Immobilization Remediation Effect of Several Passivation Materials on Heavy Metals in Soil of Lead Smelting Sites
A soil incubation experiment was conducted to study the effects of cement,Mn-P modified biochar and Mn-P modified rice husk ash on soil pH and the available concentration of Cd,Pb and trace elements(Zn,Fe and Mn)in lead smelting site soils under four application rates of 0％,1％,2％and 4％.The results showed that with the increase of cement application rate,the pH of the lead smelting site soils significantly increased,and the availability of Cd and Pb decreased gradually.The soil pH of a smelting site in Jiyuan and a smelting site in Zhuzhou treated with cement increased by 0.89-1.84 and 0.89-1.76 units,respectively.The DTPA-Cd concentration treated with cement decreased by 34.3％-53.1％(P＜0.05)and 59.6％-73.2％(P＜0.05),and DTPA-Pb concentration decreased by 21.6％-44.7％(P＜0.05)and 38.4％-44.3％(P＜0.05),respectively.With the increase of application rates of Mn-P modified biochar and Mn-P modified rice husk ash,the soil pH,and Cd and Pb availability in lead smelting sites gradually decreased.The treatment of 4％Mn-P modified biochar reduced the soil pH of two lead smelting sites by 0.51(Jiyuan)and 0.40(Zhuzhou)units,respectively.The DTPA-Cd concentration significantly decreased by 18.0％(Jiyuan)and 39.8％(Zhuzhou),and DTPA-Pb concentration significantly decreased by 37.8％(Jiyuan)and 63.1％(Zhuzhou).The soil pH value of the two lead smelting sites treated with 4％Mn-P modified rice husk ash decreased by 0.70(Jiyuan)and 0.23(Zhuzhou)units,respectively.The DTP A-Cd concentration significantly decreased by 14.9％(Jiyuan)and 30.2％(Zhuzhou),and the DTPA-Pb concentration significantly decreased by 37.3％(Jiyuan)and 54.1％(Zhuzhou).The DTPA-Zn concentration in the soil of two lead smelting sites treated with 4％cement significantly decreased by 36.5％(Jiyuan)and 59.4％(Zhuzhou),respectively,and the DTPA-Fe concentration significantly increased by 122.7％(Jiyuan)and 142.9％(Zhuzhou),and the DTPA-Mn concentration significantly decreased by 13.8％(Jiyuan)and 69.1％(Zhuzhou),respectively.The treatment of 4％Mn-P modified biochar significantly increased the soil DTPA-Zn concentration by 48.7％(Jiyuan),and the DTPA-Mn concentration significantly increased by 409.7％(Jiyuan)and 538.6％(Zhuzhou),and the DTPA-Fe concentration significantly decreased by 33.4％(Jiyuan)and 30.7％(Zhuzhou),respectively.The treatment of 4％Mn-P modified rice husk ash significantly increased the soil DTPA-Zn concentration by 63.0％(Jiyuan),and the DTPA-Mn concentration significantly increased by 290.3％(Jiyuan)and 73.5％(Zhuzhou),and the DTPA-Fe concentration significantly decreased by 9.5％(Jiyuan)and 12.0％(Zhuzhou),respectively.The order of reducing Cd availability of three passivation materials in two lead smelting sites was cement＞Mn-P modified biochar＞Mn-P modified rice husk ash,and the order of reducing Pb availability was cement＞Mn-P modified biochar＞Mn-P modified rice husk ash(Jiyuan)and Mn-P modified biochar＞Mn-P modified rice husk ash＞cement(Zhuzhou).It was necessary to select suitable passivation materials based on the Cd and Pb pollution characteristics of lead smelting sites to achieve synchronous immobilization of soil Cd and Pb.
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