土壤中镉铅锌单一和复合老化效应的研究

Single and Combined Aging of Cadmium, Lead and Zinc in Soil

重金属的形态随时间变化,即老化效应,对评价重金属污染有着重要意义。本实验采用实验室模拟方式人为加入不同浓度的镉铅锌盐溶液,于污染后的第3、7、15、30、90、180、360d采样,用0.01mol·L-1CaCl2提取可利用态。单一老化效应的结果表明:Cd、Pb、Zn的有效态浓度在开始的7d内迅速减小,7～30d内缓慢减小,而30d以后浓度趋于稳定,达到动态平衡。Pb的有效态减少相对最为显著。在Zn或Pb存在的条件下,重金属的交互作用产生的复合老化效应表现为Cd的稳态浓度显著高于单一老化效应,并且达到稳态的时间延长。Pb比Zn对有效态Cd含量的增加有着更为显著的影响。

The changes of metal speciation with time, known as aging, have been considered as an important factor in evaluating risks of metal pollution in soil. The present work investigated the single and combined aging of cadmium （Cd）, lead （Pb）, and zinc （Zn）. CaCl2 extraction was employed to examine the bioavailable speciation of Cd, Pb and Zn in soils. Cd, Pb, Zn or their mixture were added into seventeen treatments of soils, respectively. Soils were sampled at 3rd, 7th, 15th, 30th, 90th, 180th, and 360th day after pollution and then extracted using 0.01 mol·L^-1CaCl2. The results showed that in the single aging the bioavailable concentration of all the three metals decreased sharply during the first 7 days, then mildly from 7th to 30th day, and approached to nearly steady state after 30th day. The decline of concentration of Pb was the most prominent among the three metals. In the combined aging, the presence of Zn or Pb significantly influenced the aging of Cd. Compared with the single aging of Cd, concentration of bioavailable Cd in the steady state was significantly higher and incubation period before equilibrium was significantly longer in the combined aging in the presence of Zn or Pb. The presence of Pb increased the concentration of bioavailable Cd more significantly than that of Zn.