生物炭与沸石混施对不同污染土壤镉形态转化的影响

采用室内培养模拟了低(1.0 mg/kg)、高(10 mg/kg)镉污染的土壤,通过向镉污染土壤中添加0.4%,2%,10%的1∶1的生物炭和沸石的混合物,探究了生物炭及沸石混施对不同程度镉污染土壤的pH和镉形态变化的影响。结果表明:2种不同程度镉污染土壤的pH均较CK有所提高,且随钝化剂用量的增加而增大。随着培养时间的延长,低污染土壤pH呈现降低趋势,而高污染土壤pH先升高后降低最后趋于稳定。培养后期,低污染和高污染土壤在混合物添加量分别为2%和10%时有效态镉降低比例最大,降低比例分别为56.78%和27.33%。各处理土壤随生物炭和沸石混合物添加量的增加交换态镉降低比例逐渐增大,培养后期,低污染土壤的交换态镉较CK分别降低8.35%,13.81%,20.65%,高污染土壤的交换态镉较CK分别降低10.02%,22.34%,33.01%。各处理的钝化剂能够明显的降低交换态镉的含量,增加碳酸盐结合态、铁锰氧化物结合态、有机结合态和残渣态镉的含量,低污染土壤的有机结合态明显高于高污染土壤。由此可见,生物炭与沸石混施能够降低土壤重金属的生物有效性,为农田土壤修复奠定了理论基础。

Influence of Fixed Addition of Biochar and Natural Zeolite on the Fraction Transform of Cadmium in Different Contaminated Soil

The different cadmium (Cd) contaminated (1.0 and 10.0 mg/L) soils were simulated in laboratory. And the effects of fixed addition of biochar and zeolite (1:1) on soil pH and the changes of Cd morphology were studied. The addition amounts of the mixture were low (0.4%), medium (2%) and high (10%), respectively. Results showed that the values of pH were higher in the contaminated soil than the control, and increased with the increasing addition amount of mixture. With the increasing?incubation?time, the value of pH was gradually decreased in the lowly contaminated soil, whereas increased earlier, then decreased, and finally stable in the highly contaminated soil. In the late stages of incubation, the decreased percentages of effective Cd with the mixture addition of 2% and 10% were highest for the lowly contaminated and highly contaminated soil respectively, i.e. 56.78% and 27.33%. The exchangeable Cd percentage was gradually increased with the addition of biochar and zeolite mixture in soil. The percentages of exchangeable Cd were reduced by 8.35%, 13.81% and 20.65%, respectively, compared with the control soil in the lowly contaminated soil, and by 10.02%, 22.34% and 33.01%, respectively in the highly contaminated soil. The contents of exchangeable Cd could be reduced in soil with the passivation agent, through increasing the Cd contents of Carbonate bound, Fe-Mn oxide-bound, organic-bound and residual Cd. The Cd content of organic-bound Cd was higher in the lowly contaminated soil than the highly contaminated soil. Thus, the fixed addition of biochar and zeolite could reduce the bioavailability of heavy metals in soil, providing a theoretical foundation for farmland soil remediation.