Experimental Study On Phytoremediation Of Soil Polluted By Heavy Metals In Xinhuang Mercury Mine, Hunan

Hunan Xinhuang Mercury Mine is located in Xinhuang Dong Autonomous County,Huaihua City,Hunan Province.Due to long-term non-standard discharge of pollutants from mineral mining and open-pit storage of waste residues after closing the pit,the local soil environment is seriously polluted.Heavy metals pass through the soil in the natural environment.Infiltration,causing serious pollution of the main local water sources.At present,the treatment of heavy metal pollution in soil has become an international hot topic,and finding a high-efficiency,low-cost,green and environmentally friendly repair method is an urgent problem to be solved.Four local native plants,centipede grass,artemisia,raspberry,and bidens,were selected for this experiment.Through field screening and greenhouse experiment,combined with three chelating agents of citric acid,malic acid and oxalic acid for joint restoration,the aim was to screen out effective restorations.For plants that contaminate soil characterized by mercury,a chelating agent that can assist phytoremediation and improve its remediation efficiency is found at the same time,providing new ideas for cross-joint remediation.The experimental results show that:(1)The main heavy metals in the soil in and around the mining area are Hg,As and Se,and among the six wild plants in the area,wild artemisinin,ghost needle grass and weeds are selected,and hooks are added to participate in the experiment.(2)Centipede grass,raspberry,and wormwood have the best removal effects on soil Hg,As,and Se;the removal rates are 20.27%,19.61%,and 92.96%,respectively.The enrichment coefficients of centipede grass,artemisia,rubus,and bidens for different heavy metals in descending order are:Se<Hg<As,Hg<Se<As,Hg<As<Se,Hg<As<Se;The coefficients from small to large are Hg<Se<As,Hg<Se<As,As<Se<Hg,Hg<As<Se.Hg,As,and Se are mostly distributed in plant roots,and most of them accumulate in plant leaves after being transferred to the ground.(3)The best effects of promoting centipede grass to remediate soil Hg,As,Se pollution are 2.50mmol/L citric acid,7.50mmol/L citric acid and 5.00mmol/L malic acid respectively;to promote artemisia annua to remediate soil Hg,As,The best effects of Se pollution are 5.00mmol/L citric acid,5.00mmol/L oxalic acid,5.00mmol/L citric acid;for rubus,the best effects of promoting As and Se pollution are 5.00mmol/L oxalic acid and 5.00 respectively.mmol/L citric acid,but failed to promote the restoration of soil Hg by rubus.For Bidens,adding the selected three types of single chelating agents can respectively increase the enrichment or transport coefficient of heavy metals in different plants.Taken together,the addition of chelating agents can to a certain extent by activating the occurrence of heavy metals,improve the repair efficiency of some herbs to soil mercury,arsenic,selenium and other heavy metal pollution.(4)Plant planting can affect soil enzyme activity,improve soil quality and reduce heavy metal concentration;the distribution of heavy metals in plants is affected by plant physiological processes;the effect of chelating agents on the efficiency of heavy metal repair can be considered from two aspects,one is chelating The mixture itself has the ability to activate,and the other is that the soil environment changes after the chelating agent is added.