Atmospheric Environment (v.73, #C)

Approach to identifying pollutant source and matching flow field by Pang Liping; Zhang Yu; Qu Hongquan; Hu Tao; Wang Wei (1-10).
Accidental pollution events often threaten people's health and lives, and it is necessary to identify a pollutant source rapidly so that prompt actions can be taken to prevent the spread of pollution. But this identification process is one of the difficulties in the inverse problem areas. This paper carries out some studies on this issue. An approach using single sensor information with noise was developed to identify a sudden continuous emission trace pollutant source in a steady velocity field. This approach first compares the characteristic distance of the measured concentration sequence to the multiple hypothetical measured concentration sequences at the sensor position, which are obtained based on a source-three-parameter multiple hypotheses. Then we realize the source identification by globally searching the optimal values with the objective function of the maximum location probability. Considering the large amount of computation load resulting from this global searching, a local fine-mesh source search method based on priori coarse-mesh location probabilities is further used to improve the efficiency of identification. Studies have shown that the flow field has a very important influence on the source identification. Therefore, we also discuss the impact of non-matching flow fields with estimation deviation on identification. Based on this analysis, a method for matching accurate flow field is presented to improve the accuracy of identification. In order to verify the practical application of the above method, an experimental system simulating a sudden pollution process in a steady flow field was set up and some experiments were conducted when the diffusion coefficient was known. The studies showed that the three parameters (position, emission strength and initial emission time) of the pollutant source in the experiment can be estimated by using the method for matching flow field and source identification.
Keywords: Ventilated enclosed space; Pollutant source identification; Three-parameter multiple hypotheses; Location probability; Characteristic distance; Flow field matching;

Aircraft measurements of BTEX compounds around Beijing city by Kankan Liu; Jiannong Quan; Yujing Mu; Qiang Zhang; Junfeng Liu; Yang Gao; Pengfei Chen; Delong Zhao; Haijun Tian (11-15).
A high sensitive method has been developed for measuring atmospheric BTEX (Benzene, Toluene, Ethylbenzene, Xylenes) by using Gas Chromatography equipped with Photo-Ionization Detector (GC–PID). The Method Detection Limits (MDLs) were: Benzene 0.66 ng m−3, Toluene 2.03 ng m−3, Ethylbenzene 5.91 ng m−3, m,p-Xylene 6.49 ng m−3 and o-Xylene 5.45 ng m−3. Vertical distribution of BTEX from ground level to 3600 m around Beijing city was measured during flight of aircraft in July and November, 2011. Remarkable decrease of each BTEX species with increasing height was observed, and the sum concentration of BTEX decreased from 21.7 μg m−3 at ground level to 0.19 μg m−3 at height of 3600 m. The ratio of benzene to toluene (B/T) also increased pronouncedly with increasing altitude, but became flat above 1800 m. The vertical distribution characters of BTEX and B/T were ascribed to diffusion and photochemical consumption of BTEX.
Keywords: BTEX; Aircraft measurement; Cryo-enrichment; GC–PID;

A comparison study of atmospheric polycyclic aromatic hydrocarbons in three Indian cities using PUF disk passive air samplers by Hairong Cheng; Zongming Deng; Paromita Chakraborty; Di Liu; Ruijie Zhang; Yue Xu; Chunlin Luo; Gan Zhang; Jun Li (16-21).
A passive air sampling campaign was conducted to measure polycyclic aromatic hydrocarbons (PAHs) in Kolkata, Mumbai and Chennai, the three major cities of India. The measured total PAH concentrations ranged from 6480 to 54,800 ng sample−1, comparable to the highest levels across the globe. Three- to four-ring PAHs were the dominant components in the atmosphere. According to the spatial distribution, the PAH concentrations were the highest in Kolkata and the lowest in Chennai. Kolkata and Mumbai were characterized by a relatively high proportion of HMW (high molecular weight) PAHs, which can be ascribed to the difference in the economic and energy structures in the urban areas. Surprisingly, there was not significant decrease in PAH concentrations from urban to rural sites. Rural sources, generally associated with traditional biomass combustion, could be as important as urban sources in India. In this study, the total BaPeq (BaP toxic equivalent) concentrations generally exceeded the human exposure limit, posing potential risk to the health of the local residents.
Keywords: Spatial variation; PAHs; Indian cities; Passive air sampling; Human exposure;

In this work, a 40-year retrospective European radon flux inventory has been calculated. Average values of the radon exhalation rate, probability distributions and seasonal fluctuations have been obtained. To achieve this, a numerical model of radon transport through finite, heterogeneous and porous media has been implemented, enabling us to calculate the radon exhalation rate of European soils with a horizontal resolution of 0.5′ (∼1 km). Geological, geochemical and climatological parameters derived from European and international databases (FOREGS, HWSD, ERA-40) have been coupled to the model.The theoretical model is based on the fundamental equation of radon transport in porous media, taking into account the dependency of the transport coefficient on temperature and humidity. It also includes a simple model that evaluates the effect of snow cover. In general, the results show wide variations depending on location and season of the year, with a spatial standard deviation close to the annual average value (30 Bq m−2 h−1) In turn, the seasonal deviation is about 25% of the annual average value.The inventory can be easily integrated into atmospheric transport models acting as baseline that could be used for policy decisions regarding the identification of areas with a high risk of exposure to radon. The gridded data are available for the scientific community upon request. The limitations and sources of errors and uncertainties of the model are also discussed in detail.
Keywords: Radon flux; Exhalation; European radon inventory; Climatological variability; Numerical simulations;

Determination of fluxes and isotopic composition of halocarbons from seagrass meadows using a dynamic flux chamber by Ingo Weinberg; Enno Bahlmann; Walter Michaelis; Richard Seifert (34-40).
Halocarbons are important vectors of reactive halogens to the atmosphere, where the latter participate in several chemical key processes. Many efforts have been made to quantify their sources and sinks. However, those are still designated to large uncertainties. In contrast to other coastal habitats such as salt marshes and kelp communities, seagrass meadows have so far not been investigated with regard to trace gases. In order to study seagrass meadows as a potential source for halocarbons to the atmosphere, we conducted dynamic flux chamber measurements at a coastal site in List/Sylt, Northern Germany. Emissions of halocarbons from seagrass meadows into the atmosphere were found for chloromethane (CH3Cl), bromomethane (CH3Br), iodomethane (CH3I), and bromoform (CHBr3) being the main compounds, while the sediment seems to be a net sink for CH3Cl and CH3Br. Stable carbon isotopes of halocarbons were determined using a newly developed comprehensive coupled isotope and mass balance for dynamic flux chambers. Mean stable carbon isotope compositions of the emitted halocarbons were −50‰ (CH3Cl), −52‰ (CH3Br), −63‰ (CH3I) and −14‰ (CHBr3).
Keywords: Methyl halides; Halocarbons; Stable carbon isotopes; Flux; Source; Sink;

Potential impacts of circulation patterns on surface ozone (O3) concentrations over Hong Kong were investigated for the time period of 1999–2011. Synoptic weathers during the study period were classified into seven typical patterns using a semi-objective weather typing technique. Temporal and spatial variations of O3 and total oxidant (O x  = O3 + NO2) in Hong Kong were found to be closely connected with weather/circulation patterns. The highest O3 concentrations (25 ppbv in average) among the 7 categories were found to be associated with the influence of Northwest Pacific typhoons, whereas the lowest average concentrations (13 pbbv) were linked to southerly flow introduced by summer monsoons. Ozone episodes with hourly mixing ratios exceeding 120 ppbv were found to be caused primarily by regional transport under influence of the tropical cyclone and by photochemical reactions upon prevalence of anti-cyclonic circulation. Taking into account interannual variabilities in frequency and intensity of circulation patterns, a reconstructed time series of O3 captured up to 50% of the observed interannual variability and 36% of the increasing trend. The study highlights an important linkage between weather/climate and air quality.
Keywords: Synoptic weather; Photochemical pollution; Weather typing; Interannual variability; Long-term trend;

Source apportionments of PM2.5 organic carbon using molecular marker Positive Matrix Factorization and comparison of results from different receptor models by Jongbae Heo; Muaz Dulger; Michael R. Olson; Jerome E. McGinnis; Brandon R. Shelton; Aiko Matsunaga; Constantinos Sioutas; James J. Schauer (51-61).
Four hundred fine particulate matter (PM2.5) samples collected over a 1-year period at two sites in the Los Angeles Basin were analyzed for organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC) and organic molecular markers. The results were used in a Positive Matrix Factorization (PMF) receptor model to obtain daily, monthly and annual average source contributions to PM2.5 OC. Results of the PMF model showed similar source categories with comparable year-long contributions to PM2.5 OC across the sites. Five source categories providing reasonably stable profiles were identified: mobile, wood smoke, primary biogenic, and two types of secondary organic carbon (SOC) (i.e., anthropogenic and biogenic emissions). Total primary emission factors and total SOC factors contributed approximately 60% and 40%, respectively, to the annual-average OC concentrations. Primary sources showed strong seasonal patterns with high winter peaks and low summer peaks, while SOC showed a reverse pattern with highs in the spring and summer in the region. Interestingly, smoke from forest fires which occurred episodically in California during the summer and fall of 2009 was identified and combined with the primary biogenic source as one distinct factor to the OC budget. The PMF resolved factors were further investigated and compared to a chemical mass balance (CMB) model and a second multi-variant receptor model (UNMIX) using molecular markers considered in the PMF. Good agreement between the source contribution from mobile sources and biomass burning for three models were obtained, providing additional weight of evidence that these source apportionment techniques are sufficiently accurate for policy development. However, the CMB model did not quantify primary biogenic emissions, which were included in other sources with the SOC. Both multivariate receptor models, the PMF and the UNMIX, were unable to separate source contributions from diesel and gasoline engines.
Keywords: CMB; LA basin; Organic molecular markers; PMF; UNMIX;

Size distribution of water-soluble components in particulate matter emitted from biomass burning by Seung-Shik Park; Soo Young Sim; Min-Suk Bae; James J. Schauer (62-72).
Size-resolved measurements of particulate matter (PM) emissions from 10 biomass materials (rice straw, soybean stem, green perilla stem, red pepper stem, pine needles, cherry leaves, cherry stem, maple leaves, gingko leaves and gingko stem) were conducted in a laboratory hood chamber environment using a 10-stage MOUDI. Samples were analyzed to determine the mass, water soluble organic carbon (WSOC), and water soluble inorganic species. This study examines how particle emissions and size distributions of chemical components vary with biomass materials. Mass fractions of water soluble organic mass (WSOM) (=1.6 × WSOC) and ionic species to the PM1.8 emissions varied significantly depending on the biomass type burned. The percent mass of WSOM in PM1.8 emissions ranged from 19.8% (green perilla stem) to 41.9% (red pepper stem) for agricultural crop residues, while the tree category accounted for 9.6% (gingko leaves) to 44.0% (gingko stem) of the PM1.8 emissions. Total ionic species contents in the PM1.8 mass ranged from 7.4% (rice straw) to 26.9% (green perilla stem) for the agricultural waste category, and 5.8% (maple leaves) to 23.5% (gingko stem) for the tree category. The ionic species fraction of the PM1.8 emission was dominated by K+, Cl, and SO 4 2 − , while Ca2+ was important in the coarse mode particles (>3.1 μm). PM1.8 emissions of K+, Cl, and SO 4 2 − were as high as 16.9%, 9.0%, and 5.8%, respectively, and were from the green perilla stem, red pepper stem, and gingko stem emissions.Normalized size distributions of mass, WSOC, K+, Cl, SO 4 2 − , and oxalate in the biomass burning emissions showed a unimodal size distribution, peaking in the size ranges of 0.32–0.55 μm and 0.55–1.0 μm. Size-resolved PM mass fractions of WSOM, K+, Cl, and SO 4 2 − showed fairly consistent distributions for each biomass type, with higher fractions in the ultrafine mode (<0.10 μm) and lower fractions in the accumulation mode of 0.32–1.0 μm. The size distributions of WSOC were strongly correlated (mostly R 2 > 0.90) with those of K+ in the particle size range of <0.1 μm and 0.1–1.8 μm and the biomass types. Strong correlations between the concentrations of K+–Cl and K + − SO 4 2 − were observed for the following size ranges; <0.1 μm, 0.1–1.0 μm, 1.0–1.8 μm, and 1.8–3.1 μm for most biomass burning emissions. Regression line slopes for K+/WSOC (i.e., mass of K+/mass of WSOC from biomass burning emissions) were not significantly changed for particle size and biomass type, but slopes for Cl/K+ and SO 4 2 − /K+ varied significantly with the particle size (ultrafine, condensation, droplet, and coarse modes) and biomass type.
Keywords: Biomass burning aerosols; Size distribution; Water-soluble organic carbon; Size-resolved mass fraction;

Modelling elemental carbon at regional, urban and traffic locations in The Netherlands by M.P. Keuken; P. Zandveld; S. Jonkers; M. Moerman; A.D. Jedynska; R. Verbeek; A. Visschedijk; S. Elshout van den; P. Panteliadis; G.J.M. Velders (73-80).
The annual concentration of elemental carbon (EC) has been derived for The Netherlands in 2011. National emissions contribute 55% to the average EC concentration in the Netherlands. About 65% of the national contribution comes from emissions from road traffic and about 35% from other mobile sources (15%), households (14%), shipping (4%) and other combustion sources (2%). Conversion factors were established to compare different methods of EC measurement such as Black Smoke, Black Carbon and thermal analysis. The measured regional and urban background concentrations and variability were 0.5 ± 0.1 and 0.9 ± 0.1 μg EC per m3, respectively. The ratios between modelled and measured regional and urban background concentrations were 1.6 ± 0.5 and 1.8 ± 0.4, respectively. The modelled values are likely to be overestimated. The modelled and measured traffic contributions to EC concentrations near motorways and in street canyons were in the range 1.1–1.3 μg m−3 with total EC concentrations of 2.0 and 2.2 μg m−3, respectively. Our study showed that EC concentrations near intense traffic are increased with a factor 2–4 as compared to the urban and regional background, respectively. Consequently there is a similar variation in exposure and potential health effects in the population. More measurements of EC are required to improve modelling of EC concentrations in particular at urban background and near traffic locations.
Keywords: Elemental carbon; Black carbon; Modelling; Traffic emissions;

An integrated modelling approach to estimate urban traffic emissions by Aarshabh Misra; Matthew J. Roorda; Heather L. MacLean (81-91).
An integrated modelling approach is adopted to estimate microscale urban traffic emissions. The modelling framework consists of a traffic microsimulation model developed in PARAMICS, a microscopic emissions model (Comprehensive Modal Emissions Model), and two dispersion models, AERMOD and the Quick Urban and Industrial Complex (QUIC). This framework is applied to a traffic network in downtown Toronto, Canada to evaluate summer time morning peak traffic emissions of carbon monoxide (CO) and nitrogen oxides (NO x ) during five weekdays at a traffic intersection. The model predicted results are validated against sensor observations with 100% of the AERMOD modelled CO concentrations and 97.5% of the QUIC modelled NO x concentrations within a factor of two of the corresponding observed concentrations. Availability of local estimates of ambient concentration is useful for accurate comparisons of predicted concentrations with observed concentrations. Predicted and sensor measured concentrations are significantly lower than the hourly threshold Maximum Acceptable Levels for CO (31 ppm, ∼90 times lower) and NO2 (0.4 mg/m3, ∼12 times lower), within the National Ambient Air Quality Objectives established by Environment Canada.
Keywords: Urban; Traffic; Emission; Air quality modelling; Dispersion;

Absorption characteristics of aerosols over the northwestern region of India: Distinct seasonal signatures of biomass burning aerosols and mineral dust by Mukunda M. Gogoi; S. Suresh Babu; K. Krishna Moorthy; M.R. Manoj; Jai Prakash Chaubey (92-102).
Continuous measurements of aerosol black carbon (BC) mass concentrations made over a period of 3 years from a semi-arid, near-coastal, remote and sparsely inhabited location along with satellite-based data of aerosol absorption index, optical depth and extinction profiles in western India are used to characterize the distinct nature of aerosols near the surface and in the free troposphere and their seasonality. Despite being far remote and sparsely inhabited, significant levels of BC are observed in the ambient during winter (1.45 ± 0.71 μg m−3) attributed to biomass burning aerosols, advected to the site from the north and west; while during summer the concentrations are far reduced (0.23 ± 0.11 μg m−3) and represent the apparent background concentrations. The spectral absorption coefficients suggest the BC during summer be mostly of fossil fuel combustions. The strong convective boundary layer dynamics produces significant diurnal variation during winter and modulates to a lesser extent the seasonal variation. Examination of aerosol (absorption) index from OMI data for the study period showed a seasonal pattern that is almost opposite to that seen at the surface; with high aerosol index in summer, showing a significant difference between the surface and columnar aerosol types in summer. MISR and MODIS-derived columnar AOD follow the OMI pattern. Analysis of the vertical profiles of aerosol extinction and volume depolarization ratio (VDR), derived from CALIPSO data indicates the presence of strong dust layers with VDR ∼ 0.3 in the altitude region 4–6 km, contributing to the high aerosol index in the OMI data, while the surface measurements show absorptive properties representing fossil fuel BC aerosols.
Keywords: Black carbon; Dust; Absorption coefficient; Long-range transport; Western India;

Numerical study of the urban heat island over Athens (Greece) with the WRF model by Theodore M. Giannaros; Dimitrios Melas; Ioannis A. Daglis; Iphigenia Keramitsoglou; Konstantinos Kourtidis (103-111).
In this study, the Weather Research and Forecasting (WRF) model coupled with the Noah land surface model was tested over the city of Athens, Greece, during two selected days. Model results were compared against observations, revealing a satisfactory performance of the modeling system. According to the numerical simulation, the city of Athens exhibits higher air temperatures than its surroundings during the night (>4 °C), whereas the temperature contrast is less evident in early morning and mid-day hours. The minimum and maximum intensity of the canopy-layer heat island were found to occur in early morning and during the night, respectively. The simulations, in agreement with concurrent observations, showed that the intensity of the canopy-layer heat island has a typical diurnal cycle, characterized by high nighttime values, an abrupt decrease following sunrise, and an increase following sunset. The examination of the spatial patterns of the land surface temperature revealed the existence of a surface urban heat sink during the day. In the nighttime, the city surface temperature was found to be higher than its surroundings. Finally, a simple data assimilation algorithm for satellite-retrieved land surface temperature was evaluated. The ingestion of the land surface temperature data into the model resulted to a small reduction in the temperature bias, generally less than 0.2 °C, which was only evident during the first 4–5 h following the assimilation.► The urban heat island in Athens, Greece, is studied with a meteorological model. ► The model shows a global satisfactory performance. ► The canopy-layer heat island is strongest during the night (up to 4 °C). ► The city surface is cooler than its surroundings during the day. ► The assimilation of skin temperature data slightly improves model performance.
Keywords: Urban heat island; Numerical modeling; Remote sensing; Observations; Athens; Data assimilation;

Investigation of the airborne submicrometer particles emitted by dredging vessels using a plume capture method by Alamsyah M. Juwono; G.R. Johnson; M. Mazaheri; L. Morawska; F. Roux; B. Kitchen (112-123).
A method for investigating ship emissions, known as the plume capture and analysis system (PCAS) is described. The PCAS is applied to the task of measuring airborne pollutant emission factors (EFs) and particle size distributions aboard two dredgers, although the technique is also suitable for remote measurements. EFs were measured relative to the fuel consumption using the fuel combustion derived plume CO2. Each measurement typically took 6 min to complete and during one day, 40–50 measurements were possible. EFs for particle number (PN), NO x , SO2, and PM2.5 were independent within a targeted dilution factor range of 50–1000 suitable for onboard and remote sampling.For the Amity, the EF ranges were PN: 2.2–9.6 × 1015 (kg-fuel)−1; NO x : 35–72 g (NO2) (kg-fuel)−1, SO2 0.6–1.1 g (SO2) (kg-fuel)−1and PM2.5: 0.7–6.1 g (PM2.5) (kg-fuel)−1. For the Brisbane they were PN: 1.0–1.5 × 1016 (kg-fuel)−1, NO x : 3.4–8.0 g (NO2) (kg-fuel)−1, SO2: 1.3–1.7 g (SO2) (kg-fuel)−1 and PM2.5: 1.2–5.6 g (PM2.5) (kg-fuel)−1.Particle number emission factors as a function of size as well as the count median diameter (CMD), and geometric standard deviation of the size distributions are provided. This size distributions were consistently uni-modal in the range below 500 nm for both vessels, and this CMD always lay within the accumulation mode range.
Keywords: PCAS; Emission factor; Particle number concentration; NO x ; SO2; PM2.5; Relative size distribution; Dilution ratio;

Sources of metals and bromine-containing particles in Milwaukee by Alison M. Smyth; Samantha L. Thompson; Benjamin de Foy; Michael R. Olson; Nicholas Sager; Jerome McGinnis; James J. Schauer; Deborah S. Gross (124-130).
An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was deployed in summer 2010 in central Milwaukee as part of a study to understand the sources of primary and secondary aerosol in the non-attainment area of Southeast Wisconsin. Measurements were made continually from mid-July to mid-August, collecting time, size, and chemical composition data on aerosol particles. Trace metals including Se, Cd, Mo, and Sb were detected in the particles. These metals were found to be related and provided information on source types in Milwaukee, generally located southwest of the sampling site, from plumes that appear to originate from point sources. Additionally, Br was detected in individual particle mass spectra during this study, the first such observation at an inland site. Particles that contained Br were found in two different size modes, each of which had a different representative chemical composition. In combination with an analysis of wind direction, the data suggest that the two different size modes of Br-containing particles originate from chemically distinct sources.
Keywords: Aerosols; Bromine; Metal-containing aerosols; Urban air quality;

Salt marsh vegetation as a carbonyl sulfide (COS) source to the atmosphere by Mary E. Whelan; Dong-Ha Min; Robert C. Rhew (131-137).
Carbonyl sulfide (COS) is the most abundant and longest-lived reduced sulfur compound in the atmosphere; changes in its atmospheric concentration could significantly affect global climate and the biogeochemical sulfur cycle. The largest sink of COS in the troposphere is its destruction in plant leaves by the enzymes involved in photosynthesis. In this study, net fluxes of COS were measured from a coastal salt marsh on a subtropical barrier island on the Texas shore of the Gulf of Mexico. We find net emissions from sites with the common salt marsh plant Batis maritima compared to the net uptake from vegetated plots of most previously investigated biomes. The magnitude of the COS production from vegetated plots in this study was twice the emissions of soil-only salt marsh plots. This is the first time that emissions of COS have been found to be significantly enhanced by the presence of vegetation compared to soil alone. COS fluxes exceeded +110 pmol m−2 s−1 for non-inundated plots during daytime hours and were correlated with soil temperature at the depth of 5 cm. Tidal flooding inhibited soil COS exchange; however, we found continued net emissions from emergent B. maritima. This study suggests that emissions of COS resulted from interactions with the plants themselves, which would mean that B. maritima can mediate the production of atmospheric COS.► We found a plant-mediated COS source from a coastal wetland halophyte Batis maritima. ► Plots containing B. maritima produced up to 4 times more COS than soil-only plots. ► Plant interactions may account for a missing source of atmospheric sulfur.
Keywords: Carbonyl sulfide; Sulfur cycle; Salt marsh biogeochemistry; Batis maritima;

Comparing the impact of fine particulate matter emissions from industrial facilities and transport on the real age of a local community by Loes M.J. Geelen; Mark A.J. Huijbregts; Henk W.A. Jans; Ad M.J. Ragas; Henri A. den Hollander; Jan M.M. Aben (138-144).
For policy-making, human health risks of fine particulate m(PM2.5) are commonly assessed by comparing environmental concentrations with reference values, which does not necessarily reflect the impact on health in a population. The goal of this study was to compare health impacts in the Moerdijk area, The Netherlands resulting from local emissions of PM2.5 from industry and traffic in a case study using the risk advancement period (RAP) of mortality. The application of the RAP methodology on the local scale is a promising technique to quantify potential health impacts for communication purposes. The risk advancement period of mortality is the time period by which the mortality risk is advanced among exposed individuals conditional on survival at a baseline age. The RAP showed that road traffic was the most important local emission source that affects human health in the study area, whereas the estimated health impact from industry was a factor of 3 lower. PM2.5 due to highway-traffic was the largest contributor to the health impact of road traffic. This finding is in contrast with the risk perception in this area.
Keywords: Health impact assessment; Risk advancement period; Local scale; Air pollution;

We report measured solubilities of five aminium (i.e., monomethyl, dimethyl, trimethyl, diethyl, and triethyl) sulphate salts in water at 24 °C, and the densities of their aqueous solutions. Using these results, we have converted hygroscopic growth factors determined by Qiu and Zhang (Environ. Sci. Technol. 2012, 46, 4474–4480) to a moles of water per mole of solute basis, and obtained the relationships between concentration and equilibrium relative humidity (water activity) for solutions of the five salts. The results are compared with values predicted using the Extended Aerosol Inorganics Model (E-AIM) of Clegg and co-workers (J. Geophys. Res. 2002, 107, D14, Art. No. 4207). It is assumed in this model that ion and water activities in the solutions are the same as those for aqueous (NH4)2SO4 at the same molality. The experimental and modelled growth factors agree well in all cases, within the uncertainties of the data, which supports this assumption. Equations for the apparent molar volumes of the aminium sulphate salts in aqueous solutions are presented (based upon the measured densities and literature data), and also activity products of the salts in saturated aqueous solutions (based upon the measured solubilities and assumption of similarity with (NH4)2SO4). Simulations of the deliquescence curves of 1:1 and 1:9 mass ratio mixtures of monomethyl and dimethyl aminium sulphate with (NH4)2SO4 are shown to agree well with the measurements. The treatment of amines and aminium salts in the E-AIM model is described.
Keywords: Amine sulphate salts; Aminium sulphates; Ammonium sulphate; Hygroscopic growth factor; Density; Solubility; Deliquescence;

The mass loss of particulate matter (PM) due to EDXRF analysis was gravimetrically evaluated on co-located PM10 loaded filters analyzed both using EDXRF under vacuum and using Ion Chromatography. Then, this comparison was repeated with air and helium (He) instead of evacuating the measurements chamber of the EDXRF spectrometer. It was shown that EDXRF application using vacuum medium led to mass loss of water soluble ionic compounds and other volatile constituents of PM10. The use of a He and air medium considerably reduced the PM mass losses. It is demonstrated that the mass loss of PM and ionic compounds mainly resulted from vacuum medium and from a lower extent to the level of X-ray energy. The influence of EDXRF application using vacuum medium on the mass losses of ionic compounds were further investigated. Different amounts of NO3 , NH4 +, Cl, Na+, Mg++ and Ca++ were lost whereas SO4 −− and K+ remained unchanged. The relationship between vacuum and application time was also studied for quartz and Teflon filters. The longer the application time, the higher the PM mass loss was observed. The mass loss of PM on quartz filter was shown by experiments to be 2 times higher than on Teflon filter.
Keywords: Mass loss; PM10; EDXRF; Vacuum; Helium;

Distribution, sources and health risk assessment of mercury in kindergarten dust by Guangyi Sun; Zhonggen Li; Xiangyang Bi; Yupeng Chen; Shuangfang Lu; Xin Yuan (169-176).
Mercury (Hg) contamination in urban area is a hot issue in environmental research. In this study, the distribution, sources and health risk of Hg in dust from 69 kindergartens in Wuhan, China, were investigated. In comparison with most other cities, the concentrations of total mercury (THg) and methylmercury (MeHg) were significantly elevated, ranging from 0.15 to 10.59 mg kg−1 and from 0.64 to 3.88 μg kg−1, respectively. Among the five different urban areas, the educational area had the highest concentrations of THg and MeHg. The GIS mapping was used to identify the hot-spot areas and assess the potential pollution sources of Hg. The emissions of coal-power plants and coking plants were the main sources of THg in the dust, whereas the contributions of municipal solid waste (MSW) landfills and iron and steel smelting related industries were not significant. However, the emission of MSW landfills was considered to be an important source of MeHg in the studied area. The result of health risk assessment indicated that there was a high adverse health effect of the kindergarten dust in terms of Hg contamination on the children living in the educational area (Hazard index (HI) = 6.89).
Keywords: Mercury; Methylmercury; Kindergarten dust; Risk assessment; Wuhan city;

Air–water partition coefficient (K AW) is one of the key parameters determining environmental behavior of Persistent Organic Pollutants (POPs). Experimentally measured values of K AW are still unavailable for majority of POPs, thus alternative methods of supplying data, including Quantitative Structure–Property Relationships (QSPR) modeling, are often in use. In this paper, applicability of two QSPR methods of predicting K AW were compared with each other in the context of further application of the predicted data in environmental transport and fate studies. According to the first (indirect) method, K AW is calculated from previously predicted values of octanol–water (K OW) and octanol–air (K OA) partition coefficients. In the second (direct) approach, K AW is calculated, based on the estimated value of Henry's law constant (K H) and then adjusted to ensure its consistency with the other two partition coefficients (K OW and K OA). Although the indirect method carries theoretically twice as much error as the direct method, when the predicted values of K AW are then utilized as an input to the environmental fate model The OECD P OV and LRTP Screening Tool, ver. 2.2, the indirect method elicits much higher and therefore much more restrictive values of overall persistence (P OV) and transfer efficiency (TE) than its equivalent (direct method). High uncertainties related to the application of the direct method result mainly from the necessary adjustment procedure.
Keywords: Air–water partition coefficient; Multimedia mass modeling; QSPR; POPs;

Ultrafine particle exposures while walking, cycling, and driving along an urban residential roadway by David C. Quiros; Eon S. Lee; Rui Wang; Yifang Zhu (185-194).
Elevated concentrations of ultrafine particles (UFPs, <0.1 μm), which have been linked to adverse health effects, are commonly found along roadways. This study reports UFP and PM2.5 concentrations and respiratory exposures among four transportation modes on an urban residential street in Santa Monica, California while walking, cycling, and driving with windows open and windows closed (with air recirculation on). Repeated measurements were made for nine days during morning (7:30–9:30), afternoon (12:30–14:30), and evening (17:00–19:00) periods. Median UFP concentrations ranged 1–3 × 104 particles cm−3, were 70% lower in afternoon or evening periods compared to the morning, and were 60% lower when driving with windows closed than open. Median PM2.5 ranged 2–15 μg m−3, well below the annual National Ambient Air Quality standard of 15 μg m−3. Respiratory UFP exposure (particles inhaled trip−1) was ∼2 times higher while driving with windows open, ∼15 times higher when cycling, and ∼30 times higher walking, than driving with windows closed. During one evening session with perpendicular rather than parallel wind conditions, absolute UFP concentration was 80% higher, suggesting influence of off-roadway sources. Under parallel wind conditions, a parameter called emissions-weighted traffic volume, used to account for higher and lower emitting vehicles, was correlated with beach-site-subtracted UFP using second-order polynomial model (R 2 = 0.61). Based on this model, an 83% on-roadway UFP reduction could be achieved by (1) requiring all trucks to meet California 2007 model-year engine standards, (2) reducing light-duty vehicle flows by 25%, and (3) replacing high-emitting light-duty vehicles (pre 1978) with newer 2010 fleet-average vehicles.
Keywords: Ultrafine particle; PM2.5; Exposure science; Cyclist; Pedestrian; Vehicle emissions;

On-line measurements of gaseous nitro-organic compounds in diesel vehicle exhaust by proton-transfer-reaction mass spectrometry by Satoshi Inomata; Hiroshi Tanimoto; Yuji Fujitani; Kanako Sekimoto; Kei Sato; Akihiro Fushimi; Hiroyuki Yamada; Shigeo Hori; Yasuko Kumazawa; Akio Shimono; Toshihide Hikida (195-203).
Nitro-organic compounds, some of which cause adverse health effects in humans, are emitted in diesel engine exhaust. Speciation and quantification of these nitro-organic compounds in diesel engine exhaust particles have been extensively conducted; however, investigations into the emissions of gaseous nitro-organic compounds in diesel engine exhaust have not. In the present study, the properties of gaseous nitro-organic compounds in diesel engine exhaust were investigated through time-resolved measurement with a proton-transfer-reaction mass spectrometer and a chassis dynamometer. Three diesel trucks were tested, each with a different type of exhaust-gas treatment system (i.e., aftertreatment). Among the nitro-organic compounds detected, the emission of nitromethane was commonly observed and found to be related to the emissions of carbon monoxide, benzene, and acetone. The emission of other nitro-organic compounds, such as nitrophenol, depended on the vehicle, possibly due to the type of aftertreatment installed.
Keywords: Proton-transfer-reaction mass spectrometry (PTR-MS); Nitro-organic compounds; Diesel vehicle exhaust; Nitromethane; Nitrophenol;

To evaluate the cancer risk due to non-dietary PAHs exposure in home environment (inhalation and ingestion), exposure to fine particles (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) of PM2.5, total suspend particles (TSP) and dust in homes at two urban centers of Pearl River Delta were assessed. House PM2.5 bound PAHs in Guangzhou (GZ) ranged from 10.0 to 61.9 ng m−3 and 0.72 to 8.15 ng m−3 in Hong Kong (HK). PAH profiles found in PM2.5, TSP and dust were different than that in hair (dominated by Nap and Phe). Pyr and Flu in house dust significantly correlated with that in hair (r = 0.69; 0.55, p < 0.05) but no correlation was found between PAHs in hair and PM2.5. High correlation coefficients (r 2 = 0.97/0.95, p < 0.01) were noted between dibenzo(a,h)anthracene (DBA) and Toxicity Equivalent Concentrations (TEQs) of dust and PM2.5. The lung cancer risks based on PM2.5 bound PAHs exposure in houses of GZ (10−5–10−4) were significantly higher than those of HK (10−6–10−5), which were also significantly higher than the cancer risks associated with house dust intake (10−7–10−5) in GZ. PAHs exposure via non-dietary route (PM2.5 and dust) was found to be 1–3 times higher than fish consumption for children and contributed to 52–76% of total PAHs intake for children and 24–50% for adults in GZ.
Keywords: Polycyclic aromatic hydrocarbons (PAHs); PM2.5; House dust; Non-dietary exposure; Risk assessment;