SO2 and NO2 pollution and exposure in Ulaanbaatar, Mongolia
Date Issued
2012
Date
2012
Author(s)
Huang, Yu-Kai
Abstract
Objectives: To study SO2 and NO2 pollution and to estimate exposure levels of these two pollutants for residents in Ulaanbaatar, Mongolia.
Methods: For the purpose of this study we collected 2-week ambient SO2 and NO2 samples at 38 sites, which were classified by whether they were near Gers and/or major roads, on September, 2011 (warm season), November to December, 2011 (cold season), and March, 2012 (moderate season) in Ulaanbaatar, Mongolia. SO2 and NO2 were collected by Ogawa ambient air passive samplers and analyzed by ion chromatography and spectrophotometry methods, respectively. Spatial and temporal differences in ambient SO2 and NO2 levels were compared by student t, Wilcoxon rank sum, ANOVA and the K-W tests. Stepwise regression was used to estimate the contribution of emission proxies predicting variables of distance to major roads, Gers, power plants, the city center, and power plants. The developed models were then used to predict ambient SO2 and NO2 levels at the center of each sub district in Ulaanbaatar. SO2 and NO2 exposures were estimated by multiplying model-predicted concentrations of each sub district and the population size of that district.
Results: SO2 and NO2 concentrations in the cold season were significantly higher than those in warm and moderate seasons at all 38 ambient sampling sites. SO2 concentrations at 20 Ger sites (46.60 ppb in cold season and 17.82 ppb in moderate season) were significantly higher those at 18 non-Ger sites (23.35 ppb in cold season and 12.53 ppb in moderate season). NO2 concentrations at 19 traffic sites (12.85 ppb in warm season and 20.48 ppb in moderate season) were significantly higher than those at 19 urban sites (7.60 ppb and 14.39 ppb in moderate season). Multiple regression models show that SO2 and NO2 concentrations at Ulaanbaatar can be explained by the distance to emission sources, including Ger areas, city centers, main roads, and power plants. SO2 concentrations at 0.70 km away from Ger areas, an average of all sampling sites, decreased by 23% in the cold season and 14% in the moderate season; SO2 concentrations at 4.83 km away from city center, an average of all sampling sites, decreased by 29% in the moderate season. NO2 concentrations at 4.83 km away from city center decreased by 38% in the warm season and 29% in the moderate season; NO2 concentrations at 0.16 km away from main roads decreased by 15% in the warm season and 9% in the moderate season. NO2 concentrations in the cold season decreased by 14% at the location 0.70 km away from Ger areas, by 18% at the location 4.83 km away from the city center, and by 21% at the location 4.79 km away from the power plants. The exposure models estimated about 50% of all residents in Ulaanbaatar experienced SO2 exposures greater than 41.92 ppb during the cold season of 2011-2012.
Conclusions:
The need for heating in Ger areas in cold season is main cause of elevated SO2 and NO2 concentrations in Ulaanbaatar. Emissions from traffic and power plants in warm and moderate seasons are another major sources of NO2 pollution in Ulaanbaatar. Residents in Ulaanbaatar experience relatively high SO2 and NO2 exposure in the cold season.
Subjects
SO2
NO2
Air pollution
Ulaanbaatar
Mongolia
SDGs
Type
thesis
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