Chemical composition and source apportionment of PM2.5 a?? A case study from one year continuous sampling in the Chang-Zhu-Tan urban agglomeration

摘要

To understand the characteristics and source of atmospheric PM2.5 in Chang-Zhu-Tan urban agglomeration, PM2.5 samples were simultaneously collected at 11 monitoring sites within three cities of Changsha, Zhuzhou and Xiangtan from September 2013 to August 2014. Spatial and temporal variations of PM2.5 mass concentration and chemical compositions were analyzed based on the average values over the measurement sites in a specific urban area, including a comparison of PM2.5 at urban and urban background sites. Source apportionment was performed by PMF 5.0 (positive matrix factorization) model and potential source area affecting PM2.5 mass concentration was simulated using CWT (concentration-weighted trajectory analysis) analysis. The result showed the seasonal variation of PM2.5 mass concentration followed the order of winter????autumn????spring????summer. The OC/EC ratio in each season and each city were greater than 4.0, secondary inorganic ions accounted for at least 91% of the total water soluble inorganic ion concentration, presenting obvious secondary pollution characteristics. Coal combustion and vehicle emissions were two major sources of PM2.5 in all three cities, which accounted for about 35 percent and nearly 26 percent of contributions respectively. In addition, industrial emission and biomass burning were also significant sources in Changsha, while urban dust and biomass burning were significant sources in Zhuzhou and Xiangtan. Chang-zhu-tan urban agglomeration was the main source area of its PM2.5 and easy to form overlapping pollution areas. Meanwhile, northern neighboring city Yueyang and western bordering region Pingxiang also had a certain transmission influence on the formation of PM2.5.