State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China; Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Huazhong Agricultural University, Wuhan 430070, China.
State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
Chemosphere. 2018 Feb;193:943-950. doi: 10.1016/j.chemosphere.2017.11.100. Epub 2017 Nov 21.
The accurate modeling of heavy metal adsorption in complex systems is fundamental for risk assessments in soils and associated environments. Bacteria-iron (hydr)oxide associations in soils and sediments play a critical role in heavy metal immobilization. The reduced adsorption of heavy metals on these composites have been widely reported using the component additivity (CA) method. However, there is a lack of a mechanism model to account for these deviations. In this study, we established models for Cd adsorption on goethite-Pseudomonas putida composites at 1:1 and 5:1 mass ratios. Cadmium adsorption on the 5:1 composite was consistent with the additivity method. However, the CA method over predicted Cd adsorption by approximately 8% on the 1:1 composite at high Cd concentration. The deviation was corrected by adding the site blockage reactions between P. putida and goethite. Both CA and "CA-site masking" models for Cd adsorption onto the composites were in line with the ITC data. These results indicate that CA method in simulating Cd adsorption on bacteria-iron oxides composites is limited to low bacterial and Cd concentrations. Therefore the interfacial complexation reactions that occur between iron (hydr)oxides and bacteria should be taken into account when high concentrations of bacteria and heavy metals are present.
准确地模拟复杂体系中重金属的吸附对于土壤及相关环境中的风险评估至关重要。土壤和沉积物中的细菌-铁（氢）氧化物组合在重金属固定化方面起着关键作用。已经广泛报道了使用组分加和（CA）方法来降低这些复合材料对重金属的吸附。然而，目前缺乏一种机制模型来解释这些偏差。在这项研究中，我们建立了在 1:1 和 5:1 质量比下，针铁矿-假单胞菌复合体系中 Cd 吸附的模型。在 5:1 复合材料上，Cd 的吸附符合加和性方法。然而，在高 Cd 浓度下，CA 方法对 1:1 复合材料上 Cd 吸附的预测值偏高约 8%。通过添加假单胞菌和针铁矿之间的点位封闭反应，可以修正这种偏差。CA 法和“CA-点位掩蔽”法都适用于模拟 Cd 在复合材料上的吸附。这些结果表明，CA 方法在模拟细菌-铁氧化物复合材料上 Cd 吸附时的应用受到限制，只能在低细菌和低 Cd 浓度下适用。因此，当存在高浓度的细菌和重金属时，应考虑铁（氢）氧化物和细菌之间发生的界面络合反应。
