The Passivation And Remediation Of Heavy Metals In Compound Contaminated Soil After Simultaneously Applying Rice Husk-derived Biochr And Fertilizers

The contamination of soils with heavy metals has become a major environmental concern in many parts of the world.Heavy metal pollution not only affects the soil ecological environment,but also damage to the animals,plants and human.Biochar is a kind of solid products which is obtained by thermos-chemical conversion when biomass under the condition of limited oxygen.Application of biochar can potentially provide a new solution for remediation of the soils contaminated by heavy metals.Relatively few laboratory or field studies address compound contaminant types,usually focusing on metals individually.The research for heavy metal compound pollution is less especially for the restoration by simultaneously applying biochar and fertilizers.In this paper,the experiments were took under the condition of laboratory pot and field experiment,on the basis of the detection method of heavy metals in soil and crop by ICP-MS.The rice husk-derived biochar was took as the research object in view of the heavy metal lead(Pb),arsenic(As),chromium(Cr)and cadmium(Cd)compound contaminated soil,the transferring disciplinarian of heavy metal in soil-rice system and vegetable,and the control of biochar combined with fertilizer.The main research results as follows:1.When ICP-MS operated under the parameters for power 1500 W,auxiliary gas flow rate of 0.6 L/min,carrier gas flow rate of 1.0 L/min,the sampling depth 8mm and peristaltic pump speed 0.1 ps,the detection limit of Pb,As,Cr and Cd in the are:0.01?g/L,0.01?g/L,0.22?g/L and 0.01?g/L.2.The plant samples was treated by plate digestion,and the optimal digestion condition through the orthogonal experiment is:acid system with 5 mL of nitric acid,digestion for 3h,decomposition temperature for 105?.The soil was treated by microwave digestion method and the optimal digestion condition for the third stage:under 190?,keep 20 min,power for 800 W after the optimization through orthogonal experiment for third stage.3.After the addition of Pb,As,Cr and Cd in soil,the content of heavy metals in soil and plants increase with the increase of adding amount of content had significant linear positive correlation,Y=0.62+21.43X,Y=0.92+2.90X,Y=0.98+21.86 X and Y=21.86X-0.01,the R~2 of 0.9078~0.9769.Heavy metal contamination of soil with biochar and fertilizer,the content of heavy metals in plants and heavy metal enrichment coefficients and applying biochar content has significant linear negative correlation,R~2 is0.8404~0.9307,shows that biochar and NPK fertilizers can effectively reduce the heavy metals in potting soil to plant in the migration.4.In vegetable field experiment,compared with the black control(CK),the content of Pb,As,Cr,Cd in vegetables after applying bichar(BR),biochar combined with NPK fertilizer(BRC)and biochar combined with microbial fertilizer(BRM).After treatments,the weigh,dry weigh and plant height increased and the content of nitrogen decreased.The results showed biochar can effectively control the migration of heavy metal from soil to plants,and it can increase the weigh and edible quality of vegetables.The treatment of biochar combined with microbial fertilizer(BRM)show the best control of heavy metal.5.In rice field experiment,the content of Pb,As,Cr and Cd decreased after applying rice husk combined with fertilizer.The element concentration in plants in turn shows root>stem>grain,the enrichment coefficient in turn As,Cd>Pb,Cr.Compared with blank treatment,the treatment of BRC and BRM increased the yield by 6%and 5%.It shows rice husk biochar combined with NPK fertilizer has obvious advantages in heavy metal compound pollution farmlands.