蒙古國烏倫巴托地區二氧化硫及二氧化氮之汙染與暴露

SO2 and NO2 pollution and exposure in Ulaanbaatar, Mongolia

黃郁凱(Yu-Kai Huang)

指導教授 ： 詹長權

國立臺灣大學/公共衛生學院/職業醫學與工業衛生研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.00285

摘要

目標：探討蒙古國烏蘭巴托都市大氣中二氧化硫及二氧化氮空氣汙染以及其對當地居民潛在暴露。
方法：利用Ogawa被動式採樣器，從2011年9月到2012年3月間分別於研究地區較溫暖（2011年9月）、寒冷（2011年11月至12月）以及溫和季節（2011年3月），進行兩周空氣採樣，共有38個室外採樣地點分布在道路或蒙古包居住區旁，量測空氣指標汙染物二氧化氮以及二氧化硫之濃度是否。之後以統計模式分析空間因子諸如主要道路或蒙古包居住區等與季節間空氣汙染物濃度之關係利用土地利用資料，諸如採樣地點至主要道路、蒙古包居住區、火力發電廠或市中心之距離已即採樣區域人口數，建構複回歸模式預測空氣汙染情形，並以模式預測市區內126次區居民受二氧化硫以及二氧化氮暴露程度。
結果：空氣汙染在冬季較為嚴重。20個靠近蒙古包居住區測站大氣平均二氧化硫濃度（寒冷季節為46.60ppb，溫和季節為17.82ppb）顯著高於18個遠離蒙古包居住區之測站（寒冷季節為23.35ppb，溫和季節為12.53ppb）；19個靠近主要道路測站大氣平均二氧化氮濃度（溫暖季節為12.85ppb，溫和季節為20.48ppb）顯著高於18個遠離主要道路之測站（溫暖季節為7.60ppb，溫和季節為14.39ppb）。複回歸預測模式顯示大氣二氧化硫和二氧化氮濃度和蒙古包居住區、市中心、主要道路、火力發電廠等汙染源的距離呈現指數遞減的關係。以所有採樣點距蒙古包居住區平均距離約0.7公里的地點為例，寒冷季節二氧化硫濃度下降23%而溫和季節二氧化硫濃度下降14%；以所有採樣點平均距市中心平均距離約4.83公里的地點為例，溫和季節二氧化硫濃度也約有29%下降幅度。以採樣點距離市中心4.83公里的地點為例，溫暖季節二氧化氮濃度下降38%而溫和季節二氧化氮濃度下降29%；以所有採樣點距主要道路平均距離約0.16公里的地點為例，溫暖季節二氧化氮濃度下降15%而溫和季節二氧化氮濃度下降9%。然而寒冷季節二氧化氮濃度高低則同時受到採樣地點至蒙古包居住區、市中心、火力發電廠距離之影響，二氧化氮濃度在距離這三個汙染源平均距離的地方分別會有14%、18%、21%的下降幅度。綜合人口密度和空氣汙染濃度資料後的暴露評估結果顯示，烏蘭巴托半數市民在寒冷季節時二氧化硫暴露值高於41.92 ppb。
結論：烏倫巴托市民於寒冷季節時，所受之大氣中二氧化硫與二氧化氮汙染暴露值為三採樣季節最高，取暖導致之燃燒為都市大氣中二氧化硫與二氧化氮之主要來源，其中二氧化硫汙染與暴露最為嚴重；而在溫暖與溫和季節，由交通和火力發電廠排放汙染所貢獻之二氧化氮汙染亦不可忽視。

關鍵字

二氧化硫 ； 二氧化氮 ； 空氣汙染 ； 烏倫巴托 ； 蒙古包

並列摘要

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.

並列關鍵字

SO2 ； NO2 ； Air pollution ； Ulaanbaatar ； Mongolia

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