Chemical characteristics and source analysis of atmospheric precipitation in the eastern Tarim River Basin

This study collected a total of 128 atmospheric precipitation samples along a north-south gradient in the eastern Tarim River Basin (Bayingolin Mongol Autonomous Prefecture) during 2021-2022, and systematically analyzed their chemical composition characteristics and ion sources using multiple analytical methods. The results show that the precipitation in the eastern Tarim River Basin is generally near neutral, with no strongly acidic rain, although some samples had pH values ranging from 6.62 to 6.99 and EC values ranging from 158.84 to 383.17 μS·cm-1. Ion concentrations exhibited a spatial pattern of ’higher in the south and lower in the north’ and showed seasonal characteristics of higher values in spring and winter and lower values in summer and autumn. Ca2+ and SO42- were the dominant ions, with average concentrations of 1401.20 μeq·L-1 and 516.21 μeq·L-1, respectively. The SO42-/NO3- ratio indicated overall mixed pollution. Source analysis revealed that Na+ and Cl- mainly originated from inland saline soil wind erosion; Mg2+ and Ca2+ were primarily from terrestrial sources; while NH4+, SO42-, and NO3- were mainly influenced by human activities. The PMF model quantitatively indicated that the contributions of six major sources were as follows: secondary inorganic aerosols (28.41%), evaporite/salt soil weathering (26.81%), dust (21.46%), biomass burning (9.83%), industrial emissions (8.32%), and agricultural sources (5.17%). This study enriched the precipitation chemistry database of arid regions in China and provided a scientific basis for regional air pollution prevention and control.