基于LCD模型的土壤砷动态平衡分布多因子耦合机理

土壤中三价五价砷共存且可相互转化，二者比例和在土壤微界面吸附受pH、Eh、Ca、P、天然有机质等物理化学因素和植物根系活动等生物因素的交互影响，干扰了土壤砷行为准确评估。本项目旨在揭示多因子叠加效应下土壤砷形态分布变化的特征和机理，建立能准确预测不同土壤环境下砷及镉分布变化的土壤微界面模型。利用针铁矿、纯化腐殖质吸附实验，完善CD-MUSIC和NICA-Donnan模型参数。通过土壤淹水、真实和模拟根系、因子和分子探针等实验，利用AsFFFF、SEC和DMT等分析手段，揭示土壤砷形态与多种因子变化的动态耦合关系，明确土壤砷富集界面特征及其数量的测定方法。基于LCD模型，创立能计算多重因子对阴离子砷和阳离子镉土壤化学行为影响的分子机理模型。通过模型分析，指出砷、镉低活性的共同土壤条件窗口，为科学评价和治理砷及砷镉复合污染土壤提供科学支撑，为研究和精准预测环境体系中其它元素的化学行为奠定基础。

In soils, As(III) and As(V) exist simultaneously and are convertible. The ratio of As(III) and As(V) and their adsorption on the micro-interface in soils are influenced in a complicated manner by physical-chemical factors including pH, Ca, P and natural organic matter as well as biological factors such as plant root activities. These interactions interfered the assessment of As behavior in soils. The aims of this project are to accurately clarify the characteristics and mechanisms of As speciation and distribution when the influence of multiple factors are present, and to develop soil micro-interface models that are able to accurately predict chemical speciation of As and co-existing Cd under different soil conditions. Firstly, adsorption experiments will be carried out with goethite and purified humic substances, and the parameters of CD-MUSIC and NICA-Donnan model will be further optimized. With the experiments of soil flooding, plant growth, artificial roots, factor treatments and molecular probes, combined with AsFFFF, SEC and DMT techniques, the dynamic coupling between As speciation and distribution in soils and various factors will be revealed, and the characteristics of soil surfaces to which As accumulates and the method to estimate the amount of these reactive surfaces will be determined. Based on the LCD model, a molecular mechanistic model will be developed that can simultaneously predict the effects of multiple factors on the chemical behavior of both anions (such as As) and cations (such as Cd) in soils. With scenario model calculations, the common soil condition window in which both As and Cd have a low activity will be identified. The outcome of this project will provide scientific support for evaluation, usage and remediation of As contaminated as well as As and Cd contaminated soils. Further, the results achieved in this project will lay the foundation for research and accurate prediction of chemical behavior of other elements in environmental systems.