| 181. |
- McLachlan, Michael S, et al.
(författare)
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Precipitation scavenging of particle-bound contaminants : A case study of PCDD/Fs
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier Ltd. - 1352-2310 .- 1873-2844. ; 43:38, s. 6084-6090
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Precipitation scavenging of particles is a major mechanism for atmospheric deposition of organic contaminants, but there have been few field studies. We studied precipitation scavenging of PCDD/Fs with the aim of deepening understanding of environmental variables influencing this process. Bulk deposition of PCDD/Fs and their concentrations in ambient air measured at a background site in Sweden were used to calculate precipitation scavenging ratios. Contrary to expectations, increasing scavenging ratios with decreasing degree of chlorination of the PCDD/F congeners were observed when the particle-associated PCDD/F concentrations in air were used for the calculation. This was attributed to differences in temperature and thereby in the gas - particle partitioning of the PCDD/Fs between ground level and clouds where much of the particle scavenging occurs. When the particle-associated PCDD/F concentrations were recalculated for a 10-20 degrees C lower temperature, the scavenging ratios of the different PCDD/F congeners were similar. Hence differences between ground level and in-cloud temperature should be considered when calculating scavenging ratios from field observations and when modeling this process. The scavenging ratios averaged similar to 200 000, with lower values when the particle-associated PCDD/F concentration in air was lower. The soot concentration in air was a good predictor of bulk deposition of PCDD/Fs.
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| 182. |
- Mercer, Laina D., et al.
(författare)
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Comparing universal kriging and land-use regression for predicting concentrations of gaseous oxides of nitrogen (NOx) for the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air)
- 2011
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 45:26, s. 4412-4420
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Tidskriftsartikel (refereegranskat)abstract
- Background: Epidemiological studies that assess the health effects of long-term exposure to ambient air pollution are used to inform public policy. These studies rely on exposure models that use data collected from pollution monitoring sites to predict exposures at subject locations. Land-use regression (LUR) and universal kriging (UK) have been suggested as potential prediction methods. We evaluate these approaches on a dataset including measurements from three seasons in Los Angeles, CA. Methods: The measurements of gaseous oxides of nitrogen (NOx) used in this study are from a "snapshot" sampling campaign that is part of the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). The measurements in Los Angeles were collected during three two-week periods in the summer, autumn, and winter, each with about 150 sites. The design included clusters of monitors on either side of busy roads to capture near-field gradients of traffic-related pollution. LUR and UK prediction models were created using geographic information system (GIS)-based covariates. Selection of covariates was based on 10-fold cross-validated (CV) R-2 and root mean square error (RMSE). Since UK requires specialized software, a computationally simpler two-step procedure was also employed to approximate fitting the UK model using readily available regression and GIS software. Results: UK models consistently performed as well as or better than the analogous LUR models. The best CV R-2 values for season-specific UK models predicting log(NOx) were 0.75, 0.72, and 0.74 (CV RMSE 0.20, 0.17, and 0.15) for summer, autumn, and winter, respectively. The best CV R-2 values for season-specific LUR models predicting log(NOx) were 0.74, 0.60, and 0.67 (CV RMSE 0.20, 0.20, and 0.17). The two-stage approximation to UK also performed better than LUR and nearly as well as the full UK model with CV R-2 values 0.75, 0.70, and 0.70 (CV RMSE 0.20, 0.17, and 0.17) for summer, autumn, and winter, respectively. Conclusion: High quality LUR and UK prediction models for NOx in Los Angeles were developed for the three seasons based on data collected for MESA Air. In our study, UK consistently outperformed LUR. Similarly, the 2-step approach was more effective than the LUR models, with performance equal to or slightly worse than UK. (C) 2011 Elsevier Ltd. All rights reserved.
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| 183. |
- Mills, G., et al.
(författare)
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A synthesis of AOT40-based response functions and critical levels of ozone for agricultural and horticultural crops
- 2007
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 41:12, s. 2630-2643
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Tidskriftsartikel (refereegranskat)abstract
- Crop-response data from over 700 published papers and conference proceedings have been analysed with the aim of establishing ozone dose-response functions for a wide range of European agricultural and horticultural crops. Data that met rigorous selection criteria (e.g. field-based, ozone concentrations within European range, full season exposure period) were used to derive AOT40-yield response functions for 19 crops by first converting the published ozone concentration data into AOT40 (AOT40 is the hourly mean ozone concentration accumulated over a threshold ozone concentration of 40ppb during daylight hours, units ppmh). For any individual crop, there were no significant differences in the linear response functions derived for experiments conducted in the USA or Europe, or for individual cultivars. Three statistically independent groups were identified: ozone sensitive crops (wheat, water melon, pulses, cotton, turnip, tomato, onion, soybean and lettuce); moderately sensitive crops (sugar beet, potato, oilseed rape, tobacco, rice, maize, grape and broccoli) and ozone resistant (barley and fruit represented by plum and strawberry). Critical levels of a 3 month AOT40 of 3 ppm It and a 3.5 month AOT40 of 6ppm h were derived from the functions for wheat and tomato, respectively. (c) 2006 Elsevier Ltd. All rights reserved.
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| 184. |
- Mills, Gina, 1959, et al.
(författare)
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New stomatal flux-based critical levels for ozone effects on vegetation
- 2011
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1873-2844 .- 1352-2310. ; 45:28, s. 5064-5068
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Tidskriftsartikel (refereegranskat)abstract
- The critical levels for ozone effects on vegetation have been reviewed and revised by the LRTAP Convention. Eight new or revised critical levels based on the accumulated stomatal flux of ozone (POD gamma, the Phytotoxic Ozone Dose above a threshold flux of Y nmol m(-2) PLA s(-1), where PLA is the projected leaf area) have been agreed. For each receptor, data were combined from experiments conducted under naturally fluctuating environmental conditions in 2-4 countries, resulting in linear dose response relationships with response variables specific to each receptor (r(2) = 0.49-0.87, p
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| 185. |
- Molnár, Peter, 1967, et al.
(författare)
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Domestic wood burning and PM2.5 trace elements: Personal exposures, indoor and outdoor levels
- 2005
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 39:14, s. 2643-2653
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Tidskriftsartikel (refereegranskat)abstract
- Personal exposures as well as indoor and outdoor levels of PM2.5 were measured with cyclones and impactors simultaneously in the winter of 2003 in a residential area where wood burning for domestic space heating is common. Twenty-four-hour samples from both wood-burning households ("wood burners") and a reference group were analysed for mass and elemental concentration using energy dispersive X-ray fluorescence (EDXRF) and for black smoke (BS) concentration using an EEL 43 reflectometer. Wood-smoke particles made statistically significant contributions of K, Ca, and Zn for both personal exposure and indoor concentration, the median levels of these elements being 66-80% higher for the wood-burning group. In addition, Cl, Mn, Cu, Rb, and Pb were found to be possible markers of wood smoke, though levels of these were only significantly higher among the wood-burning group for either personal exposure or indoor concentrations. PM2.5 mass and S levels were not significantly elevated in wood burners, probably due to large variations in outdoor concentrations from long-distance transported air pollution. Personal exposure and indoor levels showed high correlations for all species, and the personal exposure levels were usually higher than or equal to the indoor levels. The associations between personal exposure and outdoor levels were generally weak except for outdoor S and PM2.5 levels that were both highly correlated with personal S exposure levels (r(s) > 0.8). (c) 2005 Elsevier Ltd. All rights reserved.
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| 186. |
- Molnár, Peter, 1967, et al.
(författare)
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Residential NOx exposure in a 35-year cohort study. Changes of exposure, and comparison with back extrapolation for historical exposure assessment
- 2015
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 115, s. 62-69
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Tidskriftsartikel (refereegranskat)abstract
- In this study we aimed to investigate the effects on historical NOx estimates on time trends, spatial distributions, exposure contrasts, the effect of relocation patterns and the effects of back extrapolation. Historical levels of nitrogen oxides (NOx) from 1975 to 2009 were modeled with high resolution in Gothenburg, Sweden, using historical emission databases and Gaussian models. Yearly historical addresses were collected and geocoded from a population-based cohort of Swedish men from 1973 to 2007, with a total of 160,568 address years. Of these addresses, 146,675 (91%) were within our modeled area and assigned a NOx level. NOx levels decreased substantially from a maximum median level of 43.9μg/m3 in 1983 to 16.6μg/m3 in 2007, mainly due to lower emissions per vehicle km. There was a considerable variability in concentrations within the cohort, with a ratio of 3.5 between the means in the highest and lowest quartile. About 50% of the participants changed residential address during the study, but the mean NOx exposure was not affected. About half of these moves resulted in a positive or negative change in NOx exposure of >10μg/m3, and thus changed the exposure substantially. Back extrapolation of NOx levels using the time trend of a background monitoring station worked well for 5-7 years back in time, but extrapolation more than ten years back in time resulted in substantial scattering compared to the "true" dispersion models for the corresponding years. These findings are important to take into account since accurate exposure estimates are essential in long term epidemiological studies of health effects of air pollution.
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| 187. |
- Monks, P. S., et al.
(författare)
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Atmospheric composition change : global and regional air quality
- 2009
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 43:33, s. 5268-5350
-
Forskningsöversikt (refereegranskat)abstract
- Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems heritage and, climate. In this review the state of scientific understanding in relation to global and regional air quality is outlined. The review discusses air quality, in terms of emissions, processing and transport of trace gases and aerosols. New insights into the characterization of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. Trends in anthropogenic emissions both by region and globally are discussed as well as biomass burning emissions. In terms of chemical processing the major air quality elements of ozone, non-methane hydrocarbons, nitrogen oxides and aerosols are covered. A number of topics are presented as a way of integrating the process view into the atmospheric context; these include the atmospheric oxidation efficiency, halogen and HOx chemistry, nighttime chemistry, tropical chemistry, heat waves, megacities, biomass burning and the regional hot spot of the Mediterranean. New findings with respect to the transport of pollutants across the scales are discussed, in particular the move to quantify the impact of long-range transport on regional air quality. Gaps and research questions that remain intractable are identified. The review concludes with a focus of research and policy questions for the coming decade. In particular, the policy challenges for concerted air quality and climate change policy (co-benefit) are discussed.
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| 188. |
- Mulder, Marie D., et al.
(författare)
-
Long-range atmospheric transport of PAHs, PCBs and PBDEs to the central and eastern Mediterranean and changes of PCB and PBDE congener patterns in summer 2010
- 2015
-
Ingår i: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 111, s. 51-59
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Tidskriftsartikel (refereegranskat)abstract
- The central and eastern Mediterranean is a receptor area for persistent organic pollutants (POPs) emitted in western, central and eastern Europe, particularly during summer. Atmospheric concentrations of PCBs, DDXs, PBDEs, penta- and hexachlorobenzene were measured during a ship-borne survey in the summer of 2010. The concentration of PCBs (sum of 7 congeners) was 3.61 (2.08-7.72) pg m(-3), of which 6.7% was associated with the particulate phase. The mean concentration of DDT isoi-ners and their metabolites, DDE and DDD, was 2.60 (0.46-7.60) pg m(-3) (particulate mass fraction theta = 0.097), of penta- and hexachlorobenzene 0.22 (<039-2.80) pg m(-3) and 6.29 (2.48-24.16) pg m(-3), respectively, and of PBDEs (sum of 8 congeners) 7.31 (2.80-19.89) pg m(-3). The air masses studied had been transported mostly across central Europe, some crossing western Europe. The observed changes of PCB congener patterns along transport routes are in agreement with the perception that the reaction with the OH radical is dominating PCB atmospheric lifetime, and indicate an overestimation of the second order gas-phase reaction rate coefficient of PCB:153 with OH by structure-activity relationship.
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| 189. |
- Mulder, Marie D., et al.
(författare)
-
Reprint of : Long-range atmospheric transport of PAHs, PCBs and PBDEs to the central and eastern Mediterranean and changes of PCB and PBDE congener patterns in summer 2010 (Reprinted from Atmospheric Environment, vol 111, pg 51-59)
- 2015
-
Ingår i: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 121, s. 66-74
-
Tidskriftsartikel (refereegranskat)abstract
- The central and eastern Mediterranean is a receptor area for persistent organic pollutants (POPs) emitted in western, central and eastern Europe, particularly during summer. Atmospheric concentrations of PCBs, DDXs, PBDEs, penta- and hexachlorobenzene were measured during a ship-borne survey in the summer of 2010. The concentration of PCBs (sum of 7 congeners) was 3.61 (2.08-7.72) pg m(-3), of which 6.7% was associated with the particulate phase. The mean concentration of DDT isomers and their metabolites, DDE and DDD, was 2.60 (0.46-7.60) pg m(-3) (particulate mass fraction theta = 0.097), of penta- and hexachlorobenzene 0.22 (<0.39-2.80) pg m(-3) and 6.29(2.48-24.16) pg m(-3), respectively, and of PBDEs (sum of 8 congeners) 7.31 (2.80-19.89) pg m(-3). The air masses studied had been transported mostly across central Europe, some crossing western Europe. The observed changes of PCB congener patterns along transport routes are in agreement with the perception that the reaction with the OH radical is dominating PCB atmospheric lifetime, and indicate an overestimation of the second order gas-phase reaction rate coefficient of PCB153 with OH by structure-activity relationship.
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| 190. |
- Munthe, John, et al.
(författare)
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Distribution of atmospheric mercury species in Northern Europe: Final results from the MOE-project
- 2003
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 37:Suppl 1, s. S9-S20
-
Tidskriftsartikel (refereegranskat)abstract
- The mercury species over Europe (MOE) project was aimed at identifying sources, occurrence and atmospheric behaviour of atmospheric Hg species. Within MOE, emission measurements, ambient air measurements, process and regional-scale modelling and laboratory measurements were conducted. In this work, a summary of some of the main results is given. From the emission measurements, information on stack gas concentrations and emission factors for five coal fired power plants and three waste incinerators are presented. Results from field measurements of mercury species in ambient air at five locations in Northern Europe are presented. Examples from regional-scale atmospheric modelling are also given. The results emphasise the importance of information on Hg species for instance in emission inventories and measurement data from background sites. Furthermore, the importance of considering the role of the global cycling of mercury in future control strategies is emphasised
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