1-site/2-pK_(a)表面络合模型预测土壤中Cd^(2+)的吸附及生物有效性  

Predicting the adsorption and bioavailability of Cd^(2+) in soils using the 1-site/2-pK_(a) surface complexation model

作　　者：郁何敏 李焱[1,2] 石振清 王玉军 YU Hemin;LI Yan;SHI Zhenqing;WANG Yujun(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;School of Environment and Energy,South China University of Technology,Guangzhou 510006,China)

机构地区：[1]中国科学院土壤环境与污染修复重点实验室(南京土壤所),南京210008 [2]中国科学院大学,北京100049 [3]华南理工大学环境与能源学院,广州510006

出　　处：《农业环境科学学报》2022年第6期1211-1220,共10页Journal of Agro-Environment Science

基　　金：国家重点研发计划项目(2021YFC1809100)。

摘　　要：土壤中重金属的生物有效性与其在土壤中的吸附行为密切相关,本研究选取我国9个不同类型的非石灰性土壤,探究了Cd^(2+)在土壤中的吸附过程。通过电位滴定获得土壤表面酸碱性质(pK_(a1)和pK_(a2)),基于1-site/2-pK_(a)模型,使用ECOSAT和FIT拟合得到土壤与Cd^(2+)的络合常数(lg K(SOCd^(+))),结果显示该模型能很好地描述Cd^(2+)在土壤中的吸附过程。为了进一步探究土壤性质对Cd吸附固定的影响,通过逐步回归分析了pK_(a1)、pK_(a2)、lg K(SOCd^(+))与土壤性质间的关系,发现土壤pH和CEC是pK_(a1)的主控因子,土壤pH同时也是pK_(a2)、lg K(SOCd^(+))的主控因子。为了验证模型的可靠性,结合历史文献,基于土壤pH和CEC预测了历史文献中土壤表面酸碱性质和lg K(SOCd^(+)),利用得到的参数预测了Cd的吸附过程,发现预测值与实测值之间有很好的相关性,该模型能解释86%的变异。此外,利用回归模型得到的结合常数预测了历史文献中土壤溶液中的Cd含量,发现模型预测的Cd含量与蚯蚓体内Cd含量同样具有很好的相关性,能解释83%的变异。本研究基于Cd^(2+)在不同性质土壤中的吸附行为,使用广义复合法建立的表面络合模型可以描述Cd^(2+)在非石灰性土壤中的吸附与分配过程。The bioavailability of heavy metals in soil is closely related to their adsorption behavior.In this study,nine different non calcareous soils in China were selected to explore the adsorption process of Cd^(2+).The surface acid-base properties(pK_(a1) and pK_(a2))of the soil were obtained by potentiometric titration.Based on the 1-site/2-pK_(a) model,the complexation constant(lg K(SOCd^(+))) of Cd^(2+) was obtained by ECOSAT and FIT.The results showed that this model could well describe the adsorption process of Cd^(2+) in soils.To further explore the influence of soil properties on Cd^(2+) adsorption,the relationship between pK_(a1),pK_(a2),lg K(SOCd^(+))and soil properties was analyzed using stepwise regression.Soil pH and CEC were the main controlling factors of pK_(a1),and soil pH was also the main controlling factor of pK_(a2) and lgK(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 Cd^(2+) 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 Cd^(2+) in non-calcareous soils,thereby providing theoretical support for regional soil heavy metal environmental risk prediction.

关 键 词：CD 表面络合模型 吸附行为 表面络合常数 生物有效性 

分 类 号：X53[环境科学与工程—环境工程]