Distribution Characteristics Of Mercury And Arsenic And Their Source Analysis In Snow Of The Northern China

Mercury（Hg）and arsenic（As）as two heavy metal pollutants can enter the environment through geochemical processes such as atmospheric deposition transport and hydrosphere circulation.Their strong enrichment and high toxicity can have adverse effects on the ecosystem.Snow as a special environmental medium can effectively save atmospheric dry and wet deposition information,therefore,it is of great significance to the climate and ecological environment.To evaluate the local atmospheric deposition and the influence of heavy metal pollution on the atmosphere,the spatial distribution characteristics and sources of Hg and As were investigated in northeast China snow.First,snow samples were taken from 143 sampling points in northern China（northeast China and north Xinjiang）during January to February 2018.The total mercury（THg）and total arsenic（TAs）in the snow samples were then measured by atomic fluorescence spectroscopy（AFS）.Furthermore the As species in the snow sample were separated and determined by liquid chromatography coupled to AFS.After that,the concentration levels of Hg and As in snow samples from different regions were analyzed by inverse distance weighted interpolation.Finally,the sources of Hg and As were analyzed using the backward trajectory model.The results show that:（1）The concentration of THg and TAs in snow ranged from 1.14-168.29 ng L^-1 and 0.166-17.314μg L^-1,respectively.The concentrations of pollutants in snow in different regions were significantly different.Compared with the northern Xinjiang,higher THg and TAs concentrations were observed in northeast China snow,attributing to the different degree of urbanization and industrialization.In addition,differences in the structure of energy consumption may also contribute to this phenomenon.（2）The As species of the snow samples in the south and north northeast China were measured.It is found that As mainly existed in the form of inorganic As.The concentration of inorganic trivalent arsenic(0.557-11.194μg L^-1)was higher than that of pentavalent arsenic(<0.02-2.55μg L^-1),which may be caused by the weaker oxidizing environment in the snow.（3）Overall,in northeast China,Hg and As pollutants are distributed less in the study area near the Siberian border than in the Northern Three-Province with mainly industrial zones;the distribution of Hg and As pollutants from southwest to northeast is generally low-high-low in northern Xinjiang,and the higher distribution were observed in Northern Tianshan Slope and Junggar Basin.Specifically,the regions with higher pollutant distribution are:southeast Heilongjiang Province,northwest Jilin Province,Hohhot City and Xing’an League in eastern Inner Mongolia,and Urumqi,Shihezi City and Changji Prefecture in northern Xinjiang.The distribution of pollutants is not only affected by local human and industrial activities,but also affected by local climatic conditions and landforms.（4）The close transport air masses of local activities and the surrounding cities make an important contribution to the source of pollutants in snow.The Northern Tianshan Slope and Yili Valley in northern Xinjiang are more affected by local area due to their unique geographical location,but the Eastern Inner Mongolia is less affected by human activities due to its border area.Moreover,it also is affected by the long-range transport air masses of neighboring countries.These results clearly demonstrates variations and industrial structures may remarkably lead to complex spatial characteristics in pollutant concentration.The spatial characteristics and meteorological effects suggest the governments should concern the regional cooperation and collaboration in environment regulation and pollution prevention.