This paper is the result of agricultural geological survey engineering.

Objective Liuxin Town and Maocun Town in Tongshan District, Xuzhou City, have drawn attention due to the elevated levels of soil selenium (Se). We elucidate the distribution of Se-enriched zones and identify the underlying sources.

Methods A comprehensive sampling was conducted, including 3067 surface soil samples, 3 vertical soil profiles, 4 atmospheric dry deposition samples, 8 sets of irrigation water and sediment samples, 4 coal gangue samples, and 1 fly ash sample.

Results The surface soil Se concentrations ranged from 0.08 to 15.80 mg/kg, with an average of 0.57 mg/kg and a coefficient of variation (CV) of 1.14, indicating strong spatial heterogeneity. Significant Se enrichment was observed in the soil surface layer, atmospheric dry deposition, and river sediments, primarily driven by coal-related anthropogenic activities. These included Se volatilization and fly ash dispersal during coal combustion, Se leaching and migration from accumulated fly ash and coal gangue, discharge of mining and washing wastewater, and land reclamation in coal mining subsidence areas, etc. Point-source Se hotspots were linked to open-pit coal gangue stockpiles and coal-fired atmospheric emissions, whereas non-point-source was mainly attributed to hydrological transport. For instance, in the areas of Liuwu-Dazhuang-Maocun-Tanshan village corridor, high-Se fly ash was transported via runoff through river networks, subsequently entering farmland soils via irrigation. A comprehensive evaluation of Se-enriched cultivated land resources revealed that there were 8145.61 hectares of Se-enriched area, of which premium Se-enriched land accounted for 79.39% of the total area, and the estimated total selenium resource in the topsoil was 13.34 tons, indicating significant potential for agricultural development and utilization.

Conclusions The present study provided foundational data to support the exploitation and utilization of Se-enriched soils in the study area. Future efforts should focus on monitoring selenium levels in agricultural products and human dietary intake, while promoting selenium industrial upgrading through optimized land-use planning, technological innovation, policy incentives, brand establishment, financial support, and resource management.