Study On The Effect Of DOM On The Bioavailability Of Heavy Metals Under Poyang Lake Water Level

Heavy metal pollution in freshwater ecosystem has been a prominent problem in China.Strengthening the comprehensive prevention and control of heavy metal pollution has been included in the major planning.In recent years,the heavy metal pollution in Poyang Lake Basin is becoming more and more serious,and the ecological environment is becoming more and more severe.Dissolved Organic Matter is one of the important factors to control the speciation and bioavailability of heavy metals.However,most of the research on the interaction between heavy metals and DOM in Poyang Lake is in the laboratory,which has some limitations.The practicability of heavy metal pollution control and ecological restoration of water environment in Poyang Lake is not very high,and Poyang Lake is a typical large-scale overflow lake In order to restore and protect the ecosystem of Poyang Lake,it is necessary to consider its hydrological characteristics,and explore the impact of DOM heavy metal microbe interaction on the bioavailability of heavy metals under the change of hydrological conditions.This is of great reference value and practical significance for the treatment of heavy metal pollution and the restoration and protection of the ecosystem in Poyang Lake It’s just.In this study,Carex cinerea,a wet plant in Poyang Lake,was used as the research object to simulate the aquatic ecological environment of Poyang Lake and explore the effects of DOM from different sources on the bioavailability of heavy metals and its mechanism under different water levels.In the outdoor simulation experiment,by analyzing the biomass of plants,the speciation changes of heavy metals in soil,and the enzyme activities in soil,the migration and transformation of heavy metals in plant soil system under the influence of DOM and water level were explored,as well as the influence of heavy metals on the bioavailability of microorganisms and plants.The results show that hydrological conditions and DOM are important factors affecting the migration,transformation and bioavailability of heavy metals.The main conclusions are as follows:(1)The addition of DOM can promote the growth of plants under certain conditions.The ability of Cu accumulation and transportation of Carex is higher than that of Pb.The addition of DOM weakened the accumulation of heavy metals in the roots of Carex,and promoted the transfer of heavy metals from the roots to the stems and leaves.(2)The increase of pH is accompanied by the decrease of Eh,and there is significant negative correlation between them.EC overall is down.Under the same DOM treatment,the increase of pH and the decrease of EH were the largest during flooding;At the same water level,the addition of DOM increased the amplitude of soil pH increase and eh decrease.(3)DOM can restore or promote the activity of microorganisms,increase soil fertility,provide nutrients for microorganisms,stable environmental conditions are more conducive to enzyme activity,and the effects of DOM and soil environmental conditions on enzyme activity are complex and changeable.(4)When not flooded,adding DOM can activate Cu,but passivate Pb;When flooding,the addition of DOM can activate both Cu and Pb;The effect of DOM on heavy metals is not stable under the condition of alternate flooding.