Study On The Passivation Effect Of Biomass Compound Passivator On Heavy Metal Polluted Soil

At present,due to the heavy metal pollution in farmland soil in China,the passivation remediation technology has excellent ecological advantages and application prospects in the field of soil remediation due to its characteristics of simple operation,quick effect and suitable for large-scale remediation.In this study,the soil in the HBS experimental field of heavy metal contaminated farmland in She Feng village,Zhongming town,Tongling county,Anhui province,China was taken as the research object to carry out the research on soil passivation and remediation.Through the soil passivation experiment in the laboratory,an environmentally friendly biomass compound passivator formula was preliminarily screened out,and the screened biomass compound passivator formula was respectively applied to the soil and soil contaminated by compound heavy metals in the HBS experimental field of tongling city,for the potted experiment of cabbage and amaranth.Effect of this biomass compound passivator was evaluated by analyzing the changes of soil p H,heavy metal morphology and the content of edible heavy metals in crops.The main results show:(1)The soil p H value of HBS test field was 5.54.It is acidic,with high content of total nitrogen,available phosphorus and available potassium,and good soil fertility.Pb,Cr,Ni,and heavy metal elements in soil As failed more than agricultural land soil pollution risk control risk screening value of the standard,Cu,zinc and Cd than risk control value of 2.42,1.09,and 3.87 times,respectively in pollution,light pollution and heavy pollution condition,but has not been over risk control value,the field of soil pollution in the overall level;According to the analysis of risk assessment code method(RAC),the ecological risk of heavy metals in the test field was Cd,Cr,Cu,Zn,Ni,As and Pb from strong to weak.Except for the low risk of Pb,the ecological risk of other metal elements was medium and high risk.Cd in the crops around the HBS experimental field exceeded the limit of heavy metals in food by an average of 1.28 times,and Cd was the main pollutant of crops.Among them,the content of Cd in rice was 4.3 times higher than the limit of food,and the rice was heavily polluted.(2)Using different ratio of biomass composite passivator for Cu,Cd and Pb compound passivation experiment of heavy metal contaminated soil,the results show that when the ratio of biochar and hydroxyapatite 4:1,p H value is 5.54,compared with the CK increased by 0.84;From the passivation rate,the passivation rate of Cu,Cd and Pb reached 75.14%,40.73% and 75.38%,respectively,which could well reduce the exchangeable state of heavy metals in the soil.From the point of biological availability,biological availability of Cu,Cd,Pb,reduced to 21.85%,47.12% and24.27%,respectively,have a good passivation effect on soil heavily.(3)HBS plots soil pot experiment results show that when adding 4% of the biomass composite passivator,reducing the heavy metals in soil can exchange state content of Cu,Cd,was reduced by 79.3% and 32.1% respectively;The contents of Cu and Cd in edible parts of Chinese cabbage reached 0.313mg/kg and 0.041mg/kg respectively,which were both lower than the limits of Cu ? 10mg/kg and Cd ?0.2mg/kg in the limit standards for contaminants in food.(4)Composite potted plant experiment results show that the heavy metal polluted soil under the adding amount of 0.5%,the soil heavy metal content of Cu,Cd,Pb bioavailable state was reduced by 45.61%,50.34% and 52.43%,respectively,the edible part of the amaranth heavy metals of Cu,Cd and Pb content dropped to 1.04mg/kg,0.12 mg/kg and 0.18 mg/kg,all below the evaluation standard of set limit to food contaminants,achieve the goal of planted to protect the safety of amaranth.Results show that the biomass composite passivator is effective passivation HBS plots and Cu,Cd,Pb compound pollution of heavy metals in the soil,to ensure food safety of agricultural products.