Distribution Characteristics And Influencing Factors Of Heavy Metals In Sediment-Plant-Epiphytic Biofilm System In Caohai Wetland,Guizhou

In order to systematically grasp the content distribution,potential ecological risk and possible sources of heavy metals in the wetland.Water and sediment samples were collected from Caohai wetland in Guizhou Province to determine the concentration of heavy metals（Cu,Cr,Pb,Cd,As and Hg）in water and sediment samples.And analyze the metal forms in the sediments.The results showed that the concentration of Pb,Cd and Hg in the six heavy metals selected in this study all exceeded the background critical values in the sediments of Guizhou Province.However,heavy metal pollution in wetland sediments may not lead to excessive heavy metal pollution in water bodies.Risk assessment methods such as PLI,Hakanson,RAC were used to reveal that Caohai wetland sediment is mainly regulated by ecological risk of heavy metal Cd.The bioconcentration coefficients of six heavy metals in 9 plants are arranged in order:As>Cu>Pb>Hg>Cr>Cd,which shows that these plants are more inclined to accumulate metal As.The concentration of As and Pb in plants is significantly correlated with NH⁴⁺,TN and TLI in the water environment.The concentration of C N P in plant has a significant correlation with the concentration of As,Cd and Hg in plants,but has almost no relationship with the concentration of Cr,Cu and Pb in plants.And the concentration of C N P in the sediments hardly affects the accumulation of heavy metals in plants.To understand the accumulation characteristics of heavy metals in wetland submerged plants and epiphytic biofilms.To grasp the relationship between heavy metals in submerged plants and epiphytic biofilms and the concentration of heavy metals in the environment.We collected Caohai submerged plants（P.lucens）and（M.verticillatum）and their epiphytic biofilms.The concentration of heavy metals such as Pb,Cd,Cu,Cr,Hg and As was analyzed.The results showed that the concentrations of Pb,Cu,Cr and As in the epiphytic biofilms were higher than those in plants.The concentration of Hg in plants is greater than that in epiphytic biofilm.Cd has no obvious distribution pattern in plants and epiphytic biofilm.There is no significant correlation between the concentration of heavy metals in plants and epiphytic biofilms and the concentration of environmental heavy metals.Except for the extremely significant negative correlation between Hg and As with some elements in plants,the correlation between other elements is not significant,and no co-accumulation has been found.However,there are co-accumulation and competition between different heavy metal elements in the epiphytic biofilm.This difference may be related to the different accumulation mechanisms of heavy metals in plants and biofilms.The above research and findings provide scientific basis and basic data for the environmental risk management,pollution prevention and control of the Caohai wetland and ecological restoration in the reservoir area.This is of great significance for understanding the geochemical cycles of heavy metals in the Caohai wetland ecosystem.The discovery and resolution of these problems has an important guiding role for the protection of birds in the Caohai Wetland and the regulation of ecological risks.