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Published on: October 16, 2018
Reactive transport modeling of pollutants in heterogeneous layered paddy soils: a) Cadmium migration and vertical
Han Zhang1, Shujia Ke1, Shihong Zhang1
1State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Abstract:
Cadmium (Cd) pollution in soil has attracted more attention recently for its high toxicity and easy accumulation in crops. This study aims to investigate the mechanisms governing the transport behavior of Cd, and to simulate and predict the long-term migration of Cd in different paddy soil layers. Therefore, a layer-by-layer (LBL) model based on the geochemical model PHREEQC was developed. A dual-porosity finite difference method was applied to model the two-region diffusion process. The solute transport parameters were obtained by field measurement, literature review, or inversely estimation using PHREEQC based on the experimental results. Modeling and experimental results both indicate that different mechanisms (cation exchange reaction, preferential flow, etc.) control the transport and vertical distribution of Cd. The prediction results show that only the surface soil (< 0.3 m) would pose the risk of Cd2+ pollution. The coupled LBL model could correctly simulate the migration of Cd under near-field conditions.
