Spatial Distribution And Potential Sources Of Chemical Composition Of Snow Pack In Northern Xinjiang

As a reservoir of various chemical substances in the atmosphere,snow can effectively preserve the information of atmospheric deposition and have an impact on the geochemical cycle process.The northern Xinjiang is one of the largest snowfall areas in China.Pollutants migrate to the ground with snow through atmospheric particles.Snowmelt runoff is an important water resource for agriculture and industry.To understand the impact of chemical components in snow on northern Xinjiang ecological environment,the spatial distribution and potential sources of water-soluble ions and dissolved arsenic（As）in snow were analyzed.Snow samples were collected from 136 sites in the northern Xinjiang from December 2018 to March 2019.The p H,conductivity and water-soluble ions were analyzed by ion chromatography,as well as the concentration of As in snow at Ili River Valley（IRV）by Atomic Fluorescence Spectrometer.Inverse distance weighting was used to evaluate the ion and As spatial distributions in the snow samples.Correlation and principal component analysis,enrichment factor（EF）analysis,and backward trajectory modelling were applied to evaluate the transportation trajectory and sources of chemical materials in snow.The dominant anion and cation of snow in northern Xinjiang were SO₄^2-and Ca²⁺,accounting for 36.96%and 23.62%of the total ions,respectively.The distribution of water-soluble ions from southwest to northeast is generally low-high-low in northern Xinjiang,and the high distribution were observed in Northern Tianshan Slope,and the variation of ion concentrations was small during the sampling period.The correlation and principal component analysis suggested that the mixed sources of agricultural activities,industrial activities,surface dust and salt lake aerosol have a large impact on the concentrations of ion in the snow.The EFs and Non-sea-salt fractions showed that SO₄^2-and NO₃^-were mainly influenced by human activities and crustal sources.The backward trajectory model analysis showed that the regional/local anthropogenic activities was likely the sources of ions in the snow.However,these chemical materials in surface snow were less affected by the long-range transport of air pollution.Ca²⁺and SO₄^2-were the dominant ions,and the concentrations of As ranged from 0.09 to 0.503μg L^-1 in the snow of the IRV.High concentrations of As were distributed in the northwest and middle of the IRV,and the concentrations of the major ions were high in the west of the IRV.The strong correlation of As with F^-,SO₄^2-,and NO₂^-demonstrates that As mainly originated from coal-burning and agricultural activities.Principal component analysis showed that the ions originated from a combination of anthropogenic and crustal sources.The EFs showed that K⁺,SO₄^2-,and Mg²⁺were mainly influenced by human activities and soil dust.Backward trajectory cluster analysis suggested that the chemical composition of snow was affected by soil dust transport from the western air mass,the unique terrain,and local anthropogenic activities.These results provide important scientific insights for atmospheric environmental management and agricultural production,and it is of great significance to reveal the quality of the local ecological environment and regional biogeochemical cycles.