Atmospheric Environment (v.42, #37)

The concentrations of phthalates in settled dust in Bulgarian homes in relation to building characteristic and cleaning habits in the family by Barbara Kolarik; Carl-Gustaf Bornehag; Kiril Naydenov; Jan Sundell; Petra Stavova; Ole Faurskov Nielsen (8553-8559).
Phthalate esters are chemical compounds with a broad range of applications. Recently, we have shown that significantly higher dust concentration of di(2-ethylhexyl) phthalate (DEHP) was found in Bulgarian homes of children with asthma or allergies compared to healthy children. The concentration of DEHP was found to be significantly associated with wheezing in the last 12 months as reported by parents. The objective of the current study was to examine the associations between concentrations of phthalates in settled dust collected in Bulgarian homes and building characteristics and cleaning habits. Dust samples from the child's bedroom were collected in 177 homes and analysed for the content of dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBzP), di-n-octyl phthalate (DnOP) and DEHP. Information on building characteristics and family habits were collected from parental reports in questionnaires and from inspectors' observations in the homes. Significantly higher concentrations of BBzP, DEHP and DnOP in indoor dust were found in homes where polishing agents were used, compared to homes where such products were not used. The highest concentrations of DEHP, BBzP and DnOP were found in homes with the combination of a low frequency of dusting and the use of polish. There was no difference in phthalate concentrations between inspector-observed balatum flooring (PVC or linoleum) and wood flooring as well as between PVC, as determined by Raman spectra, and wood flooring. However, in a sub-group of homes with no use of polish, the concentration of DEHP was higher in homes with inspector-observed balatum compared with wood flooring but the difference was not significant may be due to a too small sample size.
Keywords: Phthalates; PVC flooring; Building characteristic; Raman spectroscopy; Polishing products;

A comprehensive sensitivity analysis of the WRF model for air quality applications over the Iberian Peninsula by Rafael Borge; Vassil Alexandrov; Juan José del Vas; Julio Lumbreras; Encarnacion Rodríguez (8560-8574).
Meteorological inputs play a vital role on regional air quality modelling. An extensive sensitivity analysis of the Weather Research and Forecasting (WRF) model was performed, in the framework of the Integrated Assessment Modelling System for the Iberian Peninsula (SIMCA) project. Up to 23 alternative model configurations, including Planetary Boundary Layer schemes, Microphysics, Land-surface models, Radiation schemes, Sea Surface Temperature and Four-Dimensional Data Assimilation were tested in a 3 km spatial resolution domain. Model results for the most significant meteorological variables, were assessed through a series of common statistics. The physics options identified to produce better results (Yonsei University Planetary Boundary Layer, WRF Single-Moment 6-class microphysics, Noah Land-surface model, Eta Geophysical Fluid Dynamics Laboratory longwave radiation and MM5 shortwave radiation schemes) along with other relevant user settings (time-varying Sea Surface Temperature and combined grid-observational nudging) where included in a “best case” configuration. This setup was tested and found to produce more accurate estimation of temperature, wind and humidity fields at surface level than any other configuration for the two episodes simulated. Planetary Boundary Layer height predictions showed a reasonable agreement with estimations derived from routine atmospheric soundings. Although some seasonal and geographical differences were observed, the model showed an acceptable behaviour overall. Despite being useful to define the most appropriate setup of the WRF model for air quality modelling over the Iberian Peninsula, this study provides a general overview of WRF sensitivity and can constitute a reference for future mesoscale meteorological modelling exercises.
Keywords: Air quality modelling; Meterological modelling; Sensitivity analysis; WRF setup; Iberian Peninsula;

Evidence shows a strong correlation between human mortality/morbidity and atmospheric ultrafine carbon particle (UFCP with aerodynamic diameter <18 nm). Theoretical and experimental studies have attempted to use mass concentration/dose as exposure dosimetry to construct the dose-response relationships. Yet little attention has been given to the problem of using surface area dosimetry in UFCP-related risk assessment. We introduced an integrated risk assessment framework based on surface area dosimetry to estimate the adverse health potential risk exposed to atmospheric UFCP. We used the neutrophil cells elevation effect as adverse health effect endpoint. We reanalyzed the published data of UFCP particle diameter (dp) and associated specific surface area (SSA) to reconstruct their relationship through log-linear regression method. Our results show that smaller particle size (dp  < 51 nm) demonstrated steep slope (ln SSA = 11.0–2.03 ln dp), whereas larger particle size (dp  > 51 nm) was found close to the theoretical relationship (ln SSA = 8.65–1.20 ln dp). We applied the modeled relationships to estimate the surface area doses of human inhaled particles in specific scenarios or subgroups. Our findings show that Adult and Youth subgroups in northern Taiwan region posed the highest potential risk, indicating that the median 10% exceedance risks are 39.6 (95%CI: 36.4–42.9) fold compared to control based on neutrophil cells elevation effect. The result provides a preliminary aspect for discussing the human health adverse effect exposed to atmospheric UFCP for specific groups based on particle surface area dosimetry.
Keywords: Ultrafine carbon particles; Human health; Risk assessment; Surface area dosimetry;

Performance evaluation of an air quality forecast modeling system for a summer and winter season – Photochemical oxidants and their precursors by Chenxia Cai; Christian Hogrefe; Petros Katsafados; George Kallos; Mark Beauharnois; James J. Schwab; Xinrong Ren; William H. Brune; Xianliang Zhou; Yi He; Kenneth L. Demerjian (8585-8599).
The predictions of O3, precursor species and the key transit species from an Air Quality Forecast Modeling System (AQFMS) are evaluated for July 2001 and January 2004 utilizing an extensive measurement data set from the PMTACS-NY “Supersite” program. The AQFMS, consisting of a chemical transport model coupled with a mesoscale meteorological forecasting model, operated routinely over the course of the six-year study. The domain-wide 8-h average O3 predictions in the summer season have an average mean normalized bias (MNB) of 8.6%. The AQFMS captured the day-to-day variations of O3, CO, NO x (NO y ) and SO2 at the Queens College (urban) and Pinnacle State Park (rural) sites during both summer and winter. During July 2001, the linear regressions of CO vs. NO x at Queens College and CO vs. NO y at Pinnacle State Park are in reasonable agreement with observations. However, during January 2004 the slopes of the linear regressions are significantly overestimated suggesting more uncertainties with the winter emission inventories. The Ozone Production Efficiency (OPE) is under predicted by 45% at Pinnacle State Park during July 2001 which may be caused by the underestimation of NO z removal and/or the underestimation of OH concentrations. Concentrations of HONO, a key transient species for OH production are significantly under predicted by the AQFMS indicating deficiencies in the chemical mechanism in the AQFMS. The underestimation of OH concentrations is much more significant during January 2004 which suggests larger uncertainties with chemical mechanism for winter conditions.
Keywords: Air quality forecast model; Ozone; Precursor gases; Hydroxyl radical; Nitrous acid;

A regional scale chemical transport modeling of Asian aerosols with data assimilation of AOD observations using optimal interpolation technique by B. Adhikary; S. Kulkarni; A. Dallura; Y. Tang; T. Chai; L.R. Leung; Y. Qian; C.E. Chung; V. Ramanathan; G.R. Carmichael (8600-8615).
A regional chemical transport model assimilated with monthly mean satellite and ground based aerosol optical depth (AOD) observations was used to produce three dimensional distributions of aerosols throughout Asia for a period of four years. The model was evaluated with daily assimilation of AOD for the month of April 2005. Sulfur Transport dEposition Model (STEM), a regional chemical transport model, was used to simulate aerosol distributions at a resolution of 50 × 50 km with a time interval of 3 h. Monthly mean Moderate Resolution Imaging Spectroradiometer (MODIS) AOD along with AErosol RObotic NETwork (AERONET) AOD was used in an optimal interpolation assimilation scheme to yield regional distributions of aerosols. The MODIS AOD and aerosol fine mode fraction information (where available) were used in the assimilation technique. The daily assimilation of AOD results shows that the optimal interpolation algorithm is able to significantly improve model aerosol mass prediction skills at the two sites in Asia. Sensitivity studies were also conducted with different assimilation parameters on a daily assimilation scale and these results are discussed. The assimilation results of four-year aerosol fields were used to study the spatial and temporal distribution of aerosols in Asia. Two remote sites, Hanimaadhoo and Gosan were chosen as the case studies to study the outflow from the Indian subcontinent and East Asia. Seasonal and vertical structures of the aerosols are presented at these two sites. Positive Matrix Factorization (PMF), a factor analytic method was also used to characterize the source profile and source contribution at these two locations. A three-factor solution was able to explain more than 80% of the variation in the individual species at Hanimaadhoo and 90% variation of aerosol loadings at Gosan. The four-year averaged PMF model results were able to capture the seasonality of anthropogenic and dust loadings at both these locations. In addition, the PMF model identified the differences in the composition of anthropogenic aerosols over Hanimaadhoo and Gosan reflecting the differences in regional emissions. The PMF derived factors could be used as additional constraints for future assimilation studies.
Keywords: Aerosol transport modeling; Data assimilation; Receptor modeling;

Heavy metals from pyrotechnics in New Years Eve snow by Georg Steinhauser; Johannes H. Sterba; Michaela Foster; Friedrich Grass; Max Bichler (8616-8622).
Pyrotechnics and fireworks cause pollution with barium aerosols, which is a result of the utilization of barium nitrate as a combined pyrotechnic oxidizer and coloring agent. In this study, the washing-out of barium-rich aerosols by snowflakes during the New Years Eve celebrations in an Austrian village in the Alps has been investigated. It could be shown that the fireworks caused an increase in the barium concentration in snow of up to a factor of 580 compared to the blank value. An increase of the concentrations of strontium and occasionally arsenic in snow was also observed. The geographic distribution of the pyrotechnic combustion products on this snowy evening was restricted to a relatively small area and even in a very local scale, the variations in the concentrations were remarkable. Post-firework snow from the summits of nearby located mountains was found to be as clean as pre-firework snow. However, snow that was visibly contaminated with smoke residues contained exorbitant concentrations of Ba, K, Sr, and Fe.
Keywords: Snow wash-out; Precipitation; Wet deposition; Scavenging; Barium; Strontium; INAA;

Seasonal PM10 dynamics in Kathmandu Valley by Rupak Kumar Aryal; Byeong-Kyu Lee; Rahul Karki; Anup Gurung; Jaya Kandasamy; Bipin Kumar Pathak; Suman Sharma; Nirita Giri (8623-8633).
Data on ambient PM10 levels from six locations in the Kathmandu Valley recorded by means of continuous sampling using low volume air samplers from October 2002 to March 2007 were used to investigate PM10 concentration dynamics in the valley. Monthly average data of the urban areas, which have much higher concentrations than the rural areas, even exceeded the daily standard level of PM10, in Nepal, 120 μm m−3. Repetitive peaks and troughs each year indicated annual patterns. Monthly average showed seasonal patterns are different between rural area and urban sites. The highest monthly average concentration was observed in February, the end of winter in urban areas where as in rural found in spring, and the lowest concentration was observed in July (monsoon period). The continuous increase in PM10 concentration from December to February in urban areas showed accumulation of PM10 in the ambient air during the wintertime. Rainfall in June and September, during the monsoon period, caused a PM10 concentration decrease, demonstrating that precipitation is effective in removing PM10 from the valley. Cross correlation analyses among the PM10 levels measured simultaneously at the sampling stations showed a poor relationship in winter; however, there were good relationships in the monsoon and post-monsoon seasons. Both the PM10 concentration and the air-mixing environment in the valley were closely associated with the temperature and wind speed.
Keywords: Kathmandu valley; PM10; Seasons; Correlation;

Anti-radon coating for mitigating indoor radon concentration by Grace W.W. Gao; Y.H. Tang; C.M. Tam; X.F. Gao (8634-8639).
Sufficient data has proven that radon and its decay products are the principal noso-genesis to lung and other related cancers. To reduce and control the effects of radon pollution, standards to limit indoor radon concentration have been issued in China and other countries or regions. To echo this, an anti-radon coating has been studied and developed with partial funding support from the Innovation and Technology Fund of the Government of the Hong Kong Special Administrative Region. The coating had been experimented in a newly constructed building where the recorded maximum and average hourly background radon concentrations were recorded at 130,000 Bq m−3 and 100,000 Bq m−3 respectively under a concealed condition. The experimental results from application of the coating have shown an anti-radon efficiency of up to 99.85%, which decreases the indoor radon background concentration down to a safe level in a 72-h measurement. The coating still remains in a good condition currently and effective in anti-radon three years after the application.
Keywords: Anti-radon coating; Indoor radon-emission experiment; Radon background concentration; Environment-protection standard requirement;

This paper is devoted to the study of flow and traffic exhaust dispersion in urban street canyons with avenue-like tree planting. The influence of tree planting with different crown porosity was investigated. Wind tunnel experiments for perpendicular approaching flow showed that avenue-like tree planting cause increases in exhaust concentrations at the leeward wall as tree crowns reduce the vortex found in the outer regions of the tree-free street canyon and the vertically entering volume flow rate at the canyon–roof top interface. This results in less ventilation and consequently larger concentrations in proximity of the leeward wall. At the windward wall, decreases in concentration are due to the upward moving stream in front of the leeward wall which extends farther into the skimming above roof flow and is better mixed. The clean air entrained in front of the windward wall mixes with air inside the street canyon leading to smaller concentrations. Experiments performed in the wind tunnel with different tree crown porosities did not indicate substantial changes in the flow and concentration fields. The porous model crowns investigated behaved almost like impermeable objects when arranged in a sheltered position and wind speeds are relatively small as in the street canyon.The above described experiments have been also investigated by means of numerical simulations with the CFD code FLUENT™, rarely applied to this type of problems. The standard kɛ turbulence model and the Reynolds Stress Model were used for flow while the Eulerian advection diffusion scheme has been used for dispersion. Both models reproduced qualitatively the main aspects found in wind tunnel experiments, even though they underestimated flow velocities. Improvement of CFD dispersion performance was obtained by increasing the diffusivity through the turbulent Schmidt number Sct . Overall we found that the kɛ model failed to capture the complex structure of dispersion process in the presence of tree planting as it would require unphysical low Sct values. On the other hand the RSM turbulence model agreed fairly well with experiments by slightly reducing the standard Sct .The results obtained in this work by combining wind tunnel experiments and CFD based simulations to investigate this novel aspect of research suggest ways to obtain quantitative information for assessment, planning and implementation of exposure mitigation using trees in urban street canyons.
Keywords: Street canyon; Tree planting; Pollutant dispersion; Wind tunnel measurements; CFD simulations; Turbulent Schmidt number;

The impact of forest edge structure on longitudinal patterns of deposition, wind speed, and turbulence by Karen Wuyts; Kris Verheyen; An De Schrijver; Wim M. Cornelis; Donald Gabriels (8651-8660).
The impact of forest edge structure on edge patterns of wind speed, turbulence, and atmospheric deposition was studied by means of a model forest in a wind tunnel. Tests were conducted with eight structure configurations, encompassing combinations of stem densities, crown depths, and edge transitions (steep or gradual edge). Mean wind speed and its standard deviation (as a measure for turbulence) were determined within and at the top of the canopy; deposition was simulated using Cl aerosols. Edge patterns of wind speed, turbulence, and deposition were closely related and were significantly affected by stem density and, particularly, by edge transition. In the dense forests, the edge effect on deposition extended less deeply into the forest than in the sparse forests, so the deposition in the forest edge zone was lowered with 40%. Gradual edges were able to limit the level by which deposition is enhanced at the edge in comparison with the forest interior deposition, and consequently, they reduced the deposition in the forest edge zone with 66%. Even when the deposition on the trees of the gradually ascending vegetation in front of the forest edge was taken into account, gradual edges were still advantageous in comparison with steep edges. A lower crown depth decreased the enhancement of deposition at the edge relative to the interior, but only at steep edges. We conclude that an adjusted layout of forest edges should be able to mitigate the edge effects on atmospheric deposition, through reducing the deposition enhancement at the edge or the penetration depth of the edge effect.
Keywords: Forest edge; Atmospheric deposition; Density; Crown depth; Gradual edge; Wind tunnel;

Identification of factors affecting air pollution by dust aerosol PM10 in Brno City, Czech Republic by Zuzana Hrdličková; Jaroslav Michálek; Miroslav Kolář; Vítězslav Veselý (8661-8673).
The statistical analysis of the observation of dust aerosol PM10 from four monitoring stations of the agglomeration of the city of Brno during a time period from January 1, 1998 until December 30, 2005 is presented. The main meteorological factors affecting air pollution at each station were identified by means of a generalized autoregressive linear model with gamma distribution of the response variable and log-link function. Along with meteorological factors, the influence of the heating season and weekdays on the air pollution was considered. The suggested model can be used for a prediction of the daily mean value of dust aerosol PM10 at a given station using selected factors and their previous values.
Keywords: Dust aerosol PM10; Generalized autoregressive linear model; Gamma distribution; Goodness-of-fit statistic; Anscombe residual;

Model estimate of mercury emission from natural sources in East Asia by Suraj K. Shetty; Che-Jen Lin; David G. Streets; Carey Jang (8674-8685).
East Asia is one of the largest source regions that release mercury into the atmosphere. Although extensive studies have been devoted to estimating the anthropogenic mercury emission, little is known about mercury emission from natural sources in the region. In this study, we adapt the algorithms developed previously, coupled with detailed GIS data and satellite LAI products, to estimate mercury emission from natural sources including vegetation, soil, and water surfaces in an East Asian domain containing 164 × 97 grid cells at a spatial resolution of 36 km. Seasonal simulations were performed to project the annual emission quantity. The simulated emission shows strong diurnal and seasonal variations due to meteorology and vegetation coverage. The annual emission in the form of gaseous elemental mercury (GEM) from the domain in 2001 is estimated to be 834 Mg, with 462 Mg contributed from China. The estimated GEM emission is comparable to the reported anthropogenic emission of 575 ± 261 Mg (56% GEM, 32% reactive gaseous mercury, 12% particulate mercury; Wu, Y., Wang, S., Streets, D.G., Hao, J., Chan, M., Jiang, J., 2006. Trends in anthropogenic mercury emissions in China from 1995 to 2003. Environmental Science & Technology 40, 5312–5318) in China for the year 2001, and dominates the anthropogenic emission during the warm season. Combining the anthropogenic and natural emission estimates, the total mercury emission from China is 776–1298 Mg, with GEM being in the range of 660–1000 Mg. The latter is similar to the GEM emission quantity inferred from aircraft measurement (765 Mg; Friedli, H.R., Radke, L.F., Prescott, R., Li, P., Woo, J.-H., Carmichael, G.R., 2004. Mercury in the atmosphere around Japan, Korea and China as observed during the 2001 ACE Asia field campaign: measurements, distributions, sources, and implications. Journal of Geophysical Research 109, D19 S25) and modeling estimate (1140 Mg; Pan, L., Chai, T., Carmichael, G.R., Tang, Y., Streets, G.G., Woo, J.-H., Friedli, H.R., Radke, L.F., 2007a. Top-down estimate of mercury emissions in China using four-dimensional variational data assimilation. Atmospheric Environment 41, 2804–2819) in China for the year 2001. The estimated natural emission helps explain the gap between the anthropogenic emission estimates based on activity data (e.g., Pacyna, J.M., Pacyna, E., Steenhuisen, F., Wilson, S., 2006. Global anthropogenic mercury emission inventory for 2000. Atmospheric Environment 40, 4048–4063; Wu, Y., Wang, S., Streets, D.G., Hao, J., Chan, M., Jiang, J., 2006. Trends in anthropogenic mercury emissions in China from 1995 to 2003. Environmental Science & Technology 40, 5312–5318) and the emission inferred from field observations (e.g., Jaffe, D., Prestbo, E., Swartzendruber, P., Weiss-Penzias, P., Kato, S., Takami, A., Hatakeyama, S., Kajii, Y., 2005. Export of atmospheric mercury from Asia. Atmospheric Environment 39, 3029–3038; Weiss-Penzias, P., Jaffe, D., Swartzendruber, P., Hafner, W., Chand, D., Prestbo, E., 2007. Quantifying Asian and biomass burning sources of mercury using the Hg/CO ratio in pollution plumes observed at the Mount Bachelor observatory. Atmospheric Environment 41, 4366–4379) in the region.
Keywords: Atmospheric mercury; Emission inventory; Natural/re-emission; Modeling; East Asia;

Characterization of particles from residential wood combustion and modelling of spatial variation in a low-strength emission area by M. Glasius; M. Ketzel; P. Wåhlin; R. Bossi; J. Stubkjær; O. Hertel; F. Palmgren (8686-8697).
There is growing concern regarding particle emissions from residential wood combustion due to the relatively high emission of particles compared to other sources. This study investigates the influence of wood combustion on particle levels and composition in a village residential area (Vindinge ∼2200 inhabitants). To better assess this influence, measurements were carried simultaneously in a background area (Lille Valby). The detached houses in Vindinge were primarily heated by combustion of natural gas and about one fourth used wood combustion for primary or supplementary heating. The local contribution to PM2.5 in the residential area was about 1.2 ± 0.4 μg m−3 (95% confidence interval), corresponding to about 10% of PM2.5 and reaching 2.6 ± 0.4 μg m−3 for the evening period (16:00–23:00) during 24 February–21 March 2005. Average diurnal variations of PM2.5, particle numbers and volume (10–700 nm), and soot indicate traffic as a local source during daytime and wood combustion as a local source during evenings. Levels of particulate polycyclic aromatic hydrocarbons (PAH) and monosaccharide anhydrides (levoglucosan and mannosan, MA) were higher during most evenings in Vindinge compared to the background site. The average concentration for PAH was 10.9 ± 7.1 ng m−3 and 5.9 ± 2.9 ng m−3 (one standard deviation) and for MA 313 ± 237 ng m−3 and 168 ± 89 ng m−3 in the residential and background area, respectively. The average contribution of levoglucosan to PM2.5 was 3.6% in the residential area and 1.7% in the background area.The contribution of PM2.5 from local wood combustion was modelled using a Gaussian plume dispersion model (OML-multi) in order to investigate the suitability of this type of model for estimation of population exposure. The modelled levels were in the range of the measurement results, but evaluation of parameters such as emission factor and combustion activity is recommended for future studies.
Keywords: Aerosol; Wood-stove emissions; Particle concentration; Molecular tracers;

Atmospheric deposition is now well recognised as a major source of both inorganic and organic nitrogen for many aquatic ecosystems. In the present study HPLC was used to determine d and l amino acids in remote Atlantic aerosol samples and surface seawater particulate material. This work provides molecular evidence for both microbial and phytoplankton contributions to the organic nitrogen content of the atmospheric aerosol.Samples of aerosol and surface water particulate material were collected from the Atlantic Ocean during the Atlantic Meridional Transect AMT 12 cruise. Samples were leached with water and the extracts analysed for free amino acids (DFAA) and hydrolysable amino acids (DHAA). The residual (non-leachable) particulate amino acids (PAA) were also determined in each sample. The peptidoglycan derived d-enantiomers of aspartic acid (d-Asp), glutamic acid (d-Glu), serine (d-Ser), and alanine (d-Ala) were found in significant amounts in all dissolved and suspended surface water and aerosol samples. Plant derived d-enantiomers of leucine (d-Leu) and isoleucine (d-Ile) were found mainly in the surface water samples. It is estimated that in the aerosol samples ∼60% of particulate amino acids, ∼55% of leachable combined amino acids and ∼8% of leachable free amino acids derive from bacterial sources. The bacterial contribution to the amino acid inventory of surface water particulate material ranged between 15 and 30% of the different fractions studied.Similarities between the composition of surface particulate material and marine aerosol provide evidence that these systems are coupled and that consequently the concepts of ‘new’ and ‘recycled’ nitrogen may apply across the air–sea interface as well as within ocean waters.
Keywords: Atmospheric aerosol; Surface seawater; Amino acid enantiomers; Peptidoglycan; Organic nitrogen;