| In recent years,soil heavy metal pollution has become more and more serious,and food safety issues have become increasingly serious.How to treat heavy metals in soil to reduce the threat of heavy metals in food has become a very hot issue at present.Biochar is a newly emerged environmental functional material,showing good potential and prospect in the field of soil remediation.The material can be used as a soil improver to put into the soil to passivate the heavy metal Cd in the soil,and the use effect of different addition amounts and the level of cadmium in the soil itself will affect the passivation effect.Therefore,this study starts from this aspect.Through potted rice experiments,biochar was added to low-,medium-,and high-Cd soils after adding three kinds of added amounts to study the effect of the amendment on the bioavailability of Cd in soil and the Cd content in rice..The results of the study are as follows:1)After adding biochar,the p H value of the soil increased and the increase was small.Three groups of biochar C1,C2,and C3 were added to the soil with low Cd content.The soil p H increased by 1.46%,2.19%,and 2.05% compared with the control group.Adding biochar C1,C2,and C3 to soil with medium Cd content increased soil p H by 1.77%,3.69%,and 1.18%,respectively,compared with the control group.The addition of biochar C1,C2,and C3 to soil with high Cd content increased the soil p H by 0,0.74%,and 2.81% compared with the control.The addition of rice straw biochar in the experiment showed a small increase in soil p H.2)Adding biochar,the CEC in low and medium Cd soils was higher than that in the control group.Biochar C1,C2,and C3 and plant ash H1,H2,and H3 were added to soils containing low Cd content.After the increase in soil CEC was 0.66%,6.1%,10.07% and 13.31%,16.91%,and 11.1%,respectively,compared with the control soil.After the addition of biochar C1,C2,C3,and plant ash H1,H2,and H3 to the soil with medium Cd content,Compared with the control,soil CEC increased by 12.02%,10.32%,6.56% and 11.36%,4.28%,and 2.29%,respectively.In high-Cd content paddy soils,the CEC of H2 treatment soil was the highest,an increase of 11.22%.The amount of modifier added is not directly proportional to soil CEC.3)After adding biochar,the available Cd content in soil with low L content(low Cd content)decreased.After adding three groups of biochar C1,C2,and C3 to soil,the effective Cd content in soil was higher than that in the control group.Respectively decreased 7.3%,10.9%,24.0%.The content of available Cd in the soil of M level(medium Cd content)decreased.After adding three groups of biochar C1,C2,and C3,the content of Cd in the soil was decreased by 1.0%,2.7%,and 12.3%,respectively,compared with the control group.The content of available Cd in the soil of H level(high Cd content)decreased.Adding three groups of biochar C1,C2,and C3,the effective Cd content of soil was reduced by 31.0%,36.6%,and 37.1%,respectively,compared with the control group.After addition of biochar made of rice straw,the contents of available Cd in soils at L,M,and H levels were all decreased.4)After addition of biochar,Cd content in rice with low Cd content decreased with the increase in the amount of modifier added.In medium-to-high Cd soil,Cdcontent in rice increased with the addition of modifier.Rise and no significant increase in law.In the soil with low Cd content,the Cd content of rice decreased.Adding biochar C1,C2,C3,the Cd content of rice decreased by 0.03%,0.25%,and 0.18% compared with the control.The content of Cd in rice with medium and high Cd content increased,and the content of Cd in middle Cd added with biochar C1,C2,C3.The content of Cd in rice increased by 30.52%,37.33%,and-4.81%,respectively,compared with the control.With the addition of biochar C1,C2,and C3,the Cd content of rice increased by-11.53%,43.71%,and 31.28%,respectively,compared to the control.5)According to the correlation analysis of the data,there was a significant correlation between the addition of soil amendments and soil p H(P<0.05).The total soil Cd and soil available Cd,soil Cd and rice Cd There was a significant correlation(P<0.05),and the correlation coefficients were 0.96 and 0.917,respectively.There was also a significant correlation between the content of available Cd in soil and the Cd content in rice(P<0.05).The correlation coefficient was 0.886.After addition of biochar made from straw,the enrichment coefficient showed a decreasing trend,a smaller decrease,and a poorer level in soils with low Cd content in soils with medium and high Cd levels as the added amount increased.The effect is that the enrichment coefficient is the trend of the upper body. |
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