Source Risk Assessment Of Arsenic And Heavy Metals In Stream Sediments In Typical Karst Gold Mining Areas And Analysis Of Key Influencing Factor

Gold mining brings serious water pollution of As and heavy metals,and the cumulative concentrations of As and heavy metals in sediment can reflect the extent of water pollution.However,the risk of pollution in karst areas is higher because of the fragile ecological environment.Current research often ignores the risks from different sources and interactions between factors.Hence,this study selected a karst gold mining area in Southwest China to study its cumulative concentration,spatial distribution,and fraction of As and heavy metals（Sb,Zn,Cd,Cr,Co,Ni,Cu,and Pb）in river sediment around the gold mining area.Pearson correlation analysis,principal component analysis（PCA）,and Positive Matrix Factorization model（PMF）were used as source analysis methods,and PMF model and ecological risk model（RI）were combined to identify and quantify the risk levels of As and heavy metals in different pollution sources.Finally,geographical detectors（GDM）were applied to analyze their impact factors include p H,EC,water temperature（T）,dry matter content(_dm),water content(_H2O),total organic carbon（TOC）,pore water,and lithology.The results show that,（1）As and the other heavy metals in surface water and groundwater sediment in karst gold mining areas are affected by external inputs in addition to Pb.The cumulative concentrations of As and heavy metals in groundwater sediment are higher,mainly concentrated in the first layer,and some As and Sb have been transferred.The distribution of cumulative concentrations of As and Sb,Zn and Cd,Co and Ni in the sediment in surface water is similar.To be specific,As and Sb are mainly concentrated near the gold deposit area;Cd,Zn,and Pb are mainly concentrated in the northeast of the study area,while Co,Ni,Cr,and Cu are mainly concentrated in the west of the study area.In groundwater sediment,the cumulative concentration of As and heavy metals in the first section is the heaviest,and it decreases with the increase of vertical distance.（2）As and heavy metals in sediment are mainly affected by human activities,geological settings and gold mining activity.Cr,Co,Ni,Cu,and Pb in surface water sediment are mainly affected by human activities.Geological background has a certain contribution to As and all heavy metals.Co,Ni,Zn,As,Cd,and Sb are mainly affected by gold mining activities.Geological settings and gold mining have the greatest potential ecological risk in the local area,with As contributing the most,followed by Sb.Affected by other human activities,Cu is a high risk to the local environment.Affected by geological settings and gold mining activities,the risk of As in the west,central,and southern regions,Cd in the west,southern,and eastern regions,and Sb in the west all cannot be ignored indeed.In addition,the source risk in groundwater sediment is higher than that in surface sediment.（3）As and most heavy metals in surface water sediments are most affected by EC（q value exceeds 40%）.Zn and Cd in surface water sediments and Cu,Zn,Cd,and Sb in groundwater sediments are mainly affected by the interaction between TOC and other factors.In addition,lithology and fractions can indirectly affect the cumulative concentrations of As and heavy metals in sediment.From the single factor results,it can be seen that EC has the greatest impact on As,Co,Cd,Cr,Ni,Zn,Cu,Sb,and Pb in surface water sediment.What is the second most important impact is water temperature and lithology on Zn,_H2O on Co,Pb,and Ni,TOC on Co,Ni,As,Cr,and Cu.Effects of p H on Co,Pb,Cr,Ni,Cu,and Sb,and_H2O on Co,Ni,As,Cr,and Cu.