Atmospheric deposition and flood inputs dominate paddy soil cadmium accumulation in Southern China: A multi-process...

Cadmium (Cd) contamination in paddy soils poses a serious threat to food safety in southern China, yet the dominant processes driving regional Cd accumulation remain poorly quantified. We developed a high-resolution, mass balance-based multi-process model that dynamically couples major input pathways (atmospheric deposition, irrigation, flood inundation, and agricultural inputs) with output pathways including plant uptake, surface runoff, and leaching to estimate spatiotemporal Cd fluxes from 2000 to 2023 in a mining-impacted rice-growing region. Model validation achieved coefficients of determination (R²) of 0.71 in non-floodplain and 0.65 in floodplain areas. Results indicate that atmospheric deposition and flood-induced inputs are the primary accumulation drivers, with mean fluxes of 2.97 and 13.01 mg·m⁻²·a⁻¹ , respectively, while outputs remain limited (total mean: 0.86 mg·m⁻²·a⁻¹), yielding an input-output ratio of 7.6:1. Persistent high-input areas, especially industrial belts and floodplains, show sustained or expanding contamination risk. Scenario simulations to 2080 reveal that integrated mitigation-combining atmospheric emission reduction, sediment removal, and flood control-can reverse Cd accumulation and promote soil recovery within 40 years. The proposed modeling framework is transferable to other contaminants and provides a scientific basis for regional-scale pollution process analysis and precision management, supporting the development of differentiated environmental remediation strategies.