Effect Of Forage Growth On Heavy Metals Migration In Soils Around Electrolytic Manganese Residue Storage Yard And Its Remediation

With the rapid development of electrolytic manganese industry,the environmental problems caused by extensive storage of electrolytic manganese residue(EMR)are becoming more and more serious.A large number of heavy metals are migrated to the soil and water with rainfall,causing harm to human body.Therefore,effective measures are urgently needed to deal with this pollution problem.Phytoremediation technology is one of currently the most economical and effective means,Lolium perenne and Medicago sativa not only have strong tolerance and enrichment ability to heavy metals,but also have fast growth rate,short growth period and large biomass.Using M.sativa and L.perenne as experimental materials,the growth status of M.sativa and L.perenne and their absorption characteristics of heavy metals(Mn,Cu,Zn,Cd)in the EMR-soil mixed matrix were discussed under potted-leaching conditions.In addition,heavy metals migration in soils around electrolytic manganese residue storage yard and its remediation were research.The pioneer grass species were screened out to provide scientific basis for heavy metals pollution control in mining area and ecological remediation.The main conclusions of this study are as follows:1)By sampling and analyzing the soil around the EMR yard,it was found that in addition to content of Mn,the content of Cd,Zn,Cu and Pb was also high,and the content of Mn,Zn,Cu,Pb was higher than the background value of soil in Guizhou Province.In the same yard,the closer the distance of sampling point from the yard,the higher the total Mn content and the effective Mn,well the more serious the Mn pollution.There was no obvious correlation between other heavy metals and the distance from the yard.There was mainly Mn pollution,followed Cd and As,while the pollution degree of Cu and Zn was less.2)After mixing EMR had inhibitory effect on seed germination.The inhibition of M.sativa germination was greater than that of L.perenne.But mixing proper amount of EMR can promote the growth of M.sativa and L.perenne especially L.perenne,whose growth is almost not affected by the EMR.A lot of EMR mixing reduced the content of photosynthetic pigment in M.sativa but promoted the synthesis of photosynthetic pigment in L.perenne.The content of malondialdehyde(MDA)and the activities of superoxide dismutase(SOD),catalase(CAT)and peroxidase(POD)were significantly increased in M.sativa after EMR was mixed to the soil.While content of MDA and activities of SOD,CAT,POD in L.perenne had no significant changes.The order of the plan’s tolerance was L.perenne >M.sativa.3)The early forage growth activated Mn in the soil.Alfalfa and ryegrass had different effects on the leaching and migration of heavy metals in soil with different amounts of manganese residue.M.sativa accumulates heavy metals mainly through its roots and the content of heavy metals was the root > the ground part generally.The accumulation to Zn in L.perenne was only ground part > Roots,while the enrichment of Mn,Cu and Cd were root>the ground part.On the whole,the accumulation to Mn,Cu and Cd was L.Perenne > M.sativa,while concentration to Zn was M.sativa > L.perenne.With growth of two forage,the migration of Mn,Cu,Zn,Cd to water was effectively reduced.L.perenne had a better effect on the restoration of Mn and Cd,and could be used as the dominant grass species for soil ecological restoration.4)On the contaminated soil which was collected from EMR yard,the germination of L.perenne was obviously inhibited by Mn,while the changes of ground biomass and plant height showed“hormesis effect”.CAT showed a more sensitive response to heavy metal stress.When the Mn content exceeded 10000 mg/kg,the plant was subjected to obvious stress.MDA content,SOD and POD activities were increased significantly.L.perenne not only has a strong tolerance to heavy metals,but also has a good accumulation of heavy metals in the soil.which effectively reduces the migration of heavy metals to the environment and plays a good remediation effect.It can be used as a pioneer plant for soil ecological remediation.