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| Predicting the adsorption and bioavailability of Cd2+ in soils using the 1-site/2-pKa surface complexation model |
| Received:March 25, 2022 Revised:April 25, 2022 |
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| KeyWord:Cd;surface complexation model;adsorption behavior;surface complexation constant;bioavailability |
| Author Name | Affiliation | E-mail | | YU Hemin | Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | LI Yan | Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | SHI Zhenqing | School of Environment and Energy, South China University of Technology, Guangzhou 510006, China | | | WANG Yujun | Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
1. Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China | yjwang@issas.ac.cn |
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| Abstract: |
| The bioavailability of heavy metals in soil is closely related to their adsorption behavior. In this study, nine different noncalcareous soils in China were selected to explore the adsorption process of Cd2+. The surface acid-base properties(pKa1 and pKa2)of the soil were obtained by potentiometric titration. Based on the 1-site/2-pKa model, the complexation constant(lg K(SOCd+))of Cd2+ was obtained by ECOSAT and FIT. The results showed that this model could well describe the adsorption process of Cd2+ in soils. To further explore the influence of soil properties on Cd2+ adsorption, the relationship between pKa1, pKa2, lg K(SOCd+) and soil properties was analyzed using stepwise regression. Soil pH and CEC were the main controlling factors of pKa1, and soil pH was also the main controlling factor of pKa2 and lg K(SOCd+).To verify model reliability, data from the historical literatures was selected to predict the soil surface acid-base properties and lg K(SOCd+) based on soil pH and CEC, and the Cd adsorption process was predicted using the predicted parameters. The predicted values were found to have a good correlation with the measured values, and the model explained 86% of the variation. In addition, the established binding constants were used to predict the concentration of Cd in soil solutions from historical literatures and the concentration of Cd predicted by the model was found to be well correlated with the content of Cd in earthworms, explaining 83% of the variation. In this study, based on the adsorption behavior of Cd2+ in soils with different properties, the generalized complex method was used to establish a surface complexation model to describe the adsorption and distribution process of Cd2+ in non-calcareous soils, thereby providing theoretical support for regional soil heavy metal environmental risk prediction. |
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