Contamination of mercury in paddy soils from gold mining in Tasikmalaya regency, West Java, Indonesia: spatial...

Mercury (Hg) from artisanal and small-scale gold mining (ASGM) poses significant environmental and public health risks, particularly in tropical agricultural systems. This study investigated the spatial, seasonal, and vertical distribution of Hg in paddy soils surrounding ASGM activities in Tasikmalaya Regency, Indonesia, and evaluated the associated ecological and human health risks. Soil samples were collected along a topographic gradient from an uphill area to downstream lowlands at multiple depths during the wet and dry seasons. Hg concentrations were determined using ICP-OES and a mercury analyzer with analytical validation following Eurachem guidelines. Ecological risks were assessed using the Geoaccumulation Index ( $I_{\mathrm{geo}}$ ) and Potential Ecological Risk Index (PERI), while non-carcinogenic human health risks were evaluated using the Hazard Index (HI). Results showed that Hg concentrations were highest near the ASGM hotspot and decreased with increasing distance from the source in both seasons. Kruskal-Wallis analysis revealed significant spatial differences in Hg concentrations among sampling locations but no significant differences across soil depths. Hg concentrations in ASGM-affected areas generally exceeded the Australian soil quality guideline value (1 mg kg^-1), whereas those in non-ASGM areas remained below this threshold. $I_{\mathrm{geo}}$ ranged from unpolluted to extremely polluted, while PERI ranged from low to very high ecological risk, reaching a maximum value of 5941.2. HI indicated higher non-carcinogenic health risks for children than adults, with values exceeding 1 at sampling locations nearest the ASGM hotspot. These findings demonstrate the dominant influence of ASGM on Hg distribution and risk, supporting effective mercury management in ASGM-affected regions.