Atmospheric Environment (v.102, #C)
Haagen-Smit Prize 2014 (A1).
Editorial board (i).
Natural organic matter in urban aerosols: Comparison between water and alkaline soluble components using excitation–emission matrix fluorescence spectroscopy and multiway data analysis by João T.V. Matos; Sandra M.S.C. Freire; Regina M.B.O. Duarte; Armando C. Duarte (1-10).
Understanding the complexity of Natural Organic Matter (NOM) in atmospheric aerosols has remained an important goal for the atmospheric research community. This work employs a Parallel Factor Model (PARAFAC) with Alternating Least Squares (ALS) algorithm to decompose and further compare sets of excitation-emission matrices fluorescence spectra of Water-soluble and Alkaline-soluble Organic Matter (WSOM and ASOM, respectively), sequentially extracted from urban aerosols collected during different seasons. The PARAFAC-ALS modelling identified three components in both WSOM and ASOM, whose maximum intensities follow a clear seasonal trend and which are likely to represent the dominant fluorescent moieties in NOM from urban aerosols. The PARAFAC-ALS modelling also indicated differences between the colder and warmer seasons in the fluorescence map of one WSOM component, which contrast with the results obtained for the ASOM, where the fluorescence signatures were found to be constant along the seasons, suggesting that the ASOM may have an in situ origin.Display Omitted
Keywords: Water-soluble organic matter; Alkaline-soluble organic matter; Atmospheric aerosols; Fluorescence spectroscopy; Emission–excitation matrix; PARAFAC-ALS;
Sensitivity of population smoke exposure to fire locations in Equatorial Asia by Patrick S. Kim; Daniel J. Jacob; Loretta J. Mickley; Shannon N. Koplitz; Miriam E. Marlier; Ruth S. DeFries; Samuel S. Myers; Boon Ning Chew; Yuhao H. Mao (11-17).
High smoke concentrations in Equatorial Asia, primarily from land conversion to oil palm plantations, affect a densely populated region and represent a serious but poorly quantified air quality concern. Continued expansion of the oil palm industry is expected but the resulting population exposure to smoke is highly dependent on where this expansion takes place. We use the adjoint of the GEOS-Chem chemical transport model to map the sensitivity of smoke concentrations in major Equatorial Asian cities, and for the population-weighted region, to the locations of the fires. We find that fires in southern Sumatra are particularly detrimental, and that a land management policy protecting peatswamp forests in Southeast Sumatra would be of great air quality benefit. Our adjoint sensitivities can be used to immediately infer population exposure to smoke for any future fire emission scenario.
Keywords: Equatorial Asia; Adjoint; Palm oil; Fire; Conservation; Population-exposure;
Frequent nucleation events at the high altitude station of Chacaltaya (5240 m a.s.l.), Bolivia by C. Rose; K. Sellegri; F. Velarde; I. Moreno; M. Ramonet; K. Weinhold; R. Krejci; Patrick Ginot; M. Andrade; A. Wiedensohler; P. Laj (18-29).
While nucleation may represent one of the major processes responsible for the total aerosol number burden in the atmosphere, and especially at high altitude, new particle formation (NPF) events occurring in the upper part of the troposphere are poorly documented in the literature, particularly in the southern hemisphere. NPF events were detected and analyzed at the highest measurement site in the world, Chacaltaya (5240 m a.s.l.), Bolivia between January 1 and December 31 2012, using a Neutral Aerosol and Ion Spectrometer (NAIS) that detects clusters down to 0.4 nm. NPF frequency at Chacaltaya is one of the highest reported so far (63.9%) and shows a clear seasonal dependency with maximum up to 100% during the dry season. This high seasonality of the NPF events frequency was found to be likely linked to the presence of clouds in the vicinity of the station during the wet season. Multiple NPF events are seen on almost 50% of event days and can reach up to 6 events per day, increasing the potential of nucleation to be the major contributor to the particle number concentrations in the upper troposphere. Ion-induced nucleation (IIN) was 14.8% on average, which is higher than the IIN fractions reported for boundary layer stations. The median formation rate of 2 nm particles computed for first position events is increased during the dry season (1.90 cm−3 s−1) compared to the wet season (1.02 cm− 3 s−1), showing that events are more intense, on top of being more frequent during the dry season. On the contrary, particle growth rates (GRs) are on average enhanced during the wet season, which could be explained by higher amount of biogenic volatile organic compounds transported from the Amazon rainforest. The NPF events frequency is clearly enhanced when air masses originate from the oceanic sector, with a frequency of occurrence close to 1. However, based on the particle GRs, we calculate that particles most likely nucleate after the oceanic air masses reach the land and are presumably not originating from the marine free troposphere. The high frequency of NPF events, the occurrence of multiple events per day, and the relatively high formation rates observed at Chacaltaya imply that nucleation and growth are likely to be the major mechanism feeding the upper atmosphere with aerosol particles in this part of the continent.
Keywords: Aerosols; Nucleation; High altitude;
Modeling of 1,3-butadiene in urban and industrial areas by Beata H. Czader; Bernhard Rappenglück (30-42).
1,3-butadiene is an important pollutant in terms of public health and important driver for photochemical processes influencing ozone formation in the area of Houston. Ambient levels of 1,3-butadiene were simulated with the Community Multiscale Air Quality model (CMAQ) including the SAPRC99-extended mechanism and the results were compared to spatially and temporally resolved observations of 1,3-butadiene for an episodic period during Summer 2006. Relative contributions of different type of emissions and chemical reactions to 1,3-butadiene concentrations were examined, the highest contribution was found to be from industrial emission sources. 1,3-butadiene mixing ratios in the urban area were found to be lower than in the industrial area. Although emissions of 1,3-butadiene peak during daytime its mixing ratios are lower during daytimes as compared to nighttime. 1,3-butadiene is removed from the surface through vertical upward transport (∼90%) and chemical reactions (∼10%). During daytime 1,3-butadiene reacts mainly with the OH radical (90%), during nighttime this reaction pathway is still significant in the industrial area (57% of all reaction pathways). Reaction with NO3 during nighttime contributes 33% in industrial and 56% in urban areas, where high NO x emissions occur. Reaction with ozone contributes 10% and 13% in industrial and urban areas, respectively. Analysis of measured data revealed that episodically very high emissions spikes of 1,3-butadiene occur. CMAQ often underpredicts 1,3-butadiene mixing ratios when sites are exposed to sporadic releases from industrial facilities. These releases are not accounted for in the emission inventory. It also appears that emissions of 1,3-butadiene from point sources have much more variability than those listed in the emission inventory.
Keywords: 1,3-Butadiene; CMAQ; Reaction pathways; Emission inventory; TexAQS 2006; Houston;
Aqueous-phase oxidation of green leaf volatiles by hydroxyl radical as a source of SOA: Product identification from methyl jasmonate and methyl salicylate oxidation by Amie K. Hansel; Franz S. Ehrenhauser; Nicole K. Richards-Henderson; Cort Anastasio; Kalliat T. Valsaraj (43-51).
Green leaf volatiles (GLVs) are a group of biogenic volatile organic compounds (BVOCs) released into the atmosphere by vegetation. BVOCs produce secondary organic aerosol (SOA) via gas-phase reactions, but little is known of their aqueous-phase oxidation as a source of SOA. GLVs can partition into atmospheric water phases, e.g., fog, mist, dew or rain, and be oxidized by hydroxyl radicals (˙OH). These reactions in the liquid phase also lead to products that have higher molecular weights, increased polarity, and lower vapor pressures, ultimately forming SOA after evaporation of the droplet. To examine this process, we investigated the aqueous, ˙OH-mediated oxidation of methyl jasmonate (MeJa) and methyl salicylate (MeSa), two GLVs that produce aqueous-phase SOA. High performance liquid chromatography/electrospray ionization mass spectrometry (HPLC-ESI-MS) was used to monitor product formation. The oxidation products identified exhibit higher molecular mass than their parent GLV due to either dimerization or the addition of oxygen and hydroxyl functional groups. The proposed structures of potential products are based on mechanistic considerations combined with the HPLC/ESI-MS data. Based on the structures, the vapor pressure and the Henry's law constant were estimated with multiple methods (SPARC, SIMPOL, MPBPVP, Bond and Group Estimations). The estimated vapor pressures of the products identified are significantly (up to 7 orders of magnitude) lower than those of the associated parent compounds, and therefore, the GLV oxidation products may remain as SOA after evaporation of the water droplet. The contribution of the identified oxidation products to SOA formation is estimated based on measured HPLC-ESI/MS responses relative to previous aqueous SOA mass yield measurements.
Keywords: Green leaf volatile; Methyl jasmonate; Methyl salicylate; Photochemical oxidation; Hydroxyl radical;
Modeling regional secondary organic aerosol using the Master Chemical Mechanism by Jingyi Li; Meredith Cleveland; Luke D. Ziemba; Robert J. Griffin; Kelley C. Barsanti; James F. Pankow; Qi Ying (52-61).
A modified near-explicit Master Chemical Mechanism (MCM, version 3.2) with 5727 species and 16,930 reactions and an equilibrium partitioning module was incorporated into the Community Air Quality Model (CMAQ) to predict the regional concentrations of secondary organic aerosol (SOA) from volatile organic compounds (VOCs) in the eastern United States (US). In addition to the semi-volatile SOA from equilibrium partitioning, reactive surface uptake processes were used to simulate SOA formation due to isoprene epoxydiol, glyoxal and methylglyoxal. The CMAQ-MCM-SOA model was applied to simulate SOA formation during a two-week episode from August 28 to September 7, 2006. The southeastern US has the highest SOA, with a maximum episode-averaged concentration of ∼12 μg m−3. Primary organic aerosol (POA) and SOA concentrations predicted by CMAQ-MCM-SOA agree well with AMS-derived hydrocarbon-like organic aerosol (HOA) and oxygenated organic aerosol (OOA) urban concentrations at the Moody Tower at the University of Houston. Predicted molecular properties of SOA (O/C, H/C, N/C and OM/OC ratios) at the site are similar to those reported in other urban areas, and O/C values agree with measured O/C at the same site. Isoprene epoxydiol is predicted to be the largest contributor to total SOA concentration in the southeast US, followed by methylglyoxal and glyoxal. The semi-volatile SOA components are dominated by products from β-caryophyllene oxidation, but the major species and their concentrations are sensitive to errors in saturation vapor pressure estimation. A uniform decrease of saturation vapor pressure by a factor of 100 for all condensable compounds can lead to a 150% increase in total SOA. A sensitivity simulation with UNIFAC-calculated activity coefficients (ignoring phase separation and water molecule partitioning into the organic phase) led to a 10% change in the predicted semi-volatile SOA concentrations.
Keywords: MCMv3.2; CMAQ model; Isoprene epoxydiol; Glyoxal; Surface reactive uptake;
Temporal and spatial variation of the metal-related oxidative potential of PM2.5 and its relation to PM2.5 mass and elemental composition by Aileen Yang; Bryan Hellack; Daan Leseman; Bert Brunekreef; Thomas A.J. Kuhlbusch; Flemming R. Cassee; Gerard Hoek; Nicole A.H. Janssen (62-69).
Oxidative potential (OP) of particulate matter (PM) has been proposed as a more health relevant metric than PM mass. However, little is known about the temporal and spatial variation of OP, which is crucial if OP were to be used as an exposure metric in epidemiological studies. We studied OP on routinely collected PM2.5 samples (every 6th day) from three regional, five urban background, and three street sites over a one-year period across the Netherlands. OP was measured as the ability to generate hydroxyl radicals in the presence of hydrogen peroxide using the electron spin resonance (OPESR).OPESR correlated poorly with PM2.5 mass both spatially (Spearman's r s = 0.29) and temporally (median r s = 0.34). The temporal correlations across sites for OPESR were moderate (median r s = 0.50) compared to PM2.5 (median r s = 0.87), suggesting that exposure misclassification is higher when using OPESR as an exposure metric in time series studies. Street/urban background and street/regional background ratios for OPESR were 1.4 and 2.4 respectively; higher than for PM2.5 (ratio of 1.1 for both street/urban background and street/regional background).This large scale, nationwide study found that PM2.5 correlated poorly with OPESR in space and time. Spatial contrasts were much larger for OPESR than for PM2.5, which offers the possibility to use OPESR to assess long-term exposure health effects.
Keywords: Oxidative potential; ESR; Spatial variation; Temporal variation; Particulate matter; Metal composition;
Below-cloud scavenging of aerosol particles by precipitation in a typical valley city, northwestern China by Suping Zhao; Ye Yu; Jianjun He; Daiying Yin; Bo Wang (70-78).
To fill the blank information for aerosol precipitation-scavenging research in north-west of China, the aerosol particle and raindrop size distributions were measured simultaneously during 1 September 2012 to 31 August 2013 in urban Lanzhou. The scavenging coefficients of thunderstorm and non-thunderstorm rain and snow events were studied and presented on the basis of nine selected precipitation cases including 3 snow and 6 rain events. The variation of scavenging coefficients of snowfall across the size distribution clearly exhibited a trough of lower values for particles of 1000 nm–2000 nm in diameter, while the particles smaller than 500 nm were scavenged efficiently by non-thunderstorm rain, and thunderstorm rain more effectively scavenged the particles in 500–1000 nm. The snow scavenging coefficients varied between 3.11 × 10−7 s−1 and 1.18 × 10−3 s−1 in the 10–10,000 nm size range. The scavenging coefficients of thunderstorm (non-thunderstorm) rain were between 8.25 × 10−7 s−1 (7.48 × 10−6 s−1) and 1.23 × 10−3 s−1 (7.46 × 10−4 s−1). Additionally, the number of particles in 10–50 nm was more sensitive to duration of snow, while snowfall intensity was more responsible for particle number concentrations in 50–100 nm and 100–1000 nm. The longer period of precipitation with lower raindrop velocity can more effectively scavenge the particles in the size range of 10–50 nm.
Keywords: Scavenging; Particles; Precipitation; Valley city;
Effect of gasoline/methanol blends on motorcycle emissions: Exhaust and evaporative emissions by Lan Li; Yunshan Ge; Mingda Wang; Jiaqiang Li; Zihang Peng; Yanan Song; Liwei Zhang (79-85).
The emission characteristics of motorcycles using gasoline and M15 (consisting of 85% gasoline and 15% methanol by volume) were investigated in this article. Exhaust and evaporative emissions, including regulated and unregulated emissions, of three motorcycles were investigated on the chassis dynamometer over the Urban Driving Cycle (UDC) and in the Sealed Housing for Evaporative Determination (SHED), respectively. The regulated emissions were detected by an exhaust gas analyzer directly. The unregulated emissions, including carbonyls, volatile organic compounds (VOCs) and methanol, were sampled through battery-operated air pumps using tubes coated with 2,4-dintrophenylhydrazine (DNPH), Tenax TA and silica gel, respectively. The experimental results showed that, for exhaust emission, compared with those from gasoline fueled motorcycles, the concentration of total hydrocarbons (THC) and CO from motorcycles fueled with M15 decreased by 11%–34.5% and 63%–84% respectively, while the concentration of NO x increased by 76.9%–107.7%. Compared with those from gasoline fueled motorcycles, BTEX from motorcycles fueled with M15 decreased by 16%–60% while formaldehyde increased by 16.4%–52.5%. For evaporative emission, diurnal losses were more than hot soak losses and turned out to be dominated in evaporative emissions. In addition, compared with gasoline fueling motorcycles, the evaporative emissions of THC, carbonyls and VOCs from motorcycles fueled with M15 increased by 11.7%–37%, 38%–45% and 16%–42%, respectively. It should be noted that the growth rate of methanol was as high as 297%–1429%. It is important to reduce the evaporative emissions of methanol fueling motorcycles.
Keywords: Motorcycle; Exhaust emission; Evaporative emission; VOCs; Carbonyls;
New particle formation events arising from painting materials in an indoor microenvironment by Mihalis Lazaridis; Norbert Serfozo; Sofia Eirini Chatoutsidou; Thodoros Glytsos (86-95).
Particulate matter (PM) number size distribution and mass concentration along with total volatile organic compounds (TVOC) were measured during emissions from painting materials inside an indoor microenvironment. The emission sources were derived from oil painting medium and turpentine used for painting. Two sets of measurements (10 experiments) were conducted in a laboratory room of 54 m3. New particle formation events were observed in all 10 experiments. The nucleation events lasted on average less than one hour with an average growth rate 33.9 ± 9.1 nm/h and average formation rate 21.1 ± 8.7 cm−3s−1. After the end of the nucleation event, a condensational growth of indoor particles followed with average growth rate 11.6 ± 2.8 nm/h and duration between 1.4 and 4.1 h. High concentrations up to 3.24 ppm were measured for the indoor TVOC concentrations during the experiments. Simultaneous mass and number size concentration measurements were performed outdoors where no new particle formation event was observed. It is the first time that high nucleation rates indoors were observed in conjunction with high TVOC concentrations originating from painting materials which resulted to high exposure concentration levels of particle number concentration.
Keywords: Aerosol growth; New particle formation; Indoor particle emissions; Paint emissions;
Imputation of missing data in time series for air pollutants by W.L. Junger; A. Ponce de Leon (96-104).
Missing data are major concerns in epidemiological studies of the health effects of environmental air pollutants. This article presents an imputation-based method that is suitable for multivariate time series data, which uses the EM algorithm under the assumption of normal distribution. Different approaches are considered for filtering the temporal component. A simulation study was performed to assess validity and performance of proposed method in comparison with some frequently used methods. Simulations showed that when the amount of missing data was as low as 5%, the complete data analysis yielded satisfactory results regardless of the generating mechanism of the missing data, whereas the validity began to degenerate when the proportion of missing values exceeded 10%. The proposed imputation method exhibited good accuracy and precision in different settings with respect to the patterns of missing observations. Most of the imputations obtained valid results, even under missing not at random. The methods proposed in this study are implemented as a package called mtsdi for the statistical software system R.
Keywords: Air pollution; Data imputation; EM algorithm; Environmental epidemiology; Missing data; Particulate matter; Time series;
Particle number emission factors and volatile fraction of particles emitted from on-road gasoline direct injection passenger vehicles by A. Momenimovahed; D. Handford; M.D. Checkel; J.S. Olfert (105-111).
Particle number emission factors, and the volatility of the particles, are measured on-road for five gasoline direct injection vehicles over a wide range of operating conditions including urban and highway driving conditions. Two condensation particle counters (CPC) were used to measure nascent and non-volatile (thermodenuded) particle concentrations for transient urban and highway tests. To measure the non-volatile concentration and also the volatility of the particles, a thermodenuder was employed to remove the semi-volatile material from the aerosol sample. Rapid accelerations were also studied in more detail by measuring the particle size distributions in real-time using a differential mobility spectrometer (DMS). The ratio of semi-volatile particles to total particle number is generally higher during acceleration followed by the idle operating mode. The number emission factors (for particles larger than 2.5 nm) ranged between 5.46 × 1011–3.50 × 1012/km for freshly emitted (nascent) particles and between 2.87 × 1011–3.31 × 1012/km for non-volatile (thermodenuded) particles. More particles per kilometer are produced during acceleration compared to cruise conditions where the non-volatile particle number emission factor for acceleration is 2.3 and 1.8 times higher than vehicle cruise for urban and highway driving cycles, respectively. Particle number emission factor models are also presented in terms of particle emission rate as a function of vehicle tractive power and also as a function of vehicle specific power as defined for the US Environmental Protection Agency's MOVES model.
Keywords: Gasoline direct injection; Particle number emission factor; Emission model; Volatility;
Analysis of a severe prolonged regional haze episode in the Yangtze River Delta, China by Mengya Wang; Chunxiang Cao; Guoshuai Li; Ramesh P. Singh (112-121).
A severe prolonged regional haze episode occurred over the Yangtze River Delta (YRD) from 2 to 14 December 2013. In this paper, we have discussed the probable cause of haze episode and aerosol characteristics. Analysis of visibility and meteorological parameters suggest that the meteorological conditions play a very important role in the accumulation of aerosol particles that cause haze. The height of the planetary boundary layer (PBL) is considered as one of the key factors together with other factors in the haze formation.The Principal Component Analysis (PCA) clearly shows accumulation process of air pollutants from vehicular, industrial and anthropogenic sources are major contributors for the haze formation. The aerosol optical properties (aerosol optical depth – AOD, Ångström exponent – α and Ultra Violet Aerosol Index – UVAI) are analyzed to study the temporal and spatial variations of aerosol loadings. The results show concentrations of fine mode particles during the haze episode, the dust could have been also entered in the region from the northwestern China. Analysis of vertical aerosol profiles indicate that dust aerosols concentrated in the lower part of the haze layers.
Keywords: Visibility; PM2.5; Backscatter and depolarization ratio; Regional haze episode; Yangtze River Delta;
HFC-134a emissions from mobile air conditioning in China from 1995 to 2030 by Shenshen Su; Xuekun Fang; Li Li; Jing Wu; Jianbo Zhang; Weiguang Xu; Jianxin Hu (122-129).
Since 1995, 1,1,1,2-tetrafluoroethane (CH2FCF3, HFC-134a) has become the most important substitute of CFC-12 in mobile air conditioning (MAC) in China and MAC sector has dominated all the emissions of HFC-134a. In this study, we developed an accurate, updated and county-level inventory of the HFC-134a emissions from MAC in China for the period of 1995–2030 with an improved bottom-up method. Our estimation indicated that the total HFC-134a emissions kept growing at increase rates of ∼100% per year for 1995–2000 and ∼34% per year for 2001–2010. In 2010, HFC-134a emissions from MAC in China reached 16.7 Gg (10.5–22.7 Gg at 95% confidential interval), equivalent to 21.7 Tg CO2 (CO2-eq). Furthermore, the emissions in China estimated in this study accounted for 9.8% of global HFC-134a emissions and 29.0% of total emissions from Non-Annex_I countries in 2010. Due to the more advanced social-economic conditions and more intensive ownership of automobiles, greater HFC-134a were observed to come from big cities in East China. Under a Business-as-usual (BAU) Scenario, projected emissions will grow to 89.4 (57.9–123.9) Gg (about 75.3–161.1 Tg CO2-eq) in 2030, but under an Alternative Scenario, 88.6% of the projected emissions under BAU scenario could be curbed. Our estimation demonstrates huge emission mitigation potential of HFC-134a in China's MAC sector.
Keywords: Halocarbon; Emission inventory; Projection; China; GHGs reduction;
Influence of the physicochemical characteristics of pollutants on their uptake in moss by Z. Varela; J.A. Fernández; C. Real; A. Carballeira; J.R. Aboal (130-135).
Bryophytes are commonly used as biomonitors to estimate the atmospheric deposition of heavy metals and metalloids. However, the tissue concentrations of these elements in moss do not always accurately reflect atmospheric levels. The aim of the present study was to investigate whether element uptake in moss is affected by the physicochemical characteristics of the elements. Factor analysis was used to identify any patterns of covariance in the accumulation of elements in samples of the moss Pseudoscleropodium purum collected from the surroundings of different factories and from control sites. The variation in the concentrations of elements was similar in moss from both types of sites and was related to the binding properties of the elements. This suggests that the physicochemical characteristics of the elements determine the uptake of metals and metalloids from the atmosphere. Therefore, in studies that use multiple correlations among elements as indicators of a common origin of contaminants, erroneous conclusions may be reached by overlooking the adsorption properties of the moss.
Keywords: Biomonitoring; Factor analysis; Heavy metals; Pseudoscleropodium purum;
Partitioning of Black Carbon between ultrafine and fine particle modes in an urban airport vs. urban background environment by F. Costabile; F. Angelini; F. Barnaba; G.P. Gobbi (136-144).
In this work, we characterize the Black Carbon (BC) aerosol in an urban airport vs. urban background environment with the objective to evaluate when and how the ultrafine BC dominates the bulk aerosol. Aerosol optical and microphysical properties were measured in a Mediterranean urban area (Rome) at sites impacted by BC sources including fossil fuels (FF), and biomass burning (BB). Experimental BC data were interpreted through measurement-constrained simulations of BC microphysics and optical properties. A “scheme” to separate the ultrafine BC was experimented on the basis of the relation found between changes in the BC partitioning between Aitken and accumulation mode particles, and relevant changes in particle size distribution and optical properties of the bulk aerosol. This separation scheme, applied to experimental data, proved useful to reveal the impact of airport and road traffic emissions. Findings may have important atmospheric implications. The experimented scheme can help separating different BC sources (FF, BB, “aged” BC) when BC size distributions may be very difficult to obtain (satellite, columnar observations, routine monitoring). Indeed, separating the ultrafine BC from the fine BC may provide significant benefits in addressing BC impact on air quality and climate.
Keywords: Black carbon; Single Scattering Albedo; Ultrafine BC; Mediterranean; Urban areas; Airport;
Numerical modeling of particle generation from ozone reactions with human-worn clothing in indoor environments by Aakash C. Rai; Chao-Hsin Lin; Qingyan Chen (145-155).
Ozone-terpene reactions are important sources of indoor ultrafine particles (UFPs), a potential health hazard for human beings. Humans themselves act as possible sites for ozone-initiated particle generation through reactions with squalene (a terpene) that is present in their skin, hair, and clothing. This investigation developed a numerical model to probe particle generation from ozone reactions with clothing worn by humans. The model was based on particle generation measured in an environmental chamber as well as physical formulations of particle nucleation, condensational growth, and deposition. In five out of the six test cases, the model was able to predict particle size distributions reasonably well. The failure in the remaining case demonstrated the fundamental limitations of nucleation models. The model that was developed was used to predict particle generation under various building and airliner cabin conditions. These predictions indicate that ozone reactions with human-worn clothing could be an important source of UFPs in densely occupied classrooms and airliner cabins. Those reactions could account for about 40% of the total UFPs measured on a Boeing 737-700 flight. The model predictions at this stage are indicative and should be improved further.
Keywords: Ozone; Skin-oils; Particles; Nucleation; Condensation; Indoor environment;
Exposure and dose assessment to particle components among an elderly population by M. Almeida-Silva; S.M. Almeida; P.N. Pegas; T. Nunes; C.A. Alves; H.T. Wolterbeek (156-166).
People spend the majority of their time indoors and the composition and toxicity of indoor particles is very complex and present significant differences comparing with outdoor aerosols. Consequently, ambient particles cannot represent a real exposure. The aim of this work was to determine the daily exposure and the daily inhaled dose to particle components of elders living in Elderly Care Centers. A questionnaire was applied to 193 institutionalized elders in order to achieve their daily time pattern and to define the micro-environments where PM10 and its components (carbonaceous components and trace elements) were assessed. Daily exposure was calculated by integrating the elder's time spend in each micro-environment and the concentration of the pollutants for the period of interest. This parameter, together with the inhalation rate and the standard body weight, were used to calculate the daily inhaled dose. PM10 daily exposure and daily inhaled dose ranged between 11 – 16 μg m−3 and 20 × 10−3 – 28 × 10−3 μg kg−1, respectively. This work not only allowed a fully quantification of the magnitude of the elders exposure, but also showed that the assessment of the integrated exposure to PM components is determinant to accomplish the dose inhaled by elders living in ECCs.
Keywords: Elderly; Exposure; Dose; Particles; Carbonaceous components; Trace elements;
Suitability and uncertainty of two models for the simulation of ammonia dispersion from a pig farm located in an area with frequent calm conditions by Mark R. Theobald; Alberto Sanz-Cobena; Antonio Vallejo; Mark A. Sutton (167-175).
We used two atmospheric dispersion models (ADMS and AERMOD) to simulate the short-range dispersion of ammonia emitted by two pig farms to assess their suitability in situations with frequent calm meteorological conditions. Simulations were carried out both using constant and temporally-varying emission rates to evaluate the effect on the model predictions. Monthly and annual mean concentrations predicted by the models at locations within one kilometre of the farms were compared with measured values. AERMOD predicted higher concentrations than ADMS (by a factor of 6–7, on average) and predicted the atmospheric concentrations more accurately for both the monthly and annual simulations. The differences between the concentrations predicted by the two models were mainly the result of different calm wind speed thresholds used by the models. The use of temporally-varying emission rates improved the performance of both models for the monthly and annual simulations with respect to the constant emission simulations. A Monte Carlo uncertainty analysis based on the inputs judged to be the most uncertain for the selected case study estimated a prediction uncertainty of ± a factor of two for both models with most of this due to uncertainty in emission rates.
Keywords: Ammonia emissions; Atmospheric dispersion modelling; Uncertainty analysis;
Modeling the spatio-temporal heterogeneity in the PM10-PM2.5 relationship by Hone-Jay Chu; Bo Huang; Chuan-Yao Lin (176-182).
This paper explores the spatio-temporal patterns of particulate matter (PM) in Taiwan based on a series of methods. Using fuzzy c-means clustering first, the spatial heterogeneity (six clusters) in the PM data collected between 2005 and 2009 in Taiwan are identified and the industrial and urban areas of Taiwan (southwestern, west central, northwestern, and northern Taiwan) are found to have high PM concentrations. The PM10-PM2.5 relationship is then modeled with global ordinary least squares regression, geographically weighted regression (GWR), and geographically and temporally weighted regression (GTWR). The GTWR and GWR produce consistent results; however, GTWR provides more detailed information of spatio-temporal variations of the PM10-PM2.5 relationship. The results also show that GTWR provides a relatively high goodness of fit and sufficient space-time explanatory power. In particular, the PM2.5 or PM10 varies with time and space, depending on weather conditions and the spatial distribution of land use and emission patterns in local areas. Such information can be used to determine patterns of spatio-temporal heterogeneity in PM that will allow the control of pollutants and the reduction of public exposure.
Keywords: Spatio-temporal variation; Particulate matter; Spatial clustering; PM10-PM2.5 relation; GTWR; GWR;
Inter-annual trend of the primary contribution of ship emissions to PM2.5 concentrations in Venice (Italy): Efficiency of emissions mitigation strategies by Daniele Contini; Andrea Gambaro; Antonio Donateo; Paolo Cescon; Daniela Cesari; Eva Merico; Franco Belosi; Marta Citron (183-190).
Ships and harbour emissions are currently increasing, due to the increase of tourism and trade, with potential impact on global air pollution and climate. At local scale, in-port ship emissions influence air quality in coastal areas impacting on health of coastal communities. International legislations to reduce ship emissions, both at Worldwide and European levels, are mainly based on the use of low-sulphur content fuel. In this work an analysis of the inter-annual trends of primary contribution, ε, of tourist shipping to the atmospheric PM2.5 concentrations in the urban area of Venice has been performed. Measurements have been taken in the summer periods of 2007, 2009 and 2012. Results show a decrease of ε from 7% (±1%) in 2007 to 5% (±1%) in 2009 and to 3.5% (±1%) in 2012. The meteorological and micrometeorological conditions of the campaigns were similar. Tourist ship traffic during measurement campaigns increased, in terms of gross tonnage, of about 25.4% from 2007 to 2009 and of 17.6% from 2009 to 2012. The decrease of ε was associated to the effect of a voluntary agreement (Venice Blue Flag) for the use of low-sulphur content fuel enforced in the area between 2007 and 2009 and to the implementation of the 2005/33/CE Directive in 2010. Results show that the use of low-sulphur fuel could effectively reduce the impact of shipping to atmospheric primary particles at local scale. Further, voluntary agreement could also be effective in reducing the impact of shipping on local air quality in coastal areas.
Keywords: Ship traffic emissions; Harbour pollution; Particle number concentration; Low-sulphur fuel; PM2.5;
Modelled atmospheric contribution to nitrogen eutrophication in the English Channel and the southern North Sea by G. Djambazov; K. Pericleous (191-199).
Keywords: Atmospheric transport; Pollutants; Eutrophication; Lagrangian particle dispersion;
Nonlinear response of nitric oxide emissions to a nitrogen application gradient: A case study during the wheat season in a Chinese rice-wheat rotation system by Miao Zhao; Yuhua Tian; Min Zhang; Yuanlin Yao; Yuqin Ao; Bin Yin; Zhaoliang Zhu (200-208).
The response of nitric oxide (NO) emissions to nitrogen (N) input in agricultural ecosystems is generally assumed to be linear, but the availability of inorganic soil N exceeding crop N demands may cause a threshold response of NO. We conducted a four-rotation field measurement with discrepant N fertilizer rates during the wheat season of the rice-wheat rotation in the Taihu Lake region in China to test the hypothesis. Across all years, a nonlinear model well characterized the response of cumulative NO emissions to N fertilizer rates. The direct emission factors of NO induced by fertilizer also increased nonlinearly with increasing N doses, with a mean of 1.06% (ranging from 0.54% to 1.49%). NO emissions were low (<1.81 kg N ha−1 yr−1) over the 0–180 kg N ha−1 fertilizer additions; above these additions, the increasing N rates resulted in substantial NO increases ranging from 73% to 245% but only elevated crop yields by 6%. The results suggested defining the N rate of 180 kg N ha−1 as a promising level for achieving decreased NO emissions without greatly affecting the economic return from grain yield.
Keywords: Nitric oxide; Nitrogen fertilizer; Crop yield; Wheat field; Taihu Lake region;
Emission inventory of non-methane volatile organic compounds from anthropogenic sources in India by Sumit Sharma; Anju Goel; Divya Gupta; Atul Kumar; Arabinda Mishra; Seema Kundu; Satoru Chatani; Zbigniew Klimont (209-219).
This paper presents a new inventory of NMVOC emissions from anthropogenic sources in India for the year 2010. The main new element of this inventory, compared to previous work for India, is the use of new and more detailed data on solvent use sectors and oil production and distribution system. The results are presented at the national and state level for major sectors and VOC species. Finally, the annual emissions were spatially distributed at a fine resolution of 36 × 36 km2 using detailed spatial information. The total anthropogenic NMVOC emissions in India in 2010 were estimated at 9.81 Tg which is in the range of the estimates made in most other studies. The majority of emissions (60%) originated from residential combustion of biomass for cooking. Solvent use sectors and oil production and distribution contributed about 20% followed by transport (12%) and open burning of agricultural residues (7%). Specie-wise distribution shows highest contribution from alkenes and alkynes (38%), followed by alkanes (22%), and aromatics (16%).
Keywords: NMVOC emissions; Inventory; Speciation; Solvents; India;
Indoor radon variations in central Iran and its geostatistical map by Kamal Hadad; Javad Mokhtari (220-227).
We present the results of 2 year indoor radon survey in 10 cities of Yazd province in Central Iran (covering an area of 80,000 km2). We used passive diffusive samplers with LATEX polycarbonate films as Solid State Nuclear Track Detector (SSNTD). This study carried out in central Iran where there are major minerals and uranium mines. Our results indicate that despite few extraordinary high concentrations, average annual concentrations of indoor radon are within ICRP guidelines. When geostatistical spatial distribution of radon mapped onto geographical features of the province it was observed that risk of high radon concentration increases near the Saqand, Bafq, Harat and Abarkooh cities, this depended on the elevation and vicinity of the ores and mines.
Keywords: Indoor radon; SSNTD; ICRP; Geostatistical map; Radon prone areas; Yazd;
Effects of fuels, engine load and exhaust after-treatment on diesel engine SVOC emissions and development of SVOC profiles for receptor modeling by Lei Huang; Stanislav V. Bohac; Sergei M. Chernyak; Stuart A. Batterman (228-238).
Diesel exhaust emissions contain numerous semivolatile organic compounds (SVOCs) for which emission information is limited, especially for idling conditions, new fuels and the new after-treatment systems. This study investigates exhaust emissions of particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and sterane and hopane petroleum biomarkers from a heavy-duty (6.4 L) diesel engine at various loads (idle, 600 and 900 kPa BMEP), with three types of fuel (ultra-low sulfur diesel or ULSD, Swedish low aromatic diesel, and neat soybean biodiesel), and with and without a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF). Swedish diesel and biodiesel reduced emissions of PM2.5, Σ15PAHs, Σ11NPAHs, Σ5Hopanes and Σ6Steranes, and biodiesel resulted in the larger reductions. However, idling emissions increased for benzo[k]fluoranthene (Swedish diesel), 5-nitroacenaphthene (biodiesel) and PM2.5 (biodiesel), a significant result given the attention to exposures from idling vehicles and the toxicity of high-molecular-weight PAHs and NPAHs. The DOC + DPF combination reduced PM2.5 and SVOC emissions during DPF loading (>99% reduction) and DPF regeneration (83–99%). The toxicity of diesel exhaust, in terms of the estimated carcinogenic risk, was greatly reduced using Swedish diesel, biodiesel fuels and the DOC + DPF. PAH profiles showed high abundances of three and four ring compounds as well as naphthalene; NPAH profiles were dominated by nitronaphthalenes, 1-nitropyrene and 9-nitroanthracene. Both the emission rate and the composition of diesel exhaust depended strongly on fuel type, engine load and after-treatment system. The emissions data and chemical profiles presented are relevant to the development of emission inventories and exposure and risk assessments.
Keywords: Polycyclic aromatic hydrocarbons (PAHs); Nitro-PAHs (NPAHs); Hopanes; Steranes; Biodiesel; Diesel particulate filter (DPF);
Artificial intelligence based approach to forecast PM2.5 during haze episodes: A case study of Delhi, India by Dhirendra Mishra; P. Goyal; Abhishek Upadhyay (239-248).
Delhi has been listed as the worst performer across the world with respect to the presence of alarmingly high level of haze episodes, exposing the residents here to a host of diseases including respiratory disease, chronic obstructive pulmonary disorder and lung cancer. This study aimed to analyze the haze episodes in a year and to develop the forecasting methodologies for it. The air pollutants, e.g., CO, O3, NO2, SO2, PM2.5 as well as meteorological parameters (pressure, temperature, wind speed, wind direction index, relative humidity, visibility, dew point temperature, etc.) have been used in the present study to analyze the haze episodes in Delhi urban area. The nature of these episodes, their possible causes, and their major features are discussed in terms of fine particulate matter (PM2.5) and relative humidity. The correlation matrix shows that temperature, pressure, wind speed, O3, and dew point temperature are the dominating variables for PM2.5 concentrations in Delhi. The hour-by-hour analysis of past data pattern at different monitoring stations suggest that the haze hours were occurred approximately 48% of the total observed hours in the year, 2012 over Delhi urban area. The haze hour forecasting models in terms of PM2.5 concentrations (more than 50 μg/m3) and relative humidity (less than 90%) have been developed through artificial intelligence based Neuro-Fuzzy (NF) techniques and compared with the other modeling techniques e.g., multiple linear regression (MLR), and artificial neural network (ANN). The haze hour's data for nine months, i.e. from January to September have been chosen for training and remaining three months, i.e., October to December in the year 2012 are chosen for validation of the developed models. The forecasted results are compared with the observed values with different statistical measures, e.g., correlation coefficients (R), normalized mean square error (NMSE), fractional bias (FB) and index of agreement (IOA). The performed analysis has indicated that R has values 0.25 for MLR, 0.53 for ANN, and NF: 0.72, between the observed and predicted PM2.5 concentrations during haze hours invalidation period. The results show that the artificial intelligence implementations have a more reasonable agreement with the observed values. Finally, it can be concluded that the most convincing advantage of artificial intelligence based NF model is capable for better forecasting of haze episodes in Delhi urban area than ANN and MLR models.
Keywords: Artificial Neural Network; Neuro-Fuzzy logic; Multiple Linear Regression; Haze episode; Statistical analysis;
Measurement of atmospheric amines and ammonia using the high resolution time-of-flight chemical ionization mass spectrometry by Jun Zheng; Yan Ma; Mindong Chen; Qi Zhang; Lin Wang; Alexei F. Khalizov; Lei Yao; Zhen Wang; Xing Wang; Linxi Chen (249-259).
Ammonia (NH3) and amines play important roles in the nucleation and growth of atmospheric aerosols. To identify the sources of these chemicals in the densely populated and industrialized Yangtze River Delta region of China, we conducted measurements of NH3 and several amines, including methylamine (CH3NH2), C2-amines (C2H7N), and C3-amines (C3H9N) at a suburban site of Nanjing, China, during summer 2012. Using a high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS, Aerodyne), 1-min-averaged concentrations of NH3 and amines ranged from a few parts per trillions by volume (pptv) to dozens of parts per billion by volume (ppbv). The average ± 1σ concentrations of NH3 and total amines during the measurement period were 1.7 ± 2.3 ppbv and 7.2 ± 7.4 pptv, respectively. Among the amines, C2-amines were the most abundant, accounting for 54% of the total amine loading. Significant correlations between NH3 and all three types of amines (0.65 < r 2 < 0.80) indicate similar emission sources. Analysis of meteorological conditions indicated that these NH3 and amine laden air masses mainly originated from nearby industrial areas where NH3 was used for selective catalytic reduction of nitrogen oxides (NOx). The results of this work indicate that industrial emissions in Nanjing, China may have a significant impact on local and regional aerosol chemistry by supplying considerable amount of amines.
Keywords: Amines; Ammonia; HRToF-CIMS; Selective catalytic reduction; Emission ratio; Yangtze River Delta;
How well do satellite AOD observations represent the spatial and temporal variability of PM2.5 concentration for the United States? by Jing Li; Barbara E. Carlson; Andrew A. Lacis (260-273).
Due to their extensive spatial coverage, satellite Aerosol Optical Depth (AOD) observations have been widely used to estimate and predict surface PM2.5 concentrations. While most previous studies have focused on establishing relationships between collocated, hourly or daily AOD and PM2.5 measurements, in this study, we instead focus on the comparison of the large-scale spatial and temporal variability between satellite AOD and PM2.5 using monthly mean measurements. A newly developed spectral analysis technique – Combined Maximum Covariance Analysis (CMCA) is applied to Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging Spectroradiometer (MISR), Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Ozone Monitoring Instrument (OMI) AOD datasets and Environmental Protection Agency (EPA) PM2.5 data, in order to extract and compare the dominant modes of variability. Results indicate that AOD and PM2.5 agree well in terms of interannual variability. An overall decrease is found in both AOD and PM2.5 across the United States, with the strongest signal over the eastern US. With respect to seasonality, good agreement is found only for Eastern US, while for Central and Western US, AOD and PM2.5 seasonal cycles are largely different or even reversed. These results are verified using Aerosol Robotic Network (AERONET) AOD observations and differences between satellite and AERONET are also examined. MODIS and MISR appear to have the best agreement with AERONET. In order to explain the disagreement between AOD and PM2.5 seasonality, we further use Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) extinction profile data to investigate the effect of two possible contributing factors, namely aerosol vertical distribution and cloud-free sampling. We find that seasonal changes in aerosol vertical distribution, due to the seasonally varying mixing height, is the primary cause for the AOD and PM2.5 seasonal discrepancy, in particular, the low AOD but high PM2.5 observed during the winter season for Central and Western US. In addition, cloud-free sampling by passive sensors also induces some bias in AOD seasonality, especially for the Western US, where the largest seasonal change in cloud fraction is found. The seasonal agreement between low level (below 500 m AGL), all sky CALIOP AOD and PM2.5 is significantly better than column AOD from MODIS, MISR, SeaWiFS and OMI. In particular, the correlation between low level, all sky AOD and PM2.5 seasonal cycles increases to above 0.7 for Central and Western US, as opposed to near zero or negative correlation for column, clear sky AOD. This result highlights the importance of accounting for the seasonally varying aerosol profiles and cloud-free sampling bias when using column AOD measurements to infer surface PM2.5 concentrations.
Keywords: PM2; Aerosol optical depth; Satellite remote sensing; Principal component analysis; Spatial and temporal variability;
Improvement of simulation of fine inorganic PM levels through better descriptions of coarse particle chemistry by Erica R. Trump; Christos Fountoukis; Neil M. Donahue; Spyros N. Pandis (274-281).
Atmospheric chemical transport models (CTMs) have often serious difficulties reproducing the observed aerosol nitrate levels. We hypothesize that one of the reasons for these errors is their treatment of the competition between the accumulation and coarse-mode particles for the condensing nitric acid. The hybrid mass transfer method is used in the CTM PMCAMx to test this hypothesis. The simulation approach combines the dynamic calculation of mass transfer to coarse-mode particles while maintaining computational efficiency by assuming that the fine mode particles are in equilibrium. The resulting model is applied to Europe and evaluated for the period of May 2008 against ground-based and airborne Aerosol Mass Spectrometer measurements from the EUCAARI campaign.PMCAMx using the default equilibrium approach to calculate the partitioning of semi-volatile PM components between the gas and particle phases seriously overpredicts PM1 nitrate levels especially for locations in which there were relatively high coarse-mode particle concentrations (significant sea-salt or dust concentrations). This shortcoming was especially apparent for the Mace Head site in Ireland, where a large amount of nitrate was associated with sea-salt. The improved simulation of the coarse-mode particle chemistry results in significant improvement of the predictions of PM1 nitrate and ammonium. Sea-salt emissions in areas with high nitric acid levels reduce the PM1 nitrate concentrations.
Keywords: Particulate matter; Modeling; Sea-salt;
Influence of ozone initiated processing on the toxicity of aerosol particles from small scale wood combustion by Erik Z. Nordin; Oskari Uski; Robin Nyström; Pasi Jalava; Axel C. Eriksson; Johan Genberg; Pontus Roldin; Christoffer Bergvall; Roger Westerholm; Jorma Jokiniemi; Joakim H. Pagels; Christoffer Boman; Maija-Riitta Hirvonen (282-289).
Black carbon containing emissions from biomass combustion are being transformed in the atmosphere upon processing induced by tropospheric ozone and UV. The knowledge today is very limited on how atmospheric processing affects the toxicological properties of the emissions.The aim of this study was to investigate the influence of ozone initiated (dark) atmospheric processing on the physicochemical and toxicological properties of particulate emissions from wood combustion.Emissions from a conventional wood stove operated at two combustion conditions (nominal and hot air starved) were diluted and transferred to a chamber. Particulate matter (PM) was collected before and after ozone addition to the chamber using an impactor. Detailed chemical and physical characterization was performed on chamber air and collected PM. The collected PM was investigated toxicologically in vitro with a mouse macrophage model, endpoints included: cell cycle analysis, viability, inflammation and genotoxicity.The results suggest that changes in the organic fraction, including polycyclic aromatic hydrocarbons (PAHs) are the main driver for differences in obtained toxicological effects. Fresh hot air starved emissions containing a higher organic and PAH mass-fraction affected cell viability stronger than fresh emissions from nominal combustion. The PAH mass fractions decreased upon aging due to chemical degradation. Dark aging increased genotoxicity, reduced viability and reduced release of inflammatory markers. These differences were statistically significant for single doses and typically less pronounced. We hypothesize that the alterations in toxicity upon simulated dark aging in the atmosphere may be caused by reaction products that form when PAHs and other organic compounds react with ozone and nitrate radicals.
Keywords: Biomass combustion; Polycyclic aromatic hydrocarbons; Aging; Cell studies;
Characteristics and applications of size-segregated biomass burning tracers in China's Pearl River Delta region by Zhisheng Zhang; Jian Gao; Guenter Engling; Jun Tao; Fahe Chai; Leiming Zhang; Renjian Zhang; Xuefang Sang; Chuen-yu Chan; Zejian Lin; Junji Cao (290-301).
Biomass burning activities in China are ubiquitous and the resulting smoke emissions may pose considerable threats to human health and the environment. In the present study, size-segregated biomass burning tracers, including anhydrosugars (levoglucosan (LG) and mannosan (MN)) and non-sea-salt potassium (nss-K+), were determined at an urban and a suburban site in the Pearl River Delta (PRD) region. The size distributions of biomass burning tracers were generally characterized by a unimodal pattern peaking in the particle size range of 0.44–1.0 μm, except for MN during the wet season, for which a bimodal pattern (one in fine and one in coarse mode) was observed. These observed biomass burning tracers in the PRD region shifted towards larger particle sizes compared to the typical size distributions of fresh biomass smoke particles. Elevated biomass burning tracers were observed during the dry season when biomass burning activities were intensive and meteorological conditions favored the transport of biomass smoke particles from the rural areas in the PRD and neighboring areas to the sampling sites. The fine mode biomass burning tracers significantly correlated with each other, confirming their common sources. Rather high ΔLG/ΔMN ratios were observed at both sites, indicating limited influence from softwood combustion. High Δnss-K+/ΔLG ratios further suggested that biomass burning aerosols in the PRD were predominately associated with burning of crop residues. Using a simplified receptor-oriented approach with an emission factor of 0.075 (LG/TC) obtained from several chamber studies, average contributions of biomass burning emissions to total carbon in fine particles were estimated to be 23% and 16% at the urban and suburban site, respectively, during the dry season. In contrast, the relative contributions to total carbon were lower than 8% at both sites during the wet season.
Keywords: Biomass combustion; Size distribution; Anhydrosugars; Potassium; Source-receptor study;
Analysis of monitoring data of ground-level ozone in Japan for long-term trend during 1990–2010: Causes of temporal and spatial variation by Hajime Akimoto; Yasuaki Mori; Kansuke Sasaki; Hiroto Nakanishi; Tsuyoshi Ohizumi; Yasuyuki Itano (302-310).
The puzzling increase of annual average mixing ratio of ozone (oxidant) in spite of the decrease of those of the ambient NOx and NMHC was analyzed using the twenty-one years monitoring data during 1990–2010 focusing on four high O3 areas in Japan, Tokyo Metropolitan Area (TMA), Nagoya Area (NA), Osaka/Kyoto Area (OKA) and Fukuoka Area (FA). During the period, the NOx and NMHC mixing ratios have decreased by 40–50 % and 51–54 %, respectively, in these areas. Nevertheless, the annual averaged increasing trends of O3 by linear regressions during the whole period are all positive, 1.23 ± 0.09, 0.85 ± 0.17, 1.41 ± 0.12 and 1.42 ± 0.17(1σ)% yr−1 for TMA, NA, OKA and FA, respectively. Three causes of long-term trends of O3 have been discussed: (1) the decrease of NO titration effect, (2) the increase of transboundary transport, and (3) the decrease of in situ photochemical production. The total ozone (TO) was defined by [TO] = [O3] + [NO2] – 0.1[NOx] as an index to indicate the net O3 removing the perturbation by in situ NO titration. TO shows statistically significant annual increasing trends, 0.20 ± 0.04 and 0.56 ± 0.08% yr−1 only in OKA and FA, and the increase of TO is not discernible in TMA and NA. In springtime (March–May), TO shows larger increasing rates of 0.44 ± 0.08, 0.59 ± 0.09 and 0.96 ± 0.18% yr−1 for TMA, OKA, and FA. The statistically significant increase of TO at higher rates in spring and western part of Japan suggests the increase of transboundary transport during the period. The reduction of domestic emissions of precursors was found to result the decreasing trend of the high mixing ratio range of 98-percentile most clearly in TMA, but is not enough yet to result in the decrease of annual mean mixing ratio of O3, which is compensated by the increase of transboundary transport and the decrease of the NO titration effect. The similar situation has been reported in Taiwan (Chou et al., 2006), and would apply more or less to other outflow region of Pacific rim, Korea and Hoang Kong, where the emission control started to reduce the O3 precursors. Further reduction of NOx emissions over a certain limit will negate the NO titration effect, and the decrease of net O3 due to the reduction of in situ photochemical production is expected.
Keywords: Ground-level ozone; Photochemical oxidants; NO titration effect; Transboundary transport; Ozone control strategy;
Radioactivity impacts of the Fukushima Nuclear Accident on the atmosphere by W. Lin; L. Chen; W. Yu; H. Ma; Z. Zeng; J. Lin; S. Zeng (311-322).
The Fukushima Nuclear Accident (FNA) resulted in a large amount of radionuclides released into the atmosphere and dispersed globally, which has greatly raised public concerns. The state of the art for source terms of 19 kinds of radionuclides derived from the FNA was comprehensively collected and compared with levels of the global fallout and the Chernobyl Nuclear Accident (CNA). The atmospheric impacts of the FNA were evaluated from three aspects including radioactive baseline of the atmosphere, the concentration limits in standards and radiological protection. The FNA should not impose significant radiological risk on the public members in the countries excluding Japan. A conceptual scheme of Fukushima-derived radionuclides with physical and physicochemical insights on different temporal–spatial timescales was discussed and illustrated to understand their fates in the atmosphere.
Keywords: Fukushima Nuclear Accident; Atmosphere; Radioactivity; Radiation dose; Chernobyl Nuclear Accident; Global fallout;
Development of a mobile tracer correlation method for assessment of air emissions from landfills and other area sources by Tierney A. Foster-Wittig; Eben D. Thoma; Roger B. Green; Gary R. Hater; Nathan D. Swan; Jeffrey P. Chanton (323-330).
A standardized version of a mobile tracer correlation measurement method was developed and used for assessment of methane emissions from 15 landfills in 56 field deployments from 2009 to 2013. Using cavity ring-down spectroscopy and acetylene tracer gas, this method has potential implementation and cost advantages over other mobile tracer correlation approaches. The field deployment, data acquisition and analysis procedures, and a range of use conditions are discussed. To test real-world method application, the field studies were conducted by engineering technician-level personnel under randomly-encountered daytime atmospheric conditions. A total of 1876 mobile tracer correlation measurement transects were attempted over 131 field sampling days. Of these, 1366 transect (73%) were successfully completed and passed basic data acceptance criteria as valid measurement attempts. Invalid data were caused primarily by equipment failures, transect execution errors, or poor plume transport conditions. Valid transects were further analyzed using signal-to-noise ratio, plume correlation, and emission rate difference method quality indicators described here. Encountered scenarios that can result in high emission measurement uncertainty or bias are discussed in term of these indicators. Reasonable values for the acceptance levels of the method quality indicators that help protect against method errors and reduce measurement noise are discussed. The application of a default indicator set to the valid data yield 456 transects (33%) that pass data acceptance criteria. Transects that fail were associated with insufficient advected plume transport, poor correlation between the tracer and source plumes, and potential emissions pooling conditions.
Keywords: Landfill; Area source; Tracer correlation; EPA OTM 33B; Methane;
Ship-based MAX-DOAS measurements of tropospheric NO2 and SO2 in the South China and Sulu Sea by S.F. Schreier; E. Peters; A. Richter; J. Lampel; F. Wittrock; J.P. Burrows (331-343).
In November 2011, ship-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed within the SHIVA campaign on board RV Sonne in the South China and Sulu Sea. Spectral measurements for a total of eleven days could be used to retrieve tropospheric slant column densities (SCDs) of nitrogen dioxide (NO2) and sulfur dioxide (SO2) in the marine environment. The NO2 fit was performed following recommendations developed during the CINDI campaign and adapted for the ship-based measurements. We found that the inclusion of a cross section for liquid water and an empirical correction spectrum accounting for the effects of liquid water and vibrational Raman scattering (VRS) slightly improved the NO2 fit quality, especially at lower elevation angles and for lower NO2 levels. The conversion of SCDs into tropospheric NO2 vertical columns (TVC NO2) has been achieved using both a simple geometric approach and the Bremian advanced MAX-DOAS Retrieval Algorithm (BREAM), which is based on the optimal estimation method and accounts for atmospheric radiative transfer. We found good agreement between the geometric approach using the 15° measurements and BREAM, revealing that measurements at 15° elevation angle can be used for retrieving TVC NO2 in tropical marine environments when SZA is smaller than 75°. As expected, the values of TVC NO2 were generally low (<0.5 × 1015 molec cm−2) when no sources of NO x were in proximity to the RV Sonne. However, we found increased values of TVC NO2 (>2 × 1015 molec cm−2) in the morning when the RV Sonne was heading along the coast of Borneo. This is in good agreement with satellite measurements. The results of the profile retrieval show that the boundary layer values of NO2 are <30 pptv in the open and clean tropical marine environment. Interestingly, we also found elevated tropospheric SO2 amounts for measurements taken in a busy shipping lane, consistent with the time series of tropospheric NO2.
Keywords: Ship-based MAX-DOAS measurements; Tropospheric NO2; Geometric approximation; Profile retrieval; Tropospheric SO2; Shipping emissions;
Characteristics of the disastrous wind-sand environment along railways in the Gobi area of Xinjiang, China by Jian-jun Cheng; Fu-qiang Jiang; Chun-xiao Xue; Guo-wei Xin; Kai-chong Li; Yin-hai Yang (344-354).
Based on detailed long-term data of wind regimes collected from typical ventilation sites along the railways in the Gobi area of Xinjiang, this study systematically analyzes the characteristics of the disastrous wind-sand environment along the railways by combining gradient sand sampling data collected by a wind-drift sand monitoring system and site survey data. Wind direction and speed rose diagrams revealed the prevailing wind direction in each wind area along the railways, and this is the wind direction from which the maximum frequency of sandstorms occurred. Drift potential characteristic parameters (RDP, RDD) and the direction variability (RDP/DP) showed that each wind area along the Gobi railway featured a long wind period, with strong power in a single wind direction. The special geological environment of the Gobi determines the wind-drift sand that features gravel of large grain size and unsaturation, which are different from the wind-drift sand in deserts. With increasing wind velocity, the density of the wind-drift sand increased steadily; however, at a certain critical value, the density surged. This study on the wind-sand environment of the Gobi has significance for railway safety. The critical value of wind velocity corresponded to an abrupt increase in the wind-drift sand density and should be taken into account during the planning process of railway safety passage, since this will lead to a decrease in frontal visual distance, and an associated decrease in safety. Additionally, the specific features of wind-drift sand activities, such as the abruptness and higher than usual sand height, should be considered during the process of designing sand-damage-control engineering measures.
Keywords: Wind-sand environment; Wind-sand disaster; Preponderant strong wind flow; Atmospheric boundary layer; Windblown sand damage; Windblown gravel damage;
A method to optimize sampling locations for measuring indoor air distributions by Yan Huang; Xiong Shen; Jianmin Li; Bingye Li; Ran Duan; Chao-Hsin Lin; Junjie Liu; Qingyan Chen (355-365).
Indoor air distributions, such as the distributions of air temperature, air velocity, and contaminant concentrations, are very important to occupants' health and comfort in enclosed spaces. When point data is collected for interpolation to form field distributions, the sampling locations (the locations of the point sensors) have a significant effect on time invested, labor costs and measuring accuracy on field interpolation. This investigation compared two different sampling methods: the grid method and the gradient-based method, for determining sampling locations. The two methods were applied to obtain point air parameter data in an office room and in a section of an economy-class aircraft cabin. The point data obtained was then interpolated to form field distributions by the ordinary Kriging method. Our error analysis shows that the gradient-based sampling method has 32.6% smaller error of interpolation than the grid sampling method. We acquired the function between the interpolation errors and the sampling size (the number of sampling points). According to the function, the sampling size has an optimal value and the maximum sampling size can be determined by the sensor and system errors. This study recommends the gradient-based sampling method for measuring indoor air distributions.
Keywords: Gradient method; Kriging interpolation; CFD simulation; Error analysis;
An approach to investigate new particle formation in the vertical direction on the basis of high time-resolution measurements at ground level and sea level by He Meng; Yujiao Zhu; Greg J. Evans; Xiaohong Yao (366-375).
In this study, we investigated new particle formation (NPF) in the vertical direction using high time-resolution (1 s) measurements made by Fast Mobility Particle Sizers at ground level and at sea level. The coefficient of variation (CV), i.e., the ratio of standard deviation to mean value for <100-nm particle number concentration (N100) in every 30 s, is introduced as a metric to distinguish horizontal and vertical transport of atmospheric particles. We first examined the CV metric using the data collected at a semi-urban site in Toronto during the summer of 2007. The 50th and 95th percentiles of CVs associated with horizontal transport were 1–13 times smaller than those during strong vertical transport. We then compared the N100, GMD55 (geometric mean diameter of <55-nm particles) and GMD100 corresponding to the 0–5th percentiles of CVs with those corresponding to the 95–100th percentiles of CVs in five NPF events. The comparative results are discussed in terms of different formation and growth rates in the vertical direction. The similar analysis was also conducted in various marine atmospheres. We found that the CV metric can improve our understanding of NPF in the vertical direction.
Keywords: New particle formation; Particle growth; FMPS; Vertical transport; Coefficient of variation;
Change characteristic of atmospheric particulate mercury during dust weather of spring in Qingdao, China by Yuqing Zhang; Ruhai Liu; Yan Wang; Xueqing Cui; Jianhua Qi (376-383).
Atmospheric aerosol samples were collected during dust weather of spring from 2008 to 2011 in Qingdao, in which the concentrations of atmospheric particulate mercury (PHg) were measured to analyze its distribution characteristics and source. PHg concentration during the study ranged from 0.050 ng m−3 to 0.788 ng m−3 with the average 0.292 ng m−3 in dust day, while 0.085 ng m−3 to 0.444 ng m−3 with the average 0.188 ng m−3 in non-dust day. PHg concentration in dust day is far higher than that in some cities of South Korea and Japan and comparable to some cities in China. There was a statistically power function between PHg/TSP and TSP concentrations, which meant that intense dust (high TSP) brought particles with low mercury content. The estimated dry deposition flux of PHg is 0.9–14.2 ng m−2 h−1 with the mean 5.26 ng m−2 h−1 in dust day. The mercury deposition flux in a dust day accounts for almost 1% annual flux, which should be paid attention in the regional and global cycle of mercury. The trajectories are categorized into 4 sectors. Cluster 1 and cluster 4 were the main routes of dust to Qingdao, coming from Kazakhstan and north of Mongolia individually. There is higher TSP, and lower PHg/TSP in dust of cluster 4 compared with cluster 1, because of longer transport distance and faster movement speed. There is highest PHg/TSP in cluster 2 because of passing polluted East China. The slow transport speed, long stay at polluted developed region caused pollutants to accumulate in the aerosols. Differences of transport route, movement speed affects the mercury content significantly.High particulate Hg concentration during dust weather of spring suggest the important function in global mercury cycle.Display Omitted
Keywords: Particulate mercury; Dust weather; Dry deposition; Transport route; Qingdao;
Greenhouse gas emissions from naturally ventilated freestall dairy barns by H.S. Joo; P.M. Ndegwa; A.J. Heber; J.-Q. Ni; B.W. Bogan; J.C. Ramirez-Dorronsoro; E. Cortus (384-392).
Greenhouse gas (GHG) emissions from two naturally-ventilated dairy freestall barns measured for a total of 21 d, one week each in May, July, and September 2009, are presented in this article. The holding capacity of Barn 1 (B1) was 400 Holstein cows, while that for Barn 2 (B2) was 850 cows. Air samples were taken from inlets and outlets of the barns via a custom made multiplexer gas sampling system for measurement of gas concentrations using a photoacoustic infrared multigas analyzer. Barn ventilation rates were based on air velocity measured with arrays of 3-D ultrasonic anemometers at inlets and outlets. Gas concentrations (10 min means) in the barns ranged from: 443–789 ppm for CO2, 0.0–39.4 ppm for CH4, and 0.25–0.39 ppm for N2O; with mean concentrations ranging from 6 to 20%, 0 to 4%, and 26 to 180% above the average background concentrations for CO2, N2O, and CH4, respectively. The correlations between CO2 and CH4 enhanced concentrations were relatively stronger (R of 0.67–0.74) than between CO2 and N2O enhanced concentrations (R of 0.10–0.20). Environmental conditions did not significantly (p = 0.46) impact the enhanced concentrations of N2O in the barns. All three parameters (T, RH, and v) had significant (p < 0.01) influences on CO2 enhanced concentrations; while only T (p < 0.01) and v (p < 0.01) had significant influences on CH4 enhanced concentrations. Enhanced concentrations of CO2 and CH4 correlated negatively with all three parameters. The influence of the temperature-humidity index (THI) on CO2 enhanced concentrations was higher than that of v; while the effect v had on CH4 enhanced concentrations was slightly higher than that of the temperature-humidity index. The average emissions, based on hourly means, ranged from 5.3 to 10.7 kg d−1 AU−1 for CO2; 0.3 to 2.5 g d−1 AU−1 for N2O; and between 67 and 252 g d−1 AU−1 for CH4. Nitrous oxide emissions from the smaller barn, B1 (0.4–2.5 g d−1 AU−1), were significantly higher than from the larger barn, B2 (0.3–0.5 g d−1 AU−1) most probably because 50% of B1 was open (no stalls) loose dirt floor.
Keywords: Greenhouse gases; Enhanced concentrations; Freestall barns; Environmental factors;
A spatially varying coefficient model for mapping PM10 air quality at the European scale by N.A.S. Hamm; A.O. Finley; M. Schaap; A. Stein (393-405).
Particulate matter (PM) air quality in Europe has improved substantially over the past decades, but it still poses a significant threat to human health. Accurate regional scale maps of PM10 concentrations are needed for monitoring progress in mitigation strategies and monitoring compliance with statutory limit values. Chemistry transport models (CTM) use emission databases and simulate the transport and deposition of pollutants. They deliver such maps but are known to be inaccurate. A promising approach is to use geostatistics to model the relationship between the in situ observations and the CTM. This has been shown to be more accurate than using either observations or CTM's alone. This paper presents a spatially varying coefficients (SVC) geostatistical model as an extension of the standard spatially varying intercept (SVI) geostatistical model. SVC allowed the regression coefficient to vary spatially according to a covariance function, the parameters of which were estimated from the data. It was built as a Bayesian hierarchical model and implemented using Markov chain Monte Carlo. The procedure was applied to Airbase PM10 observations and LOTOS-EUROS simulated PM10 for central, southern and eastern Europe. Model-fit diagnostics showed that SVC delivered a better fit to the data than SVI. Mapping the spatially varying coefficients allowed identification of the locations where the CTM performed well or poorly. This could be used for objective CTM evaluation purposes. The posterior predictive simulations were also used to map median PM10 concentrations as well as the probability of exceeding the 50 μg m−3 EU daily PM10 concentration threshold. Although posterior median prediction accuracy was similar for SVI and SVC, SVC better modelled the process and yielded narrower credible intervals. As such, SVC was more appropriate for quantifying uncertainty and for mapping threshold exceedances. The resulting maps may be used to guide air quality assessment and mitigation strategies, including those related to health impacts.
Keywords: PM10; Geostatistics; Model evaluation; Spatially varying coefficient (SVC); LOTOS-EUROS;
Indoor air pollution from burning yak dung as a household fuel in Tibet by Qingyang Xiao; Eri Saikawa; Robert J. Yokelson; Pengfei Chen; Chaoliu Li; Shichang Kang (406-412).
Yak dung is widely used for cooking and heating in Tibet. We measured real-time concentrations of black carbon (BC) and fine particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) emitted by yak dung burning in six households with different living conditions and stove types in the Nam Co region, Tibet. We observed a much lower average BC/PM2.5 mass ratio (0.013, range 0.006–0.028) from dung combustion in this area than previously reported estimates, ranging between 0.05 and 0.11. Based on our measurements, estimated fuel use, and published emission factors of BC and PM2.5, about 0.4–1.7 Gg/year of BC is emitted by yak dung combustion in Tibet in addition to the previously estimated 0.70 Gg/year of BC for Tibetan residential sources. Our survey shows that most residents were aware of adverse health impacts of indoor yak dung combustion and approximately 2/3 of residents had already installed chimney stoves to mitigate indoor air pollution. However, our measurements reveal that, without adequate ventilation, installing a chimney may not ensure good indoor air quality. For instance, the 6-h average BC and PM2.5 concentrations in a stone house using a chimney stove were 24.5 and 873 μg/m3, respectively. We also observed a change in the BC/PM2.5 ratios before and after a snow event. The impact of dung moisture content on combustion efficiency and pollutant emissions needs further investigation.
Keywords: Black carbon; Particulate matter; Cookstove; Indoor air pollution; Yak dung;
New Directions: Potential impact of changing the coal-natural gas split in power plants: An emissions inventory perspective for criteria pollutants by Anirban Roy; Yunsoo Choi (413-415).