镉在次级河流底泥中吸附-解吸特性及其风险评估

摘要

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23.09 μg/mL时,底泥的最大吸附质量比为1655.575μg/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1766.15 L/kg,99 968.76 L/kg,表明Cd2+在环境中迁移的风险较低.%The adsorption-desorption behaviors of Cd2+ in branch river sediments were studied using the adsorption-desorption test, and the transport characteristics and environmental risk of Cd2 + were assessed. The results show that the adsorption capacity of the sediments for Cd + increased, while the adsorption rate decreased, with the increase of the equilibrium concentration of Cd + . The maximum adsorption capacity was 1 655.575 μg/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 Cd2 + 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 Cd2+ , and it decreased with the increase of the equilibrium concentration. The practical distribution coefficient (Kd) and retention factor (R') of Cd2+ in the Daxi River were 1766.15 L/kg and 99968.76 L/kg, respectively, indicating a low transport risk of Cd2+ .