were 80%∼85% and 120%∼430% of emission inventories respectively. Also the recently phased-out species of CCl4 and CH3CCl3 were 586%–1173% and 330%–660% of the emission inventories respectively. The estimated emissions from the different studies for China during 2000–2010 were summarized. It was shown that HCFC-22 increased by 49.1% accompanied with CFC-12 decreasing by 48.9% during 2007–2010 and a significant decrease trend in CH3CCl3 emission which dropped from 6.5 Gg/year in 2001 to 2.1 Gg/year in 2010.
Keywords: Halocarbons; Emissions; Mixing ratios; Tracer ratio;
Diurnal and seasonal carbon sequestration potential of seven broadleaved species in a mixed deciduous forest in India by Soumyajit Biswas; Sanjay Bala; Asis Mazumdar (827-834).
The objective of the study was to measure annual carbon sequestration rate of mixed deciduous forest by measuring that of seven young broadleaved tree species (6 years age) as well as selection of better carbon sequestered plant species for future plantation. The diurnal net assimilation rate of Carbon dioxide (CO2) at leaf level was measured with LI-6400 Portable Photosynthesis System at daytime on seasonal basis in a man-made forest at Budge Budge (N 22°28′ E 88°08′) of South 24 Parganas, West Bengal, INDIA. Net assimilation rate of carbon at canopy level was calculated by measuring Leaf Area Index with LAI-2200 and using analytical model with non-rectangular hyperbolic light response curve. The average net assimilation rate of CO2 at leaf level was found maximum in Albizzia lebbek (8.13 μmol m−2 s−1) and that of canopy level in Eucalyptus spp. (4.851 g h−1). The minimum was found for Swietenia mahagoni (1.058 g h−1). The annual carbon sequestration rate of the mixed forest in natural condition was estimated 6.01 t ha−1 year−1 by consolidating the potential of all seven species.
Keywords: Broadleaved; Canopy; Carbon sequestration; Leaf area index; Light response curve; Net assimilation rate;
Brown carbon in atmospheric outflow from the Indo-Gangetic Plain: Mass absorption efficiency and temporal variability by Bikkina Srinivas; M.M. Sarin (835-843).
The simultaneous measurements of brown carbon (BrC) and elemental carbon (EC) are made in ambient aerosols (PM2.5), collected from a site in north-east India during November'09–March'10, representing the atmospheric outflow from the Indo-Gangetic Plain (IGP) to the Bay of Bengal (BoB). The absorption coefficient of BrC (b abs), assessed from water-soluble organic carbon (WSOC) at 365 nm, varies from 2 to 21 M m−1 and exhibits significant linear relationship (P < 0.05) with WSOC concentration (3–29 μg m−3). The angstrom exponent (α: 8.3 ± 2.6, where b abs ≈ λ −α.) is consistent with that reported for humic-like substances (HULIS) from biomass burning emissions (BBE). The impact of BBE is also discernible from mass ratios of nss-K+/EC (0.2–1.4) and OC/EC (3.4–11.5). The mass fraction of WSOC (10–23%) in PM2.5 and mass absorption efficiency of BrC (σ abs-BrC: 0.5–1.2 m2 g−1) bring to focus the significance of brown carbon in atmospheric radiative forcing due to anthropogenic aerosols over the Indo-Gangetic Plain.Display Omitted
Keywords: Brown carbon; Mass absorption efficiency; Biomass burning emissions; Indo-Gangetic Plain; Bay of Bengal;