Atmospheric Environment (v.55, #C)

Climatic parameters and pollution data from the 6FP NOAHs ARK project ‘Global Climate Change Impact on Built Heritage and Cultural Landscapes’ together with chloride deposition data have been used to predict atmospheric corrosion of metals in 2010–2039 and 2070–2099. Maps of carbon steel and zinc show that future atmospheric corrosion of metals in Europe are dominated by the effects of chloride deposition in coastal and near-coastal areas. The change can in extreme cases be as high as one corrosivity category and in coastal areas of southern Europe corrosion can be higher than the highest values experienced today in Europe.► We predict atmospheric corrosion of metals in 2010–2039 and 2070–2099. ► Inland corrosion low or medium depending on pollution level. ► Coastal corrosion high or very high depending on temperature and chloride deposition. ► Coastal corrosion in southern Europe higher than the highest values of today.
Keywords: Atmospheric corrosion; Climate change; SO2 pollution; Corrosivity categories; Carbon steel; Zinc;

Thirty re-suspended dust samples were collected from building surfaces in an oilfield city, re-suspended and sampled through PM2.5, PM10 and PM100 inlets and analyzed for 18 PAHs by GC–MS technique. PAHs concentrations, toxicity and profiles characteristic for different districts and size were studied. PAHs sources were identified by diagnostic ratios and primary component analysis. Results showed that the total amounts of analyzed PAHs in re-suspended dust in Dongying were 45.29, 23.79 and 11.41 μg g−1 for PM2.5, PM10 and PM100, respectively. PAHs tended to concentrate in finer particles with mass ratios of PM2.5/PM10 and PM10/PM100 as 1.96 ± 0.86 and 2.53 ± 1.57. The old district with more human activities and long oil exploitation history exhibited higher concentrations of PAHs from both combustion and non-combustion sources. BaP-based toxic equivalent factor and BaP-based equivalent carcinogenic power exhibited decreasing sequence as PM2.5 > PM10 > PM100 suggesting that the finer the particles, the more toxic of the dust. NaP, Phe, Flu, Pyr, BbF and BghiP were the abundant species. Coefficient of divergence analysis implied that PAHs in different districts and size fractions had common sources. Coal combustion, industrial sources, vehicle emission and petroleum were probably the main contributions according to the principal component analysis result.► PAHs tend to concentrate in finer particles of re-suspended dust. ► Old district exhibited higher PAHs concentrations. ► The finer the particles, the more toxic of the dust. ► Re-suspended dust in different districts and size had common sources.
Keywords: Polycyclic aromatic hydrocarbons; Re-suspended dust; Size; Sources; Oilfield city;

Quantification and seasonal pattern of atmospheric reaction products of gas phase PAHs in PM2.5 by Ji Yi Lee; Douglas A. Lane; Jong Bae Heo; Seung-Muk Yi; Yong Pyo Kim (17-25).
Six unique OH-reaction products of naphthalene and phenanthrene were detected and quantified in ambient PM2.5 collected in Seoul, Korea between 2006 and 2007. The range of annual average concentrations of six reaction products, 2-formylcinnamaldehyde, phthalic acid, phthalide, dibenzopyranone, 9-fluorenone, and 1,2-naphthalic anhydride extended from 2.45 to 49.9 ng m−3 and all of these values were higher than the average concentration of single particulate PAH compounds in Seoul, Korea. The seasonal pattern of six reaction products generally showed higher concentrations in winter months than in summer months. This indicates that the formation of these compounds by atmospheric photochemical reactions is significant both in winter and summer and that enhanced primary sources and higher particle to gas partitioning activity due to lower ambient temperature may contribute to the high concentrations of these compounds in the winter months in Seoul, Korea. The high correlation of the formation of 2-formylcinnamladehyde and dibenzopyranone with the estimated SOC concentration, suggests that the formation of SOA from gas phase PAH reactions in the real atmospheres is significant. Also, we suggest that (E)-2-formylcinnamaldehyde and dibenzopyranone could be used as unique indicators for the atmospheric oxidative reactions of naphthalene and phenanthrene, respectively.► Quantification of unique reaction products of gas phase PAH in real ambient PM2.5. ► Observation of seasonal pattern of PAH reaction products for the first time. ► Evaluation of the significance for the formation of SOA from gas phase PAH reaction. ► Suggestion of unique indicators for the reactions of PAH in the real atmospheres.
Keywords: Gas phase PAHs reaction; OH radical; Secondary organic aerosol (SOA); OH-reaction products; 2-formylcinnamaldehyde; Dibenzopyranone; GCxGC-TOFMS; Seoul in Korea;

To investigate the effects of Fe(II) and Fe(III) ions on secondary organic aerosol (SOA) formation, we conducted a series of photooxidation experiments with α-pinene and toluene in the presence of nitric oxides (NOx) with/without FeSO4 or Fe2(SO4)3 seed aerosols. The FeSO4 seed aerosols suppressed SOA formation, while Fe2(SO4)3 seed aerosols did not display a noticeable effect on SOA formation. We did not observe effects of FeSO4 and Fe2(SO4)3 seed aerosols on gas phase compounds, including ozone, NOx, and hydrocarbons (HCs). The negative effect of Fe(II)-containing seed aerosols on SOA formation due to the reduction of condensable compounds (CCs) generated from hydrocarbon oxidation is discussed. The mean molecular weight of CCs reduced by Fe(II) is tentatively estimated to be larger than 300, indicating a possibility that many of the CCs reduced by Fe(II) are oligomers. Reduction of oligomer precursors may interrupt the oligomerization of other aldehyde products. If Fe(II) regeneration from photoreduction of Fe(III) is considered, the estimated mean molecular weight of the CCs reduced would be smaller. However, the negligible effect of Fe(III)-containing seed aerosols on SOA formation indicates that Fe(III) photoreduction is negligible in our experiments.► FeSO4 seed aerosols suppress secondary organic aerosol (SOA) formation from photooxidation of α-pinene/NOx and toluene/NOx. ► Fe2(SO4)3 seed aerosols have no noticeable effect on SOA formation. ► Fe(II) effect on condensable compounds, which are likely to be oligomers, is considered. ► Reduction of oligomer precursors by Fe(II) may interrupt oligomerization.
Keywords: Ferrous/Ferric sulfate seed aerosols; α-Pinene photooxidation; Toluene photooxidation; Secondary organic aerosol; Suppression effect;

A pollution gradient of polycyclic aromatic hydrocarbons (PAHs) was observed in tree foliage sampled in the vicinity of a large aluminium production facility in Patagonia (Argentina). Leaves of Eucalyptus rostrata, Populus hybridus and one-year-old needles of Pinus radiata were collected, and concentrations of 12 PAHs including the so-called EPA priority pollutants as well as heavy metals (Cd, Cu, Fe, Mn, Ni and Zn) were analysed. The PAH concentrations indicated a steep pollution gradient in the study area associated with the Al-industry, while the heavy metal content was unrelated to this activity. The present study confirms that aluminium smelting results in the deposition of PAH in the study area, and therefore further studies should be carried out taking into account the potentially adverse effects of these compounds on human and ecosystem health.► PAH concentrations indicate a pollution gradient in the vicinity of the smelter. ► Eucalyptus.rostrata and Pinus.radiata were the most efficient PAHs biomonitors. ► Heavy metal content showed no clear association with the aluminium industry.
Keywords: Persistent toxic pollutants; PAH deposition; Atmosphere-vegetation; Biomonitoring;

Syringol (2,6-dimethoxyphenol) is a potential marker compound for wood smoke emissions in the atmosphere. To investigate the atmospheric reactivity of this compound, the rate constant for its reaction with hydroxyl radicals (OH) has been determined in a simulation chamber (8 m3) at 294 ± 2 K, atmospheric pressure and low relative humidity (2–4%) using the relative rate method. The syringol and reference compound concentrations were followed by GC/FID (Gas chromatography/Flame Ionization Detection). The determined rate constant (in units of cm3 molecule−1 s−1) is k syringol = (9.66 ± 1.11) × 10−11. The calculated atmospheric lifetime for syringol is 1.8 h, indicating that it is too reactive to be used as a tracer for wood smoke emissions. Secondary Organic Aerosol (SOA) formation from the OH reaction with syringol was also investigated. The initial mixing ratios for syringol were in the range 495–3557 μg m−3. The aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer). The SOA yields (Y) were determined as the ratio of the suspended aerosol mass corrected for wall losses (M 0) to the total reacted syringol concentration assuming a particle density of 1.4 g cm−3. The aerosol formation yield increases as the initial syringol concentration increases, and leads to aerosol yields ranging from 0.10 to 0.36. Y is a strong function of M 0 and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. To our knowledge, this work represents the first investigation of the rate constant and SOA formation for the reaction of syringol with OH radicals. The atmospheric implications of this reaction are also discussed.► k syringol + OH = (9.66 ± 1.11) × 10−11 cm3 molecule−1 s−1. ► Atmospheric lifetime for syringol with respect to its reaction with OH = 1.8 h. ► Secondary Organic Aerosol (SOA) yields for the reaction syringol + OH = 0.10–0.36. ► SOA yields expressed by a one-product gas/particle partitioning absorption model.
Keywords: Simulation chamber; Syringol; OH rate constant; Secondary organic aerosol yields;

This study investigates the weekly periodicity of PM10 (aerosol particulate matter with a diameter <10 μm) mass concentrations over Beijing and Tianjin as well as its relationship with synoptic-scale weather variability. The two cities are large air pollutant source regions that are often affected by the same weather system due to their close proximity. Comparison of the two cities, therefore, advances our understanding of the contributions of the weather variability (or anthropogenic emissions) to the weekly periodicity of PM10. Here we analyze PM10 anomalies against weekly means over the past 10 years (2000–2009) on the frequency domain using a fast Fourier transform. Results show that the interannual variabilities of PM10 weekly periodicity, defined as the ratio of 6–8-day variance to 2–14-day variance, between Beijing and Tianjin are correlated in the summer and fall, but are uncorrelated in the spring. In the fall, the higher correlation of PM10 weekly periodicity between the two cities may be associated with strong influence of the natural weather variability as represented by 850-hPa geopotential height, surface diurnal temperature range, and 1000-hPa wind. However, in the spring and summer, the influence of the weather variability on the PM10 weekly periodicity was not identified. The weather variability accounts for 0–85% of the PM10 weekly periodicity variation, with the maximal value in Beijing in the fall. These findings suggest that contribution of the weather variability to shaping the PM10 weekly periodicity over Beijing and Tianjin is restrictive and transient.► We analyze PM10 weekly periodicity in Beijing and Tianjin, 2000–2009. ► The PM10 weekly periodicities between 2 cities are correlated in summer and fall. ► The higher correlation is associated with stronger weather variability. ► The weather system restrictively shapes the weekly periodicity over the 2 cities.
Keywords: Weekly cycle; PM10; Aerosol; Spectral analysis; Weekly periodicity;

Diagnosis of air quality through observation and modeling of volatile organic compounds (VOCs) as pollution tracers by Wen-Tzu Liu; Hsin-Cheng Hsieh; Sheng-Po Chen; Julius S. Chang; Neng-Huei Lin; Chih-Chung Chang; Jia-Lin Wang (56-63).
This study used selected ambient volatile organic compounds (VOCs) as pollution tracers to study the effects of meteorology on air quality. A remote coastal site was chosen as a receptor to monitor pollutants transported upwind from urban traffic and industrial sources. Large concentration variability in VOC concentrations was observed at the coastal site due to rapid changes in meteorology, which caused periodic land-sea exchange of air masses. To assure the quality of the on-line measurements, uniform concentrations of chlorofluorocarbon-113 (CFC-113) were exploited as an internal check of the instrument’s stability and the resulting data quality.A VOC speciated air quality model was employed to simulate both temporal and spatial distributions of VOC plumes. The model successfully captured the general features of the variations of toluene as a pollution tracer, which suggests that emissions and meteorology were reasonably well simulated in the model. Through validation by observation, the model can display both the temporal and spatial distribution of air pollutants in a dynamic manner. Thus, a more insightful understanding of how local air quality is affected by meteorology can be obtained.► This study used VOC as pollution tracers. ► Concentration of CFC-113 was exploited as an internal check. ► A VOC model simulate temporal and spatial distributions of VOC plumes. ► The model can display the temporal and spatial distribution of air pollutants.
Keywords: VOC; CFC; PAMS-AQM;

Investigation of organic aerosol sources using fractionated water-soluble organic carbon measured at an urban site by Seung Shik Park; Sung Yong Cho; Kyung-Won Kim; Kwon-Ho Lee; Kweon Jung (64-72).
Concentrations of carbonaceous aerosols in PM2.5, including elemental carbon (EC), organic carbon (OC), bulk water-soluble organic carbon (WSOC), fractionated WSOCs, and water-soluble inorganic species were measured between December 27, 2010 and January 20, 2011, at an urban site of Seoul, Korea. PM2.5 samples were collected twice a day, e.g., for the daytime (10:00–16:00) and nighttime (16:00–10:00), respectively. A macro-porous XAD7HP resin was used to separately group the liquid extracts into hydrophilic and hydrophobic WSOC (WSOCHPI and WSOCHPO). To better understand the contributions of primary and secondary OC (SOC) to WSOC, estimates of SOC were derived using the EC-tracer method and compared with the WSOC fractions. Good correlations among the WSOC, SO 4 2 − , and oxalate suggest that some of the observed WSOC originated from similar formation processes as those of SO 4 2 − and oxalate, i.e., formed by an in-cloud or aerosol droplet process. Primary OC was more highly correlated with the WSOCHPO (R 2 = 0.56) than the WSOCHPI (R 2 = 0.33), while a better correlation between predicted SOC and WSOCHPI (R 2 = 0.63) was found than between the predicted SOC and WSOCHPO (R 2 = 0.47). These results suggest that WSOCHPI at the site during the winter could be formed by a similar production pathway such as the secondary organic carbon, while primary combustion emissions were a dominant source for the WSOCHPO during the study period. Sources of WSOC, WSOCHPI and WSOCHPO inferred based on the correlations were also clearly demonstrated by source categories identified by principle component analysis. Measurement results suggest that group separation of bulk WSOC extracts could provide important clues for better understanding the sources of OC (or WSOC).► Sources of fractionated water-soluble organic carbon (WSOC) were examined. ► Primary combustion emissions were dominant sources of hydrophobic WSOC. ► Hydrophilic WSOC could be formed by processes similar to S O 4 2 − and secondary OC.
Keywords: Carbonaceous aerosols; Secondary organic carbon; Hydrophilic and hydrophobic water-soluble organic carbons; EC-tracer method;

Air samples were collected using a HiVol air sampler for 24 hours every week from September 2008 to August 2009 in the city of Dalian, a typical coast city in Northeast China. 12 polybrominated diphenyl ethers (PBDEs) congeners (BDE-17, -28, -47, -66, -85, -99, -100, -138, -153, -154, -183 and -209) and Dechlorane Plus (DP) were measured and analyzed. Annual arithmetic mean concentrations of ∑12PBDEs (gas + particle phase) and DP (Particle phase) in air samples were 104 ± 95 pg m−3 and 3 ± 6 pg m−3, respectively. BDE-209 was the dominating congener in all seasons with the contribution of 56 ± 21% of ∑12PBDEs, followed by BDE-28, -47 and -99. The mean fractional abundance of the syn-DP isomer (f syn) in all samples was 0.31 ± 0.14, lower than the value reported for technical DP mixture produced in China (f syn  = 0.4), indicating depletion of syn-DP in Chinese air. A year monitoring of PBDE in air produced a large dataset that provided a gas-particle partitioning analysis based on a wide temperature range and also individual PBDE congeners. The values of the portion of PBDEs in particle phase to the whole PBDEs in air had a general trend that became higher with the increasing number of bromine atoms at the same temperature and with decreasing temperature for the same congener. The result of PBDEs gas-particle partitioning analysis indicated that PBDEs in gas and particle phases were closer to equilibrium at higher temperature periods. For the first time, the K OA-based absorption model was evaluated for individual PBDE congeners. The results showed that, the model is more suitable for predicting low brominated congeners than high brominated ones, and the accuracy of model predictions decreases along with decrease of temperatures for individual PBDE congeners.► A whole year HiVol air sampling was conducted in Dalian, China. ► Mean air concentrations (pg m−3) were104 ± 95 for ∑12PBDEs and 3 ± 6 for DP. ► K OA-based model was more suitable for predicting lower PBDEs than higher ones. ► The accuracy of predictions decreases along with decrease of temperatures.
Keywords: PBDEs; DP; Air concentration; Gas-particle partitioning; China;

Indoor and outdoor characterisation of organic and inorganic compounds in city centre and suburban elementary schools of Aveiro, Portugal by P.N. Pegas; T. Nunes; C.A. Alves; J.R. Silva; S.L.A. Vieira; A. Caseiro; C.A. Pio (80-89).
Pollutants inside school buildings may affect children's health and influence learning performance and attendance. This study investigated pollutant concentrations inside and outside school buildings at different locations (city centre and suburban) in Aveiro, Portugal, between April and June 2010. The aim was to evaluate simultaneously comfort parameters (temperature, relative humidity, CO2 and CO) and indoor and outdoor concentrations of VOCs, NO2, PM10 and bioaerosols. PM10 samples were analysed and characterised, for the first time, for the water soluble inorganic ions (WSII), organic carbon (OC), elemental carbon (EC), carbonates, and detailed organic speciation. The CO2 and bioaerosol levels were higher than the acceptable maximum values to the occupants' comfort. Concentrations of the traffic tracer NO2 were higher outdoors. The daily indoor PM10 levels were always higher than those outdoors, except on weekends, suggesting that the physical activity of pupils and class works highly contributed to the emission and resuspension of particles. Almost all identified VOCs showed I/O ratios higher than one, which denotes an important contribution from indoor sources at both schools. The suburban school was more exposed to industrial emissions than the institution located in the city centre. Especially at the city centre, infiltration of outdoor particulates leads to contamination of school indoor environment with vehicle emissions and biomass burning smoke likely coming from biofuel use in nearby restaurants and bakeries.► For most pollutants, concentrations indoors are higher than outdoors. ► About 74% of PM10 is generated indoors. ► Pupils' physical activity and classroom works contribute to high indoor PM10 levels.
Keywords: Indoor air school; Particulate matter; Inorganic pollutants; Organic pollutants;

Size-segregated composition of particulate matter (PM) in major roadways and surface streets by W. Kam; J.W. Liacos; J.J. Schauer; R.J. Delfino; C. Sioutas (90-97).
A sampling campaign was conducted to assess on-road particulate matter (PM) composition for three size fractions (PM10 2.5, PM2.5 0.25, and PM0.25) on three representative roadways in Los Angeles: 1) the I-110, a high-traffic freeway composed mostly of light-duty vehicles (LDVs), 2) the I-710, a major freeway for heavy-duty vehicles (HDVs) traveling to and from the Ports of Los Angeles and Long Beach, and 3) Wilshire/Sunset Blvd, two major surface streets. Concurrent sampling was conducted at the University of Southern California (USC), which was used as an urban background site. Two sets of PM samples were collected for each roadway, with a sampling duration of approximately 50 h for each set. The samples were analyzed for inorganic ions, elemental carbon (EC), organic carbon (OC), water-soluble OC (WSOC), and trace elements and metals. Results showed that the PM0.25 fraction is heavily influenced by on-road vehicular emissions, as indicated by average roadway PM concentrations that were 48.0 ± 9.4% higher than those observed at USC (p < 0.05), while the PM10 2.5 fraction is mostly influenced by resuspension of road dust and the PM2.5 0.25 fraction is mainly composed of secondary species. Overall, the composition of inorganic ions (%) was relatively consistent across the three roadway environments. With very low EC levels in PM10 2.5, the most notable difference among the three roadway environments was the PM2.5 EC levels observed on the I-710, which are 2.0 ± 0.2 μg m−3 and 4.1 times greater than USC, while levels on the I-110 and Wilshire/Sunset were 1.0 ± 0.2 μg m−3 and 0.6 ± 0.01 μg m−3 and 2.1 and 1.2 times greater, respectively. PM2.5 OC and WSOC concentrations were observed to be 1.6, 2.0, and 1.7 times greater on the I-110, I-710, and Wilshire/Sunset than corresponding levels at USC, respectively. Results from this study may have major public health implications for passengers who commute frequently on high-traffic roadways. Finally, a comparison of EC levels to previous studies conducted at fixed sites near the I-110 and I-710 showed substantial decreases in EC concentrations over the past years, which may be a result of the recent Port of Los Angeles Clean Truck Program.► A sampling campaign was conducted to assess on-road PM chemical characterization. ► Three roadways were sampled (a low and a high HDV freeway and major street). ► The PM0.25 fraction is most heavily influenced by on-road sources. ► EC levels on the high HDV freeway are substantially higher than background site's. ► Decrease in EC levels may be one of the results of Port of Los Angeles Clean Truck Program.
Keywords: On-road emissions; Particulate matter; Los Angeles; Mass balance;

Condensed-phase versus gas-phase ozonolysis of catechol: A combined experimental and theoretical study by Timothy J. Barnum; Nicholas Medeiros; Ryan Z. Hinrichs (98-106).
Anthropogenic emissions of volatile aromatic compounds contribute to the formation of secondary organic aerosols (SOA), especially in urban environments. Aromatic SOA precursors typically require oxidation by hydroxyl radicals, although recent work suggests that ozonolysis of 1,2-benzenediols produces SOA in high yields. We employed attenuated total reflectance and transmission infrared spectroscopy to investigate the heterogeneous ozonolysis of catechol thin films. Formation of the dominant condensed-phase product muconic acid was highly dependent on relative humidity (RH) with few products detected below 40% RH and a maximum reactive uptake coefficient of γ = (5.6 ± 0.5) × 10−5 measured at 81.2% RH. We also performed quantum chemical calculations mapping out several reaction pathways for the homogeneous ozonolysis of gaseous catechol. 1,3-cycloaddition transition states were rate limiting with the most favorable activation energies at 45.4 and 47.1 kJ mol−1 [CCSD(T)/6-311++G(d,p)] corresponding to addition across and adjacent to the diol C=C, respectively. Gas-phase rate constants, calculated using transition state theory, were six orders of magnitude slower than experimental values. In contrast, a calculated activation energy was lower for the ozonolysis of a catechol•H2O complex, which serves as a first-approximation for modeling the ozonolysis of condensed-phase catechol. These combined results suggests that homogeneous ozonolysis of catechol may not be important for the formation of secondary organic aerosols but that ozonolysis of surface-adsorbed catechol may contribute to SOA growth.► ATR-FTIR identified muconic acid as main product from catechol thin film ozonolysis. ► Thin film catechol + O3 reactive uptake coefficient increased with humidity. ► 1,3-Cycloaddition transition states were rate limiting for gaseous catechol ozonolysis. ► Theoretical rate constant for catechol ozonolysis 106 times slower than experiment. ► Theoretical activation energies for O3 + catechol•H2O much lower than catechol.
Keywords: Ozonolysis; Secondary organic aerosol; Catechol SOA; Cycloaddition; Quantum chemical calculations; Heterogeneous chemistry;

Trends in wintertime particulate sulfate ion and nitrate ion concentrations were computed for 2000–2010 using data from remote and rural sites across the United States from the Interagency Monitoring of Protected Visual Environments (IMPROVE) program. Several sites in the northern and central Great Plains had increasing sulfate and nitrate ion concentrations in December at the rate of over 5% yr−1. The positive trends are in contrast to the decreasing national annual trends in nitrogen oxides (NOx) and sulfur dioxide (SO2) emissions as reported by the Environmental Protection Agency. Increasing trends in particulate nitrate and sulfate ion concentrations have important implications for air pollution mitigation strategies, considering concentrations at these sites counter the reductions in emissions from controlled sources across the United States.
Keywords: Aerosol trends; Rural aerosols; Great Plains;

Motorised traffic generates large numbers of small-sized, magnetisable particulate pollutants in the urban environment. Exposure to these small particles has been associated with adverse effects on human health. Magnetic properties of these particles are, therefore, increasingly used for assessing environmental stress. Biomonitoring of magnetic particles accumulated on leaf surfaces may provide information on the concentration of, and exposure to, atmospheric particles at high spatial resolution. In this study, leaf saturation isothermal remanent magnetisation (SIRM) of three urban tree types (Carpinus betulus and Tilia sp. with hairy and non-hairy leaves) was measured at high spatial resolution in the city of Gent, Belgium, in June and September 2009. We compared leaf SIRM between land use classes with different urban habitat quality. In a multiple regression model, we tried to explain the spatial variability in leaf SIRM by tree species, sampling height, distance to the nearest road and its traffic intensity, tram frequency and a measure for regional traffic emissions (derived from traffic intensity of and the distance to the most important highways around and in the city in the main four wind directions). We found that the leaf SIRM was significantly influenced by tree species, distance to the nearest road and its traffic intensity and tram frequency. The SIRM significantly increased with increasing traffic intensity and tram frequency and by decreasing distance to the nearest road. It is concluded that leaf SIRM is a good bio-indicator for monitoring spatial variation of magnetic particles in urban environments.► Tree leaf SIRM distinguished between sites with contrasting urban habitat quality. ► Leaf SIRM correlated positively with traffic and negatively with distance to road. ► Local traffic emission is the main magnetic PM source in urban environments. ► Inter-species calibration of leaf SIRM allows a high coverage of the study area. ► Leaf SIRM is a good indicator of the spatial variation of urban magnetic particles.
Keywords: Biomagnetic monitoring; Particulate pollution; Road traffic; Tree leaves;

Enhanced trimethylamine-containing particles during fog events detected by single particle aerosol mass spectrometry in urban Guangzhou, China by Guohua Zhang; Xinhui Bi; Lo Yin Chan; Lei Li; Xinming Wang; Jialiang Feng; Guoying Sheng; Jiamo Fu; Mei Li; Zhen Zhou (121-126).
Trimethylamine (TMA) plays an important role in atmospheric chemistry, yet its pathway towards aerosol is not clear. We report in this study the measurement of TMA in submicron particles using a single particle aerosol mass spectrometer (SPAMS) in urban Guangzhou, China for the period of 30 April through 22 May, 2010. The number fraction of TMA-containing particles relative to total detected particle number dramatically increased within the occurrence of fogs. It changed from an average of ∼7% for clear days to ∼35% for the fog events. For particles with size larger than 0.5 μm, the fraction could even account up to ∼60%. Averaged relative intensity of TMA was correlated well with relative humidity, indicating the important role of aerosol water content in the gas-to-particle partitioning of TMA. During the fog events, number based size distribution of TMA-containing particles shifted towards larger mode, peaking at droplet mode (0.5–1.2 μm), corresponding to the build-up of aerosol mass, suggesting the significant mass transfer of TMA and other semi-volatile species from gas to aerosol. Results also reveal that most of TMA-containing particles also contained signals from ammonium, nitrate and sulfate. A much larger fraction of TMA-containing particles was found to contain nitrate during the fog events than on clear days. During the fog events, nitrate and sulfate were more strongly associated with TMA compared to ammonia, which was oppositely observed on clear days. These results indicate that gas-to-particle partitioning of TMA in urban Guangzhou occurs preferentially during fog processing. The study could help improve our understanding in fog processing and potential roles of TMA-containing particles in urban Guangzhou.► TMA-containing particles accounted for ∼7% for clear days to ∼35% for the fog events. ► Averaged relative intensity of TMA was correlated well with relative humidity. ► Most of TMA particles were internally mixed with ammonium, nitrate and sulfate. ► The fog events led to the rise of nitrate. ► Nitrate and sulfate were more strongly associated with TMA than ammonium during the fog events.
Keywords: Trimethylamine; Single particle; Mixing state; Fog; SPAMS; PRD;

Hydrogen peroxide (HOOH) is an important trace constituent in snow and ice, including in Arctic and Antarctic ice cores. To better understand the budget of snowpack HOOH, here we examine its production in illuminated snow and ice. To evaluate what types of compounds might be important photochemical sources of HOOH, we first illuminated laboratory ice samples containing 10 different model organic compounds: guaiacol, phenol, syringol, benzoate, formate, octanal, octanoic acid, octanedioic acid, phenylalanine, and mixtures of oxalate with iron (III). Half of these compounds produced little or no HOOH during illumination, but two classes of compounds were very reactive: phenolic compounds (with rates of HOOH of 6–62 nM-HOOH h−1  μM−1-phenolic) and mixtures of Fe(III) with a stoichiometric excess of oxalate (with rates of HOOH production as high as 2,000,000 nM h−1 per μM iron). To quantify rates of HOOH production in the environment we also illuminated snow samples collected from the Arctic and Antarctic. The average (±1σ) HOOH production rate in these samples was low, 5.3 ± 5.0 nM h−1 and replicate measurements showed high variability. In some natural samples there was an initial burst of HOOH production (with a rate approximately 10 times higher than the average production rate), followed by reduced rates at subsequent time points. Although our laboratory ice samples reveal that illuminated organics and metal-organic complexes can form HOOH, the low rates of HOOH formation in the Arctic and Antarctic snow samples suggest this process has only a modest impact on the HOOH budget in the snowpack.► Illumination of ice containing model organics can rapidly produce HOOH. ► Illumination of natural polar snow produces HOOH at low rates. ► Photoproduction in polar snow has a modest effect on the HOOH budget.
Keywords: Polar photochemistry; Iron-oxalate complexes; Organic photochemistry; H2O2 budget;

Trifluoromethyl sulfur pentafluoride (SF5CF3), sulfur hexafluoride (SF6) and dichlorodifluoromethane (CCl2F2) (also referred to as CFC-12) were measured simultaneously in the atmosphere at a site 25 km north of New York City over a period of 6 months with continuous measurements every 25 min for 4 months. The SF5CF3 record showed little variability and its concentration appeared close to the remote atmospheric concentration. The concentrations of SF6 and CFC-12 had numerous spikes well in excess of their remote atmospheric concentrations indicating the presence of local sources. The lack of SF5CF3 spikes reveals that the usage of SF6 in the New York metropolitan area does not result in significant production of SF5CF3, and also that there is no significant production by industrial and manufacturing processes in the region.
Keywords: Trifluoromethyl sulfur pentafluoride (SF5CF3); Sulfur hexafluoride (SF6); Dichlorodifluoromethane (CFC-12); New York City;

Greenhouse gas emissions from two-stage landfilling of municipal solid waste by Yuanyuan Zhang; Dongbei Yue; Yongfeng Nie (139-143).
Simulations were conducted to investigate greenhouse gas emissions from aerobic pretreatment and subsequent landfilling. The flows in carbon balance, such as gas, leachate, and solid phases, were considered in the simulations. The total amount of CO2 eq. decreased as organic removal efficiency (ORE) increased. At ORE values of 0, 0.30, 0.41, and 0.54, the total amounts of CO2 eq. were 2614, 2326, 2075, and 1572 kg CO2 eq. per one ton dry matter, respectively; gas accounted for the main contribution to the total amount. The reduction in CO2 eq. from leachate was the primary positive contribution, accounting for 356%, 174%, and 100% of total reduction at ORE values of 0.30, 0.41, and 0.54, respectively. The CO2 eq. from energy consumption was the negative contribution to total reduction, but this contribution is considerably lower than that from gas. Aerobic pretreatment shortened the lag time of biogas production by 74.1–97.0%, and facilitated the transfer of organic carbon in solid waste from uncontrolled biogas and highly polluting leachate to aerobically generated CO2.► Carbon balance in aerobic pretreatment and subsequent landfilling was investigated. ► CO2 eq. from gas was the main contribution to total CO2 eq. emission. ► The total amount of CO2 eq. decreased with increasing aerobic pretreatment level. ► Reduction from leachate contributed primarily to total CO2 eq. reduction. ► Aerobic pretreatment decreased the lag time of biogas production by 74.1–97.0%.
Keywords: Two-stage landfilling; Biogas; Greenhouse effect; Aerobic pretreatment; Municipal solid waste;

Emission consequences of introducing bio ethanol as a fuel for gasoline cars by Morten Winther; Flemming Møller; Thomas C. Jensen (144-153).
This article describes the direct vehicle emission impact of the future use of bio ethanol as a fuel for gasoline cars in Denmark arising from the vehicle specific fuel consumption and emission differences between neat gasoline (E0) and E5/E85 gasoline-ethanol fuel blends derived from emission tests using primarily the European NEDC and ARTEMIS driving cycles. The E0-E5 test vehicles (nine cars) represent today’s gasoline car traffic well where most of the driving is being made with cars certified as Euro 3+. The FFV test cars (25 cars) are all certified according to the Euro 4 emission standard introduced in Europe from the mid-2000s. This matches well with the propagation of the FFV technology in Europe.For vehicles using E5 rather than E0, the average fuel consumption and emission differences are small. For CO, VOC and NOx the derived average differences are 0.5%, −5% and 7%, respectively. For FFVs using E85 rather than E5, the emission differences become even smaller for VOC and NOx, but greater for CO. The derived average emission differences are in this case 18%, −1% and 5% for CO, VOC and NOx, respectively. In both comparative cases there is a large variation in the emission difference values calculated for the individual cars. The large standard deviations introduce some uncertainties in the final averages computed for each emission component.The vehicle based emissions are made up for two fossil fuel baseline scenarios (FS), characterised by high and low traffic growth rates. For each FS, two biofuel scenarios (BS1, BS2) are presented. BS1 reaches the Danish policy targets (10% biofuel share in 2020). BS2 is more ambitious (25% in 2030). By definition the biofuel part of the combusted fuel is CO2 neutral and the maximum CO2 emission difference between FS and BS2 becomes 27% in 2030. As predicted by the vehicle specific emission differences the calculated emission impacts of using bio ethanol are small for NOx, VOC and CO. Instead, for FS, BS1 and BS2 large emission reductions are due to the gradually cleaner new sold gasoline cars and the decline in total mileage until the mid-2010s.► Emission impacts of using bio ethanol as a fuel for gasoline cars. ► Bio ethanol scenarios; 10% in 2020 and a more ambitious case (25% in 2030). ► The maximum CO2 difference becomes 27% in 2030 for fossil vs. ambitious case. ► Bio ethanol impact is small for NOx, VOC and CO, as predicted from literature review. ► The literature based bio ethanol emission differences are suited for European models.
Keywords: Bio ethanol emissions; CO2; NOx; VOC; CO; E5; E85; Road transport; Denmark;

Added value of stress related gene inductions in HepG2 cells as effect measurement in monitoring of air pollution by Ingrid Nobels; Caroline Vanparys; Rosette Van den Heuvel; Jordy Vercauteren; Ronny Blust (154-163).
In this study we studied the effects of particulate matter samples (PM) through gene expression analysis in a routine air quality monitoring campaign by the Flemish Environment Agency (VMM, Belgium). We selected a human hepatoma (HepG2) multiple endpoint reporter assay for targeted stress related endpoint screening. Organic extracts of air samples (total suspended particles, TSP) were collected during one year in an industrial, urban and background location in Flanders, Belgium. Simultaneously, meteorological conditions (temperature, wind speed and precipitation) and particulate matter size ≤ 10 μM (PM10), organic (OC), elemental (EC) and total (TC) carbon were monitored and air samples were collected for chemical analysis (11 PAHs). Correlations between the induction of the different stress genes and the chemical pollutants were analysed.Exposure of HepG2 cells to daily air equivalents (20 m3) of organic TSP extracts revealed the dominant induction of the xenobiotic response element (Xre) and phase I (Cyp1A1) and phase II (GstYa) biotransformation enzymes. Additional effects were the induction of c-Fos, a proto-oncogen and Gadd45, a marker for cell cycle disturbance and responsive to genotoxic compounds. Inductions of other relevant pathways, such as sequestration of heavy metals, retinoids response, protein misfolding and increased cAMP levels were measured occasionally.A significant correlation was found between the genes Cyp1A1 (a typical marker for presence of PAHs and dioxin like compounds), c-Fos, Gadd45, (responsive to DNA damaging compounds) and the amount of PM10 and elemental carbon (EC) whereas no correlation was found between these genes and total PAHs content. This may suggest that the observed induction of Cyp1A1 and DNA damage related genes was provoked (partially) by other particle bound compounds (e.g. pesticides, PCBs, brominated flame retardants, dioxins, …), than PAHs. The contribution of particle bound compounds, other than PAHs might be important to take into account in risk evaluation of air pollution.► Successful inclusion of effect monitoring in current air quality monitoring campaigns. ► Exposure to daily equivalents of air sample induced several stress related pathways. ► PM bound compounds, other than PAHs have a contribution to the induced pathways.
Keywords: Air pollution; Reporter assay; Stress related endpoints;

PAHs, carbonyls, VOCs and PM2.5 emission factors for pre-harvest burning of Florida sugarcane by Danielle Hall; Chang-Yu Wu; Yu-Mei Hsu; James Stormer; Guenter Engling; Krisha Capeto; Jun Wang; Scott Brown; Hsing-Wang Li; Kuei-Min Yu (164-172).
Emission factors (EFs) for hazardous polycyclic aromatic hydrocarbons (PAHs), carbonyls, and volatile organic compounds (VOCs) as well as other species such as PM2.5, elemental carbon (EC), organic carbon (OC), and tracer compounds (e.g., levoglucosan (LG) and other sugars) were investigated for sugarcane pre-harvest burning in Florida. A combustion chamber was used to simulate field burning conditions for determining EFs of both dry leaf and whole stalk biomass burning. Samples were collected from the chamber's exhaust duct following EPA sampling methods. The total PAH EFs were 7.13 ± 0.94 and 8.18 ± 3.26 mg kg−1 for dry leaf and whole sugarcane stalk burning, respectively. Carbonyl EFs were 201 ± 39 and 942 ± 539 mg kg−1 for dry leaf and whole stalk burning, respectively. PAH and carbonyl emissions were dominated by lower molecular weight compounds (e.g., naphthalene and formaldehyde, respectively). Of the aromatic VOCs studied, benzene was the predominant species. The PM2.5 EF was 2.49 ± 0.66 g kg−1, which is in range of the current published AP-42 EFs for particulate matter emissions from sugarcane burning and other sugarcane studies. The OC, EC and LG EFs were 0.16 ± 0.09 g kg−1, 0.71 ± 0.22 g kg−1, and 7.87 ± 5.42 mg kg−1, respectively. EFs of gaseous pollutants were generally lower than EFs from studies of agricultural residue combustion, likely due to the high combustion efficiency observed in this study.► Air toxic EFs from sugarcane burning are lower than from other residue combustion. ► EFs are highly influenced by burning conditions and biomass conditions. ► EC, OC and anhydrosugar compounds can serve as tracers for source apportionment.
Keywords: Biomass burning; PAH; Particulate matter; Carbonyls; VOC; Levoglucosan;

Comment on “Effect of coal-fired power generation on visibility in a nearby National Park ()” by W.H. White; R.J. Farber; W.C. Malm; M. Nuttall; M.L. Pitchford; B.A. Schichtel (173-178).
Few electricity generating stations received more environmental scrutiny during the last quarter of the twentieth century than did the Mohave Power Project (MPP), a coal-fired facility near Grand Canyon National Park. examine regional aerosol monitoring data collected before and after the plant’s 2006 retirement for retrospective evidence of MPP’s impact on visibility in the Park. The authors’ technical analysis is thoughtfully conceived and executed, but is misleadingly presented as discrediting previous studies and their interpretation by regulators. In reality the Terhorst–Berkman analysis validates a consensus on MPP’s visibility impact that was established years before its closure, in a collaborative assessment undertaken jointly by Federal regulators and MPP’s owners.
Keywords: Sulfate; Aerosol; IMPROVE; MOHAVE; Grand Canyon; Clean Air Act;

There is high demand for accurate and reliable airborne carbonyl measurement methods due to the human and environmental health impacts of carbonyls and their effects on atmospheric chemistry. Standardized 2,4-dinitrophenylhydrazine (DNPH)-based sampling methods are frequently applied for measuring gaseous carbonyls in the atmospheric environment. However, there are multiple short-comings associated with these methods that detract from an accurate understanding of carbonyl-related exposure, health effects, and atmospheric chemistry. The purpose of this brief technical communication is to highlight these method challenges and their influence on national ambient monitoring networks, and to provide a logical path forward for accurate carbonyl measurement. This manuscript focuses on three specific carbonyl compounds of high toxicological interest—formaldehyde, acetaldehyde, and acrolein. Further method testing and development, the revision of standardized methods, and the plausibility of introducing novel technology for these carbonyls are considered elements of the path forward. The consolidation of this information is important because it seems clear that carbonyl data produced utilizing DNPH-based methods are being reported without acknowledgment of the method short-comings or how to best address them.
Keywords: 2,4-dinitrophenylhydrazine (DNPH); Formaldehyde; Acetaldehyde; Acrolein; Solid sorbents;

The atmospheric reactions of alkylamino radicals, R1R2N, with O2 and NO2 were studied by theoretical methods to elucidate the possible pathways to imine formation at the atmospheric conditions. The calculations show that all relevant routes proceed via initial additions to the nitrogen atom of the amino radical, R1R2N–NO2, R1R2N–ONO and R1R2N–OO that then may undergo dissociation via five-center-ring transition states resulting in imines and HONO or HO2. The rate coefficient for amino radical reaction with O2 is shown to be several orders of magnitude smaller than the corresponding reaction with NO2. N-nitro amines are the major product in secondary amino radical reactions with NO2. For primary amino radical reactions with NO2 the amounts of N-nitro amines and imines will depend upon pressure and chain length. Results from TDDFT studies of N-nitro and N-nitrooxy amine photo stability indicate fast photolysis of N-nitrooxy amines at atmospheric conditions.► The atmospheric formation of imines from R n NH2−n  + NO2/O2 reactions were studied theoretically. ► The reaction starts from the addition to form RNOO, and then undergo dissociation to imines. ► The dominant product with NO2 reaction is nitroamines. ► Nitroamines are difficult to photolyze in the sunlight.
Keywords: Nitroamines; Imines; Photolysis; Atmospheric reaction;

Aerosol optical properties at Pasadena, CA during CalNex 2010 by Jonathan E. Thompson; Patrick L. Hayes; Jose L. Jimenez; Kouji Adachi; Xiaolu Zhang; Jiumeng Liu; Rodney J. Weber; Peter R. Buseck (190-200).
Aerosol optical properties measured at the Pasadena, CA site during the CalNex field campaign in May–June 2010 are summarized. Average measurements of PM2.5 aerosol extinction, scattering, absorption coefficients, and single scattering albedo (b ext, b scat, b abs and SSA) at λ = 532 nm were 62 Mm−1, 58 Mm−1, 4 Mm−1, and 0.92, respectively. The aerosol optical densities were 5 times lower than during the SCAQS study in 1987, highlighting major progress in PM control in the Los Angeles area in the last two decades. The period May 30–June 8 2010 was characterized by exceptionally high aerosol loading (b ext up to 250 Mm−1). During this period, b ext, b scat, and SSA tended to peak during the mid-morning. Correlation of PM2.5 b ext, b scat with mass concentration data yielded mass scattering and mass extinction coefficients of 3.5–5.1 m2 g−1 for 532 nm. Aerosol b abs were compared directly to mass concentration of elemental carbon (EC) yielding a campaign average mass absorption cross section (M.A.C.) of 5.7 ± 1.8 m2 g−1. TEM analysis of particles suggests soot was often internally mixed or adhering to sulfate and/or organics. Total non-refractory PM1 mass was a good quantitative indicator of coated soot fraction. Alteration of M.A.C. with mixing/coating state was not detected, however, increases in M.A.C. were linked to the presence of light absorbing, water-soluble organic carbon (WSOC) suggesting a possible role of this material invisible light absorption in the LA basin.► Mass scatter, mass extinction, and mass absorption coefficients are reported. ► Aerosol optical densities are 5 times less than 1987. ► The LA basin aerosol is currently not very light absorbing. ► TEM study suggests soot is often internally mixed, but not in core-shell morphology. ► Aerosol phase water soluble organic compounds absorb light.
Keywords: Aerosol optics; Single scatter albedo; Scattering coefficient; Extinction coefficient; Absorption coefficient; Mass absorption cross section; Mass scatter efficiency; Direct climate forcing; CalNex; Albedometer; Brown carbon; WSOC; Absorption enhancement;

A unified analytical solution of the steady-state atmospheric diffusion equation by J.S. Pérez Guerrero; L.C.G. Pimentel; J.F. Oliveira-Júnior; P.F.L. Heilbron Filho; A.G. Ulke (201-212).
A unified analytical solution of the steady-state atmospheric diffusion equation for a finite and semi-infinite/infinite media was developed using the classic integral transform technique (CITT) which is based on a systematized method of separation of variable.The solution was obtained considering an arbitrary mean wind velocity depending on the vertical coordinate (z) and a generalized separable functional form for the eddy diffusivities in terms of the longitudinal (x) and vertical coordinates (z).The examples described in this article show that the well known closed-form analytical solutions, available in the literature, for both finite and semi-infinite/infinite media are special cases of the present unified analytical solution. As an example of the strength of the developed methodology, the Copenhagen and Prairie Grass experiments were simulated (finite media with the mean wind speed and the turbulent diffusion coefficient described by different functional forms). The results indicate that the present solutions are in good agreement with those obtained using other analytical procedures, previously published in the literature. It is important to note that the eigenvalue problem is associated directly to the atmospheric diffusion equation making possible the development of the unified analytical solution and also resulting in the improvement of the convergence behavior in the series of the eigenfunction-expansion.► The three-dimensional steady-state atmospheric diffusion equation was solved analytically using the integral transform. ► The solution includes a generalized functional form for the mean wind speed and the eddy diffusivities. ► The solution for a finite domain was extended to semi-infinite and infinite domains using a unified procedure. ► The associated eigenvalue problem improves the convergence of the solution. ► The unified analytical solution showed to be robust when evaluated against literature results.
Keywords: Atmospheric diffusion equation; Analytical solution; Integral transform; Associated eigenvalue problem;

Bioaccessibility of palladium and platinum in urban aerosol particulates by Christoph Puls; Andreas Limbeck; Stephan Hann (213-219).
To evaluate potential health hazards caused by environmental Platinum Group Elements (PGEs), bioaccessibility of the metals in question needs to be assessed. To gain appropriate data, airborne particulate matter samples of different size fractions (total suspended particles as well as PM10 and PM2.5) were taken in downtown Vienna, an urban site primarily polluted by traffic. Total PGE concentrations in these samples were in the low picogram per cubic meter range, as determined by ID-ICP-MS after microwave digestion. For elimination of elements interfering with the accurate quantification, the digested samples were subjected to a cleaning procedure involving cation exchange. For determination of the bioaccessible fraction, it was assumed that inhaled particles are removed from the respiratory system by mucociliary clearance and subsequently ingested. Accordingly, the solubility of PGE in synthetic gastric juice was investigated by batch extraction of particulate matter samples followed by microwave assisted UV-digestion, cation exchange cleanup and ID-ICP-MS. The acquired data was used to calculate the bioaccessible fraction of Pd and Pt in airborne particulate matter. Average GIT-extractable fractions for Pd and Pt in TSP were 41% and 27%, in PM10 34% and 26%, respectively, thus exceeding previously determined values for bioaccessibility of PGE from ground catalyst materials by up to an order of magnitude.► Bioaccessibility of Pd and Pt in urban airborne particulate matter was examined. ► Daily samples were extracted with synthetic gastric juice to evaluate solubility. ► Values were distinctly elevated compared to extractions of road dust or ground catalyst. ► Results indicate that the impact of airborne PGE has been underestimated.
Keywords: Airborne particulate matter; Platinum group elements; Bioaccessibility;

Land-use regression (LUR) models have been developed to estimate spatial distributions of traffic-related pollutants. Several studies have examined spatial autocorrelation among residuals in LUR models, but few utilized spatial residual information in model prediction, or examined the impact of modeling methods, monitoring site selection, or traffic data quality on LUR performance. This study aims to improve spatial models for traffic-related pollutants using generalized additive models (GAM) combined with cokriging of spatial residuals. Specifically, we developed spatial models for nitrogen dioxide (NO2) and nitrogen oxides (NOx) concentrations in Southern California separately for two seasons (summer and winter) based on over 240 sampling locations. Pollutant concentrations were disaggregated into three components: local means, spatial residuals, and normal random residuals. Local means were modeled by GAM. Spatial residuals were cokriged with global residuals at nearby sampling locations that were spatially auto-correlated. We compared this two-stage approach with four commonly-used spatial models: universal kriging, multiple linear LUR and GAM with and without a spatial smoothing term. Leave-one-out cross validation was conducted for model validation and comparison purposes. The results show that our GAM plus cokriging models predicted summer and winter NO2 and NOx concentration surfaces well, with cross validation R 2 values ranging from 0.88 to 0.92. While local covariates accounted for partial variance of the measured NO2 and NOx concentrations, spatial autocorrelation accounted for about 20% of the variance. Our spatial GAM model improved R 2 considerably compared to the other four approaches. Conclusively, our two-stage model captured summer and winter differences in NO2 and NOx spatial distributions in Southern California well. When sampling location selection cannot be optimized for the intended model and fewer covariates are available as predictors for the model, the two-stage model is more robust compared to multiple linear regression models.► GAM plus cokriging predicted summer and winter NO2 and NOx concentrations well. ► GAM plus cokriging is more robust than linear LUR with non-optimal sampling locations. ► GAM plus cokriging is more robust than linear LUR with fewer spatial covariates.
Keywords: Land-use regression; Spatial residuals; Generalized additive model; Cokriging; Traffic air pollution;

Sampling artifacts of organic and inorganic aerosol: Implications for the speciation measurement of particulate matter by Yuan Cheng; Feng-kui Duan; Ke-bin He; Zhen-yu Du; Mei Zheng; Yong-liang Ma (229-233).
Sampling artifacts of organic carbon (OC) and nitrate were simultaneously evaluated in Beijing China during summer of 2010. It was demonstrated that the charcoal denuder used in this study can effectively remove not only the gaseous organics that could be adsorbed by quartz filter but also the gaseous HNO3 that could be adsorbed by nylon filter, giving rise to a new sampling method that using a charcoal denuder in combination with a quartz–nylon filter pack. Nitrate measured by the denuded quartz–nylon filter pack was approximately 1.5 times that of the value measured by the bare quartz filter, whereas comparison of organic carbon (OC) measured by the denuded and bare quartz filter showed that the OC concentration was overestimated by about 15% due to the positive sampling artifact. The new sampling method has the advantage that nitrate and OC can be accurately measured by a single sampling channel, thus it is suggested for the speciation monitoring of ambient particulate matter. It is also suggested that accurate measurement of nitrate is especially meaningful for China, because the NOx emissions continue to increase during the last decade.
Keywords: Denuder; Sampling artifact; Nitrate; OC; Chemical composition; Speciation measurement;

Sugars are important water-soluble organic constituents of atmospheric particulate matter (PM). In order to better understand the sources and seasonal variations of sugars in aerosols, primary saccharides (fructose, glucose, sucrose, and trehalose) and sugar alcohols (arabitol and mannitol), together with levoglucosan, have been studied in ambient aerosols at Gosan, Jeju Island in the western North Pacific, the downwind region of the Asian outflow, using gas chromatography–mass spectrometry. The results showed that the sugar composition varied seasonally with a total concentration range of 6.8–1760 ng m−3 (mean 246 ng m−3). The total identified sugars had the highest concentration in April, the spring bloom season at Jeju Island, when sucrose contributed up to 80% of the total sugars. The dominance of sucrose was also detected in pollen samples, suggesting that pollen can contribute significantly to sucrose in aerosols during the spring bloom. The seasonal variation of trehalose is consistent with those of non-sea-salt Ca2+ and δ13C of total carbon with elevated levels during the Asian dust storm events. This study indicates that sugar compounds in atmospheric PM over East Asia can be derived from biomass burning, Asian dust, and primary biological aerosols such as fungal spores and pollen. Furthermore, this study supports the idea that sucrose could be used as a tracer for airborne pollen grains, and trehalose as a tracer for Asian dust outflow.► Seasonal trends of saccharides have been studied in ambient aerosols at Gosan site. ► Airborne pollen is the dominant source of sucrose during the spring bloom season. ► Trehalose is a potential tracer for Asian dust outflow over the Gosan site.
Keywords: Organic aerosols; Saccharides; Sucrose; Airborne pollen; Asian dust;

Yield-scaled N2O emissions in a winter wheat–summer corn double-cropping system by Shuping Qin; Yuying Wang; Chunsheng Hu; Oene Oenema; Xiaoxin Li; Yuming Zhang; Wenxu Dong (240-244).
Emissions of nitrous oxide (N2O) from agricultural soils contribute to global warming and stratospheric ozone depletion. Applications of fertilizer nitrogen (N) increase N2O emission, but also increase agricultural production. Here, we report on the responses of crop yield, N2O emission and yield-scaled N2O emission (N2O emission per unit N uptake by grain and aboveground biomass) to different N fertilizer rates in a winter wheat–summer corn double-cropping system in the North China Plain. Soil N2O emission measurements were carried out for two years in a long-term field experiment, under semi-arid conditions with four flood irrigations events per year. Our results indicated that N2O emissions were linear functions and yield-scaled N2O emissions were cubic functions of N fertilizer application rate. Yield-scaled N2O emissions were lowest at application rates of 136 kg N ha−1 yr−1. Using a quadratic-plateau model, it was found that maximal crop yields were achieved at an application rate of 317 kg N ha−1 yr−1, which is 20% less than current practice. This level is suggested to be a compromise between achieving food security and mitigation N2O emissions.► Mitigating soil N2O emission is a challenging issue for developing countries. We examined optimum N fertilizer rates for maximal yield and minimal N2O emission. Maximized yield of a two-crop wheat-corn rotation was achieved at 317 kg N ha-1. The yield-scaled N2O emissions were not substantially increased at 317 kg N ha-1.
Keywords: Nitrous oxide; Nitrogen fertilizer; Yield-scaled N2O emission; North China plain;

Assessment of an air pollution event in the southwestern Iberian Peninsula by J.A. Adame; M.A. Hernández-Ceballos; J.P. Bolívar; B. De la Morena (245-256).
On 12 and 13 August 2006, an exceptional air pollution event occurred in the southwest of the Iberian Peninsula (western Andalusia). High concentrations of surface ozone, CO and PM10 were registered at several air quality stations, in some cases reaching record values. During the late afternoon and evening of these two dates, the information and alert thresholds of surface ozone at coastal stations were exceeded, with peaks of 270 μg m−3. Concentrations of CO and PM10 reached 1800 μg m−3 and 240 μg m−3. Surface meteorological observations, back trajectories computed with the HYSPLIT model and wind and specific humidity fields from the meso-meteorological WRF-ARW model have all been used to gain an understanding of the origin of this event. The results indicate that this event was caused by the long-range transport of air masses from the wildfires that had occurred in the northwest of the Iberian Peninsula (Galicia and northern Portugal) during the first two weeks of August 2006. Air masses loaded with pollutants were transported approximately 1000 km from north to south, over Portugal and the Atlantic Ocean, to reach the southwestern Iberian Peninsula, with the consequent negative high impact on the air quality of this region.► Air pollution event in the southwestern Iberian Peninsula. ► High hourly concentrations of surface ozone, CO and PM10 were measured. ► Observations and models have been used to investigate their origin. ► Long-range transport of the air masses from wildfires was the cause of this event.
Keywords: Forest fires; Wildfires; Biomass burning; Air quality; Air pollution event; Ozone; CO; PM10; HYSPLIT; WRF-ARW; Iberian Peninsula; Mediterranean basin;

Emissions of air pollutants from scented candles burning in a test chamber by Marco Derudi; Simone Gelosa; Andrea Sliepcevich; Andrea Cattaneo; Renato Rota; Domenico Cavallo; Giuseppe Nano (257-262).
Burning of scented candles in indoor environment can release a large number of toxic chemicals. However, in spite of the large market penetration of scented candles, very few works investigated their organic pollutants emissions. This paper investigates volatile organic compounds emissions, with particular reference to the priority indoor pollutants identified by the European Commission, from the burning of scented candles in a laboratory-scale test chamber. It has been found that BTEX and PAHs emission factors show large differences among different candles, possibly due to the raw paraffinic material used, while aldehydes emission factors seem more related to the presence of additives. This clearly evidences the need for simple and cheap methodologies to measure the emission factors of commercial candles in order to foresee the expected pollutant concentration in a given indoor environment and compare it with health safety standards.► Emissions from scented candles burning was experimentally investigated. ► Main pollutants that were detected are BTEX, aldehydes and PAHs. ► A test chamber was designed to perform measurements in an standardized environment. ► Emission factors were calculated for each pollutant detected. ► Obtained emission factors can be used to study health hazard in indoor environments.
Keywords: Scented candles; Emission factors; Test chamber; Volatile organic compounds; PAHs;

Photodegradation of (CH3CH2)2S and CH3CH2SCH3 initiated by OH radicals at atmospheric pressure. Product yields and mechanism in NOx free air by Gabriela Oksdath-Mansilla; Alicia B. Peñéñory; Ian Barnes; Peter Wiesen; Mariano A. Teruel (263-270).
The product distribution of the gas-phase reactions of OH radicals with diethyl sulfide (CH3CH2)2S and ethyl methyl sulfide, CH3CH2SCH3, determined in the absence of NOx, is presented. The experiments were performed in a 1080 L quartz-glass photoreactor and a 405 L borosilicate glass photoreactor in synthetic air at (298 ± 2) K using long path “in situ” FTIR spectroscopy for the analysis of the reactants and products. SO2 and CH3CHO were identified as major primary products for both title reactions together with HCHO as a co-product in the photodegradation of CH3CH2SCH3.Formation of CO and HCOOH was observed, however, the concentration–time behavior of these products show that they are secondary in origin and are produced from the further oxidation of major primary products. Traces of OCS were observed; its concentration–time behavior suggests that it is a minor primary product. The yields of the products obtained for the reaction of OH radicals with (CH3CH2)2S were the following: (50 ± 3)% and (91 ± 3)% for SO2 and CH3CHO, respectively. While, for the reaction of OH radicals with CH3CH2SCH3 yields of (51 ± 2)%, (57 ± 3)% and (46 ± 4)% were obtained for SO2, CH3CHO and HCHO, respectively.The present results are compared with previous results for the well studied reaction of dimethyl sulfide, CH3SCH3, with OH radicals and simple atmospheric degradation mechanisms are postulated to explain the formation of the observed products.Display Omitted► FTIR product distribution study of OH-initiated oxidation of two alkyl sulfides. ► SO2 and CH3CHO as main products and HCHO as co-product in the CH3CH2SCH3 reaction. ► Atmospheric degradation mechanisms are postulated.
Keywords: Alkyl sulfides; Product distribution; Atmospheric mechanism; Gas-phase photooxidation; Simulation chambers;

To parameterize stomatal conductance or ozone uptake modeling in the Eastern Asian tree species Zelkova serrata, measurements of stomatal conductance were carried out in several Japanese sites across the growing season. The new parameterization improved the stomatal conductance model performance relative to a previously proposed model. The results were used to compare the spatial distribution of AOT40 and Z. serrata stomatal ozone uptake in Japan. Including a soil moisture function improved the model in the short periods with low precipitation. In addition, elevated vapor pressure deficit and soil moisture deficit due to high temperature, and high ozone exposure induced stomatal closure. The consequent decoupling of stomatal ozone uptake from high ozone exposure suggests caution in using AOT40 as a standard for Z. serrata protection in Japan.► We parameterized stomatal conductance of Zelkova serrata for ozone uptake modeling. ► The new parameterization improved the performance of stomatal conductance model. ► The result was used to compare the spatial distribution of AOT40 and stomatal ozone uptake in Japan. ► Stomatal ozone uptake of Z. serrata was limited by vapor pressure deficit, soil moisture deficit and ozone. ► Our result suggests caution in using AOT40 as a standard for Z. serrata protection in Japan.
Keywords: Zelkova serrata; Ozone uptake; Stomatal conductance modeling; Japan; Ozone;

Recent chamber studies show that low-volatility gas phase precursors such as polycyclic aromatic hydrocarbons (PAHs) can be a significant source of secondary organic aerosol (SOA). In this work, formation of SOA from the photo-oxidation products of PAHs is added to the SOA modeling framework of the Community Multiscale Air Quality (CMAQ) model to determine the regional distribution of SOA products from PAHs (PAH-SOA) and the contributions from sources in Southeast Texas during the Texas Air Quality Study 2006 (TexAQS 2006). Results show that PAHs released from anthropogenic sources can produce SOA mass as much as 10% of that from the traditional light aromatics or approximately 4% of total anthropogenic SOA. In areas under the influence of wildfire emissions, the amount of PAH-SOA can be as much as 50% of the SOA from light aromatics. A source-oriented modeling framework is adopted to determine the major sources of PAH-SOA by tracking the emitted PAHs and their oxidation products in the gas and aerosol phases from different sources separately. Among the eight sources (vehicles, solvent utilization, residential wood, industries, natural gas combustion, coal combustion, wildfire and other sources) that are tracked in the model, wildfire, vehicles, solvent and industries are the major sources of PAH-SOA. Coal and natural gas combustion appear to be less important in terms of their contributions to PAH-SOA.► Regional SOA formation from gas phase PAHs is implemented in the CMAQ model. ► This is the first regional PAH-SOA simulation based on the most recent chamber data. ► PAH-SOA contributes to approximately 4% of overall anthropogenic SOA in urban area. ► Wildfire, vehicles, solvent utilization and industries are top PAH-SOA contributors.
Keywords: SOA formation; Naphthalene; PAHs; CMAQ; Source apportionment;

Global sensitivity analysis was performed to study the effects of model uncertainties on the predictions of urban ozone production and its limitation by NO x or VOCs. Uncertainties were assigned for hundreds of model parameters including measurements used to constrain the model as well as kinetic rate coefficients and product yields of chemical reactions. Monte Carlo simulations were run using a zero-dimensional box model with 76 representative base cases of different initial conditions extracted from the measurements of a field campaign conducted in Houston, Texas. The results showed that relative uncertainty (±1σ) of ozone production exhibits a pattern of higher uncertainty at morning rush hour (about 30–40%) and lower uncertainty in the afternoon (about 20–30%). The model uncertainty comes mostly from uncertainties in chemical schemes while the uncertainties in measurements are less influential. The most important model parameters are generally associated with the amounts of acetaldehyde, the photolysis of HONO and HCHO(→HO2), and the reactions of OH with NO2, HO2 with NO, and xylenes with OH. The uncertainties in these parameters could also shift the ozone–precursor relation between the NO x -sensitive and VOC-sensitive regimes. The greater values of the NO amount and the reaction rates of NO2 + OH, NO + HO2 and ISOP (isoprene peroxy radicals) + NO increase VOC-sensitivity, while greater values of aldehydes amounts and kinetic rate coefficients for reactions of OH with aldehydes and xylenes and of ISOP with HO2 increase NO x -sensitivity of ozone under the studied conditions.► Global sensitivities of modeled ozone production and limitation were analyzed. ► Uncertainty effects of model parameters were studied for urban ambient conditions. ► Uncertainty of ozone production was higher in the morning than in the afternoon. ► Uncertainties in parameters can shift O3–NO x –VOC limitation between the regimes. ► Uncertainty sources were dominated by the uncertainties in chemical schemes.
Keywords: Global sensitivity analysis; Chemical mechanism; High dimensional model representation; Ozone sensitivity; Atmospheric chemistry; Air quality;

Establishing relationships between chemical health stressors in urban traffic environments: Prediction of toluene concentration levels in European cities by Ch. Vlachokostas; E. Chourdakis; A.V. Michalidou; N. Moussiopoulos; A. Kelessis; M. Petrakakis (299-310).
Health can be impacted in many ways by exposure to chemical stressors in urban areas. Epidemiological research community has established consistent associations between traffic related air pollution and various health outcomes. Nevertheless, many urban environments, due to practical reasons (bulk of equipment) and mainly due to economical constraints, are characterised by the absence of the necessary monitoring infrastructure, for pollutants such as toluene. This chemical stressor is associated with numerous risks to human health, mainly with acute and chronic effects on the central nervous system. Due to the lack of monitoring data, it may be convenient to identify and establish a set of possible empirical relationships between health stressors in order to assess air quality trends of traffic related pollution in an urban area and support decision making. The use of environmental statistics can be meaningful towards this direction. This paper aims at developing and presenting a tractable approach, in order to reliably forecast toluene levels in EU urban environments. Multiple stepwise regression analysis is used for this purpose and a strong statistical relationship is detected mainly between toluene, benzene and CO. The adopted regression models are validated in order to depict their applicability and representativeness. In addition the models are applied to Thessaloniki, Greece, which is considered one of the most polluted cities within Europe. A comparison between available measurements, predictions based on the developed statistical models and air quality modelling output, provides discussion for transferability issues of such statistical relations between cities, but also interesting insights for the specific city. In general the presented results demonstrate that the adopted approach is capable of capturing toluene concentration trends and should be considered as complementary to air quality monitoring.► Generic approach to reliably and tractably forecast toluene trends in EU cities. ► Statistical association between traffic related health stressors. ► Strong relationship between toluene, benzene and CO. ► We established a set of possible empirical relationships between health stressors. ► We validated the adopted models to depict their applicability in EU cities.
Keywords: Air pollution; Regression analysis; Toluene; Traffic indicators; Urban areas;

Characterization of PM-PEMS for in-use measurements conducted during validation testing for the PM-PEMS measurement allowance program by M. Yusuf Khan; Kent C. Johnson; Thomas D. Durbin; Heejung Jung; David R. Cocker; Dipak Bishnu; Robert Giannelli (311-318).
This study provides an evaluation of the latest Particulate Matter-Portable Emissions Measurement Systems (PM-PEMS) under different environmental and in-use conditions. It characterizes four PM measurement systems based on different measurement principles. At least three different units were tested for each PM-PEMS to account for variability. These PM-PEMS were compared with a UC Riverside's mobile reference laboratory (MEL). PM measurements were made from a class 8 truck with a 2008 Cummins diesel engine with a diesel particulate filter (DPF). A bypass around the DPF was installed in the exhaust to achieve a brake specific PM (bsPM) emissions level of 25 mg hp−1h−1. PM was dominated by elemental carbon (EC) during non-regeneration conditions and by hydrated sulfate (H2SO4.6H2O) during regeneration. The photo-acoustic PM-PEMS performed best, with a linear regression slope of 0.90 and R 2 of 0.88 during non-regenerative conditions. With the addition of a filter, the photo-acoustic PM-PEMS slightly over reported than the total PM mass (slope = 1.10, R 2 = 0.87). Under these same non-regeneration conditions, a PM-PEMS equipped with a quartz crystal microbalance (QCM) technology performed the poorest, and had a slope of 0.22 and R 2 of 0.13. Re-tests performed on upgraded QCM PM-PEMS showed a better slope (0.66), and a higher R 2 of 0.25. In the case of DPF regeneration, all PM-PEMS performed poorly, with the best having a slope of 0.20 and R 2 of 0.78. Particle size distributions (PSD) showed nucleation during regeneration, with a shift of particle size to smaller diameters (∼64 nm to ∼13 nm) with elevated number concentrations when compared to non-regeneration conditions.► Latest PM-PEMS were evaluated for in-use driving conditions. ► All PM-PEMS showed a negative biased measurement relative to the reference method. ► Photo-acoustic PM-PEMS performed best for non-regeneration conditions. ► None of the PM-PEMS performed well for regeneration conditions. ► Good consistency was observed between different units of same PM-PEMS.
Keywords: PM-PEMS; Diesel particulate matter; Quartz crystal microbalance; Photo-acoustic; Regneration; Non-regeneration; Size distribution;

The global distribution of ammonia emissions from seabird colonies by S.N. Riddick; U. Dragosits; T.D. Blackall; F. Daunt; S. Wanless; M.A. Sutton (319-327).
Seabird colonies represent a significant source of atmospheric ammonia (NH3) in remote maritime systems, producing a source of nitrogen that may encourage plant growth, alter terrestrial plant community composition and affect the surrounding marine ecosystem. To investigate seabird NH3 emissions on a global scale, we developed a contemporary seabird database including a total seabird population of 261 million breeding pairs. We used this in conjunction with a bioenergetics model to estimate the mass of nitrogen excreted by all seabirds at each breeding colony. The results combined with the findings of mid-latitude field studies of volatilization rates estimate the global distribution of NH3 emissions from seabird colonies on an annual basis. The largest uncertainty in our emission estimate concerns the potential temperature dependence of NH3 emission. To investigate this we calculated and compared temperature independent emission estimates with a maximum feasible temperature dependent emission, based on the thermodynamic dissociation and solubility equilibria. Using the temperature independent approach, we estimate global NH3 emissions from seabird colonies at 404 Gg NH3 per year. By comparison, since most seabirds are located in relatively cold circumpolar locations, the thermodynamically dependent estimate is 136 Gg NH3 per year. Actual global emissions are expected to be within these bounds, as other factors, such as non-linear interactions with water availability and surface infiltration, moderate the theoretical temperature response. Combining sources of error from temperature (±49%), seabird population estimates (±36%), variation in diet composition (±23%) and non-breeder attendance (±13%), gives a mid estimate with an overall uncertainty range of NH3 emission from seabird colonies of 270 [97–442] Gg NH3 per year. These emissions are environmentally relevant as they primarily occur as “hot-spots” in otherwise pristine environments with low anthropogenic emissions.► Estimate of seabird ammonia emissions on a global scale using a bioenergetics model and a new global seabird population estimate. ► Temperature identified as largest uncertainty. ► Thermodynamically corrected scenario estimated NH3 emissions many times smaller than temperature independent scenario. ► Actual global emissions are expected between the two model estimates as other factors moderate theoretical temperature response.
Keywords: Coastal nitrogen; Seabird colony; Bioenergetic modelling; Emission map; Temperature; Climate change;

Inversely tracking indoor airborne particles to locate their release sources by Tengfei (Tim) Zhang; Hongzhu Li; Shugang Wang (328-338).
Airborne particles can have numerous adverse effects on human health. Knowing the release locations of airborne particulate sources is helpful in minimizing pollutant exposure. This paper describes a proposal to locate indoor particulate sources by two inverse models: the quasi-reversibility (QR) model and the zone prescription of contaminant sources with the Lagrangian-reversibility (LR) model. The QR model reverses the time marching direction of the Eulerian governing equation and replaces the second-order diffusion term with a fourth-order stabilization term. The zone prescription LR model traces individual particulate motion in a Lagrangian reference frame after reversing the flow field. The particle trajectories are solved backward to the initial release once the conservative forces acting on particles are reversed. The tracked particles are proposed to be placed at the zone boundary of the largest concentration contour within the domain at a given time, which is provided as the initially known information. By connecting all particles at t = 0, a zone is formed that can prescribe the actual contaminant source. This study finds that both models can accurately locate particulate sources released instantaneously at a spot. The QR model performs slightly better than the LR model but is much more computationally demanding.Display Omitted► We presented two inverse models to track airborne particles and locate the sources. ► The QR model is applicable for particles if the gravitational settling is included. ► The LR model is efficient to prescribe the source with discrete particles.
Keywords: Airborne particles; Inverse modeling; Source prescription; Quasi-reversibility; Lagrangian-reversibility; Indoor air pollution;

Trends of visibility on sunny days in China in the recent 50 years by Jian Wu; Chuanbo Fu; Liya Zhang; Jianping Tang (339-346).
The visibility on sunny days in 543 stations of China were analyzed, the results shows: The annual mean visibility on sunny days is higher in Northwest China and lower in Southeast China, which is similar to the distribution of aerosol optical depth. Visibility in summer is lower than in winter in southeast China, which relates to the stronger solar radiation in summer benefits to aerosol formation; Visibility in large cities is lower than small cities, and visibility of large and medium cities in summer is lower than winter but for small cities is opposite; The visibility decrease trend is revealed for most stations in recent 50 years, and the maximum trend coefficient −0.8 is found in delta regions of Pearl River and Yangtze River with climatic trend of −10 km/10a. The obvious visibility decrease for large and medium cities was from 1960s’ to 1990s’ accompanied by a slow increase later, and it was after the middle of 1990s’ visibility began to decrease for small cities; The diffuse radiation on sunny days show increase trend in recent 50 years, and it significantly correlates to visibility on sunny days with a correlation coefficient of −0.59 passing t-test at 0.001 significance level; Visibility on sunny days also correlates to total fuel consumption data and number of vehicles in China. Aerosol pollution should account for the obvious decrease of sunny visibility.► Visibility data on sunny and dry days in recent 50 year in China was analyzed. ► Different visibility changes in large, medium and small cities in China were discussed. ► Diffuse radiation on sunny days increased, and it significantly correlated to visibility.
Keywords: Visibility on sunny days; Diffuse radiation; Aerosol optical depth; Annual change;

Indoor surfaces play an important role in the transport of, and exposure to, semi-volatile organic compounds (SVOCs) in buildings. In this study, we develop a model that accounts for SVOC transport mediated by particles and find that, due to large gas-particle partition coefficients along with large differences in Brownian and gas diffusivities, SVOC transport across concentration boundary layers is significantly enhanced in the presence of particles. Two important dimensionless parameters, Bi m,g and Bi m,g /Bi m,p , were identified: Bi m,g is the ratio of 1) the characteristic time for the SVOC to transport across the concentration boundary layer to 2) the characteristic time for boundary layer to either be “swept” of SVOCs by particles or “saturated” by release of SVOCs from particles. This parameter can be regarded as a dimensionless mass transfer coefficient. Bi m,g /Bi m,p characterizes the SVOC mass associated with particles, relative to SVOCs in the gas-phase. Analysis on monodisperse particles shows that flux can be enhanced by as much as a factor of 5 over transport in the absence of particles, for a large particle/gas partition coefficient (log K part = 13), small particles (d p  ∼ 0.1 μm) and a small free stream velocity (U  = 0.01 m  s−1). As particle diameter decreases, flux enhancement tends to increase. However, as particles become very small (e.g., d p  < 0.05 μm), flux enhancement for SVOCs with log K part = 13 decreases slightly. Particles larger than 2 μm do not significantly influence the flux. An exponential correlation is found to fit the results for polydisperse particles associated with typical indoor environments, cooking and smoking. Two illustrative examples are used to show that, 1) the timescale for di(2-ethylhexyl) phthalate (DEHP) to approach equilibrium between the gas and a surface is shortened from 3.0 years to 0.45 years; and 2) in the presence of particles, the gas-phase DEHP concentration and emission rate are predicted to be as much as 4 times higher by our model than that by prior model estimates. Particle mediated gas-phase transport of SVOCs can result an increase in occupant exposure by a factor of 4–10.► Particles enhance gas-phase SVOC surface flux by ∼5 times for realistic conditions. ► Flux enhancement is an exponential function of particle mass concentration. ► SVOC flux increases as diameter decreases for equivalent particle concentrations. ► Particle mediated gas-phase transport significantly influences SVOC exposure.
Keywords: Indoor air quality; Particles; Phthalate; Dermal; Mass transfer;

Prediction of CO concentrations based on a hybrid Partial Least Square and Support Vector Machine model by B. Yeganeh; M. Shafie Pour Motlagh; Y. Rashidi; H. Kamalan (357-365).
Due to the health impacts caused by exposures to air pollutants in urban areas, monitoring and forecasting of air quality parameters have become popular as an important topic in atmospheric and environmental research today. The knowledge on the dynamics and complexity of air pollutants behavior has made artificial intelligence models as a useful tool for a more accurate pollutant concentration prediction. This paper focuses on an innovative method of daily air pollution prediction using combination of Support Vector Machine (SVM) as predictor and Partial Least Square (PLS) as a data selection tool based on the measured values of CO concentrations.The CO concentrations of Rey monitoring station in the south of Tehran, from Jan. 2007 to Feb. 2011, have been used to test the effectiveness of this method. The hourly CO concentrations have been predicted using the SVM and the hybrid PLS–SVM models. Similarly, daily CO concentrations have been predicted based on the aforementioned four years measured data. Results demonstrated that both models have good prediction ability; however the hybrid PLS–SVM has better accuracy. In the analysis presented in this paper, statistic estimators including relative mean errors, root mean squared errors and the mean absolute relative error have been employed to compare performances of the models. It has been concluded that the errors decrease after size reduction and coefficients of determination increase from 56 to 81% for SVM model to 65–85% for hybrid PLS–SVM model respectively. Also it was found that the hybrid PLS–SVM model required lower computational time than SVM model as expected, hence supporting the more accurate and faster prediction ability of hybrid PLS–SVM model.► We propose a novel method for prediction of air pollutant concentration. ► We use Partial Least Square (PLS) as a data reduction method before main process step. ► Support Vector Machine (SVM) as an intelligence tool is used for data mining. ► The modeling results show that hybrid PLS–SVM model has fewer errors and more efficiency than SVM model. ► Hybrid PLS–SVM method can noticeably save the computation time.
Keywords: CO concentration; Machine learning; Support Vector Machine; Partial Least Square; Hybrid models;

The impact of inland ships and recreational boats on measured NOx and ultrafine particle concentrations along the waterways by Saskia C. van der Zee; Marieke B.A. Dijkema; Jorrit van der Laan; Gerard Hoek (368-376).
In Amsterdam, many inhabitants reside in proximity to inland waters. The aim of this study was to assess the impact of passing inland ships and recreational boats, including touring boats, on the air quality near houses close to the water. A measurement campaign was performed at five sites in Amsterdam. Two sites were located along the inland waterways used by cargo ships and recreational boats. The other three sites were located along the canals in the historical city centre, used by touring boats and private recreational boats. At each site, measurements were performed at the waterside and at the facade of houses.Nitrogen oxides (NO and NO2) and ultrafine particles (particle number (PN) concentration), were measured continuously during one afternoon per site, while time and type of passing ships and road traffic was registered. Linear regression analysis was used to analyze the association between passing ships and concentration, adjusted for passing road traffic.There was substantial variation in the impact of passing ships on concentrations at each measuring site, as well as between sites. On average, cargo ships contributed 5 and 4 μg m−3 to NO and NO2, respectively, and 3000 particles cm−3 to PN concentration near houses during the sampling period. Peak concentrations were occasionally substantially higher. Emissions from touring boats had a small but significant impact on NO concentration near houses but not on NO2, with the exception of one site located near the edge of two canals, where boats use extra power to travel around the bent. At this site, touring boats contributed 5 μg m−3 to the local NO2 concentration. No consistent impact of touring boats on PN concentration was observed. Emissions from private recreational boats were not consistently associated with increased NOx or PN concentration.Road traffic intensity was low at the selected measurement sites. Nevertheless, a significant impact of passing diesel-operated delivery vans on house adjacent concentrations of both NOx and PN concentrations was found. On average, mopeds had a small but significant impact on PN concentration by 1100 particles cm−3 In conclusion, this study provides evidence that ship exhausts has an impact on air quality near houses along waterways.► Inland waterways are a source of air pollution. ► NOx and ultrafine particles were measured continuously at 5 sites along waterways. ► Impact of passing inland ships was calculated. ► Cargo ships have a clear impact on air quality near waterways.
Keywords: Ship emissions; Ultrafine particles; Nitrogen oxide; Vehicle exhaust; Urban air quality; Amsterdam;

Impact of the extreme meteorological conditions during the summer 2003 in Europe on particulate matter concentrations by A. Mues; A. Manders; M. Schaap; A. Kerschbaumer; R. Stern; P. Builtjes (377-391).
Due to the strong relation between meteorology and air quality, a changing climate is anticipated to significantly impact air pollution. To investigate this effect a synoptic situation in the past which is expected to occur more often in future is analyzed in terms of air quality. In this study the effect of the meteorological conditions in the extreme summer 2003 on the concentration of PM10 and its components is investigated over Europe. To this end measurements of the EMEP network in Europe of the summer 2003 were compared to the average of the summers of a five years period (2003–2007). Furthermore simulation runs were performed with the German chemistry transport model REM-Calgrid and the Dutch model LOTOS-EUROS, to analyze whether state-of-the-art chemistry transport models are able to reproduce the observed concentrations during this episode.The synoptic situation in summer 2003 resulted in 1–10 μg m−3 higher observed PM10 concentrations compared to the five years average. This increase was not reproduced to the same extent by the two models at most of the stations and the two models show evident differences in their PM10 simulations. The correlation between PM10 concentrations and meteorological parameters indicates that observed concentrations increase during weather conditions with high daily maximum temperature. The same holds for elemental carbon which is chosen as an example for a primary component. Low horizontal transport and the absence of wet deposition as a result of low wind speed and little precipitation associated with conditions with high temperatures favour the accumulation of pollutants in the lower troposphere. Although these conditions are reflected in the meteorological input data of the chemistry transport models used in this study, the models were not able to reproduce this relationship; they underestimate the observed high concentrations. This indicates that the underestimation of the variability of PM with meteorology is due to missing but important components and associated emissions or uncertainties therein, e.g. mineral dust, secondary organic aerosols and wild fires. To improve the simulation performance of the chemistry transport models as function of meteorological conditions these emission sources and the formation of secondary organic aerosols have to be included or improved and the dependency of anthropogenic emissions on meteorological conditions should be explicitly taken into account. These are essential issues for the simulation of such extreme conditions.► The extreme summer 2003 had an increasing effect on observed PM concentrations. ► Two chemistry transport models underestimate this variability of PM with meteorology. ► The two models (LOTOS-EUROS and RCG) show evident differences in their PM simulation. ► A better representation of primary components and SOA in the models is necessary. ► Model emission should be explicitly related to the meteorology.
Keywords: Chemistry transport models; PM10; Composition; Model evaluation; Meteorological variability;

Personal exposure to Black Carbon in transport microenvironments by Evi Dons; Luc Int Panis; Martine Van Poppel; Jan Theunis; Geert Wets (392-398).
We evaluated personal exposure of 62 individuals to the air pollutant Black Carbon, using 13 portable aethalometers while keeping detailed records of their time-activity pattern and whereabouts. Concentrations encountered in transport are studied in depth and related to trip motives. The evaluation comprises more than 1500 trips with different transport modes. Measurements were spread over two seasons. Results show that 6% of the time is spent in transport, but it accounts for 21% of personal exposure to Black Carbon and approximately 30% of inhaled dose. Concentrations in transport were 2–5 times higher compared to concentrations encountered at home. Exposure was highest for car drivers, and car and bus passengers. Concentrations of Black Carbon were only half as much when traveling by bike or on foot; when incorporating breathing rates, dose was found to be twice as high for active modes. Lowest ‘in transport’ concentrations were measured in trains, but nevertheless these concentrations are double the concentrations measured at home. Two thirds of the trips are car trips, and those trips showed a large spread in concentrations. In-car concentrations are higher during peak hours compared to off-peak, and are elevated on weekdays compared to Saturdays and even more so on Sundays. These findings result in significantly higher exposure during car commute trips (motive ‘Work’), and lower concentrations for trips with motive ‘Social and leisure’. Because of the many factors influencing exposure in transport, travel time is not a good predictor of integrated personal exposure or inhaled dose.► Micro-aethalometers were used to monitor personal exposure to Black Carbon. ► Exposure of 62 people was measured in different microenvironments for 7 days. ► 6% of time is spent in traffic, accounting for 21% of exposure and 30% of dose. ► Nevertheless travel time is a poor predictor of personal exposure. ► In-car concentrations are higher during traffic rush hour and on weekdays.
Keywords: Air pollution; Black Carbon; Mobile monitoring; Time-activity pattern; Traffic; Personal exposure;

We have developed a new source and process apportionment method, the Process, Age, and Source region Chasing ALgorithm (PASCAL), and implemented it in a three-dimensional chemical transport model, the Community Multiscale Air Quality (CMAQ) model. By adding new variables (tagged species), PASCAL traces 1) the source region of emissions (source apportionment), 2) the age of individual species (elapsed time from emissions), 3) net and gross production and loss amounts from individual physical and chemical processes during transport (Lagrangian way), and 4) local production and loss rates at individual grid cells (Eulerian way) for primary and secondary aerosols and their precursor gases. The main advantage of PASCAL is the third one, which can trace accumulated production and loss amounts of individual processes during transport from source regions to each grid cell (Lagrangian type of integration) for both gross (production and loss) and net (gross production − loss) concentrations. Currently the method is applied for mixing ratios of CO and SO2 and mass concentrations of black carbon and sulfate aerosols. This algorithm is not impacted by the non-linearity of chemical reactions and is computationally efficient. CMAQ/PASCAL model calculations were conducted over the East Asian region to test its performance. The overall validity of PASCAL calculations is confirmed for all species, periods, altitudes, and regions. This algorithm will be a useful tool in evaluating source regions as well as formation and loss processes of aerosols in the atmosphere in order to make effective strategies for emissions reduction.► We have developed a new source and process apportionment method, PASCAL. ► PASCAL has been implemented in a three-dimensional 3D chemical transport model, CMAQ. ► PASCAL traces sources, ages, and chemical processes of aerosols in the atmosphere. ► CMAQ/PASCAL calculations were conducted and validated over the East Asian region. ► PASCAL will be a powerful tool to make effective strategies for emissions reduction.
Keywords: Three-dimensional chemical transport model; Process analysis; Aerosol; CMAQ; Source receptor algorithm; Age tracing;

Defining a nonlinear control problem to reduce particulate matter population exposure by Claudio Carnevale; Giovanna Finzi; Enrico Pisoni; Marialuisa Volta; Fabian Wagner (410-416).
In this paper a multi-objective nonlinear approach to control air quality at a regional scale is presented. Both economic and air quality sides of the problem are modeled through artificial neural network models. Simulating the complex nonlinear atmospheric phenomena, they can be used in an optimization routine to identify the efficient solutions of a decision problem for air quality planning. The methodology is applied over Northern Italy, an area in Europe known for its high concentrations of particulate matter. Results illustrate the effectiveness of the approach assessing the nonlinear chemical reactions in an air quality decision problem.► A multi-objective nonlinear approach to control PM population exposure is presented. ► Both internal costs and health effects are modeled using artificial neural networks. ► The case study domain is Northern Italy.
Keywords: Multi-objective optimization; Years Of Lost Life; Emission control; Neural networks; GAINS model;

Frequency and longitudinal trends of household care product use by Rebecca E. Moran; Deborah H. Bennett; Daniel J. Tancredi; Xiangmei (May) Wu; Beate Ritz; Irva Hertz-Picciotto (417-424).
The use of household cleaning products and air fresheners exposes people to a variety of chemicals, including some that have been shown to be irritants, potential carcinogens and endocrine disrupting compounds. In addition, some react with ambient ozone infiltrating to the indoor environment to form potentially toxic secondary pollutants. Although realistic estimates of usage patterns are necessary for modeling potential exposures in risk assessments, few studies have documented cleaning habits and product usage to characterize how they vary between households and over time. In addition, understanding within-household temporal variability of use is important to assess the reliability of exposure questionnaires used in epidemiological surveys and improve the cost-efficiency of data collection. In the SUPERB (Study of Use of Products and Exposure-Related Behavior) study, frequencies of use of eight types of household cleaning products and air fresheners and the performance of different types of cleaning tasks are collected in three annual telephone and six quarterly web-based surveys. All-purpose and glass cleaners were the products most frequently used among all products surveyed. Use frequencies differed by demographic and other household characteristics for some products. Product usage was internally consistent, with over 75% of pairwise cross-sectional correlations between product types statistically significantly different from zero. In addition, each product type was correlated with at least one cleaning habit. Frequency of cleaning product use and performing cleaning tasks did not vary by season. An examination of intra-household variability showed moderately to highly consistent usage patterns over time, with lower temporal consistency observed among products used more frequently, such as all-purpose cleaners. Frequency of household care product usage was consistent enough that in epidemiologic studies, participants can be classified, for example, into three categories on the basis of a single assessment, with only minimal misclassification.► This paper is one of the first papers to examine the use patterns of cleaning products among adults in the US. ► Longitudinal analysis was conducted to examine changes in cleaning product use over time. ► Use frequencies were found to differ by demographic factors and other household characteristics for some products.
Keywords: Cleaning products; SUPERB; Indoor environment; d-limonene;

This paper investigates snow albedo changes in the Sierra Nevada Mountain area associated with potential deposition of absorbing aerosols in spring by using the snow albedo, aerosol optical depth, land surface temperature, and other relevant parameters available from the Moderate-Resolution Imaging Spectroradiometer (MODIS) onboard the NASA Terra satellite during 2000–2009. Satellite pixels with 100% snow cover have been selected to derive the monthly mean snow albedo value, along with aerosol optical depth, surface temperature, and days after snowfall in March and April to perform multiple regression analysis. We show that aerosol optical depth, which generally includes dust and black carbon over the Sierra Nevada as a result of the transpacific transport from East Asia and local sources, represents a significant parameter affecting snow albedo variation, second only to the land surface temperature change. The regression analysis illustrates that a one standard deviation increase in land surface temperature (2.2 K) and aerosol optical depth (0.044) can lead to decreases in snow albedo by 0.038 and 0.026, respectively. This study also shows that approximately 26% of snow albedo reduction from March to April over the Sierra Nevada is caused by an increase in aerosol optical depth, which has a profound impact on available water resources in California. However, the results show that there are no significant trends for snow albedo, surface temperature, and aerosol optical depth of snow-covered areas over the Sierra Nevada Mountain area in this 10-year period.► Snow albedo changes related to aerosols are investigated using remote sensing data. ► Pixels with 100% snow covered are selected to avoid contamination by bare land. ► Aerosol optical depth is the second most important factor in albedo variation. ► Approximately 26% of snow albedo reduction in spring is due to aerosol deposition.
Keywords: Snow albedo; Aerosol deposition; Satellite remote sensing; Sierra Nevada;

Molecular weight (mw) 247 nitrofluoranthenes and nitropyrenes and mw 273 nitrotriphenylenes (NTPs), nitrobenz[a]anthracenes, and nitrochrysenes were quantified in ambient particles collected in Riverside, CA, Tokyo, Japan, and Mexico City, Mexico. 2-Nitrofluoranthene (2-NFL) was the most abundant nitro-polycyclic aromatic hydrocarbon (nitro-PAH) in Riverside and Mexico City, and the mw 273 nitro-PAHs were observed in lower concentrations. However, in Tokyo concentrations of 1- + 2-NTP were more similar to that of 2-NFL. NIST SRM 1975 diesel extract standard reference material was also analyzed to examine nitro-PAH isomer distributions, and 12-nitrobenz[a]anthracene was identified for the first time. The atmospheric formation pathways of nitro-PAHs were studied from chamber reactions of fluoranthene, pyrene, triphenylene, benz[a]anthracene, and chrysene with OH and NO3 radicals at room temperature and atmospheric pressure, with the PAH concentrations being controlled by their vapor pressures. Sampling media were spiked with deuterated PAH to examine heterogeneous nitration. Comparing specific nitro-PAH ratios in ambient and diesel particles with those from our chamber experiments suggests that the low 2-NFL/NTPs ratios in Tokyo particulate matter are not a result of gas-phase radical-initiated chemistry since both gas-phase OH and NO3 radical-initiated reactions result in high 2-NFL/NTPs ratios. Comparisons of the relative formation of deuterated nitro-PAHs on the sampling media suggest that heterogeneous reactions with N2O5 on ambient particle surfaces also do not explain the nitro-PAH profiles of Tokyo particles. Thus, the source of NTPs in Tokyo remains unidentified.► Relative to 2-nitrofluoranthene (2NF), nitrotriphenylenes (NTPs) were high in Tokyo. ► Relative to 2NF, NTPs were low in Riverside, California and Mexico City particles. ► Chamber studies show that atmospheric formation of NTPs is likely to be minor. ► High concentrations of NTPs in Tokyo remain unexplained.
Keywords: Nitro-PAH; Atmospheric reactions; Ambient particles; Nitrotriphenylenes;

Characterization and health risk assessment of VOCs in occupational environments in Buenos Aires, Argentina by J.E. Colman Lerner; E.Y. Sanchez; J.E. Sambeth; A.A. Porta (440-447).
To detect volatile organic compounds (VOCs) in indoor air in small enterprises in La Plata city and surrounding areas, sampling was conducted using passive diffusion monitors (3M-3500) and analysis of the samples were performed byCG-FID. Analytic methodology was optimized for 23 VOCs (n-alkanes, cycloalkanes, aromatic and chlorinated compounds, ketones and terpenes compounds) by determining the recovery factor and detection limit for each analyte. Different recovery values were obtained by desorbing with a mixture of dichloromethane: methanol (50:50), with a standard deviation lower than 5%. Enterprise analyzed included chemical analysis laboratories, sewing workrooms, electromechanical repair and car painting centers, take away food shops, and a photocopy center. The highest levels of VOCs were found to be in electromechanical repair and car painting centers (hexane, BTEX, CHCl3, CCl4) followed by chemical analysis laboratories and sewing workrooms. Cancer and noncancer risks were assessed using conventional approaches (HQ and LCR, US EPA) using the benzene, trichloroethylene, chloroform for cancer risk, and toluene, xylene and n-hexane, for noncancer risks as markers. The results showed different LCR for benzene and trichloroethylene between the different indoor environments analyzed (electromechanical repair and car painting center ≫ others) and chloroform (laboratory > others), but comparing with the results obtained by other research, are in similar order of magnitude for equivalents activities. Similar finding were founded for HQ. Comparing these results with the worker protection legislation the electromechanical repair and car painting center and chemical analysis laboratories are close to the limits advised by OSHA and ACGIH. These facts show the importance of the use of abatement technologies for the complete reduction of VOCs levels, to mitigate their impact in the worker’s health and their venting to the atmosphere.► Indoor air of small enterprises was sampled whit 3M-3500 monitors. ► Desorption was developed for 23 VOCs representatives of SMEs. ► Cancer and noncancer risks were assessed using conventional approaches (US EPA).
Keywords: Monitoring; VOCs; Recovery factor; Indoor air quality; Health risk assessment;

Different organic compounds exhibit different propensities for ozone formation. Two approaches were used to study the ozone formation potentials or source reactivities of different anthropogenic organic compounds emission categories in California's South Coast Air Basin (SoCAB). The first approach was based on the combination of total organic gases (TOG) emission speciation profiles and the maximum incremental reactivity (MIR) scale of organic species. The second approach quantified ozone impacts from different emission sources by performing 3-dimensional air quality model sensitivity analysis involving increased TOG emissions from particular sources. The source reactivities derived from these two approaches agree reasonably well for 58 anthropogenic organic compounds emission categories in the SoCAB. Both approaches identify TOG emissions from mobile sources as having the highest reactivity. Source reactivities from both approaches were also combined with TOG emissions from each source category to produce a 2005 reactivity-based anthropogenic TOG emission inventory for the SoCAB. The top five reactivity-based anthropogenic TOG emission sources in the SoCAB during 2005 were: light-duty passenger cars, off-road equipment, consumer products, light-duty trucks category 2 (i.e., 3751–5750 lb), and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that livestock waste and composting emission categories were two of the five largest mass-based anthropogenic TOG emission sources. The reactivity-based TOG emission inventory is an important addition to the mass-based TOG emission inventory because it represents the ozone formation potentials from emission sources and can be used to assist in determining targeted sources for developing organic compounds reduction policies.► Ozone formation potentials were quantified for 58 TOG emission sources in the SoCAB. ► Mass-based and reactivity-based TOG emissions inventories are very different in terms of the most important sources. ► Mobile source TOG emissions have the highest ozone formation potential in the SoCAB. ► Light-duty passenger cars are the largest reactivity-based TOG emission source.
Keywords: CAMx; Maximum incremental reactivity; SAPRC; Total organic gases;

New Directions: Enduring ozone by Nadine Unger; Joshua L. Pan (456-458).
Ozone damages plants and reduces terrestrial productivity leading to increased anthropogenic carbon dioxide in the atmosphere that is an equivalent emission and thus provides an indirect radiative forcing. Through this perturbation of the carbon cycle, anthropogenic increases in ozone affect the climate system on considerably longer timescales than the ozone atmospheric lifetime of only a few weeks. The indirect global warming impact may be irreversible depending upon the uncertain ability of the land carbon sink to reabsorb the carbon dioxide excess after removal of the ozone damage.
Keywords: Ozone; Vegetation; Phytotoxicity; Short-lived climate forcers; Climate change; Carbon cycle;

Impact of neocrystallisations on the SiO2–K2O–CaO glass degradation due to atmospheric dry depositions by L. Gentaz; T. Lombardo; A. Chabas; C. Loisel; A. Verney-Carron (459-466).
The medieval SiO2–CaO–K2O stained glasses are particularly vulnerable to the impact of their environment. In the urban atmosphere, they will tend to rapidly deteriorate either by loss of matter or by addition of atmospheric material, that tend to form a crust on the surface of the glass. If the glass surface is protected from the rain run-off, this second phenomenon will be favoured. In the early stage of crust formation, it was shown that primary constituents were salts, called neocrystallisations. However, it is still not clear, if their presence induce further deterioration of the glass matrix.In order to answer this question both field exposure and laboratory experiments were carried out. Model glasses, chosen with compositions similar to those of ancient stained glasses, were exposed to the urban atmosphere in sheltered conditions. Samples exposed were analysed in order to identify the neocrystallisations and further tests were undertaken in order to observe their impact on the glass itself.The analyses of the weathering products on the glasses showed the presence of three principal minerals: syngenite, gypsum, and potassium carbonate. The observed mineral phases were then artificially deposited on model glass surfaces submitted to cycles of relative humidity. It was found that the presence of salts increased the glass degradation by extending the time of wetness of the glass surface and forming saline solutions in the case of deliquescent salts. Evidence of strong leaching could be observed on the glass surface and even more so when considering glass samples in contact with multiple salts. Finally, the impact of potassium carbonate (K2CO3) on the glass was dramatic, since it induced a loss of matter caused by the dissolution of the lattice in contact with the alkaline solution.► Gypsum, syngenite, K2CO3 and other salts form during early stages of deterioration. ► Salts act as condensation nuclei, keep water on the glass, inducing more degradations. ► K2CO3 found on the glass (alkaline solution) leads to glass congruent dissolution. ► Synergic effect of salts induces more degradation than individual effect.
Keywords: Urban atmosphere; Degradation; Model glass; Neocrystallisations; Salts; Stained glasses;

Air pollution and daily mortality: A new approach to an old problem by Frederick W. Lipfert; Christian J. Murray (467-474).
Many time-series studies find associations between acute health effects and ambient air quality under current conditions. However, few such studies link mortality with morbidity to provide rational bases for improving public health. This paper describes a research project that developed and validated a new modeling approach directly addressing changes in life expectancies and the prematurity of deaths associated with transient changes in air quality. We used state-space modeling and Kalman filtering of elderly Philadelphia mortality counts from 1974–88 to estimate the size of the population at highest risk of imminent death. This subpopulation appears stable over time but is sensitive to season and to environmental factors: ambient temperature, ozone, and total suspended particulate matter (TSP), as an index of airborne particles in this demonstration of methodology.This population at extreme risk averages fewer than 0.1% of the elderly. By considering successively longer lags or moving averages of TSP, we find that cumulative short-term effects on entry to the at-risk pool tend to level off and decrease as periods of exposure longer than a few days are considered. These estimated environmental effects on the elderly are consistent with previous analyses using conventional time-series methods. However, this new model suggests that such environmentally linked deaths comprise only about half of the subjects whose frailty is associated with environmental factors. The average life expectancy of persons in the at-risk pool is estimated to be 5–7 days, which may be reduced by less than one day by environmental effects. These results suggest that exposures leading up to severe acute frailty and subsequent risk of imminent death may be more important from a public health perspective than those directly associated with subsequent mortality.► Philadelphia daily elderly death counts (1974–88) are modeled by Kalman filtering. ► Frail subpopulation = <0.1% of elderly with mean life expectancy of 5–7 days. ► Subpopulation is stable over time but sensitive to season, temperature, O3, TSP. ► Frail life expectancies may be reduced by < one day by environmental effects. ► Frailty may be more important to public health than subsequent mortality.
Keywords: Mortality; Morbidity; Time-series; Frailty; Population dynamics; Kalman filter;

To illuminate the issue of trans-boundary O3 pollution and regional O3 reduction policies in East Asia, we have investigated the East Asian ozone (O3) response to perturbations caused by Chinese anthropogenic emissions using the Community Multiscale Air Quality (CMAQ) model, a regional chemical transport model. The O3 responses have been examined for the range between −100 and +100% changes from the Chinese emissions level in 2004 in 10% intervals. We have found that springtime and summertime O3 responses both at the source and at the downwind areas can be regarded as linear over the range between −30 and +100% changes from the current emissions level. We therefore suggest that the perturbation between −30 and +100% is sufficiently small to avoid nonlinear chemical influence on O3 formation in a model experiment to investigate East Asian scale O3 source-receptor relationships. On the other hand, the O3 response is strongly nonlinear in April at Hong Kong, where the current NMVOCs/NOx ratio is low and the O3 production regime is easily moved to the NMVOCs sensitive region. The O3 responses to the NOx emission changes have been investigated using surface O3 concentrations at remote Japanese sites and tropospheric NO2 vertical column density (NO2 VCD) over central east China both with observations and with model simulations in springtime during 2003–2009. Analysis of satellite data shows that the observed range of NO2 VCD over central east China in 2003–2009 is the range between −25 and +34% from the 2004 level, which corresponds approximately to an emission variation between −21 and +29%. The O3 concentration in the downwind region during 2003–2009 responds linearly to a change of the NO2 VCD over central east China both in the model and in the observation. The corresponding O3 responses derived from surface observations at remote Japanese sites show linear features consistent with this expectation. The doubling of emissions, i.e., approximately 1.9-fold increase in the NO2 VCD from 2004, leads to O3 increments of 5 ppbv and 8 ppbv in the model and in the observation, respectively. The modeled O3 increase due to changes in NOx emission explains approximately 60% of the observed O3 trend at remote Japanese sites. Thus, approximately 40% of the observed O3 increase is unaccounted for by the NOx emissions growth.► We investigated O3 chemical linearity in recent Chinese emission changes. ► O3 response could be regarded as linear in the range between −30% and +100% changes from the 2004 emission level. ► Recently, O3 responded linearly to the NO2 change in east central China. ► The modeled O3 increase explained 60% of the observed trend at remote Japanese sites.
Keywords: Tropospheric O3; NO2 tropospheric vertical column density; O3 chemistry; East Asian-scale transport;

Impacts of climate change on ground level gas-phase pollutants and aerosols in the Iberian Peninsula for the late XXI century by Pedro Jiménez-Guerrero; Juan Pedro Montávez; Juan José Gómez-Navarro; Sonia Jerez; Raquel Lorente-Plazas (483-495).
Climate change alone influences future air pollution levels through modifications of gas-phase chemistry, transport, removal, and natural emissions. Hence, the goal of this study is to determine at what extent concentrations of air pollutants respond to changes over the Iberian Peninsula under a climate change scenario. The methodology includes the use of the regional modeling system MM5 (regional climate model version)-CHIMERE for two nested domains covering Europe and the Iberian Peninsula. Two time slices driven by ECHO-G global circulation model covering from 1991 to 2010 and 2071 to 2100 under the SRES A2 scenario have been compared. Climate change influences the concentrations of both gas-phase pollutants and aerosols through changes in temperature, precipitation, mixing height, transport, humidity, and oxidant levels. The trends of variation of ozone (changes up to 5 ppb, +10% increase during summertime) and aerosols over southwestern Europe are influenced by the higher mean temperature modeled for the future climate (up to +5.4 K), since it favors the formation of secondary gas-phase products. It also enhances sulphates (+2 μg m−3) and secondary organic aerosols (SOA) (+2.5 μg m−3 under SRES A2 scenario) and contributes to the decomposition of ammonium nitrate, remaining in the gas phase. Further, the 17% percent decrease of precipitation modeled for 2071–2100 has a strong effect in the frequency of the washout and therefore in the levels of natural aerosols: the concentrations of aerosols decrease with increasing precipitation as wet deposition provides the main aerosol sink.► We determine the response of air pollutants to climatic changes under SRES A2. ► Climate change alone enhances the formation of gas-phase pollutants and aerosols. ► The trends of variation for O3 and PM are influenced by the future higher temperatures. ► Temperature increases favor the formation of secondary gas-phase products. ► Changes in precipitation impact on the washout and on the levels of natural aerosols.
Keywords: Regional climate modeling; Air pollution; Aerosols; Climate change; Iberian Peninsula;

Release of Bet v 1 from birch pollen from 5 European countries. Results from the HIALINE study by Jeroen T.M. Buters; Michel Thibaudon; Matt Smith; Roy Kennedy; Auli Rantio-Lehtimäki; Roberto Albertini; Gerald Reese; Bernhard Weber; Carmen Galan; Rui Brandao; Celia M. Antunes; Siegfried Jäger; Uwe Berger; Sevcan Celenk; Łukasz Grewling; Bogdan Jackowiak; Ingrida Sauliene; Ingrid Weichenmeier; Gudrun Pusch; Hakan Sarioglu; Marius Ueffing; Heidrun Behrendt; Marje Prank; Mikhail Sofiev; Lorenzo Cecchi (496-505).
Exposure to allergens is pivotal in determining sensitization and allergic symptoms in individuals. Pollen grain counts in ambient air have traditionally been assessed to estimate airborne allergen exposure. However, the exact allergen content of ambient air is unknown. We therefore monitored atmospheric concentrations of birch pollen grains and the matched major birch pollen allergen Bet v 1 simultaneously across Europe within the EU-funded project HIALINE (Health Impacts of Airborne Allergen Information Network).Pollen count was assessed with Hirst type pollen traps at 10 l min−1 at sites in France, United Kingdom, Germany, Italy and Finland. Allergen concentrations in ambient air were sampled at 800 l min−1 with a Chemvol® high-volume cascade impactor equipped with stages PM > 10 μm, 10 μm > PM > 2.5 μm, and in Germany also 2.5 μm > PM > 0.12 μm. The major birch pollen allergen Bet v 1 was determined with an allergen specific ELISA. Bet v 1 isoform patterns were analyzed by 2D-SDS-PAGE blots and mass spectrometric identification. Basophil activation was tested in an FcɛR1-humanized rat basophil cell line passively sensitized with serum of a birch pollen symptomatic patient.Compared to 10 previous years, 2009 was a representative birch pollen season for all stations. About 90% of the allergen was found in the PM > 10 μm fraction at all stations. Bet v 1 isoforms pattern did not vary substantially neither during ripening of pollen nor between different geographical locations. The average European allergen release from birch pollen was 3.2 pg Bet v 1/pollen and did not vary much between the European countries. However, in all countries a >10-fold difference in daily allergen release per pollen was measured which could be explained by long-range transport of pollen with a deviating allergen release. Basophil activation by ambient air extracts correlated better with airborne allergen than with pollen concentration.Although Bet v 1 is a mixture of different isoforms, its fingerprint is constant across Europe. Bet v 1 was also exclusively linked to pollen. Pollen from different days varied >10-fold in allergen release. Thus exposure to allergen is inaccurately monitored by only monitoring birch pollen grains. Indeed, a humanized basophil activation test correlated much better with allergen concentrations in ambient air than with pollen count. Monitoring the allergens themselves together with pollen in ambient air might be an improvement in allergen exposure assessment.► We monitored the allergen release from birch pollen at several locations in Europe simultaneously. ► The allergen content of pollen measured by ELISA varied >10-fold between days at all stations. ► The reaction of human immune cells (basophils) correlated better with allergen release from pollen than with pollen count. ► Different potency of pollen could be explained by different geographical origin of the pollen.
Keywords: Birch; Pollen; Bet v 1; Exposure; Isoforms; ELISA; HIALINE; Human; Basophils; Europe;

Airborne fine particulate pollution in Jinan, China: Concentrations, chemical compositions and influence on visibility impairment by Lingxiao Yang; Xuehua Zhou; Zhe Wang; Yang Zhou; Shuhui Cheng; Pengju Xu; Xiaomei Gao; Wei Nie; Xinfeng Wang; Wenxing Wang (506-514).
Daily PM2.5 samples were collected simultaneously at an urban site (SD) and a rural site (MP) in Jinan, China from March 2006 to February 2007. The samples were analyzed for major inorganic and organic water-soluble ions, 24 elements and carbonaceous species to determine the spatial and temporal variations of PM2.5 mass concentrations and chemical compositions and evaluate their contributions to visibility impairment. The annual average concentrations of PM2.5 were 148.71 μg m−3 and 97.59 μg m−3 at SD and MP, respectively. The predominant component of PM2.5 was (NH4)2SO4 at SD and organic mass at MP, which accounted for 28.71% and 37.25% of the total mass, respectively. The higher SOR (sulfur oxidation ratio) and ratios of OC/EC at SD indicated that the formation of secondary inorganic ions and secondary organic aerosols (SOA) could be accelerated in the urban area. Large size (NH4)2SO4 and large size organic mass were the most important contributors to visibility impairment at SD and MP, accounting for 43.80% and 41.02% of the light extinction coefficient, respectively.► Chemical components in PM2.5 and their impacts on visibility were studied in a highly polluted area. ► Formation of secondary inorganic ions and secondary organic aerosol was active at urban area. ► (NH4)2SO4 and organic mass were the most abundant species and the main contributors to b ext.
Keywords: PM2.5; Chemical composition; Mass closure; Visibility impairment;

A series of experiments were conducted to evaluate characteristics of varied flooring types which may influence dirt buildup and airborne particle levels. The experiments included investigation of typical dirt loadings found on flooring in school environments, the time necessary to effectively vacuum dirt from textile flooring (both in chamber and school conditions), and the resuspension of particles generated from walking activity on various flooring types in chamber and classroom environments. The flooring types studied included textile floored surfaces (flow through (FT) carpet and variable cushion tufted textile (VCTT) floorings) and hard surface (vinyl composition tile (VCT)).The study demonstrates that dirt buildup on textile floors will vary based on the location within the classroom. One of the primary findings of the study is that textile floor covering in schools is not a homogeneous medium. Physical characteristics vary based on the type of backing, carpet tufted type, face weight, gauge (including stitches/inch), and adhesive requirements. This variance in physical parameters contributes to significant differences in the resuspension rates (RRs) of particles into the air, generated by walking activity. FT carpet displayed significantly greater (2.5–5 times) RRs than VCTT in both chamber conditions and classroom environments at similar floor loadings and particle size ranges. Controlled chamber test runs revealed VCT flooring exhibiting 3.6 time higher RRs than FT flooring and 12.8 time greater RRs than VCTT flooring. Moreover, particle RRs and airborne concentrations are also a function of time of walking activity, floor dust loadings and particle size ranges.► VCT flooring had 3.6× higher RRs vs FT flooring & 12.8× greater RRs vs VCTT flooring. ► FT carpet showed 2.5–5× greater RRs vs VCTT in chamber conditions & in classrooms. ► New textile flooring showed greater particle RRs vs old in classrooms. ► Particle RRs & airborne levels are functions of walking activity, dust & particle size.
Keywords: Resuspension; Flooring; Airborne particles; Schools; Carpet; Exposure;

Source apportionment of airborne particulate matter using inorganic and organic species as tracers by Yungang Wang; Philip K. Hopke; Xiaoyan Xia; Oliver V. Rattigan; David C. Chalupa; Mark J. Utell (525-532).
Source apportionment is typically performed on chemical composition data derived from particulate matter (PM) samples. However, many common sources no longer emit significant amounts of characteristic trace elements requiring the use of more comprehensive chemical characterization in order to fully resolve the PM sources. Positive matrix factorization (EPA PMF, version 4.1) was used to analyze 24-hr integrated molecular marker (MM), secondary inorganic ions, trace elements, carbonaceous species and light absorption data to investigate sources of PM2.5 in Rochester, New York between October 2009 and October 2010 to explore the role of specific MMs. An eight-factor solution was found for which the factors were identified as isoprene secondary organic aerosol (SOA), airborne soil, other SOA, diesel emissions, secondary sulfate, wood combustion, gasoline vehicle, and secondary nitrate contributing 6.9%, 12.8%, 3.7%, 7.8%, 45.5%, 9.1%, 7.9%, and 6.3% to the average PM2.5 concentration, respectively Concentrations of pentacosane, hexacosane, heptacosane, and octacosane in the gasoline vehicles factor were larger compared to diesel emissions. Aethalometer Delta-C was strongly associated with wood combustion. The compounds, n-heptacosanoic acid and n-octacosanoic acid, occasionally used in the past as tracers for road dust, were found to largely associate with SOA in this study. In comparison with a standard PMF analyses without MM, inclusion of them was necessary to resolve SOA and wood combustion factors in urban areas.► Source apportionment of PM2.5 was obtained using positive matrix factorization (PMF). ► Data included elements, OC/EC, ions, molecular markers (MM), and Delta-C. ► The wood smoke factor included levoglucosan and Delta-C. ► Two secondary organic aerosol (SOA) factors were resolved. ► Without MM, organic mass was partitioned to the traffic and wood smoke factors.
Keywords: Source apportionment; Positive matrix factorization (PMF); Particulate matter (PM); Molecular markers (MM); Aethalometer Delta-C;

The Community Multiscale Air Quality (CMAQ) and the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling systems were used to simulate emissions and air quality in North Eastern Alberta where a rapid rise in oil sands development has caused air quality concerns over the last decade. The models were run on a 36/12/4 km domain for the four month period of May through August 2002. A model performance evaluation was conducted by comparing the CMAQ model estimates against ambient air quality measurements. In the Alberta oil sands region, the model tended to achieve or nearly achieve ozone model performance goals, albeit with an underestimation bias. The magnitudes of the observed PM2.5 concentrations were matched by the modeling system, except when the observed PM2.5 concentrations were influenced by emissions from forest fires in which case the model underestimated the observed PM2.5 concentrations. The CMAQ-estimated 4th highest daily maximum 8-hour ozone concentrations in the oil sands region were below the 65 ppb Canada Wide Standard (CWS) as well as the 58 ppb Alberta Management Plan Trigger Level. The highest estimated ozone concentrations occurred near the oil sands development area just north of Fort McMurray with values approaching, but below, the 58 ppb Management Plan Trigger Level; estimated ozone concentrations are much lower in the farther northern portions of the oil sands region. The acute (i.e., maximum 3-day value) SUM60 vegetative ozone exposure metric was mostly less than 100 ppb h, which is below the threshold of concern for crops. However, just north of Fort McMurray there were small areas where the acute SUM60 metric exceeded the 500–700 ppb h threshold of concern for crops with maximum values in plumes from sources in the oil sands mine area of ∼900 ppb h. The maximum chronic (three-month average) SUM60 ozone exposure metric was below the thresholds of concern. The CMAQ-estimated maximum 98th percentile 24-hour average PM2.5 concentration occurs in the mine area north of Fort McMurray and was below the CWS threshold (30 μg m−3), however it was above the Alberta Management Plan Trigger Level (20 μg m−3). The estimated 98th percentile 24- hour average PM2.5 concentrations were mostly in the 2–6 μg m−3 range with regions of higher PM2.5 concentrations predicted just north of Fort McMurray in the oil sands development region.► We conduct air modeling study to simulate emissions and air quality in the Alberta Oil Sands Region. ► Model performance evaluation is conducted by comparing against ambient air quality measurements. ► Highest estimated ozone concentrations occurs near the oil sands development area. ► Regions of higher PM2.5 concentrations predicts in the oil sands development region.
Keywords: MM5/CMAQ; Oil sands; Air quality modeling; PM and ozone; Model performance evaluation;

We conducted four source apportionment simulations using the Community Multiscale Air Quality (CMAQ) photochemical grid modelling system in order to investigate and assess the relative importance of specific emissions sources and/or geographic regions on ambient ozone and PM air quality in the Alberta Oil Sands Region (AOSR). Local point and area sources, medium range transport of mobile sources and biogenic emissions were examined.The elimination of emissions from local stationary point sources reduced 8-h ozone concentrations and greatly reduces the PM2.5 concentrations in AOSR; similar results are seen in the local area source zero-out simulations but with less ozone and PM2.5 reductions than seen in the local point source zero-out run. Although the mobile source medium-range transport reduced 8-h ozone concentrations in the urban plume from Edmonton that results in some ozone and PM2.5 concentration reductions in the southern part of the AOSR, it has little effect on the elevated ozone and PM2.5 concentrations in the oil sands development area of the AOSR where the highest ozone and PM2.5 concentrations are estimated. The elimination of all anthropogenic emissions in Alberta so that only biogenic emissions remained resulted in large reductions in 8-h ozone concentrations in the AOSR, with the highest remaining ozone in the 50–52 ppb range occurring south of Fort McMurray; very low PM2.5 concentrations are also estimated across Alberta, including the AOSR, when anthropogenic emissions are eliminated in Alberta.► We conduct four zero-out source apportionment simulations in the Alberta Oil Sands Region. ► Local point and area sources, medium range transport of mobile sources and biogenic emissions were examined. ► Elimination of local stationary point sources reduced ozone and PM2.5 concentrations. ► Biogenic emissions were only remained large reductions in ozone and very low PM2.5 concentrations.
Keywords: Air quality model; PM2.5; Ozone; Oil sands; Source apportionment; Emission sources;