Atmospheric Environment (v.82, #C)

A modelling study of the impact on air quality and health due to the emissions from E85 and petrol fuelled cars in Sweden by Erik Fridell; Marie Haeger-Eugensson; Jana Moldanova; Bertil Forsberg; Karin Sjöberg (1-8).
Alternative fuels are becoming more and more important for road traffic and one fuel that has been used for several years is ethanol (E85). The main discussion points regarding the environmental performance for ethanol as a fuel are related to the production. However, there are also some notable differences in the emissions between E85 and petrol fuelled vehicles. This relates to some extent to the emissions of nitrogen oxides (NO x ) and particulate matter (PM) but mainly to the composition of the emitted organic compounds. In the present study two fuel scenarios for passenger cars are investigated for the Västra Götaland Region in Sweden; one where the cars with Otto engines run on petrol and one where they run on E85. Two emission scenarios for 2020 are constructed for the whole Europe and coupled dispersion-chemistry modelling is applied to obtain the population exposure to key pollutants. The differences obtained from the modelling show decreased levels of NO x , ozone and benzene with E85 and increased levels of acetaldehyde in the Västra Götaland Region. For the latter the increase may be up to 80%, while NO x and ozone show decreases of up to a few per cent and a few tenths of per cent, respectively. Exposure to the different air pollutants is calculated as population-weighted concentrations. The health risk assessment, using the calculated exposure and published exposure–response functions for the relevant pollutants, shows decreased health risks in the E85 scenario relative the all-petrol scenario, due to the decreased NO x exposure, correlated with both preterm deaths and asthma. However, NO x (and NO2) may partly be indicators of unmeasured causal exhaust components in the epidemiological studies and thus the exposure–response functions for these may not be applicable in the present case where there is a difference in NO x exposure but not a proportional difference in exposure to other exhaust components normally associated with NO x . Smaller effects are expected from the changes in ozone, acetaldehyde, PM2.5 and benzene exposure. The overall difference is about 1.6 preterm deaths per year for the Västra Götaland Region, with lower values for the E85 scenario, when the uncertain differences due to the differences in NO x exposure are not considered.
Keywords: Ethanol fuel; Emissions; Air pollution modelling; Health impact assessment;

Occupant exposure to indoor air pollutants in modern European offices: An integrated modelling approach by Andrew C. Terry; Nicola Carslaw; Mike Ashmore; Sani Dimitroulopoulou; David C. Carslaw (9-16).
A new model (INDAIR-CHEM) has been developed by combining a detailed indoor air chemistry model with a physical and probabilistic multi-compartment indoor/outdoor air exposure model. The detailed indoor air chemistry model was used to produce a simplified chemistry scheme for INDAIR-CHEM, which performs well for key indoor air pollutants under a range of conditions when compared to the parent model. INDAIR-CHEM was used to compare indoor pollutant concentrations in naturally ventilated offices in 8 European cities for typical outdoor conditions in summer, with those experienced during the European heat-wave in August 2003 for different air exchange rates. We also investigated the effect of cleaning with limonene based products on the subsequent exposure to secondary reaction products from limonene degradation.Extreme climatic conditions, such as a heat-wave which often leads to poor outdoor air quality, can increase personal exposure to both primary and secondary species indoors. Occupant exposure to indoor air pollutants may also be exacerbated by poor ventilation in offices. Reduced ventilation reduces maximum exposure to ozone, as there is less ingress from outdoors, but allows secondary species to persist indoors for much longer. The balance between these two processes may mean that cumulative exposures for office workers increase as ventilation decreases. Cleaning staff are at lower risk of exposure to secondary oxidation products if they clean before office hours rather than after office hours, since ozone is generally at lower outdoor (and hence indoor) concentrations during the early morning compared to late afternoon. However, from the viewpoint of office workers, reduced exposure would occur if cleaning was performed at the end of the working day.
Keywords: Indoor air chemistry; INDAIR-CHEM; Ozone; Limonene; Cleaning; Heat-wave;

Aerosol size distributions of observed mass concentrations at the Naiman site in Inner Mongolia that is one of the major Asian dust source regions have been examined for the period from April 2010 to July 2012. The total number of 262 sampled data using the 10-stage quartz crystal microbalance (QCM) cascade impactor is obtained by presetting the frequency changes of 40 Hz during April 2010, 60 Hz for the period of 28 April–16 September 2010 and 70 Hz from 1 November 2010–29 July 2012. The total mass concentrations (PM10) measured by the QCM cascade impactor are modified to have the same sampling time of 60 min with the help of the 1-h averaged PM10 concentration measured by the beta gauge at the same site. These modified QCM data are classified into the local dust emission case of 196 and the dust advection case of 66. The local dust emission case is defined when the calculated dust flux with the two-level (3 m and 15 m high) measured PM10 concentrations by the beta-gauge is upward and the PM10 concentration measured at 3 m high exceeds 100 μg m−3 while all the rest of QCM sampled data are classified as the dust advection case. The results indicate that the spectral mass concentration distribution of the local dust emission case shows a two-modal distribution with one additional mode of the large particle that cannot be resolved by the QCM cascade impactor whereas that of the advection case reveals a three-modal distribution with one additional unresolved large particle mode. The percent spectral mass concentration distribution of the unresolved mode (stage 1) for the local dust emission case is larger than that for the dust advection case. The modal distributions of both cases can be regressed optimally with log-normal distribution functions. The resolved log-normal distribution functions of the mass concentration distribution by the QCM cascade impactor are found to be the particle mean diameter (the standard deviation) of 0.28 (2.07) and 3.15 μm (1.41 μm) for the local emission case and 0.16 (1.51), 0.60 (1.41) and 2.88 μm (1.38 μm) for the advection case. This clearly suggests that the spectral mass concentration shifts toward the larger particle size for the local emission case.
Keywords: Aerosol size distribution; Asian dust particle; Dust source region; Naiman site; Spectral mass concentration distribution;

Estimation of VOC emission factors from flux measurements using a receptor model and footprint analysis by Sri Harsha Kota; Changhyoun Park; Martin C. Hale; Nicholas D. Werner; Gunnar W. Schade; Qi Ying (24-35).
Fluxes of 18 volatile organic compounds (VOCs) collected during May to July 2008 from a tower platform 60 m above the surface in an urban Houston residential area were analyzed using receptor-oriented statistical models and an analytical flux-footprint model to resolve daytime source specific emissions rates. The Multilinear Engine version 2 (ME-2) was used to determine that five sources were responsible for the measured flux at the tower: (i) vehicle exhaust, (ii) a foam plastics industrial source with significant pentane emissions, (iii) consumer and commercial solvent use emissions, (iv) a biogenic emissions source dominated by isoprene, and, (v) evaporative fuel emissions. The estimated median daytime (0700–1900 CST) hourly emission rate from the foam plastics industry was 15.7 ± 3.1 kg h−1, somewhat higher than its permitted hourly emission rates. The median daytime vehicle exhaust VOC emission rate of 14.5 ± 2 g h−1 vehicle−1, was slightly higher than our estimation using the Motor Vehicle Emission Simulator (MOVES) with a county-representative vehicle fleet of year 2008 (11.6 ± 0.2 g h−1 vehicle−1). The median daytime evaporative fuel VOCs emission rate from parked vehicles was 2.3 ± 1.0 g h−1 vehicle−1, which is higher than MOVES estimations and could not be explained by the age of the vehicle fleet, indicating either locally higher evaporative emission sources in the footprint or an underestimation of evaporative emissions by MOVES, or both.
Keywords: Source apportionment; Positive Matrix Factorization (PMF); Multilinear Engine (ME-2); Motor Vehicle Emission Simulator (MOVES); Vehicle exhaust; Evaporative emissions; Foam plastics industry;

Deliquescence and efflorescence behavior of individual NaCl and KCl mixture aerosol particles by Xue Li; Dhrubajyoti Gupta; Hyo-Jin Eom; HyeKyeong Kim; Chul-Un Ro (36-43).
The hygroscopic behavior of laboratory-generated, micrometer sized NaCl and KCl mixture aerosol particles in nine mixing ratios (mole fractions of KCl (X KCl) = 0.1–0.9) was investigated systematically to observe their deliquescence and efflorescence behavior, obtain experimental phase diagrams for their deliquescence and efflorescence, and understand the efflorescence mechanism. Aerosol particles with a eutonic composition of X KCl = 0.3 showed only one phase transition during the humidifying process at the mutual deliquescence relative humidity (MDRH) of 72.3(±0.5)%, whereas the aerosol particles with other mixing ratios showed two distinct deliquescence transitions. First, the eutonic component dissolved at the MDRH and second, the remainder in the solid phase dissolved completely at various DRHs, resulting in a phase diagram composed of four different phases. During the dehydration process, droplets at all mixing ratios showed a single transition at their efflorescence RHs (ERHs), resulting in a phase diagram composed of two different phases. The minimum ERH of 43.7–43.2% was observed for X KCl = 0.4. This suggests that short-range ionic interactions and the common-ion effect may substantially affect the mutual solubility of NaCl and KCl at high ionic-strengths, and hence the supersaturation of the salts. Elemental X-ray mapping of the effloresced NaCl–KCl mixture particles at all mixing ratios suggests that more supersaturated salt nucleated homogeneously to crystallize in the center, and the other salt underwent the heterogeneous crystallization on the former.
Keywords: Hygroscopic properties of multi-component aerosols; NaCl–KCl; DRH; ERH; Single particle analysis; Optical microscopy; SEM/EDX;

A review of chamber experiments for determining specific emission rates and investigating migration pathways of flame retardants by Cassandra Rauert; Borislav Lazarov; Stuart Harrad; Adrian Covaci; Marianne Stranger (44-55).
The widespread use of flame retardants (FRs) in indoor products has led to their ubiquitous distribution within indoor microenvironments with many studies reporting concentrations in indoor air and dust. Little information is available however on emission of these compounds to air, particularly the measurement of specific emission rates (SERs), or the migration pathways leading to dust contamination. Such knowledge gaps hamper efforts to develop understanding of human exposure. This review summarizes published data on SERs of the following FRs released from treated products: polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs), tetrabromobisphenol-A (TBBPA), novel brominated flame retardants (NBFRs) and organophosphate flame retardants (PFRs), including a brief discussion of the methods used to derive these SERs. Also reviewed are published studies that utilize emission chambers for investigations/measurements of mass transfer of FRs to dust, discussing the chamber configurations and methods used for these experiments. A brief review of studies investigating correlations between concentrations detected in indoor air/dust and possible sources in the microenvironment is included along with efforts to model contamination of indoor environments. Critical analysis of the literature reveals that the major limitations with utilizing chambers to derive SERs for FRs arise due to the physicochemical properties of FRs. In particular, increased partitioning to chamber surfaces, airborne particles and dust, causes loss through “sink” effects and results in long times to reach steady state conditions inside the chamber. The limitations of chamber experiments are discussed as well as their potential for filling gaps in knowledge in this area.
Keywords: Emission chamber; Specific emission rate; Flame retardants; Mass transfer to dust;

Scanning mobility particle sizers (SMPS) are common instruments in laboratory and field aerosol studies. They are, however, complex instruments whose accuracy depends in part on reproducible size calibration. The commonly recommended calibration procedure uses polystyrene latex spheres in a solution with surfactant added to minimize coagulation of the particles. The surfactant can contribute significantly to the overall particle number size distribution and in some cases overlap the peak due to the latex spheres. We describe here the application of surfactant-free latex spheres which to the best of our knowledge have not been used in atmospheric applications before but which have significant advantages, including ease of use and cost.
Keywords: Particles; Aerosols; SMPS; Calibration;

Spatial distribution of hydrogen sulfide from two geothermal power plants in complex terrain by S. Olafsdottir; S.M. Gardarsson; H.O. Andradottir (60-70).
Concerns have arisen about the health impact and odor annoyance of hydrogen sulfide (H2S) emissions associated with geothermal power production. Measurements have been made at stationary measuring stations in inhabited areas but little is known about the spatial behavior of the H2S plumes. This study presents field measurements of the spatial distribution of the ground concentration of H2S within a 30 km radius of two geothermal power plants during 20 distinct events spanning one year. The results showed that high H2S concentration was correlated with high air stability, low wind speed and absence of precipitation. The odor threshold (11 μg m−3) was exceeded in all events. The instantaneous measurements exceeded the 24-h average national health limit (50 μg m−3) up to 26 km from the power plants. The shape of the measured plumes at the same location was similar between events, indicating repeated patterns in plume distribution. Convergence of plumes was observed due to spatial variability in wind direction. Plumes were found to follow mountain passes and accumulate alongside a mountain range. AERMOD modeling demonstrated that narrower plumes with higher concentration can be expected for smoother terrain, such as lakes, consistent with measurements.
Keywords: Hydrogen sulfide; Air quality; Spatial distribution; Dispersion modeling; Geothermal emissions;

Aerosol optical depth (AOD), Ångström Exponent (AE), and single scattering albedo (SSA) simulated by a new aerosol-coupled version of Nonhydrostatic ICosahedral Atmospheric Model (NICAM) have been compared with corresponding AERONET retrievals over a total of 196 sites during the 2006–2008 period. The temporal and spatial distributions of the modeled AODs and AEs match those of the AERONET retrievals reasonably well. For the 3-year mean AODs and AEs for all sites show the correlations between model and AERONET of 0.753 and 0.735, respectively, and 82.1% of the modeled AODs agree within a factor of two with the retrieved AODs. The primary model deficiency is an underestimation of fine mode aerosol AOD and a corresponding underestimation of AE over pollution region. Compared to the retrievals, the model underestimates the global 3-year mean AOD and AE by 0.022 (10.5%) and 0.329 (31.2%), respectively. The probability distribution function (PDF) of the modeled AODs is comparable to that of the retrieved ones, however, the model overestimates the occurrence frequencies of small AEs and SSAs.
Keywords: Global aerosol model; Aerosol optical depth; Ångström exponent; Single scattering albedo; AERONET;

LIDAR as an alternative to passive collectors to measure pesticide spray drift by Eduard Gregorio; Joan R. Rosell-Polo; Ricardo Sanz; Francesc Rocadenbosch; Francesc Solanelles; Cruz Garcerá; Patricia Chueca; Jaume Arnó; Ignacio del Moral; Joan Masip; Ferran Camp; Rafael Viana; Alexandre Escolà; Felip Gràcia; Santiago Planas; Enrique Moltó (83-93).
Pesticide spray drift entails a series of risks and costs in terms of human, animal and environmental well-being. A proper understanding of this phenomenon is essential to minimise these risks. However, most conventional methods used in drift measurement are based on point collectors which are unable to obtain information concerning the temporal or spatial evolution of the pesticide cloud. Such methods are also costly, labour-intensive, and require a considerable amount of time. The aim of this paper is to propose a method to measure the spray drift based on lidar (LIght Detection And Ranging) and to prove that it can be an alternative to passive collectors. An analytical model is proposed to relate the measurements obtained through passive collectors and those obtained with lidar systems considering several spray application and meteorological parameters. The model was tested through an experimental campaign involving multiple ground spray tests. A lidar system and two types of passive collectors (nylon strings and water-sensitive paper) were used simultaneously to measure the drift. The results showed for each test a high coefficient of determination (R 2 ≈ 0.90) between the lidar signal and the tracer mass captured by the nylon strings. This coefficient decreased (R 2 = 0.77) when all tests were considered together. Lidar measurements were also used to study the evolution of the pesticide cloud with high range (1.5 m) and temporal resolution (1 s) and to estimate its velocity. Furthermore, a very satisfactory adjustment (R 2 = 0.89) was observed between the tracer mass collected by the nylon lines and the coverage on water-sensitive paper sheets. These results are in accordance with the proposed analytical model and allow the conclusion that the application and meteorological parameters can be considered spatially invariant for a given test but are not invariant for different tests.
Keywords: Light detection and ranging; Remote sensing; Sprayer; Droplet; Tracer; Agriculture;

Analysis of uncertainties in the estimates of nitrous oxide and methane emissions in the UK's greenhouse gas inventory for agriculture by Alice E. Milne; Margaret J. Glendining; Pat Bellamy; Tom Misselbrook; Sarah Gilhespy; Monica Rivas Casado; Adele Hulin; Marcel van Oijen; Andrew P. Whitmore (94-105).
The UK's greenhouse gas inventory for agriculture uses a model based on the IPCC Tier 1 and Tier 2 methods to estimate the emissions of methane and nitrous oxide from agriculture. The inventory calculations are disaggregated at country level (England, Wales, Scotland and Northern Ireland). Before now, no detailed assessment of the uncertainties in the estimates of emissions had been done. We used Monte Carlo simulation to do such an analysis. We collated information on the uncertainties of each of the model inputs. The uncertainties propagate through the model and result in uncertainties in the estimated emissions. Using a sensitivity analysis, we found that in England and Scotland the uncertainty in the emission factor for emissions from N inputs (EF1) affected uncertainty the most, but that in Wales and Northern Ireland, the emission factor for N leaching and runoff (EF5) had greater influence. We showed that if the uncertainty in any one of these emission factors is reduced by 50%, the uncertainty in emissions of nitrous oxide reduces by 10%. The uncertainty in the estimate for the emissions of methane emission factors for enteric fermentation in cows and sheep most affected the uncertainty in methane emissions. When inventories are disaggregated (as that for the UK is) correlation between separate instances of each emission factor will affect the uncertainty in emissions. As more countries move towards inventory models with disaggregation, it is important that the IPCC give firm guidance on this topic.
Keywords: Greenhouse gas inventory; Agriculture; Nitrous oxide; Methane; Uncertainty;

Effect of litter layer on soil–atmosphere N2O flux of a subtropical pine plantation in China by Yidong Wang; Huimin Wang; Zhong-Liang Wang; Zeqing Ma; Xiaoqin Dai; Xuefa Wen; Yunfen Liu (106-112).
Forest soils are important sources for nitrous oxide (N2O), but how the surface litter layer affects these sources is still unclear. Seasonal rainfall in the subtropical monsoon climate provides a unique opportunity to examine soil–atmosphere N2O flux under a wide range of soil water content. We studied this question over 3 years using a litter removal method in a 20-year-old pine plantation (Pinus elliottii) in subtropical China. Annual mean chamber-based soil–atmosphere N2O fluxes of the control (F CK) and litter-free (F LF) treatments were 6.07 and 5.17 μg N2O m−2 h−1, respectively. Removal of the litter layer reduced 15% of soil N2O emissions, suggesting the mineral soil as the dominant factor that determines soil N2O emissions. Seasonal F CK and F LF were both significantly influenced by water-filled pore space (WFPS) but not by soil temperature (T S). However, F CK and F LF were both correlated with T S during the wet season (January–June) but not during the dry season (July–December). During the wet season, F CK and F LF were 84% and 132% higher than during the dry season, respectively. In contrast, seasonal litter-based N2O fluxes (F CK−LF = F CK − F LF) were not correlated with WFPS and T S. During the dry season, however, a positive relationship was observed for F CK−LF and WFPS. In the context of climate change and human activities, future changes in soil environment and surface litter management will alter the strength of soil N2O emissions of the subtropical pine forests in China.
Keywords: Litter removal; Nitrous oxide; Organic horizon; Slash pine; Soil–atmosphere N2O exchange; Subtropical forest;

The rate coefficients of the reactions of three unsaturated cyclic ethers, 2,5-dihydrofuran (2,5-DHF), 2,3-dihydrofuran (2,3-DHF), and 3,4-dihydropyran (3,4-DHP), with the major day-time tropospheric oxidants – OH (k OH) and O3 ( k O 3 ) , and that of 3,4-DHP with Cl atom (k Cl) are determined using relative rate method, at 298 K. The values of k OH are (6.45 ± 1.69), (11.95 ± 2.79) and (11.38 ± 2.64) × 10−11 cm3 molecule−1 s−1 for 2,5-DHF, 2,3-DHF and 3,4-DHP, respectively and k O 3 are (1.65 ± 0.31), (443.20 ± 79.0) and (31.36 ± 5.80) × 10−17 cm3 molecule−1 s−1 for 2,5-DHF, 2,3-DHF and 3,4-DHP, respectively. The value of k Cl for 3,4-DHP is (6.15 ± 0.84) × 10−10 cm3 molecule−1 s−1 . The dominant pathway of tropospheric degradation of 2,5-DHF is the reaction with OH, whereas that of 2,3-DHF is the reaction with O3. Reaction with both OH and O3 are equally important in the case of 3,4-DHP. Under the conditions of marine boundary layer, the reaction with Cl atom is important in the tropospheric degradation of 2,5-DHF and 3,4-DHP, but insignificant in the case of 2,3-DHF (only 1.8%). The estimated tropospheric lifetimes in the day-time are 2.0, 0.08 and 0.62 h for 2,5-DHF, 2,3-DHF and 3,4-DHP respectively. The presence of O atom, unsaturation, conjugation etc. influences the rate coefficients in a complex manner. However, there is a good correlation of k OH with HOMO energy, which further improves by treating the molecules separately, either as ethers and hydrocarbons, or as cyclic and acyclic molecules. The values of k O 3 of these ethers fit very well with the straight line regression derived for simple alkenes with their HOMO energy, except 2,3-DHF, which has a high strain enthalpy. The values of k Cl also show a similar trend of increase with HOMO energy, but the correlation is not as good as that of k OH.Major tropospheric pathways for the three unsaturated ethers.Display Omitted
Keywords: Unsaturated cyclic ethers; Reactions with OH, O3 and Cl; Rate coefficients; Tropospheric lifetime;

Biological processes in agroecosystems have been affected by atmospheric nitrogen (N) and sulfur (S) deposition, but there is uncertainty about their deposition characteristics in the monsoon season. We collected rain samples using an ASP-2 sampler, recorded rainfall and rain frequency by an auto-meteorological experiment sub-station, and determined total N, NO 3 − - N and NH 4 + - N levels in precipitation with an AutoAnalyzer 3 and SO 4 2 − - S with a chromatography, in order to characterize the wet deposition of N and S to a typical red soil agroecosystem by a ten-year monitoring experiment in Southeast China. The results indicated that N and S wet deposition had an increased trend with the flux of total N (3.34–65.17 kg ha−1 N) and total S ( SO 4 2 − - S ) (7.17–23.44 kg ha−1 S) during the monsoon seasons. The additional applications of pig mature in 2006 and 2007 led to the peaks of DON (dissolved organic nitrogen) and total N wet deposition. On average, NH 4 + - N was the major N form, accounting for 48.5% of total N wet deposition and DON was not a negligible N form, accounting for 20.8% during the ten-year monsoon seasons (except 2006 and 2007). Wet deposition of N and S has been intensively influenced by human activities in the monsoon season, and would increase the potential ecological risk in the red soil agricultural ecosystem.
Keywords: N and S deposition; Wet deposition; Monsoon season; Red soil farmland; Southeast China;

A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean by A. Kumar; W. Abouchami; S.J.G. Galer; V.H. Garrison; E. Williams; M.O. Andreae (130-143).
Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and atmospheric transport.
Keywords: Dust; Long-range transport; Africa; Caribbean; Radiogenic isotope tracers; Provenance;

Contribution of particulate water to the measured aerosol optical properties of aged aerosol by Christodoulos Pilinis; Panagiotis E. Charalampidis; Nikolaos Mihalopoulos; Spyros N. Pandis (144-153).
Measurements of aged aerosol scattering in the Eastern Mediterranean at ambient and low relative humidity (RH) are combined with measurements of its size composition distribution and its aerosol water content to gain insights about its hygroscopic and optical properties. The particle water uptake above 60% RH can be explained by the water absorption by the inorganic particulate matter in this sulphate rich environment. However, the particles were supersaturated aqueous solutions at low RH and this water cannot be explained just by the water associated with their inorganic components in a metastable state. We estimate that approximately 20% of this water may be contributed by the aged organic particulate matter. A semi-empirical equation is derived allowing the estimation of the aged aerosol Volume Growth Factor (VGF) from the ratios of scattering at ambient and low RH. The predictions of the equation are in good agreement with the measurement dataset obtained during the study.
Keywords: Aerosol water; Aerosol scattering; Supersaturation; Organic hygroscopicity; DAASS;

Biomonitoring of airborne particulate matter emitted from a cement plant and comparison with dispersion modelling results by Gabriela A. Abril; Eduardo D. Wannaz; Ana C. Mateos; María L. Pignata (154-163).
The influence of a cement plant that incinerates industrial waste on the air quality of a region in the province of Córdoba, Argentina, was assessed by means of biomonitoring studies (effects of immission) and atmospheric dispersion (effects of emission) of PM10 with the application of the ISC3 model (Industrial Source Complex) developed by the USEPA (Environmental Protection Agency). For the biomonitoring studies, samples from the epiphyte plant Tillandsia capillaris Ruíz & Pav. f. capillaris were transplanted to the vicinities of the cement plant in order to determine the physiological damage and heavy metal accumulation (Ca, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb). For the application of the ISC3 model, point and area sources from the cement plant were considered to obtain average PM10 concentration results from the biomonitoring exposure period. This model permitted it to be determined that the emissions from the cement plant (point and area sources) were confined to the vicinities, without significant dispersion in the study area. This was also observed in the biomonitoring study, which identified Ca, Cd and Pb, pH and electric conductivity (EC) as biomarkers of this cement plant. Vehicular traffic emissions and soil re-suspension could be observed in the biomonitors, giving a more complete scenario. In this study, biomonitoring studies along with the application of atmospheric dispersion models, allowed the atmospheric pollution to be assessed in more detail.
Keywords: Tillandsia capillaris; Heavy metal enrichment factors; ISC3; Emission factor estimation technique; Córdoba;

This study investigates the heterogeneous OH oxidation of folpet and dimethomorph, two fungicides identified in the atmosphere of the Champagne-Ardenne region. Kinetic experiments were conducted in the relative mode, using terbuthylazine as a reference compound. The experimental method employed makes use of a simulation chamber coupled to a GC/MS analytical system. Meanwhile, the identification of (4-chlorophenyl)(3,4-dimethoxyphenyl)methanone (CPMPM), a degradation product of the OH oxidation of dimethomorph, is achieved using SPME/GC/MS. Moreover, a degradation mechanism of dimethomorph is proposed, and the heterogeneous OH reactivity of CPMPM is evaluated. The obtained OH reaction rate constants (cm3 molecule−1 s−1) are: k Z-dimethomorph = (2.0 ± 1.2) 10−14, k E-dimethomorph = (1.7 ± 1.2) 10−14, k Folpet = (1.6 ± 0.9) 10−13 and k CPMPM = (1.9 ± 1.0) 10−12. The implicated tropospheric life-times are up to 2 months, which shows that the investigated pesticides are relatively persistent towards oxidation removal processes. CPMPM, the identified product of OH oxidation of dimethomorph, is less persistent with a life time of only 6 days relative to heterogeneous oxidation by OH radicals.Display Omitted
Keywords: Pesticides; Heterogeneous kinetics; Ozone; Mechanism; Folpet; Dimethomorph; Atmospheric life-times;

The ability of the Weather Research and Forecasting, large-eddy simulation model (WRF-LES) to model passive scalar dispersion from continuous sources in convective and neutral atmospheric boundary layers was investigated. WRF-LES accurately modeled mean plume trajectories and concentration fields. WRF-LES statistics of concentration fluctuations in the daytime convective boundary layer were similar to data obtained from laboratory experiments and other LES models. However, poor turbulence resolution near the surface in neutral boundary layer simulations caused under prediction of mean dispersion in the crosswind horizontal direction and over prediction of concentration variance in the neutral surface layer. A gradient in the intermittency factor for concentration fluctuations was observed near the surface, downwind of ground-level sources in the daytime boundary layer. That observation suggests that the intermittency factor is a promising metric for estimating source-sensor distance in source determination applications.
Keywords: WRF model; Large-eddy simulation; Passive scalar; Dispersion; Atmospheric boundary layer; Concentration fluctuations;

A study of urban pollution and haze clouds over northern China during the dusty season based on satellite and surface observations by Minghui Tao; Liangfu Chen; Zifeng Wang; Pengfei Ma; Jinhua Tao; Songlin Jia (183-192).
This paper presents a multi-scale study on formation process of urban pollution and haze clouds as well as their interactions over northern China in spring using integrated satellite and surface observations. Several extreme haze events occurred in Beijing area in March 2013, but primary atmospheric pollutants in the urban pollution exhibited inconsistent variations with the widespread haze clouds observed by satellites. Two typical types of haze event were found in Beijing area. Type-1 haze pollution appeared in stagnant weather conditions, during which PM2.5 was <200 μg m−3 with a short duration within 1–2 days. By contrast, strong northwestern winds prevailed in type-2 haze events with durative and intense temperature inversion near surface. Meanwhile, PM2.5 concentration exceeded ∼400 μg m−3 in type-2 pollution, and the heavy pollution can last 3–5 days. Different from urban pollution, our results show that the thick haze clouds were dominated by mixing of floating dust and anthropogenic pollutants in the middle and upper part, accompanied by hygroscopic growth of fine particles. Elevated coarse dust particles were prevalent over northern China, which accounted for a predominant fraction in the columnar optical volume during all the haze events. Furthermore, comparison between satellite and surface observations indicates that haze clouds above surface had no significant direct contribution to the serious urban pollution. In addition, mixing of dust and anthropogenic pollutants at high altitudes regulates regional aerosol optical properties throughout the whole March.
Keywords: Urban pollution; Satellite; Haze clouds; Dust transport; Northern China;

Seasonal and diurnal patterns of speciated atmospheric mercury at a coastal-rural and a coastal-urban site by Irene Cheng; Leiming Zhang; Huiting Mao; Pierrette Blanchard; Rob Tordon; John Dalziel (193-205).
Gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (PBM) were monitored at a coastal-rural and a coastal-urban site in Nova Scotia, Canada from 2010 to 2011. The three-hour average urban concentrations were 1.67 ± 1.01 ng m−3, 2.1 ± 3.4 pg m−3 and 2.3 ± 3.1 pg m−3 for GEM, GOM and PBM, respectively. The rural site concentrations were 1.38 ± 0.20 ng m−3, 0.4 ± 1.0 pg m−3 and 3.5 ± 4.5 pg m−3, respectively. GEM and GOM concentrations were higher at the urban site in all seasons, while PBM was higher at the rural site in winter. Both sites observed higher GEM and PBM during colder seasons and higher GOM in spring. Seasonal diurnal patterns showed daytime increases and nighttime decreases in GEM, GOM, and PBM. Rural–urban site differences may be attributed to the urban heat island effect resulting in warmer nighttime temperatures and higher GEM concentrations, urban GEM emissions, and enhanced deposition in forested areas leading to faster rural GEM decreases. Wind speeds ≥4 and ≥8 km h−1 were associated with higher rural GEM and lower PBM at night, which could be due to downward mixing from the residual boundary layer and marine airflows from the open ocean as modeled by back trajectories. The back trajectory analysis also found higher rural GEM and lower PBM overnight at both sites for open ocean airflows than all airflow conditions, suggesting the ocean is a source of GEM but not PBM.
Keywords: Atmospheric mercury; Ambient concentration; Coastal locations; Marine airflows; Trajectory analysis;

Trace elements and metal pollution in aerosols at an alpine site, New Zealand: Sources, concentrations and implications by Samuel K. Marx; Karen S. Lavin; Kimberly J. Hageman; Balz S. Kamber; Tadhg O'Loingsigh; Grant H. McTainsh (206-217).
Atmospheric aerosol samples were collected at a remote site in New Zealand's Southern Alps. Collected samples were found to be a mixture of New Zealand and Australian sourced sediment, using their trace element signatures. Aerosol concentrations and the relative contribution of different sources was found to be a function of specific air-mass trajectories influencing the study site, dust entrainment rates in source areas and rainfall. Results show that Australian dust is a major source of particulate matter in New Zealand, particularly in remote alpine locations; however, locally derived dust is also important. Metal pollutants, including Pb, Cu and Sn, were enriched in the samples by approximately 15 times and up to >100 times expected natural concentrations, confirming that metal pollution is a ubiquitous component of the atmosphere, even in relatively remote locations. Moreover, pollutants were highly enriched in otherwise clean air, i.e. during and following rainfall. Additionally, high concentrations of elements naturally enriched in sea water, e.g. Sr, Ba and Rb, were deposited alongside mineral dust, reflecting the oceanic origin of air influencing the site and the role of sea spray in contributing aerosol to the atmosphere. These elements experienced the greatest enrichment during rainfall, implying sea spray and pollution become relatively important during otherwise clean air conditions.
Keywords: Trace elements; Australia; Dust; Long-range;

Markers and influence of open biomass burning on atmospheric particulate size and composition during a major bonfire event by Ivano Vassura; Elisa Venturini; Sara Marchetti; Andrea Piazzalunga; Elena Bernardi; Paola Fermo; Fabrizio Passarini (218-225).
This study aims to characterize PM from the open burning of bonfires as well as detect a series of useful tracer species for source apportionment studies. Total suspended particulate (TSP), PM10 and PM2.5 were collected before, during, and after St. Joseph's Eve (18th of March). On this day, several bonfires are lit throughout the study area. Levoglucosan (Lvg), OC, EC, PAHs, soluble ions, and some metals (Al, Cd, Cu, Ni, and Pb) have been determined in each fraction.Results show that the contamination of the area is similar to what is generally found in suburban areas. The fine fraction makes the highest contribution to PM. This fraction is mainly related to compounds composing the PM secondarily formed, while the coarser fractions are associated with natural matrices.The bonfire event is an important source of particulate. All the combustion markers determined in PM2.5 (EC, OC, PAHs (except for Flu and Pyr), K+, Cl, and Lvg) register a higher concentration. Lvg/OC ratio confirms higher wood smoke emissions during these days. Both the concentration and the compound profile indicate a different origin of PAHs in the atmosphere. The highest concentration of K+ and OC in TSP confirm the contribution of open fire, as well, to this fraction, which can be ascribable mainly to combustion ash. Nitrates and sulphates also show a higher concentration in the PM10-TSP fraction. Surprisingly, there is also an increase in the concentration of components not usually considered combustion markers, i.e. Pb and Al in PM2.5. This is probably ascribable to their bioaccumulation. In conclusion, Lvg, OC, PAHs, Al, and Pb can be used together as specific markers of bonfires to identify this source of particulate matter.
Keywords: Open fire; Biomass combustion; Levoglucosan; Particulate chemical composition; Rimini;

New indices for wet scavenging of air pollutants (O3, CO, NO2, SO2, and PM10) by summertime rain by Jung-Moon Yoo; Yu-Ri Lee; Dongchul Kim; Myeong-Jae Jeong; William R. Stockwell; Prasun K. Kundu; Soo-Min Oh; Dong-Bin Shin; Suk-Jo Lee (226-237).
The washout effect of summertime rain on surface air pollutants (O3, CO, NO2, SO2, and PM10) has been investigated over South Korea during 2002–2012 using routinely available air-monitored and meteorological data. Three new washout indices for PM10, SO2, NO2, and CO are developed to express the effect of precipitation scavenging on these pollutants. All of these pollutants show statistically significant negative correlations between their concentrations and rain intensity due to washout or convection. The washout effect is estimated for precipitation episodes classified by rain intensity (one set included all episodes and another included a subset of moderate intensity episodes that exclude Changma and typhoons), based on the log-transformed hourly data. The most sensitive air pollutant to the rain onset among these five air pollutants is PM10. The relative effect of the rainfall washout on the air pollutant concentrations is estimated to be: PM10 > SO2 > NO2 > CO > O3, indicating that PM10 is most effectively scavenged by rainfall. The analysis suggests that the O3 concentrations may increase due to vertical mixing leading to its downward transport from the lower stratosphere/upper troposphere. The concentrations of CO are reduced, probably due to both the washout and convection. The concentrations of NO2 are affected by the opposing influences of lightning-generation and washout and this are discussed as well.
Keywords: Air pollutants; Washout; Rainfall; Surface measurement over South Korea; Statistical significance;

Use of the Chemical Mass Balance (CMB) model for aerosol source apportionment requires the input of source profiles of chemical constituents. Such profiles derived from studies in North America are relatively abundant, but are very scarce from European studies. In particular, there is a lack of data from European road vehicles. This study reports results from a comparison of road traffic source profiles derived from (1) US dynamometer studies of individual vehicles with (2) a traffic profile derived from measurements in a road tunnel in France and (3) new data derived from a twin-site study in London in which concentrations at an urban background site are subtracted from those measured at a busy roadside to derive a traffic increment profile. The dynamometer data are input as a diesel exhaust, gasoline exhaust and smoking engine profile, or alternatively as just a diesel exhaust and gasoline exhaust profile. Running the CMB model with the various traffic profiles together with profiles for other sources of organic carbon gives variable estimates of the contribution of traffic to organic carbon and to PM2.5 concentrations. These are tested in two ways. Firstly, unassigned organic carbon in the output from the CMB model, assumed to be secondary organic carbon, is compared to secondary organic carbon estimated independently using the elemental carbon tracer method. Secondly, the estimated traffic contribution to organic carbon and PM2.5 is compared with an estimate derived simply from the measured elemental carbon concentrations, and the effect on aerosol mass closure is investigated. In both cases the CMB model results correlate well with the independent measures, but there are marked differences according to the traffic source profile employed. As a general observation, it appears that the use of dynamometer data with inclusion of a smoking engine profile has a tendency to over-estimate traffic emissions at some sites whereas the tunnel profile shows a tendency to under-estimate. Overall, the traffic profile derived from the twin-site study gives probably the best overall estimate, but the quality of fit with independent estimates of secondary organic carbon and traffic particle mass depends upon the site and dataset for which the test is conducted.Display Omitted
Keywords: Receptor models; CMB; Source profile; Traffic emissions; Particulate matter;

The gas phase photolysis of two α-diketones, 2,3-pentanedione (PTD) and 2,3-hexanedione (HEX), has been studied in a Teflon simulation chamber using UV lamps in the 330–480 nm wavelength range. Photolysis rates have been determined at room temperature and atmospheric pressure. Using NO2 actinometry allows estimating the lifetime of PTD and HEX in the atmosphere to be about 2.5 h, assessing the dominance of the photolysis loss process over the OH reaction for such α-dicarbonyl compounds. Effective quantum yields for PTD and HEX have also been calculated over the whole wavelength range: ΦPTD = 0.20 ± 0.02 and ΦHEx = 0.18 ± 0.03, consistent with literature values on α-dicarbonyls. Various end-products from the photolysis of PTD and HEX have been identified and quantified. For PTD, CH2O and CH3CHO have been detected with molar yields of (48 ± 0.5)% and (41 ± 0.7)%, respectively. For HEX, CH2O and C2H5CHO have been detected with molar yields of (45 ± 1.1)% and (37 ± 0.8)%, respectively. Small amounts of CO have also been observed, with yields of about 2%, as well as organic acids. Experiments performed in the absence of OH-radical scavengers showed significantly faster photolysis rates and higher CO yields (∼7%), indicating clear formation of OH radicals in the chemical systems. A reaction mechanism was developed for PTD and HEX photolysis based on the product observations, which allowed simulating the reactant and product time profiles with very good agreement. The present work represents the first study of 2,3-pentanedione and 2,3-hexanedione photolysis, to our knowledge, and may contribute to a better understanding of the photolysis of the α-diketones in the troposphere.
Keywords: Dicarbonyl; OVOC; Oxygenated Volatile Organic Compound; Atmosphere;

Spatial and seasonal variability of measured anthropogenic non-methane hydrocarbons in urban atmospheres: Implication on emission ratios by Anne Boynard; Agnès Borbon; Thierry Leonardis; Barbara Barletta; Simone Meinardi; Don R. Blake; Nadine Locoge (258-267).
Continuous measurements of a wide range of non-methane hydrocarbons (NMHC) have been performed since 2001 in Paris megacity and three French medium-sized cities (Grenoble, Marseille, and Strasbourg). After a careful verification of the data measured, the ambient concentrations are used to analyze the spatial and seasonal variability of the anthropogenic NMHC and determine the present NMHC emission ratios relative to acetylene, a useful metric to evaluate and constraint emission inventories. We show that NMHC urban composition is consistent between all cities with no industrial influence and characteristic of the urban emission mixtures, which are mostly dominated by vehicle exhaust emissions. In winter, the urban NMHC composition generally shows an enhancement in combustion-derived products (alkenes, acetylene), C2–C3 alkanes and benzene, which presumes seasonal changes in emission ratio values. Present emission ratios of NMHC relative to acetylene are determined in Paris and Strasbourg both in summer and winter. They generally compare within a factor of two except for C7–C9 aromatics in Paris. On a seasonal basis, summertime emission ratios are three times higher than wintertime ones while they stay constant for combustion derived product (alkenes) and benzene. The unburned gasoline fraction (alkanes and C7–C9 aromatics) shows the maximum difference up to a factor of seven. These findings suggest that the emission ratios reflect seasonal changes in emissions and can be a useful metric to constraint temporally resolved emission inventories at different time of the year.
Keywords: VOC; Composition; Sources; Vehicle exhaust; Megacity;

Inverse modelling techniques can be used to estimate the amount of radionuclides and the temporal profile of the source term released in the atmosphere during the accident of the Fukushima Daiichi nuclear power plant in March 2011. In Winiarek et al. (2012b), the lower bounds of the caesium-137 and iodine-131 source terms were estimated with such techniques, using activity concentration measurements. The importance of an objective assessment of prior errors (the observation errors and the background errors) was emphasised for a reliable inversion. In such critical context where the meteorological conditions can make the source term partly unobservable and where only a few observations are available, such prior estimation techniques are mandatory, the retrieved source term being very sensitive to this estimation.We propose to extend the use of these techniques to the estimation of prior errors when assimilating observations from several data sets. The aim is to compute an estimate of the caesium-137 source term jointly using all available data about this radionuclide, such as activity concentrations in the air, but also daily fallout measurements and total cumulated fallout measurements. It is crucial to properly and simultaneously estimate the background errors and the prior errors relative to each data set. A proper estimation of prior errors is also a necessary condition to reliably estimate the a posteriori uncertainty of the estimated source term. Using such techniques, we retrieve a total released quantity of caesium-137 in the interval 11.6−19.3 PBq with an estimated standard deviation range of 15−20% depending on the method and the data sets. The “blind” time intervals of the source term have also been strongly mitigated compared to the first estimations with only activity concentration data.
Keywords: Data assimilation; Atmospheric dispersion; Fukushima accident; Source estimation;

We carried out four replicated field experiments to measure the impacts of immediate incorporation of solid manures on emissions of ammonia (NH3) and nitrous oxide (N2O). Four manures: cattle farmyard manure (FYM); pig FYM; layer manure and broiler manure were applied to the soil surface or immediately incorporated by mouldboard plough, disc or tine. Two of the experiments were carried out on a clay soil and two on a sandy soil to find out whether soil type interacted with incorporation technique to influence emissions of NH3 or N2O. Ammonia emissions were measured for 1 or 2 weeks while N2O emissions were measured for 60 days in one experiment and for a complete year in the other three experiments.Immediate incorporation by plough reduced NH3 emissions by c. 90% and by c. 60% by disc and tine (P < 0.001). There was no effect of soil type on NH3 abatement efficiency by plough or tine but the disc was less effective on the coarse sandy soil.Cross-site analysis indicated no effect of incorporation by disc or tine on emissions of N2O–N after 60 days but incorporation by plough increased direct emissions of N2O–N compared with surface application of manure (P < 0.001). Direct emissions of N2O–N, at c. 0.67% of total N applied, were substantially greater at the coarse-textured site than at the heavy clay site (0.04% of total N applied; P < 0.001). The impact of incorporation on total annual direct emissions of N2O–N differed in the three experiments where emissions were measured for a full year. There was no effect of incorporation on N2O–N emissions in the first experiment on the clay soil, and in the second experiment at this site incorporation by plough or disc, but not tine, reduced direct emissions of N2O (P = 0.006). However on the sandy soil direct emissions of N2O–N were increased when manures were incorporated by plough (P = 0.002) but not when incorporated by disc or tine.These results confirm that immediate incorporation of solid manures by plough is the most effective means of reducing NH3 emissions following the application of solid manures. The results also indicate that immediate incorporation of solid manures to reduce NH3 emissions does not necessarily increase emissions of N2O. However, the impacts of immediate incorporation on emissions of N2O may be related to soil type with a greater possibility of emission increases on coarse sandy soils.
Keywords: Ammonia; Nitrous oxide; Emission factors; Manure; Abatement; Immediate incorporation;

This study estimated both the in-port ship emissions inventory (CO2, CH4, N2O, PM10, PM2.5, NO x , SO x , CO, and HC) and the emission associated social cost in Yangshan port of Shanghai. A sophisticated activity-based methodology, supported by the ship-by-ship and real-time data from the modern automatic identification system (AIS), was introduced to obtain accurate estimates of ship emissions. The detailed spatial and temporal emission inventories can be used as input for air quality dispersion modeling in the port and vicinities. The social cost of the emission impact on the Yangshan port coastal regions was then assessed based on the emissions inventories. The social cost covers the impact on human health, the environment, and the climate of the coastal community. Finally, the ship emissions was combined with port's basic operation profiles, i.e. container throughput, ship calls, and port revenue, in an attempt to assess the port's “eco-efficiency”, which indicates the port performance with social-economic and environmental concerns. This study filled the gap of previous studies by providing the AIS-supported activity-based emission inventory to facilitate the social cost-benefit analysis for the emission abatement policies. The result shows that i) the amount of in-port ship emissions of CO2, CH4, N2O, PM10, PM2.5, NO x , SO x , CO, and HC in Yangshan port area was 578,444 tons, 10 tons, 33 tons, 1078 tons (PM10, inducing PM2.5), 859 tons (PM2.5 only), 10,758 tons, 5623 tons, 1136 tons, and 519 tons, respectively, with ii) a total social cost of $287 million; iii) the values of the three parameters of the port eco-efficiency performance were $36,528 per 1,000 TEU throughput, $43,993 per ship call, and $44 million per billion US$ port revenue (4.4% of port revenue), respectively in 2009.
Keywords: Yangshan port; Ship emissions inventory; Social cost; Eco-efficiency; AIS; Shanghai;

Characterization of particulate and vapor phase polycyclic aromatic hydrocarbons in indoor and outdoor air of primary schools by Edvinas Krugly; Dainius Martuzevicius; Ruta Sidaraviciute; Darius Ciuzas; Tadas Prasauskas; Violeta Kauneliene; Inga Stasiulaitiene; Linas Kliucininkas (298-306).
The indoor air of schools is considered as one of the most important factors affecting the health of children. The aim of the presented research was to characterize polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air of schools. The sampling campaign was conducted during the heating season of 2011/2012. Five primary schools from various urban settings in the city of Kaunas, Lithuania. 150 daily samples of particulate and vapor phases were collected during the sampling period. The ultrasonic extractions followed by the gas chromatography and mass spectroscopy (GS/MS) analyses were used for the determination of PAHs. The concentration of total PAHs in the PM2.5 fraction ranged from 20.3 to 131.1 ng m−3, while total suspended particles (TSP) fraction contained from 19.9 to 80.3 ng m−3 of total PAHs. The vapor phase concentration of PAHs ranged from 67.2 to 372.5 ng m−3. The most abundant PAH in both phases was naphthalene. In order to define sources of indoor and outdoor PAHs several source apportionment methods were applied. The analysis revealed that emissions from motor vehicles and fuel burning for heating purposes were the major sources of PAHs in the city of Kaunas.
Keywords: Air pollution; Indoor air; Schools; PAHs; Kaunas; Lithuania;

Incorporating principal component analysis into air quality model evaluation by Brian Eder; Jesse Bash; Kristen Foley; Jon Pleim (307-315).
The efficacy of standard air quality model evaluation techniques is becoming compromised as the simulation periods continue to lengthen in response to ever increasing computing capacity. Accordingly, the purpose of this paper is to demonstrate a statistical approach called Principal Component Analysis (PCA) with the intent of motivating its use by the evaluation community. One of the main objectives of PCA is to identify, through data reduction, the recurring and independent modes of variations (or signals) within a very large dataset, thereby summarizing the essential information of that dataset so that meaningful and descriptive conclusions can be made. In this demonstration, PCA is applied to a simple evaluation metric – the model bias associated with EPA's Community Multi-scale Air Quality (CMAQ) model when compared to weekly observations of sulfate (SO4 2−) and ammonium (NH4 +) ambient air concentrations measured by the Clean Air Status and Trends Network (CASTNet). The advantages of using this technique are demonstrated as it identifies strong and systematic patterns of CMAQ model bias across a myriad of spatial and temporal scales that are neither constrained to geopolitical boundaries nor monthly/seasonal time periods (a limitation of many current studies). The technique also identifies locations (station–grid cell pairs) that are used as indicators for a more thorough diagnostic evaluation thereby hastening and facilitating understanding of the probable mechanisms responsible for the unique behavior among bias regimes. A sampling of results indicates that biases are still prevalent in both SO4 2− and NH4 + simulations that can be attributed to either: 1) cloud processes in the meteorological model utilized by CMAQ, which are found to overestimated convective clouds and precipitation, while underestimating larger-scale resolved clouds that are less likely to precipitate, and 2) biases associated with Midwest NH3 emissions which may be partially ameliorated using the bi-directional NH3 exchange option in CMAQ.
Keywords: Air quality model; Model evaluation; CMAQ; Principal component analysis; Sulfate and ammonium concentrations;

Effects of meteorological conditions on the concentration and dispersion of an accidental release of H2S in Canada by Sabah A. Abdul-Wahab; Keziah Chan; Ali Elkamel; Lena Ahmadi (316-326).
This study aims to determine the effects of the land's meteorological conditions on the dispersion of an accidental release of H2S using the CALPro software. The three Canadian cities or towns of Edmonton, Yarmouth and Whitehorse, which are all of different meteorological conditions, were chosen as the domains of study. Hourly geophysical, surface and upper air meteorological data were used with CALMET to model the wind field of the three domains for the modeling period of March 11, 2012 from 00h00 to 23h00 LST. Individual 5-h modeling periods where the wind field showed the most significant variations were chosen for each region of study. CALPUFF was used to model the dispersion effects of an accidental release of H2S from a single point source due to an accidental vessel puncture using time-varying emission data modified to suit each region's modeling period. Despite the wind reversal encountered in Edmonton, its relatively flat terrain allowed H2S to disperse outwards, causing concentrations to accumulate lower than the other two regions but still to sever levels and a much greater population. Differences between the effect of land and sea breeze on H2S dispersion in Yarmouth's coastal region caused concentrations to accumulate higher than the other two regions and to life threatening levels around the source. The mountainous terrain of Whitehorse shaped the plume trajectory, causing H2S concentrations to accumulate to levels that can cause irreversible health effects at various times and locations. Results show that each area's meteorological conditions will have different impacts on dispersion.
Keywords: Accidental release of H2S; Meteorological conditions; Dispersion; Model; Canada;

Environmental chamber systems are usually employed in the testing of volatile organic compound (VOC) and formaldehyde emissions from building materials. The measurement accuracy of environmental chamber systems can be evaluated by VOC/formaldehyde emission references. However, the available VOC/formaldehyde emission references all have some limitations for applications to various scales of chambers. A framework for designing and using a target VOC/formaldehyde emission references to evaluate the performance of chamber systems for measuring VOC/formaldehyde emissions from building materials is studied. Liquid-inner tube diffusion-film-emission (LIFE) reference is improved in this study to meet the requirements of a target VOC/formaldehyde emission reference, such as reliability, similarity as building materials, efficiency for measurement. Equivalent emission characteristic parameters are designed for a toluene LIFE reference to perform similar to a building material. Chamber test of the LIFE reference is made in a 30 m3 stainless steel ventilated environmental chamber at 23 ± 1 °C and 50 ± 5% relative humidity. The experimental data match the predictions using LIFE emission model as well as building material emission model. The improvement of the LIFE reference enables its application for the evaluation of the performance of all kinds of environmental chambers as a general reference in tests of VOCs/formaldehyde emissions from building materials.
Keywords: VOC/formaldehyde emission reference; Environmental chamber; Building material; Indoor air quality;

Measurement of fugitive volatile organic compound emissions from a petrochemical tank farm using open-path Fourier transform infrared spectrometry by Chang-Fu Wu; Tzong-gang Wu; Ram A. Hashmonay; Shih-Ying Chang; Yu-Syuan Wu; Chun-Ping Chao; Cheng-Ping Hsu; Michael J. Chase; Robert H. Kagann (335-342).
Fugitive emission of air pollutants is conventionally estimated based on standard emission factors. The Vertical Radial Plume Mapping (VRPM) technique, as described in the US EPA OTM-10, is designed to measure emission flux by directly monitoring the concentration of the plume crossing a vertical plane downwind of the site of interest. This paper describes the evaluation results of implementing VRPM in a complex industrial setting (a petrochemical tank farm). The vertical plane was constructed from five retroreflectors and an open-path Fourier transform infrared spectrometer. The VRPM configuration was approximately 189.2 m in width × 30.7 m in height. In the accompanying tracer gas experiment, the bias of the VRPM estimate was less than 2% and its 95% confidence interval contained the true release rate. Emission estimates of the target VOCs (benzene, m-xylene, o-xylene, p-xylene, and toluene) ranged from 0.86 to 2.18 g s−1 during the 14-day field campaign, while estimates based on the standard emission factors were one order of magnitude lower, possibly leading to an underestimation of the impact of these fugitive emissions on air quality and human health. It was also demonstrated that a simplified 3-beam geometry (i.e., without one dimensional scanning lines) resulted in higher uncertainties in the emission estimates.Display Omitted
Keywords: Fugitive emission; Volatile organic compound; Storage tank; Optical remote sensing;

Characteristics of indoor air pollution in rural mountainous and rural coastal communities in Indonesia by Haryono S. Huboyo; Susumu Tohno; Puji Lestari; Akira Mizohata; Motonori Okumura (343-350).
The increased use of biomass fuel use among rural Indonesian households for years despite national program on subsidized LPG fuel distribution pose threat of indoor air pollution for the householders. Indoor air pollution levels of PM2.5 and CO in the kitchen of 40 households using the fuelwood as the main cooking fuel were measured in the same season in mountainous and coastal areas in Indonesia. The temporal variations of PM2.5 and its size distributions were simultaneously measured using photoelectric UCB monitor and personal cascade impactor, respectively. While carbon monoxide (CO) concentrations were measured using USB-CO monitors. Household indoor air pollution in the mountainous area was generally higher than that in the coastal area. This is because the households in coastal area have higher kitchen volume (about three times), smaller ventilation area (about 1.7 times) and shorter cooking duration with wood fuel (0.6 times) than those in mountainous area. Yet, during cooking with fuelwood, the indoor PM2.5 concentrations at the cook site showed almost comparable results for both sites. The wood stove burning in coastal area tended to be in flaming combustion than in mountainous area. This can be indicated by a higher fraction of finest particles in PM2.5, a higher fraction of EC in PM2.5 and a higher fraction of K+ and Cl ions in PM2.5 mass concentrations. The time-averaged CO concentrations for 22-h measurements at the mountainous area were higher than those in coastal area. The mountainous area showed higher positive correlation relationship between the measured concentrations of CO and PM2.5 than those in the coastal area. The use of cleaner fuel, e.g., subsidized LPG fuel in rural area should be promoted and managed intensively in mountainous area than in coastal area to avoid people exposure of health damaging indoor air pollutants.
Keywords: Biomass burning; CO; Cook stoves; Fine particles; Household energy; PM2.5;

Implementation of a high-resolution Source-Oriented WRF/Chem model at the Port of Oakland by David K. Joe; Hongliang Zhang; Steven P. DeNero; Hsiang-He Lee; Shu-Hua Chen; Brian C. McDonald; Robert A. Harley; Michael J. Kleeman (351-363).
A version of the Source-Oriented WRF/Chem (SOWC) model with 250 m spatial resolution (SOWC-HR) was developed and implemented to perform high resolution simulations over the community of Oakland, California, during March 2010. A multiscale set of nested domains was used to predict contributions to airborne particulate elemental carbon (EC) concentrations from ships, trains, and on-road diesel trucks. The final domain at 250 m resolution used Large Eddy Simulation (LES) to predict turbulent mixing at scales where traditional first order closure models are not valid. Results of the high resolution simulation with the nested LES (HR case) and without the nested LES (non-HR case) were compared to speciated particulate matter (PM) measurements and source contributions calculated using Positive Matrix Factorization (PMF). The PMF results showed that on-road diesel traffic was a major EC contributor, a result consistent with previous studies for Oakland. The average EC concentration predicted at the site by the SOWC-HR model was 0.42 μg m−3, with source contributions of 0.22 μg m−3 from on-road diesel, 0.05 μg m−3 from ship fuel combustion, 0.08 μg m−3 from trains, and 0.09 μg m−3 from other sources. Both simulation cases predicted similar total EC concentrations and source contributions at the sampling sites, but more substantial differences were predicted at other locations in the study region. The HR case predicted higher average and maximum hourly EC contributions from all sources compared the non-HR case. The greatest relative increase of maximum hourly EC was seen in the on-road diesel source, which increased by nearly a factor of 2 (3.74 μg m−3 to 6.69 μg m−3) when spatial resolution was increased from 1 km to 250 m. The SOWC-HR model predicted greater population-weighted EC concentrations from all sources when compared to the SOWC model without HR. The increase in period-averaged EC exposure from each source ranged from +1% to +17%, while the increase in maximum hourly EC exposure from each source ranged from +9% to +32%. This evaluation shows that resolving neighborhood scales through the representation of local mixing phenomena can significantly impact pollutant concentration predictions, especially when examining extreme exposures in a densely populated area with many sources and complex terrain.
Keywords: WRF/Chem; Source-oriented; High resolution; LES; Elemental carbon; Port of Oakland;

Adverse health effects of ambient particulate matters are closely related to the speciation of the constituting organic matters and toxic metals. To determine multi-parameters of the metal speciation in urban and indoor dusts, we have performed systematic bulk- to nano-scale (“multi-scale”) analysis on the speciation of Pb, Mn, and Cr in two National Institute of Standards and Technology (NIST) standard reference materials (SRMs): urban dust (SRM 1649a) and indoor dust (SRM 2584), utilizing X-ray absorption near-edge structure, powder X-ray diffraction analysis, electron microprobe analysis, scanning electron microscopy, and transmission electron microscopy.Major crystalline phases are quartz, gypsum, kaolinite, and muscovite in SRM 1649a, while quartz, gypsum, calcite, and possibly muscovite (or chabazite) in SRM 2584. A number of Pb sulfate nanoparticles (50–200 nm) occur in SRM 1649a, whereas micron-sized Pb carbonate is present containing various concentrations of Zn and Ti in the complex texture in SRM 2584. Relatively soluble Mn(II) sulfate is the bulk-averaged Mn speciation in SRM 1649a, although discrete Mn sulfate particles are not characterized by individual particle analysis, implying the diluted Mn distribution within other sulfate. In SRM 2584, Mn speciation includes a mixture of oxides and carbonates, and trace Mn in chromite. Chromite (FeCr2O4) is the major Cr speciation in SRM1694a, while unidentified Cr(III) phases with minor chromite and Pb chromate are present in SRM 2584, among which the Pb chromate is composed of Cr(VI). A significant number of the metal-bearing particles are distributed to the submicron-size fraction in the urban dust, SRM 1649a, suggesting that these metal nanoparticles can potentially penetrate into the deep respiratory system. This study demonstrates that multi-scale analysis combining nano and bulk analytical techniques is a powerful approach to investigate the multi-parameters of metal-bearing nanoparticles in heterogeneous PM samples.
Keywords: TEM; XANES; SEM; Metal speciation;

Indoor/outdoor relationships of PM10, PM2.5, and PM1 mass concentrations and their water-soluble ions in a retirement home and a school dormitory by Mohammad Sadegh Hassanvand; Kazem Naddafi; Sasan Faridi; Mohammad Arhami; Ramin Nabizadeh; Mohammad Hossein Sowlat; Zahra Pourpak; Noushin Rastkari; Fatemeh Momeniha; Homa Kashani; Akbar Gholampour; Shahrokh Nazmara; Mahmood Alimohammadi; Gholamreza Goudarzi; Masud Yunesian (375-382).
Indoor/outdoor particulate matter (PM10, PM2.5, and PM1) and their water-soluble ions were measured in a retirement home and a school dormitory in Tehran, from May 2012 to January 2013. Hourly indoor/outdoor PM concentrations were measured using GRIMM dust monitors and 24-h aerosol samples were collected by low-volume air samplers. Water-soluble ions were determined using an ion chromatography (IC) instrument. Although the mean outdoor PM concentrations in both sampling sites were almost equal, the mean indoor PM10 in the school dormitory was approximately 1.35 times higher than that in the retirement home. During a Middle Eastern dust storm, the 24-h average PM10, PM2.5, and PM1 concentrations were respectively 3.4, 2.9, and 1.9 times as high as those in normal days outdoors and 3.4, 2.8, and 1.6 times indoors. The results indicated that secondary inorganic aerosols were the dominant water-soluble ions of indoor and outdoor PM. We found that the smaller the particle, the higher the percentage of secondary inorganic aerosols. Except for PM10 in the school dormitory, strong correlations were found between indoor and outdoor PM. We estimated that nearly 45% of PM10, 67% of PM2.5, and 79% of PM1 in the retirement home, and 32% of PM10, 76% of PM2.5, and 83% of PM1 in the school dormitory originated from outdoor environment.
Keywords: PM; Water-soluble ions; Indoor/outdoor; Nursing home; School dormitory; Tehran;

Ozone in remote areas of the Southern Rocky Mountains by Robert C. Musselman; John L. Korfmacher (383-390).
Ozone (O3) data are sparse for remote, non-urban mountain areas of the western U.S. Ozone was monitored 2007–2011 at high elevation sites in national forests in Colorado and northeastern Utah using a portable battery-powered O3 monitor. The data suggest that many of these remote locations already have O3 concentrations that would contribute to exceedance of the current National Ambient Air Quality Standard (NAAQS) for O3 and most could exceed a proposed more stringent secondary standard. There were significant year-to-year differences in O3 concentration. Ozone was primarily in the mid-concentration range, rarely exceeding 100 ppb or dropping below 30 ppb. The small diel changes in concentration indicate mixing ratios of NO x , VOCs, and O3 that favor stable O3 concentrations. The large number of mid-level O3 concentrations contributed to high W126 O3 values, the metric proposed as a possible new secondary standard. Higher O3 concentrations in springtime and at night suggest that stratospheric intrusion may be contributing to ambient O3 at these sites. Highest nighttime O3 concentrations occurred at the highest elevations, while daytime O3 concentrations did not have a relationship with elevation. These factors favor O3 concentrations at many of our remote locations that may exceed the O3 NAAQS, and suggest that exceedances are likely to occur at other western rural locations.
Keywords: Air pollution; Forests; High elevation; NAAQS; Nighttime exposure; Stratospheric intrusion; W126;

Exhaust emissions of polycyclic aromatic hydrocarbons, n-alkanes and phenols from vehicles coming within different European classes by Maria Grazia Perrone; Claudio Carbone; Davide Faedo; Luca Ferrero; Angela Maggioni; Giorgia Sangiorgi; Ezio Bolzacchini (391-400).
EU emission standards for vehicles do not include many particulate (PM) and gaseous species, despite their considerable impact on air pollution and health. Emission factors (EFs) were measured for unregulated species, i.e. polycyclic aromatic hydrocarbons (PAHs) and n-alkanes (ALKs) in the particle phase, and, for the first time, EFs for phenols in both particle and gas phases. Exhaust samples were collected under controlled operating conditions (chassis dynamometer tests) for in-service vehicles (private cars, PCs and light duty vehicles, LDVs) from different EURO classes. EFs of trace organics were highest for the old EURO 1 vehicles (the tested EURO 1 vehicles were without emission-control devices), and lowest for the more recent EURO 3 and 4 vehicles. ALKs (C20–C32) were the most abundant trace organic compounds found in PM vehicle exhaust, and their EF ranged between 2034 and 101 μg km−1 (Euro 1–4 LDVs). PM-phased phenols EFs were in the range 0.42–2.50 μg km−1, and 4-nitrophenol was the most abundant one. The highest EFs were measured for phenols in the gas phase (dominated by the presence of phenol) for gasoline EURO 1 (43.16 ± 9.99 μg km−1). Emissions of PAHs changed depending on the fuel used. The PAH EFs of diesel-driven PCs were 4–5 times higher than those of gasoline vehicles, with PAHs diesel exhaust being mainly enriched in low 4-ring PAHs (85%), while 5–6 ring PAHs were prevalent (55%) in gasoline vehicles. Results of source profiles from chassis dynamometer tests were compared with ambient data, and the traffic PAH source profile derived from a tunnel study (Milan) agreed with the estimated emissions from a mix of diesel and gasoline vehicles circulating in the same area. Moreover, the impact of EURO regulatory changes on exhaust emissions was calculated, and this made it possible to estimate the downward trend of PAH emissions in the Province of Milan in the period 2005–2020.
Keywords: Traffic emissions; Dynamometer tests; Trace organics; PAHs; Emission factors; Traffic source profile;

Quantitative determination of pulp and paper industry emissions and associated odor intensity in methyl mercaptan equivalent using electronic nose by Sharvari Deshmukh; Arun Jana; Nabarun Bhattacharyya; Rajib Bandyopadhyay; R.A. Pandey (401-409).
The obnoxious odors generated from pulp and paper industries have been the cause of nuisance since the instigation of these industries. The objective of the study was to develop a metal oxide sensor based electronic nose for rapid measurement of odorant concentration and associated odor intensity of major reduced sulfur compounds emitted from different sources of these pulp and paper mills. The gas samples collected from the surroundings of major source points of industry were exposed to sensor array of the electronic nose and the change in voltage was measured and taken to PC through data acquisition cards. The same sets of samples were also tested with gas chromatography. The results of electronic nose and GC-FPD were correlated using response surface methodology to know the odorant concentration. The model fed with unknown industrial samples had more than 95% prediction capability. To determine odor intensity by electronic nose firstly a collective index was generated using SVD based 2-norm method (e-nose index) proportional to the sensors response relative to reference gas, methyl mercaptan. Secondly the e-nose index was associated with human expert evaluations. The training of the electronic nose enabled it to predict odorant concentration found at the industrial site and associated odor intensity in methyl mercaptan equivalent. The overall results of the experiments carried out suggest the potential of electronic nose as a device for on or off line measurement of odorant concentration and odor intensity.
Keywords: Electronic nose; Reduced sulfur compounds; Principal component analysis; Response surface methodology; Odor intensity; Singular value decomposition;

Application of chemical transport model CMAQ to policy decisions regarding PM2.5 in the UK by C. Chemel; B.E.A. Fisher; X. Kong; X.V. Francis; R.S. Sokhi; N. Good; W.J. Collins; G.A. Folberth (410-417).
This paper shows how the advanced chemical transport model CMAQ can be used to estimate future levels of PM2.5 in the UK, the key air pollutant in terms of human health effects, but one which is largely made up from the formation of secondary particulate in the atmosphere. By adding the primary particulate contribution from typical urban roads and including a margin for error, it is concluded that the current indicative limit value for PM2.5 will largely be met in 2020 assuming 2006 meteorological conditions. Contributions to annual average regional PM2.5 concentration from wild fires in Europe in 2006 and from possible climate change between 2006 and 2020 are shown to be small compared with the change in PM2.5 concentration arising from changes in emissions between 2006 and 2020. The contribution from emissions from major industrial sources regulated in the UK is estimated from additional CMAQ calculations. The potential source strength of these emissions is a useful indicator of the linearity of the response of the atmosphere to changes in emissions. Uncertainties in the modelling of regional and local sources are taken into account based on previous evaluations of the models. Future actual trends in emissions mean that exceedences of limit values may arise, and these and further research into PM2.5 health effects will need to be part of the future strategy to manage PM2.5 concentrations.Display Omitted
Keywords: Regional air quality; CMAQ; Limit values; Emissions inventory; Industrial footprint; Local traffic pollution;