Seasonal Characteristics of Water-Soluble Dicarboxylates Associated with PM10 in the Urban Atmosphere of Durg City, India

摘要

PM10 samples were collected between July 2009 and June 2010 in the urban area of Durg City, India, and analyzed for water-soluble dicarboxylate species. Observed PM10 concentrations varied from 94.0 to 432.1 μg/m3 with an annual average of 253.5 μg/m3. The annual average concentration of PM10 was four times higher than the Indian Central Pollution Control Board (CPCB) National Ambient Air Quality Standard (Indian NAAQS) prescribed limit of 100 μg/m3. The high PM10 mass concentration in Durg City are attributed to anthropogenic activities, including a high rate of construction activities, biomass combustion and mechanical disturbance of road dusts. The highest PM10 value was recorded during the winter, a period characterized by extensive biomass burning, especially at night, while the lowest PM10 concentration was recorded during the monsoon, when there was significant precipitation. The highest concentrations of dicarboxylates were found during winter and spring. On average, total water-soluble dicarboxylates (966 ng/m3) accounted for 0.39% of the PM10 mass. Oxalate (C2), followed by malonate (C3) and succinate (C4), dominated the total mass of dicarboxylates, the sum of these three species accounting for 77.5% of the total analyzed. The malonate to succinate concentration ratio calculated in this study was higher than those reported for vehicular emissions, suggesting that in addition to vehicular exhausts, secondary formation of particulate dicarboxylates via photo-oxidation also occurred. Principal component analysis (Varimax Rotated Component Matrix) revealed that secondary aerosol formation, coal and biomass combustion, and vehicular emissions were the major sources contributing to overall PM10 mass in Durg City, India.