镉在次级河流底泥中吸附—解吸特性及其风险评估

采用吸附解吸试验研究河流底泥对Cd2+的吸附解吸特征,评估Cd2+在底泥中的迁移性及其环境风险。结果表明:河流底泥对Cd2+的吸附质量比随Cd2+平衡质量浓度的增高而增大,Cd2+平衡质量浓度为23.09μg/mL时,底泥的最大吸附质量比为1 655.575μg/g;吸附率随Cd2+平衡质量浓度的增大而减小。底泥对Cd2+的吸附可以分为30 min前的快速吸附和60 min后的慢速吸附阶段。底泥对Cd2+的解吸质量比随吸附质量比的增高而增大,解吸率保持在1.51%~4.96%之间。保留因子R′对Cd2+平衡质量浓度的变化较敏感,随着Cd2+平衡质量浓度上升而下降。大溪河水体中Cd2+的实际分配系数Kd和保留因子R′分别为1 766.15 L/kg,99 968.76 L/kg,表明Cd2+在环境中迁移的风险较低。

Adsorption-desorption behaviors and risk assessment of cadmium in branch river sediments

The adsorption-desorption behaviors of Cd^2＋ in branch river sediments were studied using the adsorption-desorption test, and the transport characteristics and environmental risk of Cd^2＋ were assessed. The results show that the adsorption capacity of the sediments for Cd^2＋ increased, while the adsorption rate decreased, with the increase of the equilibrium concentration of Cd^2＋. The maximum adsorption capacity was 1 655. 575 /_tg/g when the equilibrium concentration was 23.09 μg/mL. The adsorbing process had two stages： the fast adsorption that occurred in the first 30 minutes, and slow adsorption that occurred after 60 minutes. The desorption capacity of the sediments for Cd^2＋ increased with the increase of the adsorption capacity, and the desorption rate ranged from 1.51% to 4.96 %. The retention factor was sensitive to the equilibrium concentration of Cd^2＋, and it decreased with the increase of the equilibrium concentration. The practical distribution coefficient （Kd） and retention factor （R＇） of Cd^2＋ in the Daxi River were 1766.15 L/kg and 99968.76 L/kg, respectively, indicating a low transport risk of Cd^2＋ .