Spatial Distribution And Sources Of Water Soluble Ions In Snow Of Typical Snow Area Across Northern China

The chemical composition of snow is closely related to water vapor source,atmospheric environment and its changes.The analysis and research on the change of chemical composition and content of snow in typical snow areas can not only reveal the source of water vapor in different regions,but also construct the environmental indication of the change of different chemical composition content in snow cover,which is of great scientific significance to the study of climate and environmental change.This paper introduced snow field observation test across Xinjiang,Qinghai and the northeast China snow area on January 4 to February 24 in 2018,obtained nearly 200 snow samples by dug 63 snow profiles and water soluble ions in different regional snow were analyzed by ion chromatographic,and the correlation analysis,principal component analysis and enrichment factor were used to discusses the sources of ions,backward trajectory clustering of typical sampling sites and potential source contribution function(PSCF)were analyzed to determine pollutants transmission path and potential source area of SO4(2-)and SO32-.The results showed that:1.The concentrations of water-soluble ions Na+?NH4+?K+?Mg2+?Ca2+?F-?Cl-?NO2-?SO42-and NO3-in snow across northern China ranged from 0.069 to 10.872mg/L,from 0.052 to 10.102mg/L,from 0.022 to 4.898mg/L,from 0.018 to 3.211mg/L,from 0.053 to 20.516mg/L,from 0.006 to 2.092mg/L,from 0.046 to 15.847mg/L,from 0.096 to 2.464mg/L,from 0.127 to 50.89mg/L and from 0.162 to 34.77mg/L,respectively.The average concentration was SO42->Ca2+>NO3->Cl->NH4+>Na+>NO2->K+>Mg2+>F-.The average regional total ion concentration in the snow was sorted as follows:Northeast China Plain>The eastern Qinhai-Tibet plateau>Tianshan mountain>Western Greater Khingan>Jungger basin.Ca2+was dominant cation,accounting for 14.46?54.72%.SO42-was dominant anion,accounting for 13.99?31.62%.The ion concentration in the snow cover was much higher than that in the Antarctic region and the Greenland ice sheet,and generally higher than that in the Himalayas,the Alps and other high Asian regions,indicating that it was affected by different degrees of mineral dust and anthropogenic pollutant emissions.2.The ratio of SO42-/NO3-in snow ranged from 0.23?to 8.07,regional population density,travel patterns and regional energy structure differences lead to spatial scale heterogeneity.The ratios of SO42-NO3-in snow of the eastern Qinghai-Tibet plateau were more than 3 indicating that the region was mainly polluted by coal burning.The large increase in the number of motor vehicles and emission of petrochemical industry,steel and other heavy industries and urban central heating near Harbin,Changchun and other cities based on rich coal and iron resources in northeast China resulted in the mixed pollution of nitric acid and sulfuric acid in the Northeast plain.The ratio of SO42-/NO3-in the snow of the rest areas is mostly between 0.5 and 3,indicating the mixed pollution caused by coal burning andmotor vehicle emissions.3.The correlation coefficient between Cl-and Na+in the snow in northern China is 0.91,indicated coming from sea salt aerosol or bubble.The correlation coefficient between F_and SO42-and NO3-were greater than 0.7,indicating that F-was also derived from anthropogenic emissions such as coal combustion.The correlation coefficients between NH4+and NO3-and SO42-were higher than 0.6 indicating that ammonium compounds are similar to exist in the form of ammonium sulfate and nitrate.The correlation between Mg2+and Ca2+was high,indicating the same continental sources such as dust.Principal component analysis(PCA)extracted 4 factors,which represented mixed sources of natural or anthropogenic sources,Marine sources,potential sources of NO2-and anthropogenic sources,respectively.The enrichment factor indicated that the average EFsea values of K+,Ca2+,Mg2+,SO42-and Cl-in snow cover are 24.47,106.69,1.97,44.9 and 1.12,respectively The average values of EFcrustal value of K+,Na+,Mg2+,SO42-,NO3-and F-relative to crustal sources were 0.25,0.65,0.35,32.24,48.25,628.27 and 29.48,respectively.K+and Mg2+were diluted relative to crustal sources indicating that they came from rock-soil dust.The high enrichment of SO42-,NO3-and F-indicated that they were mainly affected by anthropogenic emission sources.In the five regions,the input of anthropogenic source to SO42-and NO3-were more than 84.3%and 95.9%respectively.Cl-is mainly controlled by sea source,and the input ratios reached over 75.5%.K+,Mg2+and Ca2+are mainly fromcrustal sources,the input ratios accounted for 98.1%,78.4%and 85.8%,respectively.4.The results of backward trajectory clustering analysis showed that the main pollutant transport paths in Tianshan mountain region came from the northwest and southwest paths,and the main pollutant transport paths in the edge of Junggar basin came from the west and northwest paths.The main air mass transport routes in the eastern part of the Qinghai-Tibet plateau was from the western and southwestern routes.The pollutants were transported along the northwest route in the Greater Kinghan mountains region.The upwind area of the sampling point has a small population density,less developed industry,and less exogenous pollution in the snow cover.The northeast plain is mainly transported along the north path and northwest path,and the ion concentration in snow cover is high due to the combined action of the air pollutants,pollutants and dust transported over long distances in the local area.The potential sources contribution function(PSCF)indicated that the high potential source areas of SO4 2-and NO3-in the snow of the northern Xinjiang sampling site are located in the Aktoka region in the east of Balkhash lake in Kazakhstan,where industrial activities such as copper mining have contributed a lot to the secondary pollutants in the snow.The high potential sources of SO42-and NO3-of the eastern Qinghai-Tibet plateau sampling site are concentrated around the urban agglomeration in northern India.The SO42-potential source in the Northeastern plain sampling site is located in the north of Bohai bay and the north of Seoul,South Korea due to the discharge of water transport ships and fishing boats in Chinese waters.The NO3-high-potential source area is located in the north of Hulunbuir city,Mongolia.