径流入渗时土壤胶体释放对重金属截留的影响

Effect of the released soil colloids on the interception of heavy metals during runoff infiltration

以吉林黑土、北京黄土和河北砂土作为模拟下渗柱土壤介质,考察进水pH值、流速和离子强度等条件变化时土壤胶体释放对重金属截留效果的影响,并揭示其主要作用机制.结果表明,土壤胶体与土壤颗粒间静电斥力是影响土壤胶体释放的主要因素,pH值为7.0时黑土、黄土和砂土胶体释放浓度最高,分别为216.5, 182.4和272.2mg/L;土壤胶体释放浓度与下渗柱截留重金属的量呈显著负相关(r>0.70,P<0.05);进水pH值越低、流速越高,下渗柱中截留的重金属量越低、土壤胶体携带重金属迁移量越多;进水Na+浓度越高,土壤胶体越不易释放,重金属越易被截留在土壤中;与其他2种土壤胶体相比,黑土胶体Zeta电位绝对值较高、稳定性较强、可移动性较高,对重金属的携带迁移能力较强.

Black soil in Jilin, loess soil in Beijing and sandy soil in Hebei were used as the media in the simulated infiltration columns. Effect of the released soil colloids on the interception of heavy metals under the conditions of pH, flow velocity and ionic strength in influent was investigated, and the mechanisms were also detected. The results showed that the electrostatic repulsion between the soil colloids and soil particles was the main factor affecting the release of soil colloids, and the highest concentrations of the released colloids were 216.5, 182.4 and 272.2 mg/L for black soil, loess soil and sandy soil at pH 7.0, respectively. The concentration of the released soil colloids was significantly negatively correlated with the amount of heavy metals intercepted in the infiltration columns(r>0.70, P<0.05). The lower pH and higher flow rate of the influent, the lower the amount of heavy metals retained in the columns and the more the amount of heavy metals carried by soil colloids to migrate. The higher concentration of Na+in influent, the less soil colloids was released and the easier the heavy metals were retained in the soils. Compared with the other two soil colloids, the black soil colloids had higher absolute zeta potential, higher stability and higher mobility, and were more capable of carrying heavy metals to migrate.