外源Cd~(2+)在土壤各级微团聚体中的含量和形态分布

采用室内培养和室内分析相结合的方法,研究了外源Cd~(2+)进入土壤30 d后,在土壤各级微团聚体中的含量富集和形态赋存情况.研究结果表明:外源水溶性镉进入土壤30 d后,100%转化成了颗粒态,其中58.5%转化为了可交换态,0.98%转化成了碳酸盐结合态,1.26%转化成了铁锰氧化物结合态,7.68%转化成了有机结合态,31.5%转化成了残渣态,这基本与其中各粒级微团聚体中的赋存形态的情况一致.在土壤中赋存的镉主要分布在各级微团聚体中,在各粒级微团聚体中的含量分布顺序为<10μm微团聚体>10～50μm微团聚体>50～250 μm微团聚体;外源镉向小粒级微团聚体的富集倾向明显高于向大粒级微团聚体的富集倾向,其中在<10μm微团聚体中富集系数为1.43,在50～250μm微团聚体中的富集系数只有0.60.

Contents and chemical speciation of water soluble Cd~(2+) added in soil microaggregates

Contents and chemical speciation of water-soluble Cd~(2+) in several different particle size microaggregate fractions 30 days after added into the bulk soil were investigated by using laboratory incubation method. Obtained results showed that, the added wa-ter-soluble Cd~(2+) were completely transformed into other forms including exchangeable fraction, carbonate bound fraction, Fe/Mn oxide bound fraction, organic bound fraction and residual fraction, with percentages of 58.5%, 0.98%, 1.26%, 7.68% and 31.5%, respectively. Such distribution pattern of Cd chemical speciation was consistent with those in different particle size microaggregates. The Cd added into the soil was mostly concentrated in the micruaggregate, and the Cd contents in the different particle size microag-gregates declined in the order of particle size <10 μm, 10～50 μm and 50～250 μm. The added Cd was more prone to be enriched in small microaggregate than big one. The enrichment coefficient of Cd was 1.43 in <10 μm particle size microaggregate, but only 0.60 in 50～250 μm.