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Atmospheric Environment (v.57, #)
Cluster analysis of particulate matter (PM10) and black carbon (BC) concentrations by Janez Žibert; Jure Pražnikar (pp. 1-12).
The monitoring of air-pollution constituents like particulate matter (PM10) and black carbon (BC) can provide information about air quality and the dynamics of emissions. Air quality depends on natural and anthropogenic sources of emissions as well as the weather conditions. For a one-year period the diurnal concentrations of PM10 and BC in the Port of Koper were analysed by clustering days into similar groups according to the similarity of the BC and PM10 hourly derived day-profiles without any prior assumptions about working and non-working days, weather conditions or hot and cold seasons. The analysis was performed by using k-means clustering with the squared Euclidean distance as the similarity measure. The analysis showed that 10 clusters in the BC case produced 3 clusters with just one member day and 7 clusters that encompasses more than one day with similar BC profiles. Similar results were found in the PM10 case, where one cluster has a single-member day, while 7 clusters contain several member days. The clustering analysis revealed that the clusters with less pronounced bimodal patterns and low hourly and average daily concentrations for both types of measurements include the most days in the one-year analysis. A typical day profile of the BC measurements includes a bimodal pattern with morning and evening peaks, while the PM10 measurements reveal a less pronounced bimodality. There are also clusters with single-peak day-profiles. The BC data in such cases exhibit morning peaks, while the PM10 data consist of noon or afternoon single peaks. Single pronounced peaks can be explained by appropriate cluster wind speed profiles. The analysis also revealed some special day-profiles. The BC cluster with a high midnight peak at 30/04/2010 and the PM10 cluster with the highest observed concentration of PM10 at 01/05/2010 (208.0 μg m−3) coincide with 1 May, which is a national holiday in Slovenia and has very strong tradition of bonfire parties. The clustering of the diurnal concentration showed that various different day-profiles are presented in a cold period, while this is not the case for the hot season. Additional analysis of ship traffic and rain fall data showed that there is no statistically significant difference between the ship gross (bruto) registered tonnage (BRT) values in the case of BC and PM10 clusters, but that there is statistically significant differences between the rain fall in the BC and PM10 clusters. The wind-rose for clusters which included most days in the sampling period indicating that emitted PM10 and BC from Port of Koper were manly transported in the west direction over the sea and in the east direction, where there is in no populated area. Presented analysis showed that both BC and PM10 concentrations were driven by rain intensity and wind speed.► The BC/PM10 data analysis was performed using k-means clustering. ► Ten-BC and eight-PM10 different typical day-profiles occurred during the one-year. ► The clusters with low daily concentrations include the most days. ► Various different clusters are present in a cold period, but not in the hot season. ► BC pattern reveal a more-pronounced bimodality than PM10 pattern.
Keywords: PM10; Black carbon; Data-driven analysis; Data clustering; Cluster analysis; Port of Koper
Impact of meteorology and anthropogenic emissions on the local and regional ozone weekend effect in Midwestern US by Bonyoung Koo; Jaegun Jung; Alison K. Pollack; Chris Lindhjem; Michele Jimenez; Greg Yarwood (pp. 13-21).
The weekend ozone effect refers to changes in ground-level ozone concentrations on weekends resulting from anthropogenic emission changes from weekdays and weekends. This study applied a three-dimensional photochemical grid model for a three-month summer period to examine the weekend ozone effect in the Midwestern US (the north-central and north-eastern part of US) at both urban and regional scales. The model generally reproduced the observed daily maximum 1-h and 8-h ozone and also correctly predicted weekend changes in the VOC-to-NO x ratio. So-called dynamic evaluation of the modeled weekend ozone changes throughout the summer revealed that meteorology had a bigger impact on the summer 2005 weekend ozone effect than anthropogenic emission changes partly because meteorology strongly influences biogenic emissions. To avoid the confounding effect of meteorological changes, weekend ozone differences were determined by using a second simulation modeled with weekday emissions for all days of week. Ozone differences between the base case and the second simulation isolated the effect of weekday/weekend emission changes. To further distinguish local effects of weekend emission changes from transported regional ozone differences, a third simulation applied weekend emission changes only within two urban areas with all weekday emissions for the remaining areas. The ozone differences between the base case and the third simulations revealed that the effect of regional weekend emission differences is projected to be mostly lowered ozone on weekends. On the other hand, the difference between the second and third simulations revealed that weekend emission changes in two urban areas increased ozone locally in the urban centers and immediately downwind areas but lowered ozone further downwind. The sign-change in the weekend ozone effect from urban centers to downwind areas is explained by a matching change in sign of ozone sensitivity to NO x emissions which was confirmed by computing ozone sensitivities to domain-wide NO x and VOC emissions. The sensitivity analysis also showed that weekday/weekend ozone differences in the Midwestern US are due primarily to weekend reductions in NO x emissions.► Photochemical grid model simulations to examine the weekend ozone effect. ► Regional weekend emission changes mostly lowered ozone in the area on weekends. ► Weekend emission changes in the two urban areas studied increased ozone locally. ► The weekend ozone differences changed sign from the urban areas to far downwind. ► DDM showed the regional-to-urban shift from NO x-limited to VOC-limited conditions.
Keywords: Weekend ozone effect; Photochemical grid model; Ozone; CAMx; DDM
A comparative study of the number and mass of fine particles emitted with diesel fuel and marine gas oil (MGO) by Md. Nurun Nabi; Richard J. Brown; Zoran Ristovski; Johan Einar Hustad (pp. 22-28).
The current investigation reports on diesel particulate matter emissions, with special interest in fine particles from the combustion of two base fuels. The base fuels selected were diesel fuel and marine gas oil (MGO). The experiments were conducted with a four-stroke, six-cylinder, direct injection diesel engine. The results showed that the fine particle number emissions measured by both SMPS and ELPI were higher with MGO compared to diesel fuel. It was observed that the fine particle number emissions with the two base fuels were quantitatively different but qualitatively similar. The gravimetric (mass basis) measurement also showed higher total particulate matter (TPM) emissions with the MGO. The smoke emissions, which were part of TPM, were also higher for the MGO. No significant changes in the mass flow rate of fuel and the brake-specific fuel consumption (BSFC) were observed between the two base fuels.► We examined TPM emissions especially fine particles with MGO and diesel fuel. ► Both ELPI and SMPS were used for particle number emissions. ► Glass fibre filter was used for particle mass emissions. ► NOx emissions and engine performance were also investigated in the current study.
Keywords: Diesel fine particles; Diesel engine; Smoke and BSFC
The Great Cormorant ( Phalacrocorax carbo) colony as a “hot spot” of nitrous oxide (N2O) emission in central Japan by Chitoshi Mizota; Kosuke Noborio; Yoshiaki Mori (pp. 29-34).
Unusual high soil fluxes up to ca. 500mgN2Om−2h−1 emission were associated with a continued breeding/roosting colony of Great Cormorant in central Japan. This flux is nearly two-orders of magnitude higher than those hitherto documented. The flux was markedly dependent upon the soil surface temperature, i.e., higher in April–October during the prevailing high air temperatures, as compared with November to March. Integrated input of fecal N at rearing and fledging stages of chicks followed by coupled mineralization, nitrification and subsequently denitrification processes under humid and temperate regimes is responsible for such an unusual flux. The Great Cormorant colony serves as a “hot spot” of N2O emission of natural origin.► High soil fluxes of N2O emission were observed in central Japan. ► The flux was markedly dependent upon the soil surface temperature. ► The Great Cormorant colony serves as a “hot spot” of N2O emission.
Keywords: Nitrogen; Birds/avian; Fluxes
Heated stainless steel tube for ozone removal in the ambient air measurements of mono- and sesquiterpenes by H. Hellén; P. Kuronen; H. Hakola (pp. 35-40).
Heated stainless steel inlets were optimized for the ozone removal and for the measurements of mono- and sesquiterpenes in ambient air. Five different inlets were used with different flows, temperatures and ozone and biogenic volatile organic compound (BVOC) concentrations. Both ozone removal capacities and recoveries of BVOCs were determined. Ozone and BVOCs were flushed through the inlet and recoveries were measured by an ozone monitor and adsorbent tube sampling of BVOCs with subsequent analysis with thermal desorption – gas chromatograph (GC) – mass spectrometer (MS). Recovery tests of BVOCs were conducted both with zero air and with ozone rich air. Inlets were optimized especially for online-GC and adsorbent tube measurements of mono- and sesquiterpenes.The results of this study show that it was possible to remove ozone without removing most VOCs with this set-up. Setting the temperature, stainless steel grade and flow correctly for different inlet lengths was found to have a crucial role. The results show that the ozone removal capacity increases with increasing temperature and inlet length. Stainless steel grade 316 was found to be more efficient than grade 304 with respect to ozone removal. Based only on the ozone removal capacity, the longest possible stainless steel inlet with heating would be the optimum solution. However, the recoveries of studied compounds had to be considered too. Of the tested set-ups, a 3 m inlet (¼ in. grade 304) heated to 120 °C with a flow of 1 or 2 l min−1 was found to give the best results with respect to the ozone removal efficiency and compound recovery. This inlet was removing ozone efficiently for at least 4 months when used for ambient air sampling at a rural forested site with a flow of 1 l min−1 (∼170 m3 of air flushed through the tube). A heated (140 °C) 1 m inlet (¼ in. grade 304 or ⅛ in. grade 316) was able to remove ozone with a constant flow of 0.8–1 l min−1 for about two weeks (∼18 m3 of air) and had acceptable recoveries for all other studied compounds except for linalool. This inlet was found to be suitable also for ozone removal in adsorbent tube sampling when the flow is low (0.1 l min−1).► New method developed for ozone removal. ► Ozone removal method is suitable also for sesquiterpene measurements. ► Able to remove ozone for longer time than usual ozone traps and filters.
Keywords: VOCs; Monoterpenes; Sesquiterpenes; Ozone removal; Inlet; Ambient air
Diurnal and seasonal variability in size-dependent atmospheric deposition fluxes of polycyclic aromatic hydrocarbons in an urban center by Kai Zhang; Bao-Zhong Zhang; Shao-Meng Li; Lei-Ming Zhang; Ralf Staebler; Eddy Y. Zeng (pp. 41-48).
Atmospheric gaseous and size-segregated particle samples were collected from urban Guangzhou at the heights of 100 and 150m above the ground in daytime and at night in August and December 2010, and were analyzed for polycyclic aromatic hydrocarbons (PAHs). Particulate PAHs were more abundant at night than in daytime, and significantly higher in winter than in summer. The observed vertical, diurnal, and seasonal variability in the occurrences of PAH were attributed to varying meteorological conditions and atmospheric boundary layers. More than 60% of the particulate PAHs were contained in particles in the accumulation mode with an aerodynamic diameter ( Dp) in the range of 0.1–1.8μm. Different mass transfer velocities by volatilization and condensation are considered the main causes for the different particle size distributions among individual PAHs, while combustion at different temperatures and atmospheric transport were probable causes of the observed seasonal variation in the size distribution of PAHs. Based on the modeled size-dependent dry deposition velocities, daily mean dry deposition fluxes of particulate PAHs ranged from 604 to 1190ngm−2d−1, with PAHs in coarse particles ( Dp>1.8μm) accounting for 55–95% of the total fluxes. In addition, gaseous PAHs were estimated to contribute 0.6–3.1% to the total dry deposition fluxes if a conservative dry deposition velocity for gaseous species (2×10−4ms−1) were used. Finally, disequilibrium phase partitioning, meteorological conditions and atmospheric transport were regarded as the main reasons for the variances in dry deposition velocities of individual PAHs.► Distractions from atmospheric turbulence are filtered out in measuring dry deposition. ► Various meteorological factors and sources cause variability in PAH levels. ► Volatilization and condensation are main causes for the particle size distribution of PAHs. ► Particle dry deposition dominates the total dry deposition fluxes of PAHs. ► Empirical deposition velocities would overestimate deposition fluxes of PAHs.
Keywords: Diurnal and seasonal variability; Particle size segregation; Atmospheric deposition; Polycyclic aromatic hydrocarbons; Urban center
Artificial neural networks for modeling ammonia emissions released from sewage sludge composting by P. Boniecki; J. Dach; K. Pilarski; H. Piekarska-Boniecka (pp. 49-54).
The project was designed to develop, test and validate an original Neural Model describing ammonia emissions generated in composting sewage sludge. The composting mix was to include the addition of such selected structural ingredients as cereal straw, sawdust and tree bark. All created neural models contain 7 input variables (chemical and physical parameters of composting) and 1 output (ammonia emission). The α data file was subdivided into three subfiles: the learning file (ZU) containing 330 cases, the validation file (ZW) containing 110 cases and the test file (ZT) containing 110 cases. The standard deviation ratios (for all 4 created networks) ranged from 0.193 to 0.218. For all of the selected models, the correlation coefficient reached the high values of 0.972–0.981. The results show that he predictive neural model describing ammonia emissions from composted sewage sludge is well suited for assessing such emissions. The sensitivity analysis of the model for the input of variables of the process in question has shown that the key parameters describing ammonia emissions released in composting sewage sludge are pH and the carbon to nitrogen ratio (C:N).► The research on ammonia emission from the composted sewage sludge have been made. ► The prediction neural models’ file has been built. ► The optimal models for prediction of ammonia emission were tested and verified. ► It has been stated that pH was a key factor for ammonia emission from composting.
Keywords: Neural network modeling; Ammonia emission; Composting; Sewage sludge
Intraseasonal variability of surface ozone in Santiago, Chile: Modulation by phase of the Madden–Julian Oscillation (MJO) by Bradford S. Barrett; Sean J. Fitzmaurice; Sarah R. Pritchard (pp. 55-62).
In Santiago, Chile, summertime surface ozone (O3) concentrations regularly exceed local and international health thresholds due to high antecedent pollutants, frequent clear skies, and warm surface air temperatures. However, few (if any) studies exist that have examined the intraseasonal variability of surface O3 or its modulation by phase of the Madden–Julian Oscillation (MJO). Therefore, the main objectives of this study were to investigate the intraseasonal variability of surface O3 and the meteorological parameters known to affect O3 concentrations during summer months in Santiago, and connect any observed variability to phase of the MJO. Ozone concentrations at seven stations in the Chilean National Air Quality Information System (SINCA), along with upper-air, surface, and reanalysis data, were used to create composites for each phase of the MJO. Results confirm that for the Santiago metropolitan region, both maximum daily O3 concentrations, as well as the diurnal cycle of O3, depend on MJO Phase. Ozone concentrations were highest during Phases 5 and 6 and lowest during Phases 1 and 2. Cloud cover anomalies best agreed with this pattern of O3 variability, with low (high) cloud cover anomalies occurring during days with high (low) ozone. Surface temperature and strength and height of the lower-troposphere temperature inversion had similar, but less pronounced, connections to O3, with slightly warmer surface temperatures and stronger inversions closer to the ground occurring on days with higher O3. Wind velocity was found to vary little between days with low and high ozone.► Surface ozone concentration in Santiago, Chile varies intraseasonally by phase of the Madden–Julian Oscillation. ► Phase of the Madden–Julian Oscillation also affects the diurnal cycle of ozone concentration in Santiago. ► Days with low (high) ozone corresponded to days with anomalously high (low) cloud cover.
Keywords: Surface ozone; Intraseasonal; Santiago; Madden–Julian Oscillation
Long term black carbon measurements in the southwestern Iberia Peninsula by Sérgio Nepomuceno Pereira; Frank Wagner; Ana Maria Silva (pp. 63-71).
Black carbon mass concentration (BCPM10) measurements carried out at Évora, Portugal, between 2007 and 2009, were analyzed and interpreted at different timescales. Additional measurements of aerosol mass concentration (MPM10) were included and the black carbon to total mass fraction (BC mass fraction) was derived when measurements of both quantities were coincident.BCPM10 values were found to vary between 0.3 and 5 μg m−3, mainly in the range of 0.5–2 μg m−3. A clear and consistent seasonal behavior was found; an increase by a factor of two in the averageBCPM10 values was observed from summer (0.9 μg m−3) to winter (1.8 μg m−3) which is reflected in the BC mass fraction, amplified from about 4 to 10%. Comparison of the averageBCPM10 mass concentrations on week days and week ends indicate that local traffic emissions strongly influence the observed average diurnal patterns. Other factors, such as wood burning for heating, lower boundary layer height and more frequent winter-time temperature inversions, also likely influence the observedBCPM10 but were not directly studied here. When different air mass types are considered then black carbon levels show a much lower variation than PM10 mass concentrations, stressing the relevance of local emissions in theBCPM10 levels.BCPM10 values under continental or maritime influence only differ by a factor of approximately 1.4 only, much lower than the factor of 10 reported for a coastal rural site in Portugal.► Time-resolved measurements of BC for the first time in Portugal. ► Derivation of BC mass fraction. ► Analysis of temporal variations of the measurements. ► Evaluation of long-range transport.
Keywords: Black carbon; Mass concentration; Long-range transport; Rural-urban area
Exposures to volatile organic compounds (VOCs) and associated health risks of socio-economically disadvantaged population in a “hot spot” in Camden, New Jersey by Xiangmei (May) Wu; Zhihua (Tina) Fan; Xianlei Zhu; Kyung Hwa Jung; Pamela Ohman-Strickland; Clifford P. Weisel; Paul J. Lioy (pp. 72-79).
To address disparities in health risks associated with ambient air pollution for racial/ethnic minority groups, this study characterized personal and ambient concentrations of volatile organic compounds (VOCs) in a suspected hot spot of air pollution – the Village of Waterfront South (WFS), and an urban reference community – the Copewood/Davis Streets (CDS) neighborhood in Camden, New Jersey. Both are minority-dominant, impoverished communities. We collected 24-h integrated personal air samples from 54 WFS residents and 53 CDS residents, with one sample on a weekday and one on a weekend day during the summer and winter seasons of 2004–2006. Ambient air samples from the center of each community were also collected simultaneously during personal air sampling. Toluene, ethylbenzene, and xylenes (TEX) presented higher ( p < 0.05) ambient levels in WFS than in CDS, particularly during weekdays. A stronger association between personal and ambient concentrations of MTBE and TEX was found in WFS than in CDS. Fourteen to forty-two percent of the variation in personal MTBE, hexane, benzene, and TEX was explained by local outdoor air pollution. These observations indicated that local sources impacted the community air pollution and personal exposure in WFS. The estimated cancer risks resulting from two locally emitted VOCs, benzene and ethylbenzene, and non-cancer neurological and respiratory effects resulting from hexane, benzene, toluene, and xylenes exceeded the US EPA risk benchmarks in both communities. These findings emphasized the need to address disparity in health risks associated with ambient air pollution for the socio-economically disadvantaged groups. This study also demonstrated that air pollution hot spots similar to WFS can provide robust setting to investigate health effects of ambient air pollution.► We report VOC exposure levels in two minority and low-income communities. ► We quantify the contribution of ambient VOC pollution on personal exposure levels. ► The estimated risks for both communities exceeded the US EPA risk benchmarks. ► The hot spot provides a robust setting to examine health effects of ambient VOCs.
Keywords: VOCs; Community air pollution; Hot spot; Personal exposure; Health risks; Socio-economically disadvantaged population
High resolution mapping of total deposition of acidifying pollutants by Thierri de Vos; Leiming Zhang (pp. 80-90).
A framework has been developed to estimate dry and wet deposition over Southern Belgium for a variety of acidifying substances on a 5 × 5 km2 grid. Concentrations of different compounds in the atmosphere or in the precipitation are provided by the measurement networks (both stations and gauges) and are interpolated over Southern Belgium. Dry deposition velocities are calculated using local meteorology and land use information, following the approach described in . Local precipitation is provided by merged radar-gauge observations. This is the first high resolution framework for Southern Belgium computing both time- and space-dependent deposition, using a modified kriging interpolation method (for SO2 and NO2), as well as radar-based precipitation. Estimated dry and wet depositions are compared with long range transport (LRT) model results, based on the European emission inventories. Although a good agreement is observed between our results and LRT model results on the annual totals averaged over Southern Belgium, the extent of agreement for the spatial variability of the annual deposition differs significantly from one pollutant to another. This new framework provides consistent high resolution maps for several pollutants, while improving the mapping of dry and wet deposition in Southern Belgium, in order to assess critical loads exceedances.► A framework is developed to map high resolution acid deposition in Southern Belgium. ► Results for 2008–2009 are compared with results of long range transport (LRT) models. ► There is a good agreement between the annual totals averaged over Southern Belgium. ► The framework provides consistent deposition patterns for several pollutants. ► The framework provides higher resolution deposition maps than LRT models.
Keywords: Dry deposition; Wet deposition; Acidic deposition; Belgium
Analysis on source features of halogenated gases at Shangdianzi regional atmospheric background station by Xingqin An; Lingxi Zhou; Bo Yao; Lin Xu; Lin Ma (pp. 91-100).
In the study, the five-day back-trajectories collected by Shangdianzi Station were categorized by season, calculated four times a day during the period of 2008–2010, based on the Lagrangian particle integrated trajectory model HYSPLIT, and using the back-trajectory cluster analysis method. Efforts were made to understand the impacts of different trajectories on the concentration of halogenated gases over the site of Shangdianzi (SDZ) in different seasons, in line with the in-site concentration measurements of halogenated gases, including the 8 species of CFC-11, CFC-12, CCL4, CHCL3, CH3Br, SF6, H-1301, and HCFC-22. Meanwhile, the wind data collected by the same station and the concentration observed during the same period were employed to calculate the loadings of CFC-11, CFC-12, CCL4, CHCL3, CH3Br, SF6, H-1301, and HCFC-22, respectively. The result of back-trajectory cluster analysis suggests that air masses from southeast and southwest accounting for a large proportion of local air masses at SDZ always move slowly within the bottom boundary layer, which is beneficial for the accumulation of pollutants within the boundary layer and leads to the highest mean concentrations of halocarbons among all the clusters. Conversely, the mean concentration of halocarbons corresponding to the fast-moving northwest air masses at high altitude is found to have unanimously low values. The analysis of the concentration loadings proves that WSW and SW are the directions for the maximum concentration loading of all halogenated species, whereas NNW, NNE, NE and ENE are the directions for the minimum concentration loading. We also find that the sector in SW–S–SE is the high concentration loading part, while the sector in NW–N–NE is the low concentration part. The trajectory cluster analysis and concentration loading results indicate that the SE–S–SW towards SDZ is the high pollution source direction for the halogenated species mentioned above, which reflects the influence of human activities on the air pollutant transportation at SDZ in a regional scale, while NW–N–NE represents the clean direction of the station.► Source Feature of halocarbons at Shangdianzi station is analyzed. ► Trajectory cluster analysis suggests air masses from SE and SW polluted, NW clean. ► Concentration load shows WSW and SW maximum directions, NW and NE minimum.
Keywords: Shangdianzi regional atmospheric background station; Halogenated gases; Back-trajectory cluster analysis; Concentration load rose map; Source features
Characterization of ambient air pollution measurement error in a time-series health study using a geostatistical simulation approach by Gretchen T. Goldman; James A. Mulholland; Armistead G. Russell; Katherine Gass; Matthew J. Strickland; Paige E. Tolbert (pp. 101-108).
In recent years, geostatistical modeling has been used to inform air pollution health studies. In this study, distributions of daily ambient concentrations were modeled over space and time for 12 air pollutants. Simulated pollutant fields were produced for a 6-year time period over the 20-county metropolitan Atlanta area using the Stanford Geostatistical Modeling Software (SGeMS). These simulations incorporate the temporal and spatial autocorrelation structure of ambient pollutants, as well as season and day-of-week temporal and spatial trends; these fields were considered to be the true ambient pollutant fields for the purposes of the simulations that followed. Simulated monitor data at the locations of actual monitors were then generated that contain error representative of instrument imprecision. From the simulated monitor data, four exposure metrics were calculated: central monitor and unweighted, population-weighted, and area-weighted averages. For each metric, the amount and type of error relative to the simulated pollutant fields are characterized and the impact of error on an epidemiologic time-series analysis is predicted. The amount of error, as indicated by a lack of spatial autocorrelation, is greater for primary pollutants than for secondary pollutants and is only moderately reduced by averaging across monitors; more error will result in less statistical power in the epidemiologic analysis. The type of error, as indicated by the correlations of error with the monitor data and with the true ambient concentration, varies with exposure metric, with error in the central monitor metric more of the classical type (i.e., independent of the monitor data) and error in the spatial average metrics more of the Berkson type (i.e., independent of the true ambient concentration). Error type will affect the bias in the health risk estimate, with bias toward the null and away from the null predicted depending on the exposure metric; population-weighting yielded the least bias.► Geostatistical modeling of air pollution can inform measurement error assessment. ► Error amount and type present in time-series epidemiologic studies were assessed. ► Reduced statistical power in health risk estimates is expected due to spatial variability. ► Bias in risk estimates is expected due to limited number and placement of monitors. ► Results suggest large differences across pollutants and across pollutant metrics.
Keywords: Geostatistics; Exposure modeling; Air pollution; Spatial modeling; Measurement error; Spatial misalignment
Characterization and quantification of unintentional POP emissions from primary and secondary copper metallurgical processes in China by Zhiqiang Nie; Guorui Liu; Wenbin Liu; Bing Zhang; Minghui Zheng (pp. 109-115).
Field monitoring was conducted to update and develop unintentional persistent organic pollutant (unintentional POP) emission inventories for the copper metallurgy industry in China. In this study, emissions of six unintentional POPs comprised of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/PCDF), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), hexachlorobenzene (HxCBz) and pentachlorobenzene (PeCBz) in stack gas and fly ash samples from primary and secondary copper smelters using different raw materials and technologies were measured and compared. Different concentrations, congener patterns and emission factors of unintentional POPs among four copper smelters were observed. Variations in unintentional POP emissions from several areas of a primary copper smelter were also investigated. The total emissions of unintentional POPs from primary and secondary copper production in 2010 in China were estimated respectively. These results provide a useful reference for the establishment of unintentional POP emission inventories and for policymakers to formulate control strategies to reduce unintentional POPs resulting from copper metallurgy.► Emission factors of unintentional POPs from copper metallurgy were determined. ► Emission levels and variations of unintentional POPs were measured and compared. ► Unintentional POP congener patterns in stack gas and fly ash samples are presented. ► The raw material used was a key factor for unintentional POP emissions. ► Copper metallurgy is an important emission source of unintentional POPs.
Keywords: Unintentional POPs; Emission factor; Inventory; Copper metallurgy; Raw materials
Development a detailed inventory framework for estimating major pollutants emissions inventory for Yunnan Province, China by Xiaolong Tang; Yan Zhang; Honghong Yi; Jieyun Ma; Li Pu (pp. 116-125).
A Yunnan Province regional emission inventory for the year 2009 was developed, using the best available domestic emission factors and activity level data for the first time. The inventory covers major emission sources in the region and both bottom-up and top-down approaches were adopted to compile the inventory for those sources where possible. The results show that the estimated emissions for SO2, NOX, CO2 and PM10 in Yunnan Province for the year 2009 were 446.75kt, 486.91kt, 20553.91wt (104t) and 467.83kt, respectively. Coal-fired power plants and industrial sources were major contributors of SO2, NOX and CO2 emissions, accounting for 84.49%, 73.27% and 68.34% of the total emissions. Biomass burning accounted for 71.62% of total PM10 emissions. Qujing predominate the total emissions of each species, 33.58% for SO2, 31.04% for NOX, 24.19% for CO2, and 15.79% for PM10. The highest emission density value was up to 5024kg SO2 km−2 and 5063kg NOX·km−2 in Qujing, 2076 t CO2·km−2 and 3032kg PM10·km−2 in Kunming. Furthermore, a qualitative approach was used to characterize the uncertainty of emission inventories, with low uncertainty in SO2 emission estimates from coal-fired power plant sources, medium to high uncertainties for NOX emissions and CO2 emissions, and high uncertainty in PM10.► SO2, NOX, CO2 and PM10 emission of Yunnan Province are estimated for the first time. ► The total emissions of each species are 446.7kt, 486.9kt, 20,554wt, 467.8kt, 2009. ► Coal-fired power plants and industrial dominate the total emission except PM10. ► Biomass burning have 71.62% share in PM10 emissions. ► Kunming and Qujing are major contributors of each species total emission.
Keywords: Emission inventory; Spatial; Uncertainty; Yunnan Province
Predicting adult pulmonary ventilation volume and wearing complianceby on-board accelerometry during personal level exposure assessments by C.E. Rodes; S.N. Chillrud; W.L. Haskell; S.S. Intille; F. Albinali; M.E. Rosenberger (pp. 126-137).
Metabolic functions typically increase with human activity, but optimal methods to characterize activity levels for real-time predictions of ventilation volume (l min−1) during exposure assessments have not been available. Could tiny, triaxial accelerometers be incorporated into personal level monitors to define periods of acceptable wearing compliance, and allow the exposures (μg m−3) to be extended to potential doses in μg min−1 kg−1 of body weight?In a pilot effort, we tested: 1) whether appropriately-processed accelerometer data could be utilized to predict compliance and in linear regressions to predict ventilation volumes in real-time as an on-board component of personal level exposure sensor systems, and 2) whether locating the exposure monitors on the chest in the breathing zone, provided comparable accelerometric data to other locations more typically utilized (waist, thigh, wrist, etc.).Prototype exposure monitors from RTI International and Columbia University were worn on the chest by a pilot cohort of adults while conducting an array of scripted activities (all <10 METS), spanning common recumbent, sedentary, and ambulatory activity categories. Referee Wocket accelerometers that were placed at various body locations allowed comparison with the chest-located exposure sensor accelerometers. An Oxycon Mobile mask was used to measure oral-nasal ventilation volumes in-situ. For the subset of participants with complete data ( n = 22), linear regressions were constructed (processed accelerometric variable versus ventilation rate) for each participant and exposure monitor type, and Pearson correlations computed to compare across scenarios.Triaxial accelerometer data were demonstrated to be adequately sensitive indicators for predicting exposure monitor wearing compliance. Strong linear correlations ( R values from 0.77 to 0.99) were observed for all participants for both exposure sensor accelerometer variables against ventilation volume for recumbent, sedentary, and ambulatory activities with MET values ∼<6. The RTI monitors mean R value of 0.91 was slightly higher than the Columbia monitors mean of 0.86 due to utilizing a 20 Hz data rate instead of a slower 1 Hz rate. A nominal mean regression slope was computed for the RTI system across participants and showed a modest RSD of +/−36.6%. Comparison of the correlation values of the exposure monitors with the Wocket accelerometers at various body locations showed statistically identical regressions for all sensors at alternate hip, ankle, upper arm, thigh, and pocket locations, but not for the Wocket accelerometer located at the dominant side wrist location ( R = 0.57; p = 0.016).Even with a modest number of adult volunteers, the consistency and linearity of regression slopes for all subjects were very good with excellent within-person Pearson correlations for the accelerometer versus ventilation volume data. Computing accelerometric standard deviations allowed good sensitivity for compliance assessments even for sedentary activities. These pilot findings supported the hypothesis that a common linear regression is likely to be usable for a wider range of adults to predict ventilation volumes from accelerometry data over a range of low to moderate energy level activities. The predicted volumes would then allow real-time estimates of potential dose, enabling more robust panel studies. The poorer correlation in predicting ventilation rate for an accelerometer located on the wrist suggested that this location should not be considered for predictions of ventilation volume.► Adults wore exposure monitors and ventilation sensors during scripted activities. ► Protocol wearing compliance was readily characterized by accelerometric changes. ► Models of acceleration versus ventilation volume were linear and correlated for METS less than ∼<6. ► The wrist accelerometer location was the poorest predictor of ventilation volume. ► Real-time estimated dose predictions of PM could be computed along with exposures.
Keywords: Ventilation volume; Personal exposure; Potential dose; Triaxial accelerometry; Adults; Wearing complianceAbbreviations; ACCEL; designation for the composite variable computed from the triaxial accelerometer; AUC; Area Under the Curve; b; linear regression intercept; BMI; Body Mass Index; Hz; hertz; m; linear regression slope; MEMS; Micro-Electro-Mechanical Systems; METS; Metabolic Equivalent TaskS; PM; particulate matter; QC; quality control; R; Pearson correlation coefficient; R; 2; coefficient of determination; RSD; relative standard deviation; RTI; Research Triangle Institute; SBAS; Stanford Brief Activity Survey; V; ventilation volume (l pm)
Measured and modeled variation in pollutant concentration near roadways by Mark Gordon; Ralf M. Staebler; John Liggio; Shao-Meng Li; Jeremy Wentzell; Gang Lu; Patrick Lee; Jeffrey R. Brook (pp. 138-145).
This paper presents a study of the evolution of particles and gases downwind of a highway, with a focus on the diurnal variation of pollutant gradients and its controlling variables. A mobile laboratory was used to measure the concentration gradients of ultra-fine particles (UFP), black carbon (BC), CO2, NO, and NO2 at varying distances up to 850 m from a major highway. The horizontal distributions of pollutants show a strong diurnal pattern. Results suggest that the horizontal gradients are predominantly influenced by traffic levels, friction velocity, and atmospheric stability. The results were compared to a dispersion model, which showed good agreement with the measurements and was able to qualitatively capture the observed diurnal cycles. Emission rates [g km−1] calculated from the model fits are within 10% of the Mobile 6.2C inventory for CO2 and demonstrate good agreement for NOx, but are higher than the inventory by a factor between 2.0 and 5.9 for black carbon. Hourly NOx emission rates correlate with the fraction of heavy-duty vehicles in the total fleet and agree with inventory values based on maximum vehicle emission rates.► Pollutants were measured downwind of a highway throughout the day. ► Horizontal gradients dependent on traffic flow, friction velocity, and stability. ► Dispersion model shows good agreement with measurements. ► Emission rates of black carbon and NOx from trucks are higher than inventory.
Keywords: Traffic induced pollution; Boundary-layer mixing; Emission rates; Plume modeling
Bioaccessibility and health risk of arsenic and heavy metals (Cd, Co, Cr, Cu, Ni, Pb, Zn and Mn) in TSP and PM2.5 in Nanjing, China by Xin Hu; Yun Zhang; Zhuhong Ding; Tijian Wang; Hongzhen Lian; Yuanyuan Sun; Jichun Wu (pp. 146-152).
The bioaccessibility and human health risks of As and heavy metals (Cu, Pb, Zn, Ni, Co, Cr, Cd and Mn) in total suspended particulates (TSP) and fine particulate matter (PM2.5) in Nanjing, China were investigated. The average mass concentration ratios of PM2.5 to TSP were 0.61 for Gulou sampling site and 0.50 for Pukou sampling site, respectively. Zn, Pb, Mn and Cu were the most abundant elements among the studied metal(loid)s in both TSP and PM2.5. The results of a simple bioaccessibility extraction test of the studied metal(loid)s varied among elements, with Cd, Zn, Mn, Pb and As showing the higher bioaccessibility. The carcinogenic risks of As, Cd, Co, Cr and Ni in both TSP and PM2.5 via dermal contact and inhalation exposure were within the acceptable level (<1 × 10−4) for both children and adults, but there was potential carcinogenic risk posed by Pb via ingestion to children and adults. The hazard index values for all of the studied elements suggested no non-carcinogenic health risks via ingestion and dermal contact, but a potential non-carcinogenic health risk via inhalation to adults. Values of hazard quotient and hazard index indicated the non-carcinogenic risks from the studied metal(loid)s to children via ingestion, dermal contact and inhalation pathways in Nanjing given the present air quality.► Bioaccessibility of metal(loid)s in aerosols (TSP and PM2.5) were analyzed using SBET. ► Zn, Pb, Mn and Cu were the most abundant contaminants in both TSP and PM2.5. ► Pb, As and Co in TSP/PM2.5 were the main exposure contaminants for children. ► Main risks for adults resulted from inhalation exposure of TSP and PM2.5. ► Health risk from metal(loid)s in PM2.5 is higher than that in TSP.
Keywords: Aerosols; Trace elements; Bioaccessibility; Health risk
Urban NH3 levels and sources in a Mediterranean environment by Cristina Reche; Mar Viana; Marco Pandolfi; Andrés Alastuey; Teresa Moreno; Fulvio Amato; Anna Ripoll; Xavier Querol (pp. 153-164).
Urban NH3 concentrations were mapped in Barcelona (Spain) by means of passive samplers (dosimeters). Average NH3 levels were 9.5 μg m−3 in summer and 4.4 μg m−3 in winter, higher than those reported in other urban background sites in Europe, this being especially notable in summer. During this season, values were significantly higher at urban background than at traffic sites, probably indicating the impact of emissions from biological sources, such as humans, sewage systems and garbage containers. Thus, the volatilization of NH3 from the aerosol phase seems to be significant enough during summer to dominate over traffic emissions. Conversely, in winter levels were higher at traffic sites, suggesting a contribution from vehicle emissions. Indeed, NH3 levels decreased by 55% with increasing distance (50 m) to the direct emissions from traffic. A significant correlation between NH3 concentrations averaged for the different districts of the city and the number of waste containers per hm2 was also obtained, highlighting the necessity for controlling and reducing the emissions from garbage collection systems. The urban topography of the Barcelona historical city centre, characterised by narrow streets with a high population density, seemed to exert a strong influence on NH3 levels, with levels reaching up to 30 μg m−3 as a consequence of limited dispersion and ventilation conditions. The impact of the sewage system emissions was also detected with an increase of levels when measuring immediately above the source, even though further studies are required to evaluate the relevance of these emissions.► Urban NH3 levels were measured in Barcelona (Spain) by passive samplers. ► Levels in summer were found to be higher than in previous studies in European cities. ► Biological sources exert a strong influence on NH3 levels in summer. ► The impact of vehicles was detected, with levels drastically decreasing a few metres from the source. ► NH3 levels correlate with the number of waste containers, a problem in such a densely-populated city.
Keywords: Urban ammonia; Secondary inorganic aerosols; Ammonium nitrate; Passive samplers; ALPHA
Characteristics of ammonia, hydrogen sulfide, carbon dioxide, and particulate matter concentrations in high-rise and manure-belt layer hen houses by Ji-Qin Ni; Lilong Chai; Lide Chen; Bill W. Bogan; Kaiying Wang; Erin L. Cortus; Albert J. Heber; Teng-Teeh Lim; Claude A. Diehl (pp. 165-174).
Indoor air pollutants at high concentrations in poultry houses can potentially affect workers' health, and animal welfare and productivity. This paper presents research results of a 2-year continuous monitoring of ammonia (NH3), carbon dioxide (CO2), hydrogen sulfide (H2S), and particulate matter (PM) concentrations from to date the most comprehensive study on a single farm in two 180,000-bird high-rise (HR) and two 200,000-bird manure-belt (MB) layer hen houses located in Indiana, USA. Air was sampled at ventilation fans of the mechanically-ventilated houses. Concentrations of NH3 and CO2 were measured with photoacoustic multi-gas monitors. Concentrations of H2S and PM10 were monitored with pulsed fluorescence analyzers and Tapered Element Oscillating Microbalances (TEOM), respectively. The 2-year mean ± standard deviation concentrations at ventilation fans of the four layer hen houses were 48.9 ± 39 and 51.9 ± 40.7 ppm in HR, and 13.3 ± 9.1 and 12.9 ± 10.5 ppm in MB for NH3; 26.4 ± 17.6 and 24.9 ± 19 ppb in HR, 40.0 ± 21.1 and 41.2 ± 31.5 ppb in MB for H2S; 1755 ± 848 and 1804 ± 887 ppm in HR, and 2295 ± 871 and 2285 ± 946 ppm in MB for CO2; and 540 ± 303 and 552 ± 338 μg m−3 in HR, and 415 ± 428 and 761 ± 661 μg m−3 in MB for PM10. Compared with the MB houses, concentrations of the HR houses were higher for NH3, and lower for CO2, H2S, and PM10 ( P < 0.05). High concentrations of NH3 detected in winter represent potential challenges to workers' health and animal welfare. Variations in pollutant concentrations at the exhaust fans were affected by outdoor temperature, ventilation, bird condition, and farm operation. A new weekly variation, characterized by significantly lower PM10 concentrations on Sundays, was identified and was related to the weekly schedule of house operational activities.► Indoor air pollution could affect worker and animal health in layer hen houses. ► We measured pollutant concentrations in four layer houses continuously for two years. ► There were higher ammonia and lower hydrogen sulfide concentrations than swine barns. ► Several factors including house designs affect pollutant concentrations.
Keywords: Air quality; Indoor air pollution; Measurement; Poultry house; Ventilation
Evaluation of the changes in the Madrid metropolitan area influencing air quality: Analysis of 1999–2008 temporal trend of particulate matter by P. Salvador; B. Artíñano; M. Viana; A. Alastuey; X. Querol (pp. 175-185).
During the 1999–2008 period a statistically significant downward trend in the concentrations of SO2, NO x, CO and PM2.5 was determined at most of the urban and urban-background monitoring sites in the Madrid metropolitan area. However, no statistically significant trend was detected in PM10 concentrations at any urban and rural site and in NO2 concentrations at the urban sites. The reduction in the annual coal consumption and in the number of gasoline vehicles and the use of particle filters for diesel engines in this area, have contributed to this reduction of SO2, CO and fine PM concentrations, but the increase of the diesel fleet is probably the cause of an increase of the NO2/NO x ratio and the lack of a decreasing trend of NO2 concentrations. Chemical characterisation and receptor modelling analysis results showed that mean contributions to PM10 and PM2.5 levels attributed to anthropogenic sources throughout the 1999–2008 period, decreased at the Madrid urban areas mainly by reductions in their carbonaceous and SO42− contents. However, the contribution of mineral dust to PM10 bulk levels did not significantly decrease at the urban sites. Thus, strategies aimed at reducing levels of PM10 and PM2.5 concentrations focussing mainly on road traffic and coal consumption, can be insufficient to reduce the number of days exceeding the PM10 Daily Limit Value (50 μg m−3) at some metropolitan areas, such as Madrid, where crustal content due to anthropogenic activities and natural phenomena is elevated even when the African dust contribution during episodic days is excluded. Changes in the structure of the metropolitan area such as the increase of the Madrid car fleet and of its proportion of diesel vehicles, could also contribute to keep or increase the concentration of other pollutants (NO2) which resulted in increases of the NO3− contribution to PM10 and PM2.5 levels.► Trends in pollutants concentrations were analysed over the 1999–2008 period in the Madrid metropolitan area. ► PM10 and PM2.5 levels attributed to anthropogenic sources (road traffic, coal consumption) decreased. ► Contribution of mineral dust to PM10 levels did not significantly decrease. ► Abatement strategies to reduce the concentration of PM10 should quantify dust contributions. ► Changes in the structure of the metropolitan area should be also taken into account.
Keywords: PM10; PM2.5; Trend analysis; Chemical composition; Receptor modelling analysis
Organic speciation of aerosols from wildfires in central Portugal during summer 2009 by Ana Vicente; Célia Alves; Cristina Monteiro; Teresa Nunes; Fátima Mirante; Mário Cerqueira; Ana Calvo; Casimiro Pio (pp. 186-196).
The aim of this study was the detailed organic speciation of fine (PM2.5) and coarse (PM2.5–10) particles and gaseous carbonyl compounds from plumes emitted by wildfires during the summer of 2009 in Portugal. Complementary characterisation of the smoke particulate inorganic fraction, along with emission factors of major trace gases, have already been published in Atmospheric Environment. The detailed speciation of organic compounds in particle samples was carried out by gas chromatography-mass spectrometry after multi-solvent extraction, flash chromatography on silica gel and appropriate derivatisation techniques. PM2.5 constitutes an important fraction of PM10 (PM2.5/PM10 > 80%). Gaseous carbonyls were sampled from the Tedlar bags containing the smoke samples in DNHP cartridges and analysed by high-performance liquid chromatography. A clear predominance of carbonaceous constituents was observed, with OC concentrations always much higher than EC in both particle size fractions (OC/EC >> 7). The chromatographically resolved organics were dominated by diterpenoids, acids, sugars, phenols and aliphatic compounds in both size fractions. Retene, a biomarker of softwood smoke, was the dominant aromatic hydrocarbon in samples. The major anhydrosugar detected was levoglucosan, followed by mannosan and galactosan. Among the measured oxygenated volatile organic compounds, the most abundant was acetaldehyde with EFs (dry basis) between 1.03 and 1.87 g kg−1, followed by formaldehyde with values in the range of 0.09–0.96 g kg−1. Propionaldehyde was the less abundant carbonyl, with values in the range of 0.03–0.17 g kg−1.► The detailed organic speciation of smoke samples from wildfires is provided. ► The most abundant carbonyl was acetaldehyde, followed by formaldehyde. ► Retene, resin acids, vanillin and levoglucosan were major particulate compounds. ► Emissions of many organics decrease with increasing combustion efficiency.
Keywords: Wildfires; Trace gases; Particulate matter; Emission factors; Organic speciation
Yearly trend of dicarboxylic acids in organic aerosols from south of Sweden and source attribution by Murtaza Hyder; Johan Genberg; Margareta Sandahl; Erik Swietlicki; Jan Åke Jönsson (pp. 197-204).
Seven aliphatic dicarboxylic acids (C3–C9) along with phthalic acid, pinic acid and pinonic acid were determined in 35 aerosol (PM10) samples collected over the year at Vavihill sampling station in south of Sweden. Mixture of dichloromethane and methanol (ratio 1:3) was preferred over water for extraction of samples and extraction was assisted by ultrasonic agitation. Analytes were derivatized using N, O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) containing 1% trimethylsilyl chloride and analyzed using gas chromatography/mass spectrometry. Among studied analytes, azelaic acid was found maximum with an average concentration of 6.0 ± 3.6 ng m−3 and minimum concentration was found for pimelic acid (1.06 ± 0.63 ng m−3). A correlation coefficients analysis was used for defining the possible sources of analytes. Higher dicarboxylic acids (C7–C9) showed a strong correlation with each other (correlation coefficients ( r) range, 0.96–0.97). Pinic and pinonic acids showed an increase in concentration during summer. Lower carbon number dicarboxylic acids (C3–C6) and phthalic acid were found strongly correlated, but showed a poor correlation with higher carbon number dicarboxylic acids (C7–C9), suggesting a different source for them. Biomass burning, vehicle exhaust, photo-oxidation of volatile organic compounds (natural and anthropogenic emissions) were possible sources for dicarboxylic acids.► Dicarboxylic acids, phthalic acid, pinic acid and pinonic acid were analyzed from aerosol samples. ► Analytes were derivatized using and analyzed using gas chromatography mass spectrometry. ► Correlation coefficients analysis was made and was used to determine the sources of diacids. ► PCA was applied and we identified three sources of dicarboxylic acids.
Keywords: Dicarboxylic acids; Ultrasonic assisted solvent extraction; Correlation coefficient; Biomass burning; Photo-oxidation; Phthalic acid; Pinonic acid
Synergistic analyses of optical and microphysical properties of agricultural crop residue burning aerosols over the Indo-Gangetic Basin (IGB) by Amit Kumar Mishra; Takashi Shibata (pp. 205-218).
Agriculture crop residue burning is one of the important sources of trace gas emissions and aerosol loading over the Indo-Gangetic Basin (IGB). The present study deals with the spatial variability including the vertical structure of optical and microphysical properties of aerosols, during the crop residue burning season (October and November) of 2009 over the IGB. Increased number of fire counts observed by MODIS (MODerate resolution Imaging Spectroradiometer) that is associated with high aerosol optical depth (MODIS-AOD > 0.7) and enhanced tropospheric columnar NO2 concentrations observed by OMI (Ozone Monitoring Instrument), suggests agriculture crop residue burning as a main source of aerosol loading over the IGB during October and November. PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar) observations show an increase in fine mode AOD (at 865 nm) from October (0.1–0.2) to November (0.2–0.3) over the IGB, which is well corroborated with MODIS observations. CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) data shows the elevated aerosol plume (4.0–4.5 km) over the north-west IGB (associated with burning activities) that could have been caused by positive buoyancy through pyro-convection. However, large concentrations of aerosol were found below 1.0 km altitude. The averaged vertical structure of crop residue burning aerosols shows an exponential decrease with altitude (mean scale height ∼1.44 ± 0.20 km). Aerosol optical and microphysical properties coupled with backward air trajectories analyses at Kanpur indicated regional transport of biomass burning aerosols in a downwind direction from north-west IGB to south-east IGB. Aerosol classification, using AERONET (AErosol RObotic NETwork)-derived absorption properties coupled with size parameter (2006–2010) showed clear seasonal dependency of aerosol types which revealed the presence of biomass burning aerosols only during the crop residue burning season. The findings of this study will be further used for quantification of the properties of atmospheric brown clouds and their effects on global climate change.► Studied crop residue burning aerosols using multi-space and ground-borne sensors. ► Crop residue burning found as a main cause of aerosol loading in PoM season. ► Elevated smoke plumes (∼4 km) with an exponential decrease have found over the IGB. ► Analyses indicate regional transport of biomass burning aerosols in downwind path. ► A seasonal model of different aerosol types have discussed in detail.
Keywords: Agriculture crop residue burning; MODIS; CALIOP; PARASOL; Pyro-convection; Regional transport; Absorption Angstrom Exponent (AAE); Black carbon (BC)
Uncertainties in gas-phase atmospheric iodine chemistry by R. Sommariva; W.J. Bloss; R. von Glasow (pp. 219-232).
We present a comprehensive chemical mechanism for gas-phase iodine, to be used for modelling tropospheric chemistry. The mechanism has been compiled from evaluated data and individual literature studies, where available; a number of key processes have not been studied experimentally or theoretically and in these cases estimations have been made. The uncertainty associated with these assumptions is evaluated. We analyze the mechanism using a box-model under a variety of boundary layer scenarios – representative of environments where iodine species have been observed – to study the response of the chemical system to changes in the kinetic parameters of selected reactions. We focus in particular on key species such as IO, OIO, INO3 and I2Oy and the impact of iodine chemistry on ozone formation and HOx levels. The results indicate that the chemical system is most sensitive to reactions leading to comparatively stable iodine compounds, which should be a focus of future laboratory studies.► Assembled gas-phase inorganic iodine chemical mechanism. ► Analyzed mechanism using box-model under different scenarios. ► Response of mechanism to changes in kinetic parameters of selected reactions. ► Mechanism most sensitive to reactions forming stable iodine species. ► Laboratory studies of some key reactions are urgently needed.
Keywords: Iodine; Gas-phase; Gas kinetics; Chemical mechanism; Uncertainties; Troposphere; Marine boundary layer
Intake fraction of PM2.5 and NOX from vehicle emissions in Beijing based on personal exposure data by Xuan Du; Ye Wu; Lixin Fu; Shuxiao Wang; Shaojun Zhang; Jiming Hao (pp. 233-243).
The intake fraction (iF) is the portion of attributable population intake of a source emissions, and is used to link pollutant emissions and population exposure. This study is the first work that reported individual intake fraction of PM2.5 and NOX from vehicle emissions based on personal exposure data in China. We employed PM2.5 and NOX measurement data from 24-h personal exposure sampling and concentration monitoring in traffic environments in the urban area of Beijing to estimate the individual intake fraction (iF i). iF i distributions are presented in microenvironments (traffic, work, home) for adults and children. The individual results are used to calculate the intake fraction for the children group and the adults group in the urban area of Beijing. The iF of PM2.5 for the whole population of these two groups in Beijing is 153 per million, which is significantly higher than those estimates in the United States (1–50 per million) and Mexico (23–120 per million). The iF of NOX is 70 per million, among which the intake in the traffic micro-environment ranks first compared to the iF in the home and office due to a high accumulation of NOX concentration in vehicles. PM2.5 and NOX intake fraction values from vehicle emissions in this study are from at least several times to one order of magnitude higher than those from other industry sources in China. This strongly suggests the health risk from vehicle emissions is significantly higher. Therefore, to protect human health, especially for the large number of people living in the cities of China, controlling vehicle emissions should be the highest priority.► Intake fraction from Beijing vehicles was estimated by personal exposure data. ► The vehicular intake fraction in Beijing is higher than those in USA and Mexico. ► Intake fraction for vehicle is higher than those for other sources in China. ► Health risk from vehicle emissions is very high in Beijing. ► Controlling vehicle emissions should be the highest priority in Beijing.
Keywords: Individual intake fraction; PM; 2.5; NO; X; Personal exposure; Vehicle emissions
APOLLO2, a new long range Lagrangian particle dispersion model and its evaluation against the first ETEX tracer release by R. Bellasio; S. Scarpato; R. Bianconi; P. Zeppa (pp. 244-256).
APOLLO2 is a new version of the long range Lagrangian particle dispersion model integrated into ARIES (Accidental Release Impact Evaluation System), the system that I.S.P.R.A. (Italian National Institute for Environmental Protection and Research) developed to provide prognosis about the dispersion of radioactive clouds in case of nuclear accidents. In this paper the theoretical aspects of the APOLLO2 formulation are briefly described. Moreover, the model performances have been evaluated qualitatively and quantitatively against the observations of the first release of the European Tracer Experiment (ETEX). The global analysis showed a FA2 = 56%, a FA5 = 78%, and a good agreement for intermediate values within the Q–Q plot. Considering a total of 126 stations, the number of locations where NMSE < 10, PCC > 0.7 and FMT > 20% is respectively 91, 65 and 86. The number of stations where the performance evaluation criteria are satisfied is 33. The capability of APOLLO2 to predict arrival time, cloud duration and time of peak is comparable to the one shown by similar models.Finally, the sensitivity of the model to some input variables has also been investigated.► We present the APOLLO2 long range atmospheric Lagrangian particle model. ► Qualitative comparison of APOLLO2 predictions and ETEX1 observations is good. ► Quantitative comparison is also of good quality (e.g. FA2 = 56%, FA5 = 78%). ► Sensitivity analysis has given hints to improve the model performances.
Keywords: APOLLO2; Long range dispersion model; Nuclear accident; Radioactive release; Emergency preparedness; ETEX; Model validation; Lagrangian particle model
Estimation of ultrafine particle concentrations at near-highway residences using data from local and central monitors by Christina H. Fuller; Doug Brugge; Paige L. Williams; Murray A. Mittleman; John L. Durant; John D. Spengler (pp. 257-265).
Ultrafine particles (UFP; aerodynamic diameter < 0.1 μm) are a ubiquitous exposure in the urban environment and are elevated near highways. Most epidemiological studies of UFP health effects use central site monitoring data, which may misclassify exposure. Our aims were to: (1) examine the relationship between distant and proximate monitoring sites and their ability to predict hourly UFP concentration measured at residences in an urban community with a major interstate highway and; (2) determine if meteorology and proximity to traffic improve explanatory power. Short-term (1–3 weeks) residential monitoring of UFP concentration was conducted at 18 homes. Long-term monitoring was conducted at two near-highway monitoring sites and a central site. We created models of outdoor residential UFP concentration based on concentrations at the near-highway site, at the central site, at both sites together and without fixed sites. UFP concentration at residential sites was more highly correlated with those at a near-highway site than a central site. In regression models of each site alone, a 10% increase in UFP concentration at a near-highway site was associated with a 6% (95% CI: 6%, 7%) increase at residences while a 10% increase in UFP concentration at the central site was associated with a 3% (95% CI: 2%, 3%) increase at residences. A model including both sites showed minimal change in the magnitude of the association between the near-highway site and the residences, but the estimated association with UFP concentration at the central site was substantially attenuated. These associations remained after adjustment for other significant predictors of residential UFP concentration, including distance from highway, wind speed, wind direction, highway traffic volume and precipitation. The use of a central site as an estimate of personal exposure for populations near local emissions of traffic-related air pollutants may result in exposure misclassification.► We evaluated UFP concentration in a near-highway community. ► Models of outdoor home UFP were created including fixed sites and other predictors. ► A near-highway site explained more variation in home UFP than a central site. ► Other predictors: highway distance, wind speed & direction, traffic, precipitation. ► Exposure estimated by central site may misclassify near-highway groups.
Keywords: Ultrafine particles; Highway; Community-based participatory research; CBPR; Temporal variation; Residential exposure
Influence of mineral dust transport on the chemical composition and physical properties of the Eastern Mediterranean aerosol by M. Koçak; C. Theodosi; P. Zarmpas; M.J.M. Séguret; B. Herut; G. Kallos; N. Mihalopoulos; N. Kubilay; M. Nimmo (pp. 266-277).
Bulk aerosol samples were collected from three different coastal rural sites located around the Eastern Mediterranean, (i) Erdemli (ER), Turkey, (ii) Heraklion (HR), Crete, Greece, and (iii) Tel Shikmona (TS), Israel, during two distinct mineral dust periods (October, 2007 and April, 2008) in order to explore the temporal and geographical variability in the aerosol chemical composition. Samples were analyzed for trace elements (Al, Fe, Mn, Ca, Cr, Zn, Cu, V, Ni, Cd, Pb) and water-soluble ions (Cl−, NO3−, SO42−, C2O42−, Na+, NH4+, K+, Mg2+ and Ca2+). The dust events were categorized on the basis of Al concentrations >1000 ng m−3, SKIRON dust forecast model and 3-day back trajectories into three groups namely, Middle East, Mixed and Saharan desert. ER and TS were substantially affected by dust events originating from the Middle East, particularly in October, whilst HR was not influenced by dust transport from the Middle East. Higher AOT values were particularly associated with higher Al concentrations. Contrary to the highest Al concentration: 6300 ng m−3, TS showed relatively lower AI and AOT. Al concentrations at ER were similar for October and April, whilst OMI-AI and AOT values were ∼2 times higher in April. This might be attributed to the weak sensitivity of the TOMS instrument to absorbing aerosols near the ground and optical difference between Middle East and Saharan desert dusts. The lowest enhancement of anthropogenic aerosol species was observed at HR during dust events (nssSO42−/nssCa2+ ∼ 0.13). These species were particularly enhanced when mineral dust arrived at sites after passing through populated and industrialized urban areas.► The impact of dust events on aerosol chemical and physical properties is presented. ► Noted regional difference in aerosol composition during October compared to April. ► Middle Eastern dust sources influence the far Eastern Mediterranean in October. ► AI and AOT higher values (lowest fine fractions) observed with Saharan airflows.
Keywords: Mineral dust; SKIRON; The Middle East deserts; Saharan desert; Eastern Mediterranean
Enhancements to the UK Photochemical Trajectory Model for simulation of secondary inorganic aerosol by David C.S. Beddows; Garry D. Hayman; Roy M. Harrison (pp. 278-288).
Particulate matter remains a challenging pollutant for air pollution control in the UK and across much of Europe. Particulate matter is a complex mixture of which secondary inorganic compounds (sulphates, nitrates) are a major component. This paper is concerned with taking a basic version of the UK Photochemical Trajectory Model and enhancing a number of features in the model in order to better represent boundary layer processes and to improve the description of secondary inorganic aerosol formation. The enhancements include an improved treatment of the boundary layer, deposition processes (both wet and dry), attenuation of photolysis rates by cloud cover, and inclusion of the aerosol thermodynamic model ISORROPIA II to account both for chemistry within the aerosol and between the particles and gas phase. Emissions inventories have been updated and are adjusted according to season, day of the week and hour of the day. Stack emissions from high level sources are now adjusted according to the height of the boundary layer and a scheme for generating marine aerosol has been included. The skill of the improved model has been evaluated through predictions of the concentrations of particulate chloride, nitrate and sulphate and the results show increased accuracy and lower mean bias. There is a much higher proportion of the values lying within a factor of 2 of the observed values compared to the basic model and Normalised Mean Bias has reduced by at least 89% for nitrate and sulphate. Similarly, the Index of Agreement between calculated and measured values has improved by ∼10%. Considering the contribution of each enhancement to the improvement in the performance metrics, the most significant enhancement was the replacement of the parameterisation of the boundary layer height, relative humidity and temperature by HYSPLIT values calculated for each trajectory. The second most significant enhancement was the parameterisation of the photolysis rates by values calculated by an off line database accounting for the dependence of photolysis rates on zenith angle, cloud cover, land surface type and column ozone. The inclusion of initial conditions which were dependent on the starting point of the trajectory and the modulation of stack emissions made the most significant improvement to sulphate. Furthermore, in order to assess the model's response to abatement scenarios, 30% abatements of either NH3, NOx or SO2 showed a reduction in the sum of chloride, nitrate and sulphate of between 3.1% and 8.5% (with a corresponding estimated reduction of 1.6–3.7% reduction in PM10). The largest reduction in this contribution is due to the abatement of NOx.► A much enhanced Lagrangian model has been developed. ► Boundary layer structure is better described, and many new processes included. ► Inclusion of ISORROPIA II to account for gas/aerosol partitioning. ► Much improved prediction of secondary inorganic aerosol formation.
Keywords: Lagrangian model; Sulphate; Nitrate; Chloride; Master Chemical Mechanism
Uncertainties in the determination of global sub-micron marine organic matter emissions by M.F.M.A. Albert; M. Schaap; A.M.M. Manders; C. Scannell; C.D. O'Dowd; G. de Leeuw (pp. 289-300).
Organic matter (OM) constitutes an important contribution to the composition of sub-micron sea-spray aerosol produced from biologically active waters. However, OM emission estimates vary by more than an order of magnitude. To estimate the uncertainties in the OM production estimates a sensitivity analysis has been performed in which various parameters have been varied. These include different sea-spray source functions, satellite-retrieved chlorophyll distributions, and a relationship correlating in situ organic mass measurements with satellite-retrieved chlorophyll data. The starting point was a baseline model from which the annual global emission of the water insoluble organic matter (WIOM) fraction in sea spray has been estimated to be 20.4 Tg. In this baseline the global WIOM emission is dominated by the contribution (80%) of the chlorophyll-poor regions (<0.3 mg m−3). Significant deviations from this estimate are introduced by the choice of the sea-spray source function and the assumed background organic mass fraction, each of which leads to an uncertainty of at least a factor of 2. In particular the chlorophyll-poor regions which dominate the WIOM contribution are strongly affected by the choice of the organic mass fraction parameterisation. The way the chlorophyll data are handled, such as different gap filling approaches, causes deviations in the OM emission that are in the order of 10% and is therefore of less importance. The present research indicates that special attention should be given to the low chlorophyll areas in e.g. the tropics, since there the parameterisations are most uncertain and at the same time these regions dominate total WIOM emissions.► We model global emission of the organic matter (OM) fraction of sub-micron sea spray. ► The global source strength of the OM fraction is highly uncertain. ► Key uncertainties are the sea-spray source function and OM relationship. ► The tropical region was identified to be extra sensitive. ► We recommend a stronger observational basis to reduce the large uncertainties.
Keywords: Organic aerosol; Sea spray; Remote sensing; Modelling
Identification of Micro-scale Anthropogenic CO2, heat and moisture sources – Processing eddy covariance fluxes for a dense urban environment by Simone Kotthaus; C.S.B. Grimmond (pp. 301-316).
Anthropogenic emissions of heat and exhaust gases play an important role in the atmospheric boundary layer, altering air quality, greenhouse gas concentrations and the transport of heat and moisture at various scales. This is particularly evident in urban areas where emission sources are integrated in the highly heterogeneous urban canopy layer and directly linked to human activities which exhibit significant temporal variability. It is common practice to use eddy covariance observations to estimate turbulent surface fluxes of latent heat, sensible heat and carbon dioxide, which can be attributed to a local scale source area. This study provides a method to assess the influence of micro-scale anthropogenic emissions on heat, moisture and carbon dioxide exchange in a highly urbanized environment for two sites in central London, UK. A new algorithm for the Identification of Micro-scale Anthropogenic Sources (IMAS) is presented, with two aims. Firstly, IMAS filters out the influence of micro-scale emissions and allows for the analysis of the turbulent fluxes representative of the local scale source area. Secondly, it is used to give a first order estimate of anthropogenic heat flux and carbon dioxide flux representative of the building scale. The algorithm is evaluated using directional and temporal analysis. The algorithm is then used at a second site which was not incorporated in its development. The spatial and temporal local scale patterns, as well as micro-scale fluxes, appear physically reasonable and can be incorporated in the analysis of long-term eddy covariance measurements at the sites in central London. In addition to the new IMAS-technique, further steps in quality control and quality assurance used for the flux processing are presented. The methods and results have implications for urban flux measurements in dense urbanised settings with significant sources of heat and greenhouse gases.► Highly urbanized eddy covariance observations analysed. ► New filter distinguishes local scale source area and micro-scale fluxes. ► Temporal and spatial patterns and between site comparisons made. ► Building scale anthropogenic heat, water and CO2 fluxes determined from observations.
Keywords: Eddy covariance; Anthropogenic heat; CO; 2; Urban; London; Greenhouse gas; Human activities
Removal of benzene from indoor air by Dracaena sanderiana: Effect of wax and stomata by Chairat Treesubsuntorn; Paitip Thiravetyan (pp. 317-321).
From screening 8 ornamental plants, it was found that Dracaena sanderiana had the highest benzene removal efficiency. In a long-term study, 4 cycles of benzene were studied under both 24 h dark and 24 h light conditions. From the 2nd to 4th cycle, benzene uptake by plants under 24 h light condition had higher intensity than under 24 h dark conditions, and the close of D. sanderiana stomata was found only in 24 h dark condition. At the final cycle, D. sanderiana still survived, and benzene uptake continued. From the calculation, 46% of benzene was taken up by D. sanderiana crude wax, while 54% was predicted to be taken up by the stomata by 72 h.
Keywords: Dracaena sanderiana; Benzene; Phytoremediation; Stomata; Wax
Associations between personal exposures and ambient concentrations of nitrogen dioxide: A quantitative research synthesis by Q.Y. Meng; D. Svendsgaard; D.J. Kotchmar; J.P. Pinto (pp. 322-329).
Although positive associations between ambient NO2 concentrations and personal exposures have generally been found by exposure studies, the strength of the associations varied among studies. Differences in results could be related to differences in study design and in exposure factors. However, the effects of study design, exposure factors, and sampling and measurement errors on the strength of the personal-ambient associations have not been evaluated quantitatively in a systematic manner. A quantitative research synthesis was conducted to examine these issues based on peer-reviewed publications in the past 30 years. Factors affecting the strength of the personal-ambient associations across the studies were also examined with meta-regression. Ambient NO2 was found to be significantly associated with personal NO2 exposures, with estimates of 0.42, 0.16, and 0.72 for overall pooled, longitudinal and daily average correlation coefficients based on random-effects meta-analysis. This conclusion was robust after correction for publication bias with correlation coefficients of 0.37, 0.16 and 0.45. We found that season and some population characteristics, such as pre-existing disease, were significant factors affecting the strength of the personal-ambient associations. More meaningful and rigorous comparisons would be possible if greater detail were published on the study design (e.g. local and indoor sources, housing characteristics, etc.) and data quality (e.g., detection limits and percent of data above detection limits).► Associations between ambient NO2 and personal exposures to NO2 were examined. ► A meta-analysis was performed on studies conducted over the past 30 years. ► Factors determining the strength of these associations were examined. ► Season, age, and pre-existing disease significantly affected the strength of the associations. ► In general, ambient NO2 was found to be significantly associated with personal exposure to NO2.
Keywords: NO; 2; Personal exposure; Personal-ambient association; Exposure factors; Meta analysis