Nutrient Elements Flux And Influencing Factors In Guizhou Karst Damming River

Rivers are the channels connecting the land and the sea.Every year,a large number of continental weathering and human activities are transported to the lower reaches of the river and the sea.The karst area in southwest China is fragile in ecology and strongly weathered by rock chemistry.Under the influence of natural factors and human activities,the river water environment and water safety are affected.Especially in the dam-building reservoir area.A large number of nutrients and heavy metals likely remain in the reservoir due to upstream input;Soluble elements deserve more attention because of their toxicity.In this study,three karst dam-building basins with different geographical environments were selected for comparative study.Factors affecting the concentration of the main elements and the flux characteristics of the dissolved Mg,Mo,Cr,Ni,Cu and Zn of the river into the lake were studied.The following are the main findings:1.The major elements of the river in the karst dam-building basin are mainly affected by the chemical dissolution of carbonate rocks.The hydrothermal conditions of different seasons and the ratio of limestone to dolomite in different regions are the main factors affecting the concentration of the main elements in rivers.And the high conductivity and p H of river water in the study area also reflect the substantially chemical dissolution of carbonate rocks.2.The flux characteristics of Mo,Cr,Ni,Cu and Zn trace elements in karst dam basin are mainly affected by the change of river water flow.In the high-water period,the flux is large,which may come from non-point source runoff erosion or direct rainfall.The spatiotemporal variations of trace elements indicate that they have different sources.Although the natural environment of the three study areas is similar,the changes and sources of trace elements are various due to the different human environments.Hongfeng Lake basin is industrial,mining,urban,agricultural land,Boyu River basin is an agricultural area,Pingzhai reservoir upstream distribution of large areas of woodland.The atmospheric precipitation in this study area has a certain influence on the trace elements of river water,but its magnitude is limited.3.The trace element concentration of river water in the study areas is lower than the limited value of the Chinese drinking water standard.The high flux of trace elements is worth noting because they may remain in the reservoir,such as the annual flux Zn and Ni of dissolved trace elements in Hongfeng Lake reached 2791.43 kg and 1187.64 kg,respectively.In the Hongfeng Lake basin,the most massive trace flux in space is Yangchang River.In the Pingzhai reservoir basin,the flux of trace elements is the largest at the upstream sampling point and reservoir outlet.In the Boyu River basin,trace elements have the most significant dry circulation.These sites,with large fluxes of trace elements in space,are affected by human activities to some extents.