Estimation of chromium potential risk stock in karst soils: Insights from spatial and depth variations in...

Potential risk stock assessments of heavy metals are essential for informing management strategies and mitigating environmental and human health risks. This process enables cost-effective decision-making, supports regulatory compliance, and promotes sustainable land and ecosystem management; however, such studies remain limited. To investigate chromium (Cr) distribution and estimate its potential risk stock under varying soil layers, soil types, parent materials, and land-use conditions, a large dataset of surface soils, deep soils, and soil columns from a karst region in southwestern China was analyzed. The concentration of Cr in surface soils, deep soils, and soil columns was 23.3 - 1126.9, not detected - 315.6, and 36.9 - 684.0 mg/kg, respectively. The consistency in the Cr distribution across the surface and deep layers, geological structures, and mine locations indicated a main geological origin for Cr rather than anthropogenic pollution. This was further supported by principal component analysis, which identified ore stockpiling and parent-rock weathering as the primary sources. Variance analysis showed significant influences of soil type, land-use type, parent rock, landform, soil pH, and SOC on spatial distributions. Cr exhibited exponential variations with depth. Using an exponential fitting model with multiple integrations, the Cr potential risk stock was estimated at 1.78 × 10⁵ tons with middle and deep layers accounting for the highest, underscoring the complexity and challenges of managing Cr risks. Given the limited soil resources in karst regions, it is crucial for local authorities to prioritize Cr risk management and implement targeted land-use strategies.