外源水溶性镉在红壤中的迁移和形态转化

目的]为污染土壤的控制和修复治理提供科学依据。方法]采用实验室土柱法,研究外源水溶性镉在红壤中的迁移和形态转化。结果]在非饱和水分条件下,外源水溶性镉进入红壤90 d后并未向15～30 cm土层迁移,而是集中在0～15 cm层次;外源水溶性镉进入红壤(0～15 cm)30 d后水溶态镉迅速向其他形态转化,其形态分布以交换态为主,其次为残渣态、铁锰氧化物态、水溶态、碳酸盐结合态、有机结合态。在其后的60 d内,外源Cd各形态的百分比随时间的变化幅度较小,其中交换态镉分别占总量的76.55%和72.31%。结论]绝大部分外源Cd进入红壤90 d后未转化为相对稳定的形态,对土壤—植物系统的污染存在着潜在的危害。红壤对外源水溶性镉的吸附主要通过离子交换和络合作用。

Transportation and Form Transformation of Water-Soluble Cadmium in Red Soil

Objective]The research aimed to provide scientific basis for the control and the remediation of soil pollution.Method] Transportation and form transformation of water-soluble cadmium in red soil were simulated by virtue of laboratory soil column tests.Result]Exotic Cd entered soil concentrated mostly on the stratum in depth 0-15 cm and hadn’t migrated on the stratum at unsaturated condition in depth 15-30 cm after ninety days.Water-soluble cadmium added to soil were rapidly transformed to other forms.Exotic Cd mainly existed in exchangeable fraction,secondly existed in residual fraction,Fe/Mn oxide bounded fraction,water fraction,carbonate fraction,organic bound fractionin depth 0-15 cm after thirty days.In following sixty days,the percentage of exotic Cd fraction varied little with time.The quantities of exchangeable fraction Cd were 76.55% and 72.31%.Conclusion]Exotic Cd hadn’t changed into more stable fractions after ninety days,which had potential harm for soil-plant system.The absorption mechanism on Cd of red soil mainly existed in ion exchange and complexation.