冻融作用对土壤胶体及胶体结合态铅迁移的影响

以东北地区棕壤为研究对象,通过人工控温和土柱淋洗试验,研究了不同冻融处理下铅污染土柱中土壤胶体和胶体结合态铅的迁移特征。结果表明:土壤高含水量(田间持水量100%)条件下冻融作用促进土壤胶体的迁移;土壤低含水量(田间持水量10%)条件下冻融作用对土壤胶体的影响减弱。淋洗试验中,土壤胶体在前20 min内大量淋失出土体,随后淋失量急剧减少;且前20 min内的土壤胶体淋失量随着冻融次数的增加先增加后减少。污染土柱中铅主要以胶体结合态的形式迁移,其迁移特征和受冻融作用影响的趋势与土壤胶体类似。冻融处理后滞留在土柱深层的铅含量较高,表明冻融作用能够促进铅向深层土壤迁移。

Effect of freezing/thawing on transport of soil colloids and colloidal lead

Transport characteristics of soil colloids and colloidal lead (Pb)in contaminated soil columns treated with different freeze/thawing cycles were investigated by simulating the temperature conditions in soil column leaching experiments. Brown soil samples were collected from the northeast of China. The results showed that freezing/thawing accelerated the transport of soil colloids under higher soil water contents (100% of field capacity)and decreased it under lower soil water contents (10% of field capacity). A considerable proportion of soil colloids leached out during the first 20 min in the column leaching experiment, after which time the leaching amount decreased sharply. Moreover, the amount of soil colloids leached during the first 20 min increased first and then decreased with the extension in freezing/thawing time. Pb present in the contaminated soil columns was transported mainly in the form of colloidal Pb and its transport characteristics were similar to those of soil colloids. Higher proportions of Pb were retained in deeper layers of the soil columns, indicating that freezing/thawing could facilitate Pb transport.