Arsenic in groundwater and soil across China: Spatial patterns, drivers, and risks to rice security and human health

Arsenic contamination poses a dual threat to global water safety and food chain integrity, with critical implications for public health and environmental security. Effective risk management from global to national scales is hindered by unresolved questions on the interconnected yet divergent spatial patterns of arsenic in groundwater and soil, and the compounded risks they pose to both staple rice security and human exposure. To address these challenges, we conducted a national-scale environmental health risk assessment in China, a critical rice-producing region, and developed an integrated framework that systematically links mechanistic driver identification with spatial risk prediction and management implications. We first constructed high-resolution predictive maps of arsenic enrichment in groundwater and soil across China, and then quantified and ranked the dominant drivers. These mechanistic-spatial maps were subsequently coupled with remote sensing-derived trends in rice cultivation expansion and analyzed via advanced spatial statistics. Our analysis revealed a fundamental decoupling between groundwater and soil arsenic, with the former governed by climate-topography and concentrated in the arid north and southwest, and the latter driven by mining and dominating in the south and northeast. Spatial correlation analysis indicated a moderate spatial correlation (Bivariate Moran's I = 0.274, p < 0.05), and identified critical interaction patterns, including synergistic ("high-high") and decoupled ("low-high") clusters. Crucially, the population exposed to soil arsenic was orders of magnitude larger than that from groundwater (with risk clusters reaching 100-1000 persons km⁻² in major agricultural regions), and major rice-growing regions had expanded directly into these soil arsenic hotspots over the past two decades, creating an immediate food security threat. This work not only quantified the overlapping health and food security risks but also pioneered a spatially explicit method to pinpoint priority regions where rice expansion intersects severe contamination, offering critical insights for targeted environmental health management and regulatory policy.