Atmospheric Environment (v.75, #C)
Editorial board (i).
Measurement of the specific surface area and particle size distribution of atmospheric aerosol reference materials by Tomoaki Okuda (1-5).
The investigation of the surface area of atmospheric aerosols is important as it provides a metric for their adverse health effects; however, few previous studies have considered this parameter. This study investigated the BET specific surface areas of aerosols, as well as the particle size distributions and chemical compositions of the three commercially available atmospheric aerosol reference materials; namely SRM1649a, CRM#28 and CRM#8. SRM1649a and CRM#28 consist mainly of coarse particles, while CRM#8 consists mainly of fine (or ultrafine) particles. The specific surface areas of the reference materials were; SRM1649a: 2.0 ± 0.2 m2 g−1, CRM#28: 2.0 ± 0.2 m2 g−1 and CRM#8: 35.7 ± 5.3 m2 g−1. CRM#8 had a higher value for the specific surface area. The specific surface area for CRM#8 was likely to be associated with the characteristics of diesel particulate matters. When the estimation of specific surface area of aerosol particles is based on the assumption that all particles are spherical and not aggregates/agglomerates, using particle number and mass distribution, the estimated value is likely to be significantly lower than the actual value, in particular, for fine or ultrafine particles. The actual specific surface area of atmospheric aerosols should be measured to avoid the underestimation of their adverse health effects.
Keywords: BET specific surface area; Chemical composition; EC/OC; Particle size distribution; PM2.5; Standard reference materials;
Inventory of pesticide emissions into the air in Europe by D.A. Sarigiannis; P. Kontoroupis; E.S. Solomou; S. Nikolaki; A.J. Karabelas (6-14).
Creation of a reliable and comprehensive emission inventory of the pesticides used in Europe is a key step towards quantitatively assessing the link between actual pesticide exposure and adverse health effects. An inventory of pesticide emissions was generated at a 1 × 1 km grid, for the year 2000. The emission model comprises three components: estimates of active substance (AS) wind drift taking into account crop type, volatilization during pesticide application and volatilization from the crop canopy. Results show that atmospheric emission of pesticides varies significantly across Europe. Different pesticide families are emitted from different parts of Europe as a function of the main crop(s) cultivated, agro-climatic conditions and production intensity.The pesticide emission inventory methodology developed herein is a valuable tool for assessing air quality in rural and peri-urban Europe, furnishing the necessary input for atmospheric modelling at different scales. Its estimates have been tested using global sensitivity and Monte Carlo analysis for uncertainty assessment and they have been validated against national and local surveys in four European countries; the results demonstrate the robustness and reliability of the inventory. The latter may therefore be readily used for exposure and health risk assessment studies targeting farmers, applicators, but also bystanders and the general population in Europe.
Keywords: Pesticides; Air emission inventory; Atmospheric dispersion; EU-wide data;
Effect of water vapour condensation on the radon content in subsurface air in a hypogeal inactive-volcanic environment in Galdar cave, Spain by A. Fernandez-Cortes; D. Benavente; S. Cuezva; J.C. Cañaveras; M. Alvarez-Gallego; E. Garcia-Anton; V. Soler; S. Sanchez-Moral (15-23).
Fluctuations of trace gas activity as a response to variations in weather and microclimate conditions were monitored over a year in a shallow volcanic cave (Painted Cave, Galdar, Canary Islands, Spain). 222Rn concentration was used due to its greater sensitivity to hygrothermal variations than CO2 concentration. Radon concentration in the cave increases as effective vapour condensation within the porous system of the rock surfaces inside the cave increases due to humidity levels of more than 70%. Condensed water content in pores was assessed and linked to a reduction in the direct passage of trace gases. Fluctuations in radon activity as a response to variations in weather and microclimate conditions were statistically identified by clustering entropy changes on the radon signal and parameterised to predict radon concentration anomalies. This raises important implications for other research fields, including the surveillance of shallow volcanic and seismic activity, preventive conservation of cultural heritage in indoor spaces, indoor air quality control and studies to improve understanding of the role of subterranean terrestrial ecosystems as reservoirs and/or temporary sources of trace gases.
Keywords: Radon anomalies; Vapour condensation; Gas diffusion; Underground cavities; Subsoil monitoring;
Ozone and particulate matter enhancements from regional wildfires observed at Mount Bachelor during 2004–2011 by N.L. Wigder; D.A. Jaffe; F.A. Saketa (24-31).
We report observations of normalized enhancement ratios (NER) for 32 wildfires measured at Mount Bachelor Observatory in central Oregon during June–September 2004–2011. All 32 plumes resulted from wildfires originating in the western United States and Canada. The observed NER of PM1 (particulate matter < 1 micron) to carbon monoxide (ΔPM1/ΔCO) ranged from 0.06 to 0.42 μg m−3 ppbv−1. The NER of ozone to CO (ΔO3/ΔCO) ranged from 0.01 to 0.51 ppbv ppbv−1 for the 13 observed plumes with a significant ΔO3/ΔCO NER (p ≤ 0.01, R 2 ≥ 0.30). For wildfire plumes transported <540 km, or approximately <2 days, the ΔPM1/ΔCO NER is found to increase with increasing distance, suggesting that there is significant secondary organic aerosol (SOA) production in these plumes. However, two plumes transported over greater time periods have relatively low ΔPM1/ΔCO NER, indicating that PM1 loss is greater than SOA production in these plumes. Of the three plumes transported the longest distance to MBO, only two have significant O3 production. These two plumes were transported in boundary layer air masses, while the third was transported in a free tropospheric air mass, suggesting that conversion of nitrogen oxides (NO X ) to peroxyacetyl nitrate (PAN) may be a factor affecting O3 production in these plumes. Two wildfire plumes are mixed with urban emissions from the Seattle/Tacoma metropolitan area, and have relatively higher ΔO3/ΔCO NER than other wildfire plumes transported over similar distances.
Keywords: Wildfire; Enhancement ratio; Ozone; Particulate matter; Plume transport;
Comparison of the IFDM building downwash model predictions with field data by W. Lefebvre; G. Cosemans; J. Kegels (32-42).
The building downwash parameterization for plume models proposed in Cosemans et al. (2012) is integrated in a plume model (IFDM, Immission Frequency Distribution Model) and the predictions of this model are compared with real-life field data. The field data are time series for four monitoring sites of daily arsenic (As) concentrations measured over a two year period (Jan. 2010–Dec. 2011) near a plant that emits some As. In-stack emission measurements as well as measured As concentrations in ambient air show considerable time-dependent variations which prohibited a straightforward comparison of measured and computed concentrations using average emissions. Therefore, two model evaluations have been done. First, the time-variability was considered small enough during twenty months (out of the 24 months in the two-year period) to compare the central moving averages of the measured concentrations with those computed using constant emissions. Time series compare well, and none of the measured annual average concentrations has a bias larger than 50% while 7 out of 8 year averages (4 monitoring sites, two years) have a bias lower than 30%. During the four months not used in this evaluation, measured daily concentrations are about four times higher than during the other twenty months, resulting in yearly average increase up to 80%. Using a time-varying emission scenario, using information from daily As-measurements in the recirculation zone on top of the building with the sources, the model is able to reproduce the annual mean concentrations at the different locations including all the months. Finally, not only the yearly averages, but also the time series of measured and computed concentrations, pollutant roses and Q–Q plots are evaluated.
Keywords: Building downwash; Gaussian modelling; Evaluation;
A comparative analysis of two highly spatially resolved European atmospheric emission inventories by J. Ferreira; M. Guevara; J.M. Baldasano; O. Tchepel; M. Schaap; A.I. Miranda; C. Borrego (43-57).
A reliable emissions inventory is highly important for air quality modelling applications, especially at regional or local scales, which require high resolutions. Consequently, higher resolution emission inventories have been developed that are suitable for regional air quality modelling.This research performs an inter-comparative analysis of different spatial disaggregation methodologies of atmospheric emission inventories. This study is based on two different European emission inventories with different spatial resolutions: 1) the EMEP (European Monitoring and Evaluation Programme) inventory and 2) an emission inventory developed by the TNO (Netherlands Organisation for Applied Scientific Research). These two emission inventories were converted into three distinct gridded emission datasets as follows: (i) the EMEP emission inventory was disaggregated by area (EMEParea) and (ii) following a more complex methodology (HERMES-DIS – High-Elective Resolution Modelling Emissions System – DISaggregation module) to understand and evaluate the influence of different disaggregation methods; and (iii) the TNO gridded emissions, which are based on different emission data sources and different disaggregation methods. A predefined common grid with a spatial resolution of 12 × 12 km2 was used to compare the three datasets spatially.The inter-comparative analysis was performed by source sector (SNAP – Selected Nomenclature for Air Pollution) with emission totals for selected pollutants. It included the computation of difference maps (to focus on the spatial variability of emission differences) and a linear regression analysis to calculate the coefficients of determination and to quantitatively measure differences.From the spatial analysis, greater differences were found for residential/commercial combustion (SNAP02), solvent use (SNAP06) and road transport (SNAP07). These findings were related to the different spatial disaggregation that was conducted by the TNO and HERMES-DIS for the first two sectors and to the distinct data sources that were used by the TNO and HERMES-DIS for road transport.Regarding the regression analysis, the greatest correlation occurred between the EMEParea and HERMES-DIS because the latter is derived from the first, which does not occur for the TNO emissions. The greatest correlations were encountered for agriculture NH3 emissions, due to the common use of the CORINE Land Cover database for disaggregation. The point source emissions (energy industries, industrial processes, industrial combustion and extraction/distribution of fossil fuels) resulted in the lowest coefficients of determination. The spatial variability of SO x differed among the emissions that were obtained from the different disaggregation methods.In conclusion, HERMES-DIS and TNO are two distinct emission inventories, both very well discretized and detailed, suitable for air quality modelling. However, the different databases and distinct disaggregation methodologies that were used certainly result in different spatial emission patterns. This fact should be considered when applying regional atmospheric chemical transport models. Future work will focus on the evaluation of air quality models performance and sensitivity to these spatial discrepancies in emission inventories. Air quality modelling will benefit from the availability of appropriate resolution, consistent and reliable emission inventories.
Keywords: European emission inventories; Disaggregation methods; Inter-comparative analysis; Spatial variability;
Weekday/weekend differences in gasoline related hydrocarbons at coastal PAMS sites due to recreational boating by Robert F. Henry (58-65).
Analysis of PAMS (Photochemical Assessment Monitoring Stations) data at several coastal sites reveals large weekday/weekend differences in gasoline related hydrocarbons. Elevated concentrations of gasoline related constituents, including alkanes, alkenes, and aromatics, are observed on weekends at the PAMS monitors at Sherwood Island State Park in Westport, CT and at Newbury, MA. An analysis of the ratio of the concentrations of 2,3-dimethylbutane to 2,2-dimethylbutane indicates these compounds are freshly emitted, and an investigation in conjunction with wind data shows that the elevated concentrations are associated primarily with onshore winds. These elevated concentrations are most likely due to weekend recreational boating.
Keywords: PAMS; Weekday/weekend; VOCs; Boating; Gasoline;
Performance assessment of Large Eddy Simulation (LES) for modeling dispersion in an urban street canyon with tree planting by P. Moonen; C. Gromke; V. Dorer (66-76).
The potential of a Large Eddy Simulation (LES) model to reliably predict near-field pollutant dispersion is assessed. To that extent, detailed time-resolved numerical simulations of coupled flow and dispersion are conducted for a street canyon with tree planting. Different crown porosities are considered. The model performance is assessed in several steps, ranging from a qualitative comparison to measured concentrations, over statistical data analysis by means of scatter plots and box plots, up to the calculation of objective validation metrics. The extensive validation effort highlights and quantifies notable features and shortcomings of the model, which would otherwise remain unnoticed. The model performance is found to be spatially non-uniform. Closer agreement with measurement data is achieved near the canyon ends than for the central part of the canyon, and typical model acceptance criteria are satisfied more easily for the leeward than for the windward canyon wall. This demonstrates the need for rigorous model evaluation. Only quality-assured models can be used with confidence to support assessment, planning and implementation of pollutant mitigation strategies.
Keywords: Computational fluid dynamics (CFD); Large eddy simulation (LES); Wind tunnel measurements; Dispersion; Statistical analysis; Validation metrics; Model performance;
Carbon release from Sphagnum peat during thawing in a montane area in China by Xianwei Wang; Changchun Song; Jiaoyue Wang; Yuqing Miao; Rong Mao; Yanyu Song (77-82).
Soil thawing may affect the turnover of soil organic carbon (C) and the release of C to the atmosphere. Little is known about C release during thawing in the Great Hing'an Mountains, China. Through the incubations, we studied the emissions of CO2 and CH4 during thawing from the Sphagnum moss layer to the permafrost layer under aerobic and anaerobic conditions. Carbon was released quickly during thawing under different conditions. The Sphagnum moss layer produced more CO2 than the other layers. However, there was little CH4 release during thawing in the Sphagnum moss layer and burst of CH4 emissions in the peat and permafrost soils. These bursts include stored CH4 in the frozen samples and productions from microbial activity. The temperature sensitivity during thawing decreased across the freezing point in the Sphagnum moss layer, did not change greatly in the root layer, and increased greatly in the peat and permafrost layers. Changes in soil substrates and enzyme activities may affect C release during thawing.
Keywords: Peatland; Thaw; Methane; Carbon dioxide; Temperature sensitivity; Environment;
Chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons in the atmosphere of four Chinese cities by Jing Wu; Xuekun Fang; Wanyun Xu; Dan Wan; Yehong Shi; Shenshen Su; Jianxin Hu; Jianbo Zhang (83-91).
From July 2009–April 2011, 304 whole-air samples were collected at urban and suburban sites in four Chinese cities. The results indicated that recent chlorofluorocarbon (CFC) concentrations in all four cities are approaching Northern Hemispheric (NH) background levels, suggesting that the phase-out of CFCs in China is underway. However, hydrochlorofluorocarbon (HCFC) and 1,1,1,2-tetrafluoroethane (HFC-134a, CH2FCF3) concentrations have risen far above the NH background levels. Their concentration variability is evident, suggesting significant regional emissions. One-way analysis of variance (ANOVA) and independent-sample t-tests were applied to analyze the spatial distributions and emissions. Monochlorodifluoromethane (HCFC-22, CHClF2) levels at the urban sites were 30% higher than those observed at the suburban sites (P < 0.05), likely owing to larger population density in the urban areas. The largest 1-dichloro-1,1-fluoroethane (HCFC-142b, CH3CClF2) mean concentrations were detected in Beijing (131 and 52 pptv for urban and suburban sites, respectively), likely because of more widespread use of extruded polystyrene board. The variation in HFC-134a concentration levels in different cities was mainly related to the vehicle population. In addition, the different HCFC species exhibited significant positive correlations amongst themselves for each city (P < 0.05), suggesting that either they were emitted from similar or co-located sources or they shared similar emission patterns. These results are helpful to confirm the phase-out of ozone-depleting substances (ODSs) and to provide guidance for implementing effective phase-out strategies for ODSs and greenhouse gases.
Keywords: CFCs; HCFCs; HFCs; Emission; Vehicle population; Atmospheric concentration;
Spatial, seasonal and vertical distributions of currently-used pesticides in the marine boundary layer of the North Sea by Carolin Mai; Norbert Theobald; Gerhard Lammel; Heinrich Hühnerfuss (92-102).
Pesticides are transported beyond source regions and reach coastal waters and shelf seas. 23 representatives of six chemical classes of currently-used pesticides (CUPs) were simultaneously quantified in the marine boundary layer and the surface seawater of the German Bight and the central North Sea in 2009 and 2010.Terbuthylazine, metolachlor, metazachlor, pendimethalin and trifluralin exhibited the highest concentrations, seasonally highly variable. Advection of contaminated air from land and subsequent atmospheric deposition was shown to contribute to surface seawater contamination significantly, in particular in regions beyond riverine input and during the main seasons of application in agriculture. Deposition was most significant for the seasonal and spatial distributions of pendimethalin and trifluralin. Atrazine and simazine levels in the air are lower than 1–2 decades ago.
Keywords: Atmosphere; Atmospheric deposition; Currently-used pesticides; North Sea; Herbicides;
Kinetics and products of the gas-phase reactions of acenaphthylene with hydroxyl radicals, nitrate radicals and ozone by Shouming Zhou; John C. Wenger (103-112).
A series of simulation chamber experiments has been performed on the gas-phase atmospheric oxidation of acenaphthylene with the hydroxyl (OH) radical, ozone (O3) and the nitrate (NO3) radical. Using a relative rate technique the following rate coefficients (in cm3 molecule−1 s−1) were determined at (293 ± 3) K in 1 atm of purified air: (1.09 ± 0.07) × 10−10, (3.99 ± 0.15) × 10−16 and (4.42 ± 0.32) × 10−12 for the reactions with OH, O3 and NO3 respectively. The results indicate that all three oxidants effectively contribute to the removal of acenaphthylene from the atmosphere. A denuder-filter sampling system coupled with off-line analysis by gas chromatography – mass spectrometry (GC–MS) was used to determine the gas- and particle-phase products of these reactions. The major products identified in the reaction with OH were naphthalene-1,8-dicarbaldehyde, 1,8-naphthalic anhydride and a 10 carbon ring-opened dialdehyde. The products identified in the reaction with NO3 and O3 were predominantly oxygenated compounds arising from reaction at the C＝C bond in the cylcopenta-fused ring of acenaphthylene. The formation of hydroxylated and nitro-PAHs appears to be a very minor reaction pathway. Acenaphthenequinone, a compound known to generate reactive oxygen species at the cellular level, was formed from the reactions of acenaphthylene with OH and NO3. The majority of the oxidation products were found to be distributed between the gas and particle phases, with only acenaphthylenol and oxaacenaphthylen-2-one, relatively more abundant in the particle phase.
Keywords: Gas-phase; Acenaphthylene; Quinone; Atmospheric oxidation; Polycyclic aromatic hydrocarbons;
Study of aerosol effect on accelerated snow melting over the Tibetan Plateau during boreal spring by Woo-Seop Lee; Rohini L. Bhawar; Maeng-Ki Kim; Jeong Sang (113-122).
In the present study, a coupled atmosphere–ocean global climate model (CSIRO-Mk3.6) is used to investigate the role of aerosol forcing agents as drivers of snow melting trends in the Tibetan Plateau (TP) region. Anthropogenic aerosol-induced snow cover changes in a warming climate are calculated from the difference between historical run (HIST) and all forcing except anthropogenic aerosol (NoAA). Absorbing aerosols can influence snow cover by warming the atmosphere, reducing snow reflectance after deposition. The warming the rate of snow melt, exposing darker surfaces below to short-wave radiation sooner, and allowing them to heat up even faster in the Himalayas and TP.The results show a strong spring snow cover decrease over TP when absorbing anthropogenic aerosol forcing is considered, whereas snow cover fraction (SCF) trends in NoAA are weakly negative (but insignificant) during 1951–2005. The enhanced spring snow cover trends in HIST are due to overall effects of different forcing agents: When aerosol forcing (AERO) is considered, a significant reduction of SCF than average can be found over the western TP and Himalayas. The large decreasing trends in SCF over the TP, with the maximum reduction of SCF around 12–15% over the western TP and Himalayas slope. Also accelerated snow melting during spring is due to effects of aerosol on snow albedo, where aerosol deposition cause decreases snow albedo. However, the SCF change in the “NoAA” simulations was observed to be less.Display Omitted
Keywords: Aerosol optical depth; Snow darkening effect; CMIP5; Snow cover fraction; Climate change;
Calibration and application of PUF disk passive air samplers for tracking polycyclic aromatic compounds (PACs) by Tom Harner; Ky Su; Susie Genualdi; Jessica Karpowicz; Lutz Ahrens; Cristian Mihele; Jasmin Schuster; Jean-Pierre Charland; Julie Narayan (123-128).
Results are reported from a field calibration of the polyurethane foam (PUF) disk passive air sampler for measuring polycyclic aromatic compounds (PACs) in the atmosphere of the Alberta oil sands region of Canada. Passive samplers were co-deployed alongside conventional high volume samplers at three sites. The results demonstrate the ability of the PUF disk sampler to capture PACs, including polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs and parent and alkylated dibenzothiophenes. Both gas- and particle-phase PACs were captured with an average sampling rate of approximately 5 m3 day−1, similar to what has been previously observed for other semivolatile compounds. This is the first application of the PUF disk sampler for alkylated PAHs and dibenzothiophenes in air. The derived sampling rates are combined with estimates of the equilibrium partitioning of the PACs in the PUF disk samplers to estimate effective sample air volumes for all targeted PACs. This information is then applied to the passive sampling results from two deployments across 17 sites in the region to generate spatial maps of PACs. The successful calibration of the sampler and development of the methodology for deriving air concentrations lends support to the application of this cost-effective and simple sampler in longer term studies of PACs in the oil sands region.
Keywords: Alberta oil sands; Air sampling; PACs; PAHs; Alkylated PAH; Dibenzothiophenes; PUF disk; Passive air sampling;
Assessing interim objectives for acidification, eutrophication and ground-level ozone of the EU National Emission Ceilings Directive with 2001 and 2012 knowledge by Jean-Paul Hettelingh; Maximilian Posch; Guus J.M. Velders; Paul Ruyssenaars; Martin Adams; Frank de Leeuw; Anke Lükewille; Rob Maas; Johan Sliggers; Jaap Slootweg (129-140).
The National Emission Ceilings Directive regulating European Union (EU) Member State emissions of acidifying and eutrophying pollutants as well as ozone precursors was adopted in 2001. Its interim environmental objectives, to be achieved in 2010, consist of a reduction of the exceedance of critical loads for acidification and eutrophication and of critical levels of ground-level ozone relative to 1990. Objectives for acidification and ground-level ozone were to be met in every single receptor grid cell in the European Union. For eutrophication, however, the target was to be met only for the EU area as a whole. Since 2001, reported emissions for 1990 and 2010 as well as knowledge and methodologies and for computing atmospheric dispersion and critical loads and levels have changed. In this paper, it is shown that acidification and eutrophication objectives are largely met when assessing them with the knowledge of 2001. However, with 2012 knowledge the interim objectives for acidification and eutrophication are not met in most of the EU. The objectives for ground-level ozone are met in most EU Member States with both 2001 and present (2012) knowledge, with the exception of the objective for forests, which was still not met in most Member States in 2010. Therefore, it seems prudent that science is employed also in the implementation phase of policy agreements.
Keywords: Acidification; Air pollution; Critical loads; Eutrophication; NEC Directive; Ozone;
The 1970 Clean Air Act and termination of rainfall suppression in a U.S. urban area by Jeremy E. Diem (141-146).
The purpose of this paper is to determine the impact of reduced atmospheric particulate resulting from the Clean Air Act of 1970 on changes in summer rainfall in the Atlanta, Georgia USA region. In order to determine if rainfall at nine candidate stations in the metropolitan area was influenced by changes in particulate concentrations within the 1948–2009 period, predicted rainfall characteristics were derived from rainfall frequencies at nine reference stations located more than 80 km from downtown Atlanta. Both parametric and non-parametric tests were used to test for significant differences between observed values and predicted values within 34 overlapping 30-year periods. For the country as a whole, emissions of PM10 (i.e. particulates with a diameter less than or equal to 10 μm) decreased by approximately 40% from 1970 to 1975. The reduction in emissions caused a rapid rebound in summer rainfall in the Atlanta region. There was suppression of rainfall over and downwind of the Atlanta urbanized area during 30-yr periods that comprise all or portions of the decades of the 1950s, 1960s, and 1970s. This suppression occurred even while urban-related factors that promote rainfall enhancement were present. During the 1948–1977 suppression period, there was a decrease in rainfall of at least 40 mm at affected locales, which is substantial given that the mean seasonal rainfall was approximately 300 mm. The rainfall suppression involved a decrease of heavy-rainfall days. Atlanta is most likely not a unique case; therefore, particulate-induced rainfall suppression might have occurred over and downwind of other U.S. urban areas prior to the late 1970s.
Keywords: Precipitation; Particulates; Suppression; Urban; Policy; Pollution;
Predictive models for estimating the vapor pressure of poly- and perfluorinated compounds at different temperatures by Guanghui Ding; Mihua Shao; Jing Zhang; Junyi Tang; Willie J.G.M. Peijnenburg (147-152).
Poly- and perfluorinated compounds (PFCs) are a class of global environmental pollutants that are of concern regarding their environmental fate and adverse effects. However, data on the basic physicochemical property of PFCs are still limited. To fill part of the data gaps, temperature-dependent predictive models for vapor pressure of PFCs were developed based on previously reported experimental data. The applicability domain of the models was analyzed using the Williams plot and the influential points and the response outliers were identified. The statistical performance of the models was significantly improved by removing these influential points and response outliers. This procedure confirmed the importance of properly defining the applicability domain of the predictive models. It is shown that the main factors governing the vapor pressure of PFCs, are intermolecular dispersive interactions, hydrogen bonding, temperature, intermolecular dipole-induced dipole interactions and dipole–dipole interactions. Although the model obtained could be used to reliably predict the vapor pressures of certain PFCs at different temperatures, it is essential that the prediction must fall within the applicability domain of the model and the temperature range for reliable predictions.
Keywords: Vapor pressure; Poly- and perfluorinated compounds; QSPR; PLS; Temperature;
Large-eddy simulation coupled to mesoscale meteorological model for gas dispersion in an urban district by T. Michioka; A. Sato; K. Sada (153-162).
A microscale large-eddy simulation (LES) model coupled to a mesoscale LES model is implemented to estimate a ground concentration considering the meteorological influence in an actual urban district. The microscale LES model is based on a finite volume method with an unstructured grid system to resolve the flow structure in a complex geometry. The Advanced Regional Prediction System (ARPS) is used for mesoscale meteorological simulation. To evaluate the performance of the LES model, 1-h averaged concentrations are compared with those obtained by field measurements, which were conducted for tracer gas dispersion from a point source on the roof of a tall building in Tokyo. The concentrations obtained by the LES model without combing the mesoscale LES model are in quite good agreement with the wind-tunnel experimental data, but overestimates the 1 h averaged ground concentration in the field measurements. On the other hand, the ground concentrations using the microscale LES model coupled to the mesoscale LES are widely distributed owing to large-scale turbulent motions generated by the mesoscale LES, and the concentrations are nearly equal to the concentrations from the field measurements.
Keywords: Atmospheric dispersion; Large-eddy simulation; Meteorological influence; Urban district; Field measurement;
An air-mass trajectory study of the transport of radioactivity from Fukushima to Thessaloniki, Greece and Milan, Italy by A. Ioannidou; E. Giannakaki; M. Manolopoulou; S. Stoulos; E. Vagena; C. Papastefanou; L. Gini; S. Manenti; F. Groppi (163-170).
Analyses of 131I, 137Cs and 134Cs in airborne aerosols were carried out in daily samples at two different sites of investigation: Thessaloniki, Greece (40° N) and Milan, Italy (45° N) after the Fukushima accident during the period of March–April, 2011. The radionuclide concentrations were determined and studied as a function of time. The 131I concentration in air over Milan and Thessaloniki peaked on April 3–4, 2011, with observed activities 467 μBq m−3 and 497 μBq m−3, respectively. The 134Cs/137Cs activity ratio values in air were around 1 in both regions, related to the burn-up history of the damaged nuclear fuel of the destroyed nuclear reactor. The high 131I/137Cs ratio, observed during the first days after the accident, followed by lower values during the following days, reflects not only the initial release ratio but also the different volatility, attachment and removal of the two isotopes during transportation due to their different physico-chemical properties. No artificial radionuclides could be detected in air after April 28, 2011 in both regions of investigation. The different maxima of airborne 131I and 134, 137Cs in these two regions were related to long-range air mass transport from Japan, across the Pacific and to Central Europe. Analysis of backward trajectories was used to confirm the arrival of artificial radionuclides following atmospheric transport and processing. HYSPLIT backward trajectories were applied for the interpretation of activity variations of measured radionuclides.
Keywords: Nuclear accident; Fukushima accident; Radionuclides; Radioactive fallout; Back-trajectories;
Phototransformations of dinitropyrene isomers on models of the atmospheric particulate matter by Rafael Arce; María Morel (171-178).
The 1,6 and 1,8-dinitropyrenes (DNP) isomers are strong mutagens and carcinogens encountered in diesel exhaust and airborne particles. Relative photodegradation rates were determined and some products were characterized when these isomers were irradiated adsorbed onto models of the atmospheric matter. These are compared to their photochemical behavior in a polar nonprotic solvent. The 1,8-DNP isomer is three times more reactive than the 1,6-DNP when irradiated adsorbed onto silica gel surfaces, while the reverse order is observed in solution, demonstrating the influence of structural differences and environmental effects on the photoreactivity. Oxygen is a key factor in the formation of pyrenediones from 1,8-DNP in solution and on silica gel which is not the case for 1,6-DNP. The average pore diameter (2.5 versus 6.0 nm) of the silica surfaces induces a significant change in the product distribution and relative yields of 1,8-DNP because pyrenediones or 8-hydroxy-1-nitropyrene are not produced in the smaller pore silica. A 6-hydroxy-1-nitropyrene product is observed both in acidic alumina and silica (6.0 nm) surfaces. On acidic alumina the rates of phototransformation of the isomers are equal, a significant increase in the relative yield of the hydroxynitropyrene product is observed compared to the silica and unidentified products in which the absence of NO2 and pyrene absorption bands were observed, demonstrating the surface effect on the photodegradation. Overall, the presence of some products indicates the occurrence of a nitro-nitrite rearrangement on the surface with the participation of a pyrenoxy radical as their precursor.
Keywords: Surface phototransformations; Dinitropyrenes; Photodegradation rates; Adsorbed; Atmospheric chemistry;
Vertical and temporal variations of black carbon in New Zealand urban areas during winter by W.J. Trompetter; S.K. Grange; P.K. Davy; T. Ancelet (179-187).
During winter nights, topographically confined urban areas can experience episodes of particulate matter pollution as a result of combustion related emissions for domestic heating. Black carbon (BC) concentrations were measured vertically and temporally during winter evenings in four New Zealand urban locations as a proxy for combustion-related particulate matter (PM). Vertical temperature and BC profiles demonstrated the formation of inversion conditions, where the near-ground boundary layer becomes decoupled from layers above. The BC profiles indicated that PM was mostly confined to a surface layer less than 50 m in height from the surface. In addition, the BC concentrations exhibited a temporal pattern consistent with previously observed PM10 diurnal cycles, where maximum BC concentrations within the mixing height were observed near midnight. Decreasing BC concentrations during early morning were attributed to observed katabatic flows clearing the boundary layer. By dawn, BC concentrations in the vertical column were close to the much lower concentrations (<5 μg m−3) observed during the daytime, revealing that the observed night-time and morning peaks were separate events. Hence, the mid-morning peak is from new emissions due to residents re-lighting their fires. This study has contributed to our understanding of how meteorological conditions influence the build-up and dissipation of BC, and by extension, PM, during winter nights, which can result in significant air pollution events for our urban communities. Critically, the mid-morning peak can significantly contribute to exceedences of the 24-h air quality standard (50 μg m−3 PM10).
Keywords: Black carbon; Air pollution; Particulate matter; Vertical profiles; Meteorology;
Measuring a 10,000-fold enhancement of singlet molecular oxygen (1O2 *) concentration on illuminated ice relative to the corresponding liquid solution by Jonathan P. Bower; Cort Anastasio (188-195).
Much attention has focused on the highly reactive hydroxyl radical in the oxidation of trace organic compounds on snow and ice (and subsequent release of volatile organics to the atmospheric boundary layer) but other oxidants are likely also important in this processing. Here we examine the ice chemistry of singlet molecular oxygen (1O2 *), which can be significant in atmospheric water drops but has not been examined in ice or snow. To examine 1O2 * on ice we illuminate laboratory ices containing Rose Bengal (RB) as the source of 1O2 *, furfuryl alcohol (FFA) as the probe, and Na2SO4 to control the total solute concentration. We find that the 1O2 *-mediated loss of FFA (and, thus, the 1O2 * concentration) is up to 11,000 times greater on ice than in the equivalent liquid sample at the same photon flux. We attribute this large increase in the 1O2 * steady-state concentration to the freeze-concentration of solutes into liquid-like regions (LLRs) in/on ice: compared to the initial solution, in the LLRs of ice the sources for 1O2 * are highly concentrated, while the concentration of the dominant sink for 1O2 * (i.e., water) remains largely unchanged. Similar to results expected in liquid solution, rates of FFA loss in ice depend on both the initial sensitizer concentration and temperature, providing evidence that these reactions occur in LLRs. However, we find that the enhancement in 1O2 * concentrations on ice does not follow predictions from freezing-point depression, likely because experiments were conducted below the eutectic temperature for sodium sulfate, where all of the salt should have precipitated. We also explore a method for separating 1O2 * and •OH contributions to FFA oxidation in laboratory ices and show its application to two natural snow samples. We find that 1O2 * concentrations in these snows are approximately 100 times higher than observed in polluted, mid-latitude fog waters, showing that the enhancement of 1O2 * on ice is environmentally relevant and that 1O2 * could be a significant sink for electron-rich organic compounds in snow.
Keywords: Snow; Photochemistry; Freeze-concentration; Liquid-like regions; Oxidants;
The use of a housecleaning product in an indoor environment leading to oxygenated polar compounds and SOA formation: Gas and particulate phase chemical characterization by S. Rossignol; C. Rio; A. Ustache; S. Fable; J. Nicolle; A. Même; B. D'Anna; M. Nicolas; E. Leoz; L. Chiappini (196-205).
This work investigates Secondary Organic Aerosol (SOA) formed by limonene ozonolysis using a housecleaning product in indoor environment. This study combines simulation chamber ozonolysis experiments and field studies in an experimental house allowing different scenarios of housecleaning product use in real conditions.Chemical speciation has been performed using a new method based on simultaneous sampling of both gas and particulate phases on sorbent tubes and filters. This method allowed the identification and quantification of about 35 products in the gas and particulate phases. Among them, products known to be specific from limonene ozonolysis such as limononaldehyde, ketolimonene and ketolimonic acid have been detected. Some other compounds such as 2-methylbutanoic acid had never been detected in previous limonene ozonolysis studies. Some compounds like levulinic acid had already been detected but their formation remained unexplained. Potential reaction pathways are proposed in this study for these compounds. For each experiment, chemical data are coupled together with physical characterization of formed particles: mass and size and number distribution evolution which allowed the observation of new particles formation (about 87,000 particle cm−3). The chemical speciation associated to aerosol size distribution results confirmed that limonene emitted by the housecleaning product was responsible for SOA formation. To our knowledge, this work provides the most comprehensive analytical study of detected compounds in a single experiment for limonene ozonolysis in both gaseous and particulate phases in real indoor environment.
Keywords: Indoor environment; Secondary organic aerosols; Household products; Chemical speciation; Limonene;
Fluctuations in air pollution give risk warning signals of asthma hospitalization by Nan-Hung Hsieh; Chung-Min Liao (206-216).
Recent studies have implicated that air pollution has been associated with asthma exacerbations. However, the key link between specific air pollutant and the consequent impact on asthma has not been shown. The purpose of this study was to quantify the fluctuations in air pollution time-series dynamics to correlate the relationships between statistical indicators and age-specific asthma hospital admissions. An indicators-based regression model was developed to predict the time-trend of asthma hospital admissions in Taiwan in the period 1998–2010. Five major pollutants such as particulate matters with aerodynamic diameter less than 10 μm (PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO) were included. We used Spearman's rank correlation to detect the relationships between time-series based statistical indicators of standard deviation, coefficient of variation, skewness, and kurtosis and monthly asthma hospitalization. We further used the indicators-guided Poisson regression model to test and predict the impact of target air pollutants on asthma incidence. Here we showed that standard deviation of PM10 data was the most correlated indicators for asthma hospitalization for all age groups, particularly for elderly. The skewness of O3 data gives the highest correlation to adult asthmatics. The proposed regression model shows a better predictability in annual asthma hospitalization trends for pediatrics. Our results suggest that a set of statistical indicators inferred from time-series information of major air pollutants can provide advance risk warning signals in complex air pollution-asthma systems and aid in asthma management that depends heavily on monitoring the dynamics of asthma incidence and environmental stimuli.
Keywords: Asthma hospitalization; Air pollution; Statistical indicators; Fluctuation; Warning signal; Risk;
Investigating the geographical heterogeneity in PM10-mortality associations in the China Air Pollution and Health Effects Study (CAPES): A potential role of indoor exposure to PM10 of outdoor origin by Bin Zhou; Bin Zhao; Xuefei Guo; Renjie Chen; Haidong Kan (217-223).
This study gives the first-time evidence for China that the geographical heterogeneity of the acute effects of outdoor PM10 can be partially explained by differences in indoor exposure to PM10 of outdoor origin. We used data from the China Air Pollution and Health Effects Study (CAPES), which demonstrated a geographical heterogeneity of the acute effect of particulate air pollution (particulate matter with an aerodynamic diameter smaller than 10 μm, or PM10) on mortality in 16 Chinese cities. Given that a large fraction of the exposure to PM10 of outdoor origin occurs indoors, we made the hypothesis that this heterogeneity might be partially explained by inter-city differences in indoor exposure to PM10 of outdoor origin. In our analysis, we estimated PM10 exposure coefficients (the change in the estimated personal exposure to PM10 of outdoor origin per unit change in outdoor PM10 concentration) in these 16 Chinese cities and examined their correlation with PM10 mortality coefficients (the increase in mortality associated with a given increase in the concentrations of outdoor PM10). We showed that the PM10 mortality coefficients and the PM10 exposure coefficients were significantly correlated, with an R-squared (R 2) value of 0.549 (95% confidence interval: 0.201, 0.771; p < 0.01) for the 16 cities. The correlation was robust with different values of the key input parameters, and close in value to estimations found in previous studies on similar subjects.
Keywords: Air change rate; Air conditioning; Outdoor-to-indoor; Particulate matter; Exposure measurement error;
Lead isotopic composition of insoluble particles from widespread mountain glaciers in western China: Natural vs. anthropogenic sources by Guangming Yu; Jianzhong Xu; Shichang Kang; Qianggong Zhang; Jie Huang; Qian Ren; Jiawen Ren; Dahe Qin (224-232).
Stable lead (Pb) isotopic fingerprints provide opportunities to trace natural and anthropogenic Pb sources in the environment. In order to evaluate Pb deposition from different sources over mountainous areas of western China, Pb isotopic compositions were characterized from modern aeolian dust in 15 snowpit samples collected from 13 typical mountain glaciers between 2008 and 2010. Most of the snowpits sampled cover more than a whole year of accumulation and overlap with each other on deposition date. Pb isotopic variability among all the samples is small, varying in the range of 18.1399–18.9199 for 206Pb/204Pb, 15.5979–15.8743 for 207Pb/204Pb, 38.2272–39.9453 for 208Pb/204Pb, 1.1605–1.2009 for 206Pb/207Pb and 2.4433–2.5182 for 208Pb/207Pb. Three isotopic plots of the different Pb isotope ratios (207Pb/204Pb vs. 206Pb/204Pb, 208Pb/204Pb vs. 206Pb/204Pb, and 208Pb/207Pb vs. 206Pb/207Pb) in all the samples show identical geographic trends, with more radiogenic in the south and less in the north. This trend is consistent with the distribution of natural dust sources and supports the interpretation of a regional/local source for insoluble particles (IP) to snow/glaciers in this region. Comparison with the Pb isotope results from potential dust sources, however, it shows that the Pb isotopic compositions of IP samples in snow samples are relatively less radiogenic. Parts of these less-radiogenic Pb isotopes are comparable with the ice core results during recent decades, which are shown to be influenced by anthropogenic sources. At sites located along the periphery of western China, the Pb isotopic compositions are much closer to anthropogenic results. Natural and anthropogenic Pb sources are roughly assessed using a simple binary model. The sites with a high anthropogenic fraction are at lower elevations and are relatively close to population centers.
Keywords: Stable lead isotopes; Insoluble particles; Snowpit; Qinghai-Xizang (Tibet) Plateau; Western China;
Role of particulate metals in heterogenous secondary sulfate formation by Andrea L. Clements; Birnur Buzcu-Guven; Matthew P. Fraser; Pranav Kulkarni; Shankararaman Chellam (233-240).
A series of field sampling and controlled laboratory experiments were undertaken to quantify the role of trace metals found in ambient fine particulate matter and metal-rich primary sources in the heterogenous catalytic conversion of SO2 gas into sulfate particulate matter (PM) in the atmosphere. Analysis produced source profiles of three primary source materials, fluidized-bed catalytic cracking catalyst, coal-fired combustion fly ash, and paved road dust, featuring 33 elements including rare earth metals, which are not commonly reported in the literature.Subsequently three sets of experiments were conducted exposing 1) source materials, 2) ambient PM, and 3) ambient PM augmented with approximately an equal amount of source material to SO2 gas and measuring sulfate formation. Source material experiments revealed that the greatest extent of reaction was on the surface of coal fly ash with sulfate formation of 19 ± 5 mg sulfate g−1 material. Ambient fine particulate matter (PM) experiments showed sulfate formation ranging from negligible amounts to 180 ± 10 mg sulfate g−1 PM. It was much more difficult to quantify the sulfate formation on ambient filters augmented with the source materials. In these experiments, sulfate formation ranged from negligible amounts to 40 ± 8 mg sulfate g−1 of particles (ambient + augmented material). These three sets of experiments shows that heterogenous sulfate formation is often negligible but, under some conditions can contribute 10% or more to the total sulfate concentrations when exposed to high SO2 concentrations such as those found in plumes.Factor analysis of the source material experiments grouped metals into two categories, crustal components and anthropogenically emitted metals representative of catalyst material, with the former showing the strongest correlation with sulfate formation. Subsequent analysis of data collected from the ambient PM experiments showed a much weaker correlation of sulfate formation with the crustal components, including iron and titanium, remaining clustered with sulfate formation. Independent research has been previously reported in the literature establishing mechanisms for the iron and titanium catalyzed conversion of S(IV) to S(VI) suggesting there may be other metals within these crustal type metal components that behave similarly. Additional experiments spanning a wider range of variables including more sources, SO2 concentrations and exposure times, ambient PM locations, as well as more individual samples may be necessary to obtain more conclusive evidence into the role of various metals in catalyzing the conversion of S(IV) to S(VI).
Keywords: Trace metals; Surface reactions; Laboratory augmentation; Sulfur dioxide exposure; Houston, Texas; PM2.5;
Impact of current policies on future air quality and health outcomes in Delhi, India by Hem H. Dholakia; Pallav Purohit; Shilpa Rao; Amit Garg (241-248).
A key policy challenge in Indian megacities is to curb high concentrations of PM2.5 and mitigate associated adverse health impacts. Using the Greenhouse Gases and Air Pollution Interactions and Synergies (GAINS) model we carry out an integrated analysis of the air quality regulations across different sectors for the city of Delhi. Our findings show that PM2.5 concentrations for Delhi will not reach the recommended national ambient air quality standards (NAAQS) even by 2030 under the current policies scenario. Adopting advanced control technologies reduces PM2.5 concentrations by about 60% and all-cause mortality by half in 2030. Climate change mitigation policies significantly reduce greenhouse gases, but have a modest impact on reducing PM2.5 concentrations. Stringent policies to control the net flow of air pollution from trans-boundary sources will play a crucial role in reducing pollution levels in Delhi city. Achieving NAAQS requires a stringent policy portfolio that combines advanced control technologies with a switch to cleaner fuels and the control of trans-boundary pollution.
Keywords: GAINS model; Fine particulate matter; Public policy; Control scenarios;
Impact of source and atmospheric processing on Fe solubility in aerosols over the Yellow Sea, China by T.R. Zhang; J.H. Shi; H.W. Gao; J. Zhang; X.H. Yao (249-256).
Thirty four atmospheric total suspended particulate (TSP) samples collected over the Yellow Sea between February and August, 2009 were used to study Fe solubility. Samples were classified into two groups based on calculated air mass back trajectories, i.e., one originating from a northern continental source (NCS, in which Fe solubility was 5.6 ± 3.9%) and the remaining one from other regions (non-NCS, in which Fe solubility was 3.1 ± 5.3%). The calculated enrichment factor (Al is used as a reference) indicated that Fe in the NCS samples was probably derived from natural sources dominated by mineral dust. A deep analysis of soluble Fe and Fe solubility suggested that cloud processing played an important role in the increase of both. No correlation between soluble Fe and secondary inorganic ions (sulfate and nitrate) was observed in NCS samples. However, in non-NCS samples, a good correlation between soluble Fe and secondary inorganic ions was observed, probably due to acidification reactions. Enrichment factors indicated that the Fe in the non-NCS samples was probably from anthropogenic sources. Moreover, a logarithmic curve between Fe solubility and ([SO4 2−] + [NO3 −]) together with correlations between soluble Fe and K+ obtained in the non-NCS samples further indicated that soluble Fe was more likely derived from aged ambient aerosols rather than from fresh aerosols. The lower solubility of Fe in non-NCS samples was comparable to Fe solubility in coal fly ash recently reported in the literature, while it was lower than Fe solubility in mineral dust.
Keywords: Iron solubility; Marine aerosols; Seawater; Biomass burning; Aerosol acidity;
Spatial and temporal scales of new particle formation events in eastern North America by P. Crippa; S.C. Pryor (257-264).
New particle formation (NPF) events have been observed in numerous locations. However, questions remain as to the scale of the events and their importance to regional and global particle number concentrations, size distributions and climate forcing. This study presents measured particle size distributions (PSD) at multiple sites across eastern North America and evaluates the degree of coherence on large (hundreds of kilometer) scales and the site-to-site variability across scales of tens of kilometers. Long-term data from sites separated by 1500 km demonstrate frequent and synchronous NPF, that over 80% of event days at both sites are followed by another event day and that event sequences are best described by a Markov Chain of order 1. Estimates of the mean spatial scale of NPF from a site in southern Indiana range from at least 120–850 km depending on the season and the precise assumptions applied. Despite the evidence for regional coherence in NPF, detailed measurements along an 80 km transect in southern Indiana also indicate some important sub-regional variability. While PSD from individual days typically indicate NPF at all three sites or at none of the sites, PSD measured in two urban environments show greater coherence than those from a centrally located site in a forest, and both the number of ultrafine particles and their growth rates are typically (but not uniformly) higher at the forested site. Some of the site-to-site variability appears to be causally linked to planetary boundary layer dynamics and variations in land cover.
Keywords: Nucleation; Spatial scale; Markov chain; Boundary-layer dynamics;
Source identification and health impact of PM2.5 in a heavily polluted urban atmosphere in China by Lingxiao Yang; Shuhui Cheng; Xinfeng Wang; Wei Nie; Pengju Xu; Xiaomei Gao; Chao Yuan; Wenxing Wang (265-269).
Positive matrix factorization (PMF) was applied to identify the types of PM2.5 sources and corresponding mass contributions to PM2.5 mass concentrations using PM2.5 measurements obtained from Dec. 2007 to Oct. 2008 in Jinan, which is a highly polluted city in China. The reconstructed mass concentrations from six sources matched the observations, and the resolved sources constituted 98.91% of the PM2.5 mass concentrations. Secondary sources, the major source contributor, accounted for 55.15% of PM2.5 mass concentration, while several other sources, including coal burning (20.98%), soil dust (9.30%), motor vehicles (6.06%), biomass burning (4.55%), and industry (2.87%), contributed a total of 43.76%. The non-carcinogenic risk estimates showed the elemental risk for Mn, Co, S and Cr were high, with values larger than 0.1 being observed for the three groups. The total elemental risk in Jinan for the three groups was higher than 1, and the largest risk was present for children between the age of 6–12 followed by that for children between 2 and 6 years of age, indicating that citizens in Jinan, particularly children, faced more serious potential non-carcinogenic health risks.
Keywords: PM2.5; PMF; Source contributions; Risk assessment; Jinan;
Aerosol optical properties over urban and industrial region of Northeast China by using ground-based sun-photometer measurement by Hujia Zhao; Huizheng Che; Xiaoye Zhang; Yanjun Ma; Yangfeng Wang; Xuxin Wang; Chuang Liu; Bo Hou; Haochi Che (270-278).
The special and temporal characteristics of aerosol optical depth (AOD) and Angstrom exponent (Alpha) were analyzed by using the data from a CE318 sun-photometer at Shenyang, Anshan, Benxi and Fushun in urban and industrial region of northeastern China. The high AODs over Shenyang and Fushun occurred in the summer and winter with two peaks. In contrast, the monthly averaged AODs at Anshan and Benxi have a single peak distribution. The AOD frequency distribution at Shenyang and Benxi can be well fit by a bi-modal normal distribution with r 2 = 0.94 and 0.91. The AOD frequency distribution at Anshan and Fushun have identical peak value at approximately 0.40. The seasonal AOD at Benxi is larger than the other three stations, and the seasonal Alpha at Shenyang is the largest of all stations followed by Anshan, Fushun and Benxi. An analysis of the AOD and Alpha scatterplots suggests that the aerosol size in Shenyang, Anshan, Benxi and Fushun can be affected by both fine and coarse particles.
Keywords: Aerosol optical depth; Angstrom exponent; Sun-photometer; Northeast China;
Chemical characterization of polar organic markers in aerosols in a local area around Bologna, Italy by Maria Chiara Pietrogrande; Dimitri Bacco; Mauro Rossi (279-286).
The composition and seasonal variations of water-soluble organic compounds, including 18 dicarboxylic acids and 7 sugars, were determined in the atmospheric aerosol in the surroundings of Bologna, Northern Italy, during intensive summer and winter campaigns.In both seasons the most abundant compound is levoglucosan, as the major by-product from biomass burning. The abundances of dicarboxylic acids exhibit a seasonal pattern with higher winter concentrations (mean total concentrations are 60 ng m−3 and 23 ng m−3, in winter and summer, respectively). The distribution profiles and the diagnostic ratios of these markers allowed to estimate the contribution of primary emission sources (power plants, vehicular circulation, biomass burning) associated with secondary constituents from both biogenic and anthropogenic precursors. The distinct seasonal pattern of abundances suggests, overall, the dominant role of secondary formation of particulate organics in summer, and the highest strength of primary emissions in winter.
Keywords: Dicarboxylic acids and sugars; Water-soluble organic compounds; Atmospheric aerosol; Waste incineration impact; Regional area;
Contribution of the Middle Eastern dust source areas to PM10 levels in urban receptors: Case study of Tehran, Iran by Raheleh Givehchi; Mohammad Arhami; Massoud Tajrishy (287-295).
The origins and evolution of the Middle Eastern dust storms which frequently impact the residents of this arid region were studied. A methodology was adapted and developed to identify the desert regions of potential dust sources and determine their contributions to PM10 concentrations in the highly-populated receptor city of Tehran, Iran. Initially, the episodes of regional dust intrusion and the resulting amounts of increase in the particulate concentrations during these episodes were determined using a statistical analyzing methodology. The dust episodes were also inspected with the aerosol index information from the Ozone Monitoring Instrument (OMI). The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used as the main tool to determine the proportions of dust originating from different deserts during the dusty episodes of 2009–2010.Daily 5-day back trajectories were obtained from the receptor stations during the dust outbreaks in order to find and confirm the location of potential sources. After the boundaries of the potential sources were determined by 5-day backward trajectories, this region was divided into different areas to quantify their contributions to the measured PM10 levels. The proximity between the measured and simulated data confirmed the ability of HYSPLIT in modeling the Middle Eastern dust intrusion and estimating the particulate concentration in the downwind receptor sites. Results showed that the deserts in Iraq and Syria are the main contributing dust sources which comprise more than 90% of the dust related PM10 concentrations in Tehran, during the studied dust episodes. The sources in northern Iraq and eastern Syria respectively represented 44% and 32% contributions on average.
Keywords: PM10; Dust sources; HYSPLIT; Source apportionment; Middle Eastern dust; Tehran;
Elemental characterization of the airborne pollen surface using Electron Probe Microanalysis (EPMA) by Laura Duque; Fernanda Guimarães; Helena Ribeiro; Raquel Sousa; Ilda Abreu (296-302).
Recent worldwide increase in pollinoses has been attributed to the synergy between pollen and pollutants. We used EPMA for the elemental characterization of the airborne pollen surface in order to find out what occurs to the wall of pollen grains when they are together with other atmospheric pollutants. Analyses were performed both to airborne pollen and to pollen that was collected from Acer spp., Platanus spp. and Pinus spp. trees. Airborne samples were assembled using a Hirst-type volumetric spore sampler set in the coastal city of Porto, Portugal. Airborne pollen samples showed major elemental differences when compared to the control pollen sample of the same species, namely in the amounts of Cl, Na and Mg, which very significantly increased on airborne samples, revealing an important influence of the ocean. Mineral dust also contributed to modify the pollen surface, by increasing Si contents on Acer spp. and Platanus spp. airborne pollen. Our results revealed consistent positive effects of the relative humidity and the precipitation in the increase of Cl, Na and Mg relative amounts on the pollen surface. This study shows that pollen grains have the ability to adsorb and/or absorb other materials, which may contribute to enhance pollen's harmful effects on people's health.
Keywords: EPMA; Pollen wall; Elemental characterization; Atmospheric pollution; Aerosol components; Airborne pollen;
Observations of interference between portable particle counters and NO x monitors by Sarah D. Bereznicki; Ali Kamal (303-307).
Studies in environmental exposure science have developed a preference for smaller devices that can be easily co-located without need for gas standards, such as those instruments utilized in the Near-road Exposures and Effects from Urban Air Pollutants Study (NEXUS). One observation from NEXUS was the potential for instrument interference from alcohol-based particle counters on photometric-based nitrogen oxide (NO x ) monitors. This article reports the findings from laboratory tests replicating enclosed-shelter monitoring configurations and operation cycles for a common photometric-based NO x monitor and a widely used alcohol-based particle counter. These tests monitored the NO x response while the particle counter sampling interval and ambient airflow rate were varied to (1) confirm that proximity between the instruments induced interferences, (2) identify any dependencies in NO x monitor recovery on ambient airflow, and (3) determine the time needed for the NO x monitor to recover to pre-interference levels under different atmospheric conditions. During particle counter operations, NO x concentrations responded instantaneously with a several-fold jump above the measurement baseline. When the particle counter was operated for more than 10 min, this interference period also showed a marked decline in the NO x baseline. The overall recovery time of the NO x monitor depended less on the time of particle counter operation, and more on the speed of ambient airflow. If photometric-based NO x monitors need to be operated alongside alcohol-based particle counters, mechanisms must be employed to exhaust alcohol-based vapors from enclosed monitoring environments. Given the strong evidence for interference, however, it is recommended these devices not be operated within close proximity to one another.
Keywords: Interference; Particle counter; NO x monitor;
Functional group composition of organic aerosol from combustion emissions and secondary processes at two contrasted urban environments by Imad El Haddad; Nicolas Marchand; Barbara D'Anna; Jean Luc Jaffrezo; Henri Wortham (308-320).
The quantification of major functional groups in atmospheric organic aerosol (OA) provides a constraint on the types of compounds emitted and formed in atmospheric conditions. This paper presents functional group composition of organic aerosol from two contrasted urban environments: Marseille during summer and Grenoble during winter. Functional groups were determined using a tandem mass spectrometry approach, enabling the quantification of carboxylic (RCOOH), carbonyl (RCOR′), and nitro (RNO2) functional groups. Using a multiple regression analysis, absolute concentrations of functional groups were combined with those of organic carbon derived from different sources in order to infer the functional group contents of different organic aerosol fractions. These fractions include fossil fuel combustion emissions, biomass burning emissions and secondary organic aerosol (SOA). Results clearly highlight the differences between functional group fingerprints of primary and secondary OA fractions. OA emitted from primary sources is found to be moderately functionalized, as about 20 carbons per 1000 bear one of the functional groups determined here, whereas SOA is much more functionalized, as in average 94 carbons per 1000 bear a functional group under study. Aging processes appear to increase both RCOOH and RCOR′ functional group contents by nearly one order of magnitude. Conversely, RNO2 content is found to decrease with photochemical processes. Finally, our results also suggest that other functional groups significantly contribute to biomass smoke and SOA. In particular, for SOA, the overall oxygen content, assessed using aerosol mass spectrometer measurements by an O:C ratio of 0.63, is significantly higher than the apparent O:C* ratio of 0.17 estimated based on functional groups measured here. A thorough examination of our data suggests that this remaining unexplained oxygen content can be most probably assigned to alcohol (ROH), organic peroxides (ROOH), organonitrates (RONO2) and/or organosulfates (ROSO3H).
Keywords: Oxygenated functional groups; Primary organic aerosol; Secondary organic aerosol; Photochemical aging; Van Krevelen diagram;
Intercomparison of the capabilities of simplified climate models to project the effects of aviation CO2 on climate by Arezoo Khodayari; Donald J. Wuebbles; Seth C. Olsen; Jan S. Fuglestvedt; Terje Berntsen; Marianne T. Lund; Ian Waitz; Philip Wolfe; Piers M. Forster; Malte Meinshausen; David S. Lee; Ling L. Lim (321-328).
This study evaluates the capabilities of the carbon cycle and energy balance treatments relative to the effect of aviation CO2 emissions on climate in several existing simplified climate models (SCMs) that are either being used or could be used for evaluating the effects of aviation on climate. Since these models are used in policy-related analyses, it is important that the capabilities of such models represent the state of understanding of the science. We compare the Aviation Environmental Portfolio Management Tool (APMT) Impacts climate model, two models used at the Center for International Climate and Environmental Research-Oslo (CICERO-1 and CICERO-2), the Integrated Science Assessment Model (ISAM) model as described in Jain et al. (1994), the simple Linear Climate response model (LinClim) and the Model for the Assessment of Greenhouse-gas Induced Climate Change version 6 (MAGICC6). In this paper we select scenarios to illustrate the behavior of the carbon cycle and energy balance models in these SCMs. This study is not intended to determine the absolute and likely range of the expected climate response in these models but to highlight specific features in model representations of the carbon cycle and energy balance models that need to be carefully considered in studies of aviation effects on climate. These results suggest that carbon cycle models that use linear impulse-response-functions (IRF) in combination with separate equations describing air–sea and air–biosphere exchange of CO2 can account for the dominant nonlinearities in the climate system that would otherwise not have been captured with an IRF alone, and hence, produce a close representation of more complex carbon cycle models. Moreover, results suggest that an energy balance model with a 2-box ocean sub-model and IRF tuned to reproduce the response of coupled Earth system models produces a close representation of the globally-averaged temperature response of more complex energy balance models.
Keywords: Climate change; Simple climate models; Carbon cycle; Energy balance model;
Impact of sea-salt emissions on the model performance and aerosol chemical composition and deposition in the East Mediterranean coastal regions by Ulas Im (329-340).
East Mediterranean region is often exposed to significant levels of particulate matter (PM), partly due to the natural emission sources surrounding the area. The complex coastal geography together with the high water coverage of the area implies important contribution of sea-salt aerosols (SSA) to the PM levels and composition. WRF-CMAQ air quality modeling system has been employed to simulate and quantify the impacts of SSA emissions on the model performance in the region. The results show up to one order of magnitude higher SSA emissions when surf-zone emissions are added. 10–20% improvements are calculated in terms of model discrepancies of PM10 mass with regards to the observations. SSA related particles (sodium (Na+) and chloride (Cl−)) are more realistically represented. The total nitrate (NO3 −) partitioning ratio increases substantially up to 0.5 on average when SSA emissions are inserted to the model, leading to nitric acid (HNO3) levels decrease by more than 40% and total NO3 − aerosols increase by more than an order of magnitude over the source areas. Adding surf-zone emissions over those from open-ocean increase PM10 deposition by up to 11% and wet deposition by around 1%. The results suggest that coastal areas are important sources of SSA emissions and can significantly alter the PM levels and composition in their vicinities.
Keywords: Sea-salt; Surf-zone; Particulate matter; East Mediterranean; CMAQ model;
Differences in 24-h average PM2.5 concentrations between the beta attenuation monitor (BAM) and the dichotomous sampler (Dichot) by Chun-Nan Liu; Amit Awasthi; Yi-Hung Hung; Balakrishnaiah Gugamsetty; Chuen-Jinn Tsai; Yueh-Chuen Wu; Chung-Fang Chen (341-347).
In this study, PM2.5 concentrations were measured simultaneously by a Dichotomous sampler (Dichot, Model SA241, Andersen Inc., Georgia, USA) (PM2.5,D) and a beta attenuation monitor (BAM) (PM2.5,B) at each of three air monitoring stations in Taiwan. Results show that PM2.5,B concentrations measured by the VEREWA-F701 BAM (without federal equivalent method (FEM) designation) are consistently higher than PM2.5,D concentrations by 58.4 ± 37.4% at Jhongshan station, while less overestimation exists at Sinjhuang and Judong stations, which is 29.8 ± 20.2 and 28.4 ± 19.0%, respectively, where the earlier version of the Met-One BAM-1020s (without FEM designation) are used. Different factors influencing the overestimation, which include aerosol water content, volatilization of inorganic species and positive artifacts due to acid gas adsorption by the glass fiber filter tapes were studied for the BAM-1020. Results show that the overestimation is mainly caused by the positive artifacts due to acid gas adsorption by the glass fiber filter tapes used in the BAM-1020. Aerosol water content and volatilization loss of inorganic semi-volatile species are found to be less important to the overestimation.
Keywords: Beta attenuation monitor; Dichotomous sampler; PM2.5 sampling artifacts; Glass fiber filter;
Intensive measurements of gas, water, and energy exchange between vegetation and troposphere during the MONTES campaign in a vegetation gradient from short semi-desertic shrublands to tall wet temperate forests in the NW Mediterranean Basin by J. Peñuelas; A. Guenther; F. Rapparini; J. Llusia; I. Filella; R. Seco; M. Estiarte; M. Mejia-Chang; R. Ogaya; J. Ibañez; J. Sardans; L.M. Castaño; A. Turnipseed; T. Duhl; P. Harley; J. Vila; J.M. Estavillo; S. Menéndez; O. Facini; R. Baraldi; C. Geron; J. Mak; E.G. Patton; X. Jiang; J. Greenberg (348-364).
MONTES (“Woodlands”) was a multidisciplinary international field campaign aimed at measuring energy, water and especially gas exchange between vegetation and atmosphere in a gradient from short semi-desertic shrublands to tall wet temperate forests in NE Spain in the North Western Mediterranean Basin (WMB). The measurements were performed at a semidesertic area (Monegros), at a coastal Mediterranean shrubland area (Garraf), at a typical Mediterranean holm oak forest area (Prades) and at a wet temperate beech forest (Montseny) during spring (April 2010) under optimal plant physiological conditions in driest-warmest sites and during summer (July 2010) with drought and heat stresses in the driest–warmest sites and optimal conditions in the wettest–coolest site. The objective of this campaign was to study the differences in gas, water and energy exchange occurring at different vegetation coverages and biomasses. Particular attention was devoted to quantitatively understand the exchange of biogenic volatile organic compounds (BVOCs) because of their biological and environmental effects in the WMB. A wide range of instruments (GC–MS, PTR-MS, meteorological sensors, O3 monitors,…) and vertical platforms such as masts, tethered balloons and aircraft were used to characterize the gas, water and energy exchange at increasing footprint areas by measuring vertical profiles. In this paper we provide an overview of the MONTES campaign: the objectives, the characterization of the biomass and gas, water and energy exchange in the 4 sites-areas using satellite data, the estimation of isoprene and monoterpene emissions using MEGAN model, the measurements performed and the first results. The isoprene and monoterpene emission rates estimated with MEGAN and emission factors measured at the foliar level for the dominant species ranged from about 0 to 0.2 mg m−2 h−1 in April. The warmer temperature in July resulted in higher model estimates from about 0 to ca. 1.6 mg m−2 h−1 for isoprene and ca. 4.5 mg m−2 h−1 for monoterpenes, depending on the site vegetation and footprint area considered. There were clear daily and seasonal patterns with higher emission rates and mixing ratios at midday and summer relative to early morning and early spring. There was a significant trend in CO2 fixation (from 1 to 10 mg C m−2 d−1), transpiration (from 1–5 kg C m−2 d−1), and sensible and latent heat from the warmest–driest to the coolest–wettest site. The results showed the strong land-cover-specific influence on emissions of BVOCs, gas, energy and water exchange, and therefore demonstrate the potential for feed-back to atmospheric chemistry and climate.
Keywords: Vegetation; LAI; Green biomass; NDVI; Land cover; MEGAN; Latent heat; Sensible heat; Evapotranspiration; Isoprene; Monoterpenes; VOCs; CO2; N2O; CH4; O3; Vertical profiles; Tethered balloons; Aircraft; Masts; Boundary layer;
Comprehensive chemical characterisation of size-segregated PM10 in Dresden and estimation of changes due to global warming by Sebastian Scheinhardt; Gerald Spindler; Silvia Leise; Konrad Müller; Yoshiteru Iinuma; Frank Zimmermann; Jörg Matschullat; Hartmut Herrmann (365-373).
To identify current and future human health risks from urban air pollution, size-segregated particle samples were collected under various seasonal and meteorological conditions in Dresden, Germany. Sampling days were grouped into twelve categories depending on season, air mass origin and temperature. A comprehensive chemical characterisation and mass closure were performed. The particulate matter (PM) mass concentration and composition were shown to be highly dependent on these categories. The highest PM mass concentrations were found on cold winter days, mainly due to compounds of anthropogenic origin. The current annual mean PM mass concentration and composition were calculated using the occurrence frequencies of the categories (weighted mean).Information about future changes of the occurrence frequencies of the categories was deduced from climate models. Assuming that PM concentration and composition within a given category do not change, the annual mean PM mass concentration and composition were calculated for two scenarios (weighted mean, 2071–2100). As a result, it was found that the annual mean PM mass concentration is likely to decrease slightly by 2100, mainly due to a decrease of sulphate and soot mass concentrations. Generally, chemicals originating from anthropogenic emissions (PAHs, trace metals) are estimated to decrease. However, it is concluded that emission reduction measures are still necessary to control urban air quality including PM even if climate change will lead to a certain reduction in PM.
Keywords: Climate change; Particulate matter (PM); Urban aerosol; Central Europe; Berner impactor; CPI;
Sensitivity of surface ozone over China to 2000–2050 global changes of climate and emissions by Yuxuan Wang; Lulu Shen; Shiliang Wu; Loretta Mickley; Jingwei He; Jiming Hao (374-382).
We use a global chemical transport model (GEOS-Chem) driven by the GISS GCM to investigate the effect on China's surface ozone from 2000 to 2050 global changes in climate and anthropogenic emissions as projected by the IPCC A1B scenario, with a focus on the different response between East and West China where present-day anthropogenic emissions, natural conditions, and ozone source attributions differ significantly. Over East China, climate change will increase both surface ozone and the possibility of high ozone episodes, implying a significant ‘climate change penalty’ that can be attributed mainly to increasing biogenic emissions of volatile organic compounds (VOCs). Over West China on the other hand, climate change will decrease mean surface ozone as a result of an increased ozone destruction rate in low-NO x regimes, assuming constant stratosphere–troposphere exchange (STE) of ozone. Chinese emissions change in 2050 will enlarge the East–West ozone difference in China, but emissions change from the rest of the world (excluding China) will decrease it. Driven by climate change and emissions change in combination, nation-mean surface ozone will increase, whereas East–West ozone contrast will decrease. In the future climate, the sensitivity of surface ozone to a given change in Chinese emissions will decrease over West China due to the accelerated ozone destruction rate and reduced transport from East China, but increase over East China as a result of the coupling effect between anthropogenic NO x and biogenic VOCs. The latter result suggests that the emission controls over East China need to be more aggressive in future climate.
Keywords: Climate change; Ozone; China; Emissions;
A regionalized national universal kriging model using Partial Least Squares regression for estimating annual PM2.5 concentrations in epidemiology by Paul D. Sampson; Mark Richards; Adam A. Szpiro; Silas Bergen; Lianne Sheppard; Timothy V. Larson; Joel D. Kaufman (383-392).
Many cohort studies in environmental epidemiology require accurate modeling and prediction of fine scale spatial variation in ambient air quality across the U.S. This modeling requires the use of small spatial scale geographic or “land use” regression covariates and some degree of spatial smoothing. Furthermore, the details of the prediction of air quality by land use regression and the spatial variation in ambient air quality not explained by this regression should be allowed to vary across the continent due to the large scale heterogeneity in topography, climate, and sources of air pollution. This paper introduces a regionalized national universal kriging model for annual average fine particulate matter (PM2.5) monitoring data across the U.S. To take full advantage of an extensive database of land use covariates we chose to use the method of Partial Least Squares, rather than variable selection, for the regression component of the model (the “universal” in “universal kriging”) with regression coefficients and residual variogram models allowed to vary across three regions defined as West Coast, Mountain West, and East. We demonstrate a very high level of cross-validated accuracy of prediction with an overall R 2 of 0.88 and well-calibrated predictive intervals. In accord with the spatially varying characteristics of PM2.5 on a national scale and differing kriging smoothness parameters, the accuracy of the prediction varies by region with predictive intervals being notably wider in the West Coast and Mountain West in contrast to the East.Display Omitted
Keywords: Ambient air quality; Land use regression; National air quality model; Partial Least Squares; Particulate matter; Universal kriging;