The Application Of Residue Transformed From Food Waste By Fly Maggots In Cadmium And Lead Soil Passivating Remediation

Soil passivation is widely used in heavy metal soil treatment because of simple operation,low cost and high efficiency.The type of passivating agent affects the passivating effect to a large extent,so it is of great practical significance to seek more passivating agents.Farmland soil as the research object in this study was collected from the Salween area of Chengdu,through artificially adding exogenous heavy metal cadmium?Cd?,lead?Pb?in soil,the fermentation of bots transformed the kitchen waste into residue,tea biochar,straw,lime and their combination to form six treatments:Single application of fly maggot residue?R?,single application of biochar?B?,1:1 application of biochar with residue?BR?,1:1 application of straw with residue?SR?,1:1 application of biochar with residue?BRC?and 1g lime,1:1 application of straw with residue and 1g lime?SRC?.Two addition amounts of 1%and 2%were set for the six treatments,with no addition as the control group.After 4 weeks of culture in pot,Chinese cabbage was planted to verify the effect of passivation repair.In order to provide a reference for the application of fly maggots into the remediation of heavy metal contaminated soil.The main research results are as follows:?a?Different treatments reduced the contents of DTPA-Cd and DTPA-Pb in soil and the proportions of exchangeable Cd and Pb,increased the proportions of organic bond state and residue state Cd and Pb.The content of DTPA-Cd and DTPA-Pb in 2%-BRC treatment was the lowest,were 0.211mg/kg and 47.95mg/kg,respectively,which was significantly lower than the control?P<0.05?.The addition of passivating agent also improved the binding strength of Cd and Pb with soil and redistribution coefficient,2%-BRC had largest increment.?b?The addition of passivating agents increased the contents of pH,EC,DOC in soil solution,and the highest pH and EC values were found in 2%-BRC,while the contents of DOC in soil solutions were different in different treatments.Compared with the control group,the concentrations of Cl^-were decreased and SO₄^2-were increased in soil solution in each treatment,and the concentrations of 2%-BRC reached the extreme value.?c?The content of organic matter,total nitrogen,total phosphorus,available phosphorus,available potassium,NH₄⁺-N and NO₃^--N in soil were increased by adding passivating agent.At the same time,the activity of urease,phosphatase,sucrase and catalase were increased.Among them,the activities of urease,phosphatase and catalase in Cd contaminated soil increased most significantly with 2%-BRC.The activities of urease and sucrase increased most significantly in Pb polluted soil by 2%-SRC,and the activities of catalase increased most significantly by 2%-BRC.According to the redundancy analysis,DTPA-Cd,DTPA-Pb,organic matter,NH₄⁺-N and NO₃^--N contribute to the soil enzymes.?d?The results of fuzzy mathematical analysis showed that the compound combination with 2%addition was better than that with single application.Among the Cd contaminated soil,2%BRC had the highest comprehensive score.Among Pb contaminated soil,2%-BRC had the best passivation and remediation effect,but combined with the effects on soil fertility,soil enzyme environment and other aspects,the combination of2%-BR had the highest comprehensive score.This indicated that fly maggot transformed kitchen intio residue with biochar had better soil Cd and Pb passivation effect,which had certain application value.