Apportionment of Chemical Components and Sources of PM2.5 in Shihezi City of Xinjiang, China

Abstract

In order to reveal the pollution characteristics and sources of PM2.5, in this study, we collected PM2.5 filter membrane samples in Shihezi continuously from December 2020 to January 2021, and analyzed 10 kinds of water-soluble inorganic ions (WSIIs) and 24 inorganic elements (IEs), as well as organic carbon (OC) and elemental carbon (EC). The sources and transport paths of PM2.5 were also analyzed via PMF modeling and backward trajectory clustering analysis. The results show that, in winter, Shihezi can have a mean PM2.5 mass concentration as high as 164.69 ± 76.48 μg/m3, and the PM2.5 mass concentration on polluted days is 3.3 times that of clean days. Water-soluble inorganic ions (WSIIs), total carbon (TC), and inorganic elements (IEs) make up the percentage of PM2.5 mass concentration by 64.9%, 9.3%, and 2.6%, respectively. SO42−, NO3−, and NH4+ (SIAs) are the major WSIIs, accounting for 91.0% of the WSII concentration. The heavier the pollution, the more SIAs contribute to PM2.5. The OC mean mass concentration is 14.04 ± 5.32 μg/m3. As the winter pollution becomes worse and worse, the value of OC/PM2.5 decreases constantly while that of SOC/OC follows an opposite trend. During the process of heavy pollution in Shihezi, the secondary transformation of total carbon cannot be ignored. The positive definite matrix factorization (PMF) model result suggests that the main pollution origins of PM2.5 in Shihezi City comprise secondary sources, coal-burning sources, motor vehicle sources, industrial sources, and flying dust sources. The backward trajectory clustering analysis denotes that the winter pollution in Shihezi mainly comes from the local pollutants in Manas and the short-distance transport of pollutants from the Urumqi-Changji Region.