Research On Environmental Behavior And Influencing Factors Of Heavy Metals At River Water-sediment Interface Under The Action Of Macroinvertebrates

Benthic animals are the hub and important link connecting river overlying water and river bottom mud.Their life activities can change the physical structure of bottom mud,predation can effectively enrich heavy metals in bottom mud,and metabolic activities will affect the basic physical and chemical properties of river water-mud interface.In this study,crucian carp,leeches and snails with different vertical niches at the river water-mud interface were selected to build ecological simulation experiments to explore the influence of benthos with different vertical niches on the environmental behavior of heavy metals.Based on Pearson correlation analysis,the influencing factors of heavy metal migration and transformation under the action of benthos were explored,and the applicability of snails as indicators of heavy metal pollution in water was investigated.The conclusions are as follows:The study on the influence of benthic animals on the environmental behavior of heavy metals shows that the life activities of benthic animals will have an impact on the environmental factors at the water-mud interface,among which the indexes of turbidity,chemical oxygen demand,total organic carbon,ammonia nitrogen and total nitrogen of overlying water have obvious changes,and the indexes of p H,organic matter and total nitrogen of sediment have obvious changes.The contents of heavy metals in the overlying water of the three groups of animals are very low,and the most obvious effects on heavy metals Cr,Pb,Zn and Cu in the sediment are leech,leech,snail and snail;Crucian carp,leech,snail and snail have the most obvious effects on the morphological changes of heavy metals Cr,Pb,Zn and Cu in sediment The benthic animals with the highest average enrichment of heavy metals Cr,Pb,Zn and Cu are leech,crucian carp,snail and leech.The research on influencing factors of heavy metals migration and transformation under the action of benthos shows that heavy metals are generally positively correlated with water p H and negatively correlated with sediment p H,sediment organic matter and sediment total nitrogen.Therefore,water p H,sediment p H,sediment organic matter and sediment total nitrogen are the key environmental factors affecting heavy metals migration and transformation.Heavy metals Cr,Pb,Zn and Cu in Carassius auratus showed significant positive correlation,while Pb-Cu in snails had no significant correlation,while Cr-Zn,Zn-Cu in leeches had no significant correlation.The toxicological sensitivity of benthos to heavy metals shows that there is a good dose-effect relationship between the enrichment of heavy metal copper by snails,which can be used as an ideal organism to indicate heavy metal pollution in water The dry weight of snails decreases with the extension of exposure time,which can be used as a biomarker to reflect the toxic effect of pollutants on organisms before their death The activities of antioxidant enzymes SOD and CAT in snails were promoted at low concentration and inhibited at high concentration.The content of lipid peroxidation index MDA increased first and then decreased with time,which can be used as biomarkers to indicate heavy metal pollution in water.In summary,this study investigated the impacts of benthos in different vertical niches on the environmental behavior of heavy metals,identified the key environmental factors affecting the migration and transformation of heavy metals,and made clear the applicability of snails as indicator organisms and the feasibility of their dry weight,SOD,CAT and MDA as biomarkers,providing basic theoretical data for benthos to monitor and control heavy metal pollution in rivers.