Atmospheric Environment (v.45, #4)
Editorial board (i).
Methodology for assessing exposure and impacts of air pollutants in school children: Data collection, analysis and health effects – A literature review by Jaime F. Mejía; Samantha Low Choy; Kerrie Mengersen; Lidia Morawska (813-823).
The aim of this review is to explore the methodologies employed to assess the exposure of children to air pollutants, in particular traffic emissions, at school, and how these methodologies influence the assessment of the impact of this exposure on the children’s health. This involves four main steps: the measurement of air quality at school level, the association between measured air quality and children’s exposure, the association between children’s exposure and health; and source identification. The comparative advantages and disadvantages of the methods used at each of these steps are discussed.Air quality in schools can be measured at three scales: broad scale, across several city blocks using remote monitors; school-based scale, through ground-level monitors installed within the schools or their immediate surroundings (i.e. only a few metres outside the school); and personal exposure scale using portable monitors attached to a sample of children. Although studies have reported high exposure to PAHs (polycyclic aromatic hydrocarbons), submicrometre (<1.0 μm) and ultrafine particles (<100 nm) at school, no study has investigated the formation of new particles in school facilities and only a handful of studies have analysed children’s exposure at school.Associating air quality measurements at the broad and medium scale with children’s exposure is challenging: there is spatial and temporal heterogeneity in the distribution of air quality within a school, indoor measurements can often exceed outdoor measurements; and exposure in the classroom is affected by the penetration of outdoor pollutants, wall absorption, emissions from furniture and other materials, level and length of occupancy, and quality of ventilation. This is further exacerbated by the fact that children move around during their school day.Quantifying the contribution of school exposure with observed health symptoms presents further challenges. In addition to ascertaining the impact of non-school-based exposures and co-morbidities, the air pollutant dose intake is affected by daily patterns of physical and traffic activity during and outside school hours which make it difficult to compare the contribution of school-based and non-school-based exposures to the health effect under investigation. Finally, there is strong evidence that low socioeconomic level is highly correlated with the proximity of the school to pollution sources, yet this area of socioeconomic research has been largely unexplored in the assessment of traffic emission exposure.► The most common methods for assessing air pollution exposure in schools. ► Effect of daily and small-scale spatial variation in pollutant concentrations. ► Effect of daily pattern of children's activities in their exposure. ► Association between air pollution exposure and children's socioeconomic level.
Keywords: Exposure assessment; Traffic emissions; School children; Air pollution; Methodology;
Impact of cruise ship emissions in Victoria, BC, Canada by Karla Poplawski; Eleanor Setton; Bryan McEwen; Dan Hrebenyk; Mark Graham; Peter Keller (824-833).
Characterization of the effects of cruise ship emissions on local air quality is scarce. Our objective was to investigate community level concentrations of fine particulate matter (PM2.5), nitrogen dioxide (NO2) and sulphur dioxide (SO2) associated with cruise ships in James Bay, Victoria, British Columbia (BC), Canada. Data obtained over four years (2005–2008) at the nearest air quality network site located 3.5 km from the study area, a CALPUFF modeling exercise (2007), and continuous measurements taken in the James Bay community over a three-month period during the 2009 cruise ship season were examined. Concentrations of PM2.5 and nitrogen oxide (NO) were elevated on weekends with ships present with winds from the direction of the terminal to the monitoring station. SO2 displayed the greatest impact from the presence of cruise ships in the area. Network data showed peaks in hourly SO2 when ships were in port during all years. The CALPUFF modeling analysis found predicted 24-hour SO2 levels to exceed World Health Organization (WHO) guidelines of 20 μg m−3 for approximately 3% of 24-hour periods, with a maximum 24-hour concentration in the community of 41 μg m−3; however, the CALPUFF model underestimated concentrations when predicted and measured concentrations were compared at the network site. Continuous monitoring at the location in the community predicted to experience highest SO2 concentrations measured a maximum 24-hour concentration of 122 μg m−3 and 16% of 24-hour periods were above the WHO standard. The 10-minute concentrations of SO2 reached up to 599 μg m−3 and exceeded the WHO 10-minute SO2 guideline (500 μg m−3) for 0.03% of 10-minute periods. No exceedences of BC Provincial or Canadian guidelines or standards were observed.► Local air quality impacts of cruise ship emissions. ► Comparison of NO2, SO2 and PM2.5 when ships are present/absent. ► Multi-year measurements and CALPUFF modeling scenario. ► World Health Organization 24-hour SO2 guideline exceeded 16% of 24-hour periods. ► MARPOL Annex VI treaty will reduce sulphur fuel content and lower SO2 levels.
Keywords: Measurements; Modeling; SO2; NO2; Particulate matter;
Total gaseous mercury in Pearl River Delta region, China during 2008 winter period by Zheng Li; Chonghuan Xia; Xinming Wang; Yunrong Xiang; Zhouqing Xie (834-838).
Total gaseous mercury (TGM) was monitored at Wanqingsha, a rural site in the central Pearl River Delta region, south China from 23 November to 22 December, 2008. TGM ranged 0.50–18.67 ng m−3 with an average of 2.94 ng m−3. TGM was found to present a diurnal cycle with the maximum at 7:00–8:00 and the minimum at 14:00–16:00 (local time). The afternoon minimum in TGM were likely related to increased vertical mixing and the TGM oxidation by ozone, which was observed to negative correlation with TGM. A sudden increase in TGM from 6:00–7:00 could be due to activation of local surface emission sources by rising air temperature. Similar variations in TGM and trace gases including CO and SO2 suggested potential anthropogenic sources contribution as well. Wind-rose patterns further indicated that the westerly wind might carry high concentration of TGM from the high mercury emission areas of Southwest China and/or local anthropogenic emission sources.► Total gaseous mercury (TGM) was monitored in the Pearl River Delta,China. ► TGM was found to present a diurnal cycle. ► TGM sources were ascribed to the long-range transport and/or local emission.
Keywords: Total gaseous mercury (TGM); Atmosphere; Pearl River Delta (PRD); Ozone; Carbon monoxide (CO);
Development and evaluation of GRAL-C dispersion model, a hybrid Eulerian–Lagrangian approach capturing NO–NO2–O3 chemistry by Dietmar Oettl; Ulrich Uhrner (839-847).
Based on two recent publications using Lagrangian dispersion models to simulate NO–NO2–O3 chemistry for industrial plumes, a similar modified approach was implemented using GRAL-C (Graz Lagrangian Model with Chemistry) and tested on two urban applications. In the hybrid dispersion model GRAL-C, the transport and turbulent diffusion of primary species such as NO and NO2 are treated in a Lagrangian framework while those of O3 are treated in an Eulerian framework. GRAL-C was employed on a one year street canyon simulation in Berlin and on a four-day simulation during a winter season in Graz, the second biggest city in Austria. In contrast to Middleton D.R., Jones A.R., Redington A.L., Thomson D.J., Sokhi R.S., Luhana L., Fisher B.E.A. (2008. Lagrangian modelling of plume chemistry for secondary pollutants in large industrial plumes. Atmospheric Environment 42, 415–427) and Alessandrini S., Ferrero E. (2008. A Lagrangian model with chemical reactions: application in real atmosphere. Proceedings of the 12th Int. Conf. on Harmonization within atmospheric dispersion modelling for regulatory purposes. Croatian Meteorological Journal, 43, ISSN: 1330-0083, 235–239) the treatment of ozone was modified in order to facilitate urban scale simulations encompassing dense road networks.For the street canyon application, modelled daily mean NOx/NO2 concentrations deviated by +0.4%/−15% from observations, while the correlations for NOx and NO2 were 0.67 and 0.76 respectively. NO2 concentrations were underestimated in summer, but were captured well for other seasons.In Graz a fair agreement for NOx and NO2 was obtained between observed and modelled values for NOx and NO2. Simulated diurnal cycles of NO2 and O3 matched observations reasonably well, although O3 was underestimated during the day. A possible explanation here might lie in the non-consideration of volatile organic compounds (VOCs) chemistry.► GRAL-C, a hybrid Lagrangian/Eulerian chemistry, diffusion and transport model was developed. ► Simple O3–NO–NO2 chemistry was simulated with high spatial resolution. ► The model was applied successfully in two urban areas. ► Further research regarding segregation is necessary.
Keywords: GRAL-C; Lagrangian particle model; Urban air pollution; Air chemistry; NO2;
Dry deposition of gaseous elemental mercury to plants and soils using mercury stable isotopes in a controlled environment by Andrew P. Rutter; James J. Schauer; Martin M. Shafer; Joel E. Creswell; Michael R. Olson; Michael Robinson; Ryan M. Collins; Andrew M. Parman; Tanya L. Katzman; Justin L. Mallek (848-855).
Uptake of gaseous elemental mercury (Hg0 (g)) by three plant species and two soil types was measured using mercury vapor enriched in the 198 isotope (198Hg0 (g)). The plant species and soil types were: White Ash (Fraxinus Americana; WA); White Spruce (Picea Glauca; WS); Kentucky Bluegrass (Poa Partensis; KYBG); Plano Silt Loam (4% organic matter; PSL); and Plainfield Sand/Sparta Loamy Sand (1.25–1.5% organic matter: PS). The plants and soils were exposed to isotopically enriched Hg0 (g) in a 19 m3 controlled environment room for 7 days under optimal plant growth conditions (20 °C, 140 Wm−2 between 300 nm and 700 nm; 70% RH) and atmospherically relevant Hg0 (g) concentrations. Mercury was recovered from the samples using acidic digestions and surface leaches, and then analyzed for enrichments in 198Hg by ICPMS. The method was sensitivity enough that statistically significant enrichments in 198Hg were measured in the plant foliage at the end of Day 1. Whole leaf digestions and surface-selective leaches revealed that accumulative uptake was predominantly to the interior of the leaf under the conditions studied.Uptake fluxes for WA increased between the first and third days and remained constant thereafter (WA; Day 1 = 7 ± 2 × 10−5 ng m−2 s−1; Days 3–7 = 1.3 ± 0.1 × 10−4 ng m−2 s−1; where m2 refers to one sided leaf area). KYBG demonstrated similar behavior although no Day 3 measurement was available (Day 1 = 7.5 ± 0.5 × 10−5 ng m−2 s−1; Day 7 = 1.2 ± 0.1 × 10−4 ng m−2 s−1). Fluxes to White Spruce were lower, with little difference between Days 1 and 3 followed by a decrease at Day 7 (WS; Days 1–3 = 5 ± 2 × 10−5 ng m−2 s−1; Day 7 = 2.4 ± 0.2 × 10−5 ng m−2 s−1). Uptake of Hg to soils was below the method detection limit for those media (PSL = 3 × 10−2 ng m−2 s−1; PS = 3 × 10−3 ng m−2 s−1) over the 7 day study period. Foliar resistances calculated for each species compared well to previous studies.► Plants and soils were exposed to Hg0 (g) enriched in the 198 stable isotope to measure foliar accumulation in a controlled environment growth chamber. ► Plant foliage exhibited statistically significant enrichments in the Added 198 stable isotope after 1 day, and accumulation continued for the 7 day duration of the experiment. ► Accumulation occurred primarily through the leaf stomata-interior pathway, rather than to the cuticle. ► Resistances to uptake were calculated and predicted to be dominated by the interior resistance rather than the stomata at optimal growth conditions.
Keywords: Atmospheric; Mercury; Dry deposition; Plants; Foliar accumulation; Stable isotopes; ICPMS;
Stable carbon isotope ratio of secondary particulate organic matter formed by photooxidation of toluene in indoor smog chamber by Satoshi Irei; Jochen Rudolph; Lin Huang; Janeen Auld; Donald Hastie (856-862).
Laboratory studies were conducted for stable carbon isotope ratio for secondary particulate organic matter (POM) formed by photooxidation of toluene. Using an 8 m3 indoor YorkU smog chamber, three POM generation experiments were carried out under room temperature, atmospheric pressure, and RH < 6%. In this study, the different initial conditions were set from those in the previous flow reactor study for secondary POM formed by photooxidation of toluene: introduction of seed particles, and 40–80 times lower initial toluene mixing ratios (∼1900 μg m−3) and ∼60 times higher toluene to NOx ratios (∼7), respectively. The formation of secondary POM was confirmed by the size distribution measurements of particles and the POM was collected on quartz fiber filters for carbon mass and stable carbon isotope ratio analysis. The size distribution measurements showed that the POM mass yields were between 37% and 55% at the end of experiments, while the filter analysis showed that the yields of POM carbon collected then were between 7% and 21%, implying the substantial contribution of heteroatoms. The plot of the POM carbon yields from this study and the previous study indicated that the POM carbon yields were merged into a single profile. The results of isotope measurements demonstrated that the carbon isotope fractionation at the initial reaction step was predominant in the overall carbon isotope fractionations that occur in the sequence of the reactions leading to the formation of secondary POM carbon. Using the results, novel approach for estimation of secondary POM carbon yield with stable carbon isotope ratios is proposed.► δ13C and carbon yield of secondary POM formed by toluene/OH reaction are presented. ► POM carbon yields were proportional to fraction of toluene consumed. ► The results imply contribution of heteroatoms and/or of inorganic to the PM formed. ► Dependence between isotope ratio and particulate yield is presented.
Keywords: Secondary organic aerosol; Stable carbon isotope ratio; Photooxidation of toluene; Kinetic isotope effect; Isotope fractionation;
Identification of tobacco smoke components in indoor breathable particles by SEM–EDS by K. Slezakova; J.C.M. Pires; F.G. Martins; M.C. Pereira; M.C. Alvim-Ferraz (863-872).
Tobacco smoke is one of the greatest sources of indoor particles, which has been linked with serious health effects. Consequently, there has been a widespread interest in analysing tobacco related indoor particulate matter (PM). Nevertheless, the majority of performed studies focused on bulk chemical composition of tobacco related PM, but the knowledge of individual tobacco smoke particles is still limited. Therefore, more information on PM should be provided, namely concerning morphological and chemical characterisation of individual particles. Aiming to further understand the impact of tobacco smoke on human health, this work studied the influence of tobacco smoke on chemical and morphological characteristics of PM10 and PM2.5, collected at one site influenced by smoking and at one reference (non-smoking) site. Chemical and morphological characteristics of 4000 individual particles were determined by Scanning Electron Microscopy (SEM) combined with X-ray microanalysis (by Energy Dispersive Spectrometer – EDS). Cluster analysis (CA) was used to classify different particle groups that occurred in PM, aiming the identification of the respective emission sources. The results showed that tobacco smoke influenced the characteristics of both fine and coarse particles, this influence being stronger for fine fraction. The abundance of particles associated with tobacco smoke was 27% and 5% for PM2.5 and PM2.5–10, respectively; as expected, those particles were not identified in PM2.5 and PM2.5–10 of the reference (non-smoking) site. The results showed that at both sites PM was also influenced by outdoor sources. For PM2.5–10, outdoor particles essentially originated from natural sources accounting for 35% and 15% at the smoking and reference sites, respectively. For PM2.5, outdoor particles account for 38% and 29% at the smoking and reference sites, respectively; these particles showed considerable contribution (13% and 17%) from anthropogenic sources (mainly from traffic emissions). In general SEM–EDS showed to be a useful technique to complement characterisation of PM2.5 and PM2.5–10, and to identify the respective emission sources.► Tobacco smoke influenced levels and characteristics of fine and coarse particles. ► Compositions of both PM were significantly different, tobacco smoke contributed mainly to PM2.5. ► Indoor particles were also influenced by materials and age of buildings, and by outdoor sources. ► The general conclusions obtained by PIXE and SEM-EDS were consistent.
Keywords: PM10; PM2.5; SEM–EDS; Tobacco smoke; Cluster analysis;
Temporal trends in sulphate concentrations at European sites and relationships to sulphur dioxide by Alan M. Jones; Roy M. Harrison (873-882).
Temporal trends in sulphate data taken from UK networks from the period 2001–2008 have been examined, together with trends in relevant precursor gases. In general, trends in sulphate are small, and the data sets are not of sufficient length to determine the direction of trend with confidence. Since relatively short periods of high or low concentration near to the start or finish of the period have a disproportionate influence, the choice of period over which the trend is calculated is crucial to the outcome. All six sites showed a significant reducing trend in sulphur dioxide, while ammonia data appear to be affected by sampling problems and site relocations and clear trends are not apparent. Data relating annual mean airborne concentrations of sulphur dioxide and sulphate from several countries can be related through a relationship of the form: χ [SO4 2−] = a·χ [SO2]b + c in which a, b and c are constants and χ represents concentrations. While constant b remains the same for different countries, a and c can change in ways that appear to relate to either the distance from major SO2 sources, or the oxidising capacity of the atmosphere. Using the relationship between SO4 2− and SO2 derived from UK sites allows estimation of the reduction in sulphur dioxide emissions affecting UK sites needed to reduce sulphate concentrations by 1 μg m−3. This is 55% and 49% for Harwell and North Kensington respectively.► Trends in sulphate from 2001–2008 are small and variable between sites. ► Trends in sulphur dioxide are consistently downward. ► The SO4 2−:SO2 relationship is curvilinear. ► Around 50% reduction in SO2 emissions will deliver 1 μg m−3 reduction in SO4 2− in the southern UK.
Keywords: Sulphate trends; Sulphur dioxide; Abatement; Non-linearity;
Urban NO2 and NO pollution in relation to the North Atlantic Oscillation NAO by M. Grundström; H.W. Linderholm; J. Klingberg; H. Pleijel (883-888).
The North Atlantic Oscillation (NAO), a measure of the strength of the zonal wind across the North Atlantic Ocean, strongly influences weather conditions in NW Europe, e.g. temperature, precipitation and wind, especially during winter. It was hypothesised that elevated concentrations of nitrogen oxides in Gothenburg would be enhanced during negative NAO index (NAOI) conditions, representing more anticyclonic weather situations and thus leading to limited air mixing in the urban atmosphere, than situations with NAOI > 0. Hourly wintertime (December–February) concentrations (1997–2006) of NO2, NO, air pressure, temperature and wind direction from an urban rooftop (30 m above street level) in the centre of the City of Gothenburg were analysed in relation to NAOI. Air pressure, the average concentration of nitrogen oxides (NOx = NO2 + NO), as well as the fraction of hourly NO2 and NO concentrations exceeding 90 μg m−3 and the fraction of daily NO concentrations exceeding 60 μg m−3, were significantly and negatively related to NAOI. Air temperature was positively correlated with NAOI. Southerly and westerly winds were more common in months with positive NAOI, while easterly and northerly winds were overrepresented in months with negative NAOI. High pollution concentrations dominantly occurred in situations with northerly and easterly wind directions. High NO2 and NO concentrations were associated with negative NAOI, especially in the morning when the traffic rush coincided with restricted air mixing. Over the ten-year period there were trends for more negative NAOI and increased time fractions with hourly NO2 concentrations exceeding 90 μg m−3. The conclusion of this study is that a climate shift towards higher or lower NAOI has the potential to significantly influence urban air pollution in North-West Europe, and thus the possibility to reach air quality standards, even if emissions remain constant.► The North Atlantic Oscillation affected air pollution in Gothenburg 1997–2006. ► NOx and air pressure were negatively related to North Atlantic Oscillation Index. ► Air temperature was positively related to the North Atlantic Oscillation Index. ► The relationship of NO/NO2 was most pronounced in the morning rush. ► Highest pollution found in wind from north and east, more common in negative NAOI.
Keywords: North Atlantic Oscillation; NO2; NOx; Urban pollution; Climate; Gothenburg;
Modelling reacting localized air pollution using Computational Fluid Dynamics (CFD) by A.A. Karim; P.F. Nolan (889-895).
A Computational Fluid Dynamics (CFD) approach is used to model reacting NO2 dispersion of vehicle pollutants released from a dual carriageway in Maidstone, UK. The simulations are carried out over the course of one full day during January, 2008.The developed CFD model utilizes a modified k-ɛ turbulence model and Arrhenius reaction kinetics with source terms for the reactions which include a photo-stationary set with peroxy radicals. An approach is taken whereby the reactions are solved specific to the rush hour period corresponding to the availability of certain hydrocarbons released from the vehicles.The results of the simulation are compared with field measurements taken at the site which is made up of several, different sized buildings on varying terrain in Maidstone UK. The predictions and field measurements are considered over a 12 h period with averaged hourly results.It was found that the reactive pollutant approach greatly improves the predictions as compared to the experiments. Furthermore the effect of peroxy radicals during rush hour periods is found to be a major disturbance to the photo-stationary set and its inclusion improved the predictions further.► Comparisons of CFD and experimental pollutant concentrations. ► Reactive localized pollutants included in the CFD study. ► Photo-stationary reactions insufficient to predict NO2. ► Results significantly improved by modelling Peroxy Radicals.
Keywords: Reactions; CFD; Air pollution; Modelling; ANSYS Fluent;
Five years of carbon dioxide fluxes measurements in a highly vegetated suburban area by Ben Crawford; C.S.B. Grimmond; Andreas Christen (896-905).
Suburban areas continue to grow rapidly and are potentially an important land-use category for anthropogenic carbon-dioxide (CO2) emissions. Here eddy covariance techniques are used to obtain ecosystem-scale measurements of CO2 fluxes (F C) from a suburban area of Baltimore, Maryland, USA (2002–2006). These are among the first multi-year measurements of F C in a suburban area. The study area is characterized by low population density (1500 inhabitants km−2) and abundant vegetation (67.4% vegetation land-cover). F C is correlated with photosynthetic active radiation (PAR), soil temperature, and wind direction. Missing hourly F C is gap-filled using empirical relations between F C, PAR, and soil temperature. Diurnal patterns show net CO2 emissions to the atmosphere during winter and net CO2 uptake by the surface during summer daytime hours (summer daily total is −1.25 g C m−2 d−1). Despite the large amount of vegetation the suburban area is a net CO2 source of 361 g C m−2 y−1 on average.► Eddy covariance measurements of CO2 fluxes (F C) for suburban Baltimore (2002–06). ► Among the first multi-year measurements of F C in a suburban area. ► Area: low population (1500 inhabitants km−2) and abundant vegetation (67.4%). ► Source of CO2 (winter) and sink in summer (summer daily total −1.25 g C m−2 d−1). ► Despite large amount of vegetation: net source of CO2 (361 g C m−2 y−1 mean).
Keywords: Carbon dioxide; CO2; Suburban; Urban; Respiration; Photosynthesis; Fossil fuel emissions; Carbon cycling;
Ion composition of coarse and fine particles in Iasi, north-eastern Romania: Implications for aerosols chemistry in the area by Cecilia Arsene; Romeo Iulian Olariu; Pavlos Zarmpas; Maria Kanakidou; Nikolaos Mihalopoulos (906-916).
Atmospheric loadings of the aerosols coarse (particles of AED > 1.5 μm) and fine fractions (particles of AED < 1.5 μm) were determined in Iasi, north-eastern Romania from January 2007 to March 2008. Concentrations of water soluble ions (SO4 2−, NO3 −, Cl−, C2O4 2−, NH4 +, K+, Na+, Ca2+ and Mg2+) were measured using ion chromatography (IC). In the coarse particles, calcium and carbonate are the main ionic constituents (∼65%), whereas in the fine particles SO4 2−, NO3 −, Cl− and NH4 + are the most abundant. Temperature and relative humidity (RH) associated with increased concentrations of specific ions might be the main factors controlling the aerosol chemistry at the investigated site. From August 2007 to March 2008 high RH (as high as 80% for about 82% of the investigated period) was prevailing in Iasi and the collected particles were expected to have deliquesced and form an internal mixture. We found that in fine particles ammonium nitrate (NH4NO3) is important especially under conditions of NH4 +/SO4 2− ratio higher than 1.5 and high RH (RH above deliquescence of NH4Cl, NH4NO3 and (NH4)2SO4). At the investigated site large ammonium artifacts may occur due to inter-particle interaction especially under favorable meteorological conditions. A methodology for estimating the artifact free ambient ammonium concentration is proposed for filter pack sampling data of deliquesced particles. Nitrate and sulfate ions in coarse particles are probably formed via reactions of nitric and sulfuric acid with calcium carbonate and sodium chloride which during specific seasons are abundant at the investigated site. In the fine mode sulfate concentration maximized during summer (due to enhanced photochemistry) and winter (due to high concentration of SO2 emitted from coal burning). Natural contributions, dust or sea-salt related, prevail mainly in the coarse particles. From May 2007 to August 2007, when air masses originated mainly from Black Sea, in the coarse particles an nss-Cl/Na ratio of 1.11 was measured. Elevated levels of chloride in fine particles have been attributed to waste burning in the proximity of the investigated site or to NaCl salt widely spread on roads during winter. Considering the importance of atmospheric aerosols, this study may constitute a reference point for Eastern Europe.► Reference point in atmospheric aerosols measurements for Eastern Europe. ► First measurements on variation of the aerosols ionic composition at Iasi, Romania. ► Complex aerosol chemistry in the area (derived by the composition and meteorology). ► Artifact free ambient ammonium estimated in a deliquesced particles environment. ► Anthropogenic tracers in the fine fraction; natural ones in the coarse fraction.
Keywords: Aerosols; Deliquesced particles; Ionic composition; Chemistry; Iasi; Romania;
Heterogeneous reactions between NO2 and anthracene adsorbed on SiO2 and MgO by Jinzhu Ma; Yongchun Liu; Hong He (917-924).
The heterogeneous reactions of NO2 with anthracene adsorbed on SiO2 and MgO were investigated under dark conditions at 298 K using DRIFTS, GCMS, and UV–Vis. The pseudo-first-order rate constants of anthracene on SiO2 and MgO were obtained by fitting the exponential decay of adsorbed PAH concentrations versus reaction time. The reaction on SiO2 was almost two times faster than on MgO when the concentration of NO2 was 3.69 × 1012 molecules cm−3. Both 9-nitroanthracene and 9,10-anthraquinone were the products of the nitration of anthracene adsorbed on SiO2 whereas 9,10-anthraquinone was the only product formed by NO2 reaction with anthracene adsorbed on MgO. These results suggest that mineral oxides not only control the reaction kinetics of PAHs with NO2 but also alter the reaction pathway for the heterogeneous reaction of PAHs with NO2. The difference in the heterogeneous reactivity of NO2 with anthracene adsorbed on SiO2 and MgO was ascribed to the formation of HNO3 on SiO2, which can catalyze the nitration of PAHs by NO2. Due to the formation of nitro-anthracene and oxy-anthracene, the heterogeneous reactions of NO2 with anthracene also altered the optical properties of the mineral oxides on which anthracene were adsorbed.► Heterogeneous reaction of anthracene with NO2 depends on the nature of substrate. ► Reactions rate of anthracene with NO2 on SiO2 is higher than that on MgO. ► HNO3 formed on SiO2 leads to higher reactivity and formation of 9-nitroanthracene.
Keywords: PAH; Anthracene; Mineral oxides; NO2; Kinetics; Oxidation products;
Particle size distributions of metal and non-metal elements in an urban near-highway environment by Michael D. Hays; Seung-Hyun Cho; Richard Baldauf; James J. Schauer; Martin Shafer (925-934).
Determination of the size-resolved elemental composition of near-highway particulate matter (PM) is important due to the health and environmental risks it poses. In the current study, twelve 24 h PM samples were collected (in July–August 2006) using a low-pressure impactor positioned 20 m from a Raleigh, North Carolina interstate. The interstate supported ∼125,000 vehicles/d, the majority of which were light-duty gasoline passenger vehicles. The overall near-highway PM mass size distribution was trimodal with a major accumulation mode peak at 500–800 nm. PM mass levels reflected daily traffic activity, while mean near-highway PM10 (33 ± 7.5 μg m−3), PM2.5 (29 ± 6.8 μg m−3), and PM0.1 (1.4 ± 0.3 μg m−3) mass levels varied less than 24% over the two week sampling period. The elemental composition of the impactor-collected PM was investigated using magnetic sector inductively coupled plasma-mass spectroscopy (SF-ICPMS). Accumulation mode sulfur (7 ± 4% w/w) was the major inorganic constituent detected at the near-highway site followed by coarse mode group IA and IIA elements likely from re-suspension of crustal matter. As expected, elements regularly detected in asphalt, vehicle, catalyst (e.g., Pt, Rh, and Pd), brake, and tire wear (e.g., Cu and Sb) were also found in the near highway PM. Maximum concentrations of the platinum group, rare earth, and common brake and tire wear elements were observed at d 50 = 1–2 μm, d 50 = 1–4 μm, and d 50 ≥ 1–4 μm, respectively. Ten of the eleven metals listed as EPA air toxics (Mn, Cr, Sb, Ni, Pb, As, Co, Cd, Se, and Be) were detected in each PM size fraction but were generally enriched in PM0.1. Several biologically antagonistic suites of metals (Cd, Cu, and V) were found in multiple PM size modes. Some of these metals showed erratic size distributions with daily changes in enrichment (e.g., Ni, Zn, Cd, As, and Cu) and particle size, suggesting a variety of emissions and metal exposure scenarios occurring in the near-highway environment.► Daily changes in metal (Ni, Zn, Co, and Cr) size distributions and proportions in particle matter suggest a variety of metal exposure scenarios are possible in the near-highway environment. ► Hazardous metal air pollutants in the near-highway atmosphere tend to concentrate in ultrafine particles. ► Pb and As levels are well correlated, unimodally distributed, and show traffic-influenced concentration changes in the near-highway environment.
Keywords: Particulate matter; ICP-MS; Metals; Size distribution; Near-road emissions;
Landfills as sources of polyfluorinated compounds, polybrominated diphenyl ethers and musk fragrances to ambient air by Ingo Weinberg; Annekatrin Dreyer; Ralf Ebinghaus (935-941).
In order to investigate landfills as sources of polyfluorinated compounds (PFCs), polybrominated diphenyl ethers (PBDEs) and synthetic musk fragrances to the atmosphere, air samples were simultaneously taken at two landfills (one active and one closed) and two reference sites using high volume air samplers. Contaminants were accumulated on glass fiber filters (particle phase) and PUF/XAD-2/PUF cartridges (gas phase), extracted by methyl-tert butyl ether/acetone (neutral PFCs), methanol (ionic PFCs) or hexane/acetone (PBDEs, musk fragrances), and detected by GC–MS (neutral PFCs, PBDEs, musk fragrances) or HPLC–MS/MS (ionic PFCs). Total concentrations ranged from 84 to 706 pg m−3 (volatile PFCs, gas phase), from <MQL to 42 pg m−3 (ionic PFCs, particle phase), from 204 to 1963 pg m−3 (synthetic musk fragrances, gas + particle phase) and from 1 to 11 pg m−3 (PBDEs, gas + particle phase). Observed sum concentrations of PFCs and synthetic musk fragrances and partly PBDE concentrations were elevated at landfill sites compared to corresponding reference sites. Concentrations determined at the active landfill were higher than those of the inactive landfill. Overall, landfills can be regarded as a source of synthetic musk fragrances, several PFCs and potentially of PBDEs to ambient air.► Landfills are sources of synthetic musk fragrances to ambient air. ► Landfills are minor sources of PFCs to ambient air (compared to musk fragrances). ► Landfills might be sources of PBDEs to ambient air. ► Active landfills are more significant sources of these contaminants than closed landfills.
Keywords: PFC; PFAS; PBDE; Landfill; Air; Emission; Waste;
Identification and origin of nocturnal ozone maxima at urban and rural areas of Northern Portugal – Influence of horizontal transport by S.I.V. Sousa; M.C.M. Alvim-Ferraz; F.G. Martins (942-956).
Nocturnal ozone maxima have been reported by several authors in different environments. The aim of this study was to evaluate the influence of horizontal transport on the occurrence of nocturnal ozone maxima. Frequency, concentration and time of the nocturnal ozone maxima were investigated during three consecutive years (2005–2007) in two urban and two rural sites of Northern Portugal using hourly ozone concentrations. These concentrations were further related with temperature, relative humidity, wind direction and speed.Results showed that urban sites had frequencies of nocturnal ozone maxima between 40% and 50% and rural sites of 15%. Rural sites were those with higher concentrations being in average 117 ± 35 μg m−3, with minimum and maximum concentrations of, respectively, 51 μg m−3 and 283 μg m−3; information and alert thresholds were exceeded (). At urban sites, the nocturnal ozone maxima occurred most at 5 h and at rural sites at 23 h/24 h. Among the meteorological parameters analysed, wind direction was the only one that had influence on the occurrence of nocturnal O3 maxima. When nocturnal O3 maxima occurred it was possible to observe at the urban sites, prevailing winds from ESE, related with land–sea breezes, meaning that land–sea breeze influenced the occurrence of nocturnal O3 maxima trough the transport of O3 from places where its concentrations were higher. At rural sites similar behaviour has been observed, nevertheless with different wind directions according to meteorological characteristics of the sites; frequent wind directions were from WNW for LO and from the North quadrant for SM. Additionally, between 70% and 99% of the nocturnal O3 maxima for urban and rural sites occurred when there was a shift in the wind direction. Results allowed concluding that horizontal transport might have high importance on the occurrence of those maxima. Nevertheless, other factors, such as vertical transport, may also be important, as have been suggested by other authors.► Monthly frequency of nocturnal O3 maxima is lower at rural than at urban ones. ► Nocturnal O3 maxima occurred in general at 5 h in urban costal sites. ► Nocturnal O3 maxima occurred in general at 23 h in rural sites. ► Nocturnal O3 maxima were related with land–sea breeze system at urban coastal sites. ► Nocturnal O3 maxima were related with regional wind system at rural sites.
Keywords: Ozone; Nocturnal maxima; Horizontal transport; Urban area; Rural area;
Inferring deposition velocities from changes in aerosol size distributions downwind of a roadway by Dongzi Zhu; Hampden D. Kuhns; John A. Gillies; Vicken Etyemezian; Alan W. Gertler; Scott Brown (957-966).
Deposition velocities for particulate matter (PM) from road traffic in the Lake Tahoe basin were estimated with a mass-balance model and measurements using four size-specific PM profilers and meteorological instruments located at 15 m upwind and 5, 30 and 100 m downwind of major highway in the Lake Tahoe basin. Coarse PM (2.5–10 μm) concentration decreased exponentially with downwind distance from the highway. With tall aspen trees barrier, at 30 m and 100 m downwind, the PM10 mass concentrations decreased respectively to 51% and 11% from the observed concentrations at 5 m. Particles with diameters between 0.3 and 0.5 μm show almost a homogeneous distribution across the road indicating the smallest particles are unrelated to a road source. Calculated deposition velocities generally increased with particle size and ranged from <0.1 cm s−1 for particles of 1–2.5 μm diameter to 1.6 cm s−1 for particles >15 μm diameter, which is consistent with the Stokes settling velocities, implying the Stokes settling velocities may represent a reliable lower bound on the deposition rate. The wind speed and direction play important roles in determining the deposition velocities of road traffic induced particles. Higher PM concentrations were observed when strong onshore winds dominated during the daytime coupled with high traffic counts. Between late afternoon and early morning, offshore winds blew traffic induced PM towards the Lake, where they could deposit and impact the water clarity.► Novel deposition velocity measurements were consistent with Stokes settling Vs . ► Coarse PM concentration decreased faster than fine PM with distance from road. ► Night offshore winds blew suspended road dust to Lake Tahoe, impact water clarity.
Keywords: Atmospheric deposition; Fugitive dust; Road dust; Near-source deposition; Vehicle-generated dust;
Assessing the long-range transport of PAH to a sub-Arctic site using positive matrix factorization and potential source contribution function by Uwayemi M. Sofowote; Hayley Hung; Ankit K. Rastogi; John N. Westgate; Patrick F. Deluca; Yushan Su; Brian E. McCarry (967-976).
Gas-phase and particle-phase atmospheric samples collected in a sparsely populated sub-Arctic environment in the Yukon Territory, Canada were analyzed for a wide range of organic pollutants including polycyclic aromatic hydrocarbons (PAH). Receptor modeling using positive matrix factorization (PMF) was applied to a PAH data set from samples collected between August 2007 and December 2008 to afford four factors. These factors were designated as fossil fuel combustion emissions, particle-phase wood combustion emissions, gas-phase wood combustion emissions, and unburned petroleum/petrogenic emissions. The multiple linear regression-derived average contributions of these factors to the total PAH concentrations were 14% for fossil fuel combustion, 6% for particle-phase wood combustion emissions, 46% for gas-phase wood combustion emissions and 34% for petrogenic emissions. When the total PAH concentrations (defined as the sum of twenty-two PAH) and the PMF-modeled PAH concentrations set were compared, the correlation was excellent (R 2 = 0.97). Ten-day back trajectories starting at four different heights were used in a potential source contribution function analysis (PSCF) to assess the potential source regions of these PAH factors. Mapping the computed PSCF values for the four PMF factors revealed different source regions in the northern hemisphere for each PMF factor. Atmospheric transport of PAH occurred from both relatively short and long distances with both continental (North American) and trans-oceanic (Asian) sources contributing significantly to the total PAH. This study provides evidence of the transport of fossil fuel and wood combustion emissions from Asia, continental North America and northern Europe to sub-Arctic Canada (and by extension to the Canadian Arctic) primarily during cooler (fall-winter) months. This study demonstrates for the first time that the combined PMF-PSCF methodology can be used to identify geographically-disperse PAH source contributors on a hemispherical scale.► Identification of four PAH factors impacting a sub-Arctic site with PMF. ► Use of multilinear regression to generate time series of PMF factor contributions. ► Mapping of factors with back trajectories & potential source contribution function.
Keywords: Polycyclic aromatic hydrocarbons; Positive matrix factorization; Potential source contribution function; Long-range transport; Back trajectories; Arctic haze;
Methyl halide and chloroform emissions from a subsiding Sacramento–San Joaquin Delta island converted to rice fields by M.A.H. Khan; R.C. Rhew; M.E. Whelan; K. Zhou; S.J. Deverel (977-985).
Net fluxes of methyl halides and chloroform were measured from recently converted rice fields on Twitchell Island, California, using field- and laboratory-based incubations. A stable isotope tracer method was used to demonstrate that the net emissions of CH3Cl and CH3Br during the growing season were predominantly the result of large gross production rates, with gross consumption rates being relatively minor. In agreement with prior studies, the production rates for methyl halides differed significantly at different rice plant growth phases. The Twitchell Island rice field, however, had production rates of CH3Cl during the growth phases that were higher than rates reported at commercial rice fields, presumably because of higher soil chloride concentrations. Laboratory soil incubations showed that the non-flooded rice field soils acted as a small net sink for CH3Cl and as small net sources for CH3Br, CH3I and CHCl3. Despite the higher CH3Cl emissions during the growing season, the overall emissions of halomethanes from the conversion of all potential islands in the San Joaquin Delta to rice paddies is predicted to be an insignificant source of halomethanes.► The conversion of delta islands to rice paddies will increase halomethane emissions. ► Methyl chloride emissions are enhanced in these high salinity soils. ► Gross production rates are highly variable over course of season. ► This land use change has a negligible impact on the atmospheric halomethane source.
Keywords: Twitchell island; Rice paddies; Rice growth phase; Methyl halides; Chloroform;
Primary NO2 emissions and their role in the development of NO2 concentrations in a traffic environment by Pia Anttila; Juha-Pekka Tuovinen; Jarkko V. Niemi (986-992).
An assessment of the formation of NO2 concentrations in heavily traffic-influenced environments in Helsinki, Finland was carried out. The proportion of primary NO2 emissions from road traffic was estimated using a statistical model for the relationship between the mixing ratios of nitrogen oxides (NO + NO2) and total oxidant (O3 + NO2) measured in 1994–2009. Based on this analysis, a quantitative estimate was derived for the relative importance of the primary NO2 emissions, ambient NO–NO2–O3 equilibrium and background concentrations in the observed NO2 concentrations. The proportion of primary NO2 in the vehicular NO x emissions increased from below 10% in the 1990s to about 20% in 2009, with a more distinctive increase during the most recent years. This development was related to the changes in the proportion of diesel-powered passenger cars in Finland. Between 1994 and 2004, the photochemical NO-to-NO2 conversion comprised on average 51% of the mean NO2 concentration, while the primary NO2 emissions contributed 31%. The role of the primary NO2 emissions was limited by the steeply-decreasing total NO x emissions. More recent data (2005–2009) yielded higher primary NO2 emission fractions (15 –21%), with a clearly increasing trend. As a result, the contribution of chemical conversion steadily decreased from 54% in 2005 to 43% in 2009, while that of the primary NO2 emissions increased from 32 to 44%. In order not to exceed in future the annual limit of NO2 concentration, set by the European Union, in the busiest street canyons in downtown Helsinki, the primary NO2 emissions need to be addressed alongside the total NO x emissions.► The proportion of primary NO2 in the vehicular NO x emissions were about 20% in 2009. ► In 2009 the contribution of primary NO2 emissions in the observed NO2 concentrations was 44%. ► The primary NO2 emissions need to be regulated alongside the total NO x emissions.
Keywords: Nitrogen oxides; Vehicle exhaust emissions; Urban NO2 concentrations; NO–NO2–O3 equilibrium; Total oxidant model; Limit values; Helsinki; Finland;
A new method for evaluating regional air quality forecasts by H.F. Dacre (993-1002).
A Kriging interpolation method is combined with an object-based evaluation measure to assess the ability of the UK Met Office’s dispersion and weather prediction models to predict the evolution of a plume of tracer as it was transported across Europe. The object-based evaluation method, SAL, considers aspects of the Structure, Amplitude and Location of the pollutant field. The SAL method is able to quantify errors in the predicted size and shape of the pollutant plume, through the structure component, the over- or under-prediction of the pollutant concentrations, through the amplitude component, and the position of the pollutant plume, through the location component. The quantitative results of the SAL evaluation are similar for both models and close to a subjective visual inspection of the predictions. A negative structure component for both models, throughout the entire 60 h plume dispersion simulation, indicates that the modelled plumes are too small and/or too peaked compared to the observed plume at all times. The amplitude component for both models is strongly positive at the start of the simulation, indicating that surface concentrations are over-predicted by both models for the first 24 h, but modelled concentrations are within a factor of 2 of the observations at later times. Finally, for both models, the location component is small for the first 48 h after the start of the tracer release, indicating that the modelled plumes are situated close to the observed plume early on in the simulation, but this plume location error grows at later times. The SAL methodology has also been used to identify differences in the transport of pollution in the dispersion and weather prediction models. The convection scheme in the weather prediction model is found to transport more pollution vertically out of the boundary layer into the free troposphere than the dispersion model convection scheme resulting in lower pollutant concentrations near the surface and hence a better forecast for this case study.► The SAL evaluation method results are close to a visual inspection of the predictions. ► The predicted plume is too small and too peaked compared to the observations at all times. ► Initially the plume concentrations are over-predicted but are comparable at later times. ► The error in the location of the predicted plume increases with time. ► The NWP convection scheme transports more pollution vertically than the dispersion model.
Keywords: Pollution transport; Unified Model; NAME dispersion model; Feature-based evaluation; ETEX; SAL;
Free and combined amino acids in marine background atmospheric aerosols over the Eastern Mediterranean by Manolis Mandalakis; Maria Apostolaki; Thrasivoulos Tziaras; Paraskevi Polymenakou; Euripides G. Stephanou (1003-1009).
During a six-week intensive field campaign at a background marine site of the Eastern Mediterranean, consecutive 24-h air samples were collected and analyzed for combined (CAA) and free amino acids (FAA), as well as for key chemical characteristics of aerosols. The total concentration of CAA (719 ± 326 pmol m−3) was on average four times higher than that of FAA (172 ± 147 pmol m−3), while glycine was the most abundant compound detected in both FAA and CAA. Back-trajectory analysis demonstrated that the geographical origin of the air masses did not have a significant influence on the atmospheric levels of amino acids. Wind speed was found to be the most important meteorological factor and it exhibited a negative correlation with both FAA and CAA. Moreover, FAA and CAA concentrations showed a more pronounced correlation with water-soluble organic carbon (WSOC) than elemental carbon. On average, FAA and CAA accounted for 0.3 ± 0.2% and 1.8 ± 0.8% of WSOC, respectively. The levels of anionic surfactants determined as methylene blue active substances did not show any positive correlation with CAA, while the corresponding correlation with FAA was only of marginal significance. The total protein concentration measured by NanoOrange assay was six times higher compared to that measured through CAA. It is suggested that the results from the application of commercially available protein quantitation kits should always be considered with caution, as these are more prone to matrix-related interferences.► Free and combined amino acids occur in the Eastern Mediterranean marine atmosphere. ► The concentration of combined amino acids is higher than that of free ones. ► The origin of the air masses doesn’t influence the atmospheric levels of amino acids. ► Amino acid concentrations are correlated with water-soluble organic carbon.
Keywords: Marine aerosols; Mediterranean Sea; Amino acids; Proteinaceous material; Water-soluble organic carbon;
Decadal variations of rainwater formic and acetic acid concentrations in Wilmington, NC, USA by Joan D. Willey; Donna A. Glinski; Melissa Southwell; Michael S. Long; G. Brooks Avery; Robert J. Kieber (1010-1014).
Concentrations of formic and acetic acid from January 2008 through March 2009 were compared to two previous studies at this location (conducted in 1987–1990 and 1996–1998) in order to quantify the extent to which temporal changes in DOC and pH can be explained by changes in these organic acids. The volume weighted 2008 formic and acetic acid concentrations (5.6 and 2.6 μM respectively) have decreased dramatically compared with those observed during the 1996–1998 study (9.9 and 7.3 μM) and are also lower than concentrations observed in the 1987–1990 study (7.4 and 3.6 μM). Changes in formic and acetic acids between 1996–97 and 2008 can account for approximately 50% of the DOC change and 40% of the H+ change in rainwater over this same time period. These changes are most pronounced during the growing season, which is also the tourist and high traffic season at this location. Determining causation of these changes is difficult due to multiple biogenic and anthropogenic sources. However, the ratio of formic to acetic acid has also reverted back to a value consistent with reduced vehicular emissions, possibly related to the introduction of improved emission control technology including the use of reformulated gasoline in the late 1990’s. Long term monitoring of seasonal, annual, and decadal trends will be of critical importance for evaluating the effects of future changes to atmospheric inputs such as the increased use of ethanol and other alternative fuels.► Formic and acetic acid concentrations in coastal NC rain decreased over 10 years. ► The ratio of formic to acetic acid has increased. ► Changes are most pronounced during the growing season. ► Contribution to acidity from these two acids (25%) remained constant for 20 years. ► Formic and acetic acid contribute less to DOC now than in the past.
Keywords: Acetic acid; Formic acid; Organic acids; Rainwater;
Gross alpha, gross beta activities and gamma emitting radionuclides composition of rainwater samples and deposition to ground by C. Dueñas; M.C. Fernández; E. Gordo; S. Cañete; M. Pérez (1015-1024).
The radiometric composition of bulk deposition samples, collected monthly in a 5 year period (1 January 2005 until 31 December 2009) at a site located 30 m a.s.l in Málaga (4°28′ 8″W; 36° 43′40″N), are analysed in this paper. Measurement of gross alpha, gross beta, artificial and natural radionuclide activity concentrations were carried out in 60 bulk deposition samples. We analysed the time series of gross alpha, gross beta 7Be, 210Pb and 40K. The specific activities of gross alpha and gross beta measured in bulk deposition material are in the range from 0.012–0.32 and 0.045–1.81 Bq l−1 and theirs mean values are: 0.11 and 0.59 Bq l−1 respectively. The activity values of 7Be and 210Pb are in the range from 0.65–8.3 and 0.05–1.32 Bq l−1 with mean values of 2.5 and 0.41 Bq l−1 respectively. The highest specific activities of 40K in bulk deposition material were recorded in connection with high altitude Saharan dust intrusion. The time variations of the different radionuclide concentrations have been discussed in relation with various meteorological factors and the mean values have been compared to those published in recent literature for other sites located at different latitudes. To study the deposition, monthly deposition data from a funnel collector were compared from 2005 to 2009.The monthly range in deposition fluxes for gross alpha varied widely (0.40–11 Bq m−2 month−1) and the average annual deposition is 21 Bq m−2 y−1. The monthly fluxes for gross beta varied (1.3–33.8 Bq m−2 month−1) and the average annual deposition is approximately 120 Bq m−2 y−1. The total annual deposition fluxes of 210Pb varied between 64.9 and 160.8 Bq m−2 y−1 with a mean of 120 Bq m−2 y−1. The annual 7Be depositional flux varied between 432 and 1204 Bq m−2 y−1 with a mean of 676 Bq m−2 y−1. Observed seasonal variations of deposition data are explained in terms of different environmental features. The atmospheric deposition fluxes of 7Be and 210Pb were moderately well correlated with rainfall (r 2 of 0.72 and 0.76 respectively) and well correlated one with the other (r 2 of 0.79).► The radionuclides of bulk deposition over 5 years at Malaga were analysed. ► The concentrations of 40K in bulk deposition were connected with Sahara intrusion. ► The radionuclides in rainwater show seasonal variations. ► The atmospheric fluxes of 7Be and 210Pb were well correlated with rainfall.
Keywords: Rainwater; Radionuclides; Depositional flux; Gross alpha; Gross beta; 7Be; 210Pb; Mediterranean region;
Physicochemical and oxidative characteristics of semi-volatile components of quasi-ultrafine particles in an urban atmosphere by Vishal Verma; Payam Pakbin; Ka Lam Cheung; Arthur K. Cho; James J. Schauer; Martin M. Shafer; Michael T. Kleinman; Constantinos Sioutas (1025-1033).
This study examines the physicochemical and redox profiles of atmospheric semi-volatile compounds to evaluate their contribution to the oxidative potential of ambient particulate matter (PM). Concentrated ambient and thermodenuded quasi-ultrafine particles (<180 nm) were collected using the versatile aerosol concentration enrichment system (VACES) at an urban site near downtown Los Angeles. A thermodenuder (TD) was used to selectively remove the semi-volatile components of these aerosols over the temperature range of 50–200 °C. The oxidative potential of PM was measured by means of the DTT (dithiothreitol) assay. Detailed chemical analyses of PM samples, including organic and elemental carbon, water soluble elements, inorganic ions and PAHs (polycyclic aromatic hydrocarbons), were conducted to quantify the volatility profiles of different PM species, and also to investigate their effect on measured oxidative potential. Refractory constituents, such as metals and elemental carbon, were marginally affected by heating, while labile species such as organic carbon and PAHs showed progressive loss in concentration with increase in TD temperature. The DTT-measured oxidative potential of PM was significantly decreased as the aerosols were heated and their semi-volatile components were progressively removed (42 ± 5%, 47 ± 8% and 66 ± 6% decrease at 50, 100 and 200 °C, respectively). Thus, semi-volatile compounds present in quasi-ultrafine urban aerosols constitute a significant fraction of PM oxidative potential, which is associated with the cellular generation of reactive oxygen species. Regression analysis performed between chemical constituents and DTT activity showed that the oxidative potential was strongly correlated with organic carbon and PAHs (R ≥ 0.80; p ≤ 0.05).
Keywords: Semi-volatile compounds; Oxidative potential; DTT assay; Quasi-ultrafine particles;
Pulmonary toxicity study in rats with PM10 and PM2.5: Differential responses related to scale and composition by Wei Zhang; Tian Lei; Zhi-Qing Lin; Hua-Shan Zhang; Dan-Feng Yang; Zhu-Ge Xi; Jian-Hua Chen; Wei Wang (1034-1041).
To study the pollution of atmospheric particles at winter in Beijing and compare the lung toxicity which induced by particle samples from different sampling sites.We collected samples from two sampling points during the winter for toxicity testing and chemical analysis. Wistar rats were administered with particles by intratracheal instillation. After exposure, biochemically index, esimmunity indexes, histopathology and DNA damage were detected in rat pulmonary cells.The elements with enrichment factors (EF) larger than 10 were As, Cd, Cu, Zn, S and Pb in the four experiment groups. The priority control of the total concentration of polycyclic aromatic hydrocarbons (PAHs) in PM10 and PM2.5 of Near-traffic source was much higher than that of Far-traffic source, it demonstrated that near the traffic source of PAHs pollution was heavier than that of Far-traffic source, as it was close to main roads Beiyuan Road, motor vehicle emissions were much higher. The pathology of lung showed that the degree of inflammation was increased with the particle diameter minished, it was the same as the detection of biochemical parameters such as lactate dehydrogenase (LDH), Total antioxidant status(T-AOC) and total protein (TP) in BALF and inflammation cytokine(interleukin-1, interleukin-6 and tumor necrosis factor-alpha) in lung homogenate. The indexes of DNA damage including the content of DNA and Olive empennage of PM2.5 were significant higher than that of PM10 at the same surveillance point (P < 0.05), near-traffic particles were higher than the far-traffic particles at the same diameter, (P < 0.05).Near-traffic area particles had certain pollution at winter in Beijing. Meanwhile, atmospheric particulate matters on lung toxicity were related to the particles size and distance related sites which were exposed: smaller size, more toxicity; nearer from traffic, more toxicity.► We found that traffic-related PM had certain pollution at winter in Beijing. ► Biochemically index, esimmunity indexe, histopathology and DNA damage were detected. ► The lung toxicity of PM were related to the particles size and distribution.
Keywords: Traffic-related PM; PAHs; EF; Pulmonary toxicity; Oxidative damage; Comet assay;
Estimation of spatial apportionment of greenhouse gas emissions for the UK using boundary layer measurements and inverse modelling technique by D. Polson; D. Fowler; E. Nemitz; U. Skiba; A. McDonald; D. Famulari; C. Di Marco; I. Simmons; K. Weston; R. Purvis; H. Coe; A.J. Manning; H. Webster; M. Harrison; D. O’Sullivan; C. Reeves; D. Oram (1042-1049).
A technique is described to independently validate the national emission inventories produced using the methodology of the Intergovernmental Panel on Climate Change (IPCC). A boundary layer budget approach is applied to the United Kingdom and an inverse modelling technique is used to derive total and spatial apportionment of emissions for CO, CO2, CH4, N2O, HFC-134a, HCFC-141b, HCFC-142b and HCFC-22. During the summer of 2005 and September 2006 an aircraft circumnavigating the UK was used to collect data upwind and downwind of the UK coast. The concentration measurements were inverted to produce mapped emissions of the UK. The modelled overall CO flux (2900 ± 107 kt yr−1) and spatial apportionment throughout the UK are remarkably consistent with the official UK NAEI (National Atmospheric Emission Inventory) inventory. The CO2 total emissions (620 ± 105 Mt yr−1) and spatial apportionment are also close to the NAEI. However for N2O and CH4, the estimated annual fluxes, 500 ± 370 kt yr−1 and 3500 (range 0–8000 kt yr−1) respectively, are larger than the NAEI albeit with significant uncertainty. Emissions of four halocarbon compounds were also calculated with total emissions of 3.1 ± 0.4 kt yr−1 for HFC-134a, 0.9 ± 0.6 kt yr−1 for HCFC-141b, 0.56 ± 0.2 kt yr−1 for HCFC-142b and 3.8 ± 1.0 kt yr−1 for HCFC-22 consistent with other published data.► In this study use an independent technique to evaluate the UK national emissions inventories. ► Aircraft measurements of greenhouse gases around the United Kingdom coast and an inverse modelling technique are used to derive total and spatial apportionment of emissions. ► The total and spatial apportionment of CO and CO2 emissions are consistent with the official UK National Atmospheric Emission Inventory. ► The CH4 and N2O estimated annual fluxes are larger than the official UK National Atmospheric Emission Inventory.
Keywords: Emissions inventory; Inverse modelling; Boundary layer budget;
Theoretical evaluation of errors in aerosol optical depth retrievals from ground-based direct-sun measurements due to circumsolar and related effects by Miroslav Kocifaj; Christian A. Gueymard (1050-1058).
Aerosol optical depth (AOD) has a crucial importance for estimating the optical properties of the atmosphere, and is constantly present in optical models of aerosol systems. Any error in aerosol optical depth (∂AOD) has direct and indirect consequences. On the one hand, such errors affect the accuracy of radiative transfer models (thus implying, e.g., potential errors in the evaluation of radiative forcing by aerosols). Additionally, any error in determining AOD is reflected in the retrieved microphysical properties of aerosol particles, which might therefore be inaccurate.Three distinct effects (circumsolar radiation, optical mass, and solar disk’s brightness distribution) affecting ∂AOD are qualified and quantified in the present study. The contribution of circumsolar (CS) radiation to the measured flux density of direct solar radiation has received more attention than the two other effects in the literature. It varies rapidly with meteorological conditions and size distribution of the aerosol particles, but also with instrument field of view. Numerical simulations of the three effects just mentioned were conducted, assuming otherwise “perfect” experimental conditions. The results show that CS is responsible for the largest error in AOD, while the effect of brightness distribution (BD) has only a negligible impact. The optical mass (OM) effect yields negligible errors in AOD generally, but noticeable errors for low sun (within 10° of the horizon). In general, the OM and BD effects result in negative errors in AOD (i.e. the true AOD is smaller than that of the experimental determination), conversely to CS. Although the rapid increase in optical mass at large zenith angles can change the sign of ∂AOD, the CS contribution frequently plays the leading role in ∂AOD. To maximize the accuracy in AOD retrievals, the CS effect should not be ignored. In practice, however, this effect can be difficult to evaluate correctly unless the instantaneous aerosols size distribution is known from, e.g., inversion techniques.
Keywords: Aerosol optical depth; Circumsolar radiation; Light scattering; Sunphotometry; Radiometry; SMARTS;
Isolating the effects of climate change in the variation of secondary inorganic aerosols (SIA) in Europe for the 21st century (1991–2100) by Pedro Jimenez-Guerrero; Juan Jose Gomez-Navarro; Sonia Jerez; Raquel Lorente-Plazas; Juan Andres Garcia-Valero; Juan Pedro Montavez (1059-1063).
The analysis of the influence of future climatic variations on air quality needs of methods that give a space-time display of large atmospheric data related to air pollution. Here a new approach in order to assess the impacts of climate change on the patterns of variation of secondary inorganic aerosols (SIA) over Europe is presented. The most widely used method of analysis (selected time-slices, future-minus-present method) is very sensitive to the chosen control and future periods because of the internal variability of the climate system. In order to overcome this limitation, full transient simulations for the period 1991–2100 under the SRES A2 scenario are analysed by the Empirical Orthogonal Functions (EOFs) methodology in order minimise the uncertainty associated to the internal variability due to the longer time series obtained. The results indicate that the EOF1 accounts for around 30–45% of the total variance for the SIA levels and points out a general increase of its trend over the entire domain (p < 0.005), except in the case of nitrate, whose change signal is not significant (p > 0.1). The correlation between SIA and meteorological parameters indicates that the trends and patterns of variation of aerosols are related to the higher temperature projected for the future climate. It favours the formation of sulphates and ammonium (increasing the concentrations of atmospheric oxidants) and the decomposition of ammonium nitrate, remaining in the gas phase. Further, the decreases in precipitation have a strong effect on the frequency of the washout and therefore in the levels of aerosols. The concentrations of aerosols decrease with increasing precipitation as wet deposition provides the main aerosol sink. The trend from a decreasing mixing height found in several areas of Europe is frequently related to a decrease in precipitation, representing an adding effect for the enhanced future SIA concentrations.► The spatio-temporal patterns of variability for secondary inorganic aerosols (SIA) under a changing climate are determined. ► Full transient simulations for the period 1991–2100 (SRES A2) are analysed by the Empirical Orthogonal Functions (EOFs) methodology. ► The EOFs analysis allows filtering the change signal of SIA and to identify their patterns of variability. ► Climatic change will impact air quality by increasing the mean concentrations of these aerosol components matter in most regions over Europe.
Keywords: Air quality–climate interactions; Regional climate; Climate modelling; Future air quality;