生物炭与磷肥配施对棕壤中Cd形态及其有效性的影响

Effect of the Combined Application of Biochar and Phosphorus Fertilizer on Forms and Efficacy of Cd in Brown Soil

通过实验室模拟Cd污染棕壤,探讨单施不同量(20和40 g·kg^(-1))花生秸秆生物炭(PB)和棉花秸秆生物炭(CB)、20 g·kg^(-1)磷肥(P)以及两者配施对污染土壤p H值及5种形态Cd含量变化的影响,分析生物炭、磷肥及其联合作用对棕壤Cd生物有效性的影响机制。结果表明,单施磷肥可显著降低土壤p H值(较CK降低14.64%),单施生物炭以及两者配施均可提高土壤p H值(较CK增加0.99%~24.67%),以单施40 g·kg^(-1)花生生物炭处理土壤p H值增幅最显著。单施磷肥显著降低土壤可交换态、碳酸盐合态和铁锰氧化物结合态Cd含量,增加有机结合态和残渣态Cd含量;单施生物炭和配施处理均可使土壤可交换态Cd含量显著减少,碳酸盐结合态Cd含量显著增加(49.76%)。在相同施炭量(20 g·kg^(-1))下,配施处理土壤有效态Cd含量的降幅高于单施处理,且花生秸秆生物炭与磷肥配施处理效果优于棉花生物炭与磷肥配施,Cd活性系数分别为0.150和0.236,即20 g·kg^(-1)花生秸秆生物炭+20 g·kg^(-1)磷肥(P+PB_2)混合处理最有利于降低土壤Cd生物有效性。

By simulating Cd-contaminated brown soils in the laboratory,the impacts of single applications of different amounts(20,40 g·kg^-1)of peanut straw biochar(PB)or cotton straw biochar(CB)and 20 g·kg^-1 phosphate fertilizer(P),as well as the combined application of biochar and P fertilizer,on soil pH and the contents of five forms of Cd in contaminated soils were investigated.The mechanisms of the effects of biochar,phosphate fertilizer and their combination on the bioavailability of Cd in brown soil were analyzed.The results show that the single application of P fertilizer significantly reduced the pH of the soil(by 14.64%compared with CK)and that the application of biochar alone or the combination of biochar and P fertilizer increased the pH of the soil(by 0.99%-24.67%compared with CK).The single application of 40 g·kg^-1 peanut biochar yielded the most significant increase in soil pH.The application of P fertilizer alone significantly reduced the contents of exchangeable,carbonated,and iron-manganese oxide-bound forms of Cd in the soil while increasing the contents of organic-bound and residual forms.The application of biochar alone and the combined treatment significantly reduced the content of the exchangeable form of Cd in the soil and significantly increased that of carbonate-bound Cd(by 49.76%).With the same applied amount of biochar(20 g·kg^-1),the decrease in effective Cd content was higher in the soil treated with the combined application than in that of the single application treatment,and the effect of the combined application of peanut straw biochar and phosphate fertilizer was superior to that of cotton biochar and phosphate fertilizer,with Cd activity coefficients of 0.150 and 0.236,respectively.The combined application of 20 g·kg^-1 peanut straw biochar+20 g·kg^-1 phosphate fertilizer(P+PB 2)was the most beneficial for reducing the bioavailability of Cd in soil.