Effects Of In Situ Remediation Of Organic Materials To Field On Heavy Metal Pollutionin Soil-wheat System

With the continuous development of economy and technology,as well as the excessive development and unreasonable use of natural resources,heavy metal pollution has become increasingly serious,and the research of controlling heavy metal pollution has received more public attention.More and more restorative materials have been used for the remediation of soil contaminated by heavy metals.At the same time,with the development of agriculture,a large number of organic waste are output and accumulated,which also brings serious environmental problems and resources waste,thus currently more attention has been paid on how to improve resource utilization.In recent years,the study used organic waste as restorative materials in disposal of heavy metal pollution gets a lot of concern.In this study,straw,cow dung and edible fungi residue as well as biochar and fly ash were used as restorative agents returning to field,so that the effects of these organic materials and their combination on soil physical and chemical properties,wheat growth and development characteristics,the transport and enrichment regularity of heavy metals in wheat and its bioavailability in farmland contaminated by heavy metalswere studied.The main conclusions are as follows:1.In the farmland contaminated by heavy metals,after adding straw,cow dung,edible fungi residue,biochar,fly ash,the compound of straw and fly ash,the compound of cow dung and fly ash,the compound of edible fungi residue and biochar,soil pH and the contents of soil organic matter were improvedsignificantly,as well as cation exchange capacity and enzyme activity of soil,which indicated effective improvement in soil quality.2.Moreover,after adding these restorative agents into the farmland contaminated by heavy metals,the stress of heavy metals on wheat population wasalleviated,the chlorophyll relative content of wheat leaf was increased,photosynthesis was improved,and the yield of wheat wasimproved ultimately.Among them,the effects of the cow dung treatment,straw treatment,straw and fly ash combined treatment and cow dung combined with fly ash treatment on the promotion of wheat production were more obvious.3.Furthermore,in the farmland contaminated by heavy metals,with adding these restorative agents,the transport capacity of Pb,Cd from other parts to the edible parts wasreducedto a certain extent,as well as the absorption and concentration of soil Pb,Cd in wheat grain,and the ability of transferring Cu from other parts to the edible parts in wheat wasweakened also.Meanwhile the absorption and enrichment of soil Cu in wheat grain was reducedwith treatments of cow dung,edible fungi residue,biochar,fly ash,cow dung combined with fly ash,edible fungi residuecombined with biochar.The absorption and enrichment of soil As in wheat grain wasincreasedwith all restorative agents treatments.4.In addition,after adding straw,cow dung,edible fungi residue,biochar,fly ash,the compound of straw and fly ash,the compound of cow dung and fly ash,the compound of edible fungi residue and biochar in various heavy metal contaminated farmland,the proportion of effective Pb and Cd in soil was reduced at different levels,the bioavailability of Pb,Cd in soil was weakened.The bioavailability of soil Cu was decreased bycow dung,edible fungi residue,biochar,fly ash,cow dung combined with fly ash,edible fungi residue mixed with biochar,while the soil Cu bioavailability was increasedwithstraw and straw mixed with fly ash treatment.The availability of soil As was increased with all treatments of adding restoration agents.5.Besides,soil pH,organic content and cation exchange capacity(CEC)have certain correlation with the contents of soil available Pb,Cd,Cu,As.Among them,soil pH,organic content have extremely significant negative correlations with the contents of soil available Pb,Cu.And a very significant negative correlation between soil CEC and the contents of soil available Pb,Cd has been seen,while soil CEC have a very significant positive correlation with soil available As.The content of each soil available heavy metal had an extremely significant positive correlation with its content in wheat grain.6.In the end,certain remediation effect on soil heavy metal pollution has been seen afteradding these restoration agents in farmland,and the combination of absorbing materials and organic materials were more effective than the use of single material.