Distribution Characteristics And Influencing Factors Of Mercury In Different Environmental Media Of Typical Marine Glaciers On The Tibet Plateau

As a global toxic pollutant,mercury has been widely concerned by scholars at home and abroad.In 2017,the "Minamata Convention" came into effect,aiming to reduce the use of mercury-containing products and the emission of anthropogenic mercury.At present,as the country with the largest mercury production,use and emissions in the world,my country is facing the dual pressure of mercury emission reduction and mercury compliance.Therefore,probing into the distribution,source,pollution control and other issues of mercury has important theoretical and practical significance for my country’s ecological and environmental safety.The environmental safety of the aquatic ecosystem of the QinghaiTibet Plateau concerns the drinking water,lives and property safety of millions of people downstream.Global warming has accelerated the melting of glaciers,which has changed the water resources reservoirs and runoff of the Qinghai-Tibet Plateau and its surrounding areas and countries.The toxic pollutants that are originally sealed in the glaciers can enter the downstream through runoff water and atmospheric emissions.Aquatic ecosystem.This process can cause potential ecological risks to the Qinghai-Tibet Plateau and its surrounding areas,and undermine the stability of the ecosystem.The current research on the mercury cycle of the Qinghai-Tibet Plateau mainly includes the atmospheric mercury transport process,the distribution of mercury concentration in glacier runoff,and the impact of transport process on the mercury distribution.Glacier retreat areas and forest ecosystems are considered important atmospheric mercury sinks.However,there is still a lack of overall understanding of the contribution of glacial melt water to different environmental media in downstream lakes and the impact of transmission.This paper mainly focuses on the typical marine glaciers Gongga Mountain,Mingyong Glacier and Midui Glacier as the main research objects,and systematically explores the distribution characteristics and influencing factors of mercury in rainfall,runoff,groundwater,snow,and ice,with a view to the future Study the connections and contributions of various environmental media to provide basic data and strong evidence.In the glacier retreat area of Mount Gongga,a total of 6 sampling points were set up in the retreat area of 2005,1990,1980,1970,1958,and1890,mainly forests with different retreat time.A total of 108 open-air precipitation and through-rain samples were collected from May to October 2020.The Hg concentration and DOC(dissolved organic carbon)concentration in the samples were analyzed and it was found that the Hg concentration gradually increased as the retreat time increased.The concentration value of the plot in 1890 reached the maximum,which was3-6 times that of other regions.The monthly variation shows that the Hg concentration gradually decreases after reaching the maximum in June and July,until September,and the Hg concentration rises again in October with the occurrence of winter coal burning and other activities.It shows that the mercury concentration in precipitation is affected by the combined effect of atmospheric mercury concentration and forest canopy.The wet deposition flux of Hg in rainfall is mainly controlled by rainfall and THg concentration,and increases with the increase of rainfall.Four runoff water sampling points were set up in the glacier runoff area of Mt.Gongga.Two six-month sampling were conducted from June to November 2018 and May to October 2020.The results showed that the Hg concentration in the runoff water increased with Over time,it shows a gradual decreasing trend.The higher Hg concentration in May and June is mainly due to the accumulation of atmospheric mercury on snow and ice during the period from November to April.Compared with the samples from-2018-2020,there is no significant increase or decrease.In addition,the study also found that Hg’s runoff output flux is mainly controlled by runoff and watershed area.Two sampling points were set up for the groundwater and the groundwater outlet in the glacial forest area of Mt.Gongga.The comparison of the results shows that the Hg concentration in the groundwater in the forest area is significantly higher than that in the groundwater outlet(P=0.01 T-Test).The main reason for this result is that the forest surface litter settles to the soil surface after the degradation process produces a large amount of Mercury flows into the groundwater in the process of downward migration,and the Hg concentration of the water outlet is significantly affected by the water retention time and sedimentation filtration.In December 2018,three marine glaciers,namely Gongga Mountain Glacier,Mingyong Glacier,and Midui Glacier,were collected for snowice-runoff water samples.The results show that the THg concentration in different environmental media is: snow> ice> runoff water.Analysis of the trace heavy metals in the samples found that the main factors affecting the distribution of mercury concentration in the glacier area are:(1)Mainly controlled by atmospheric particulate matter deposition;(2)Influence from anthropogenic emissions,that is,the closer to the anthropogenic source,the greater the concentration of THg.high.