Based on a 1:50 000 geochemical land quality survey of Heshan District, Hebi City, and subsequent analyses of soil, rock, and crop samples, this study investigates the spatial distribution, origin, speciation, bioavailability, and soil-to-crop transfer of selenium (Se) in an alkaline environment. The results demonstrate significant Se enrichment in the central-eastern soils. The spatial pattern of Se-rich soils is primarily controlled by Carboniferous coal-bearing strata, with elevated concentrations consistently observed within these geological units and in adjacent downstream areas. Both selenium and organic matter exhibited surface enrichment, showing a depletion trend with depth, particularly confined to the upper 20-30 cm. Sequential chemical extraction revealed that soil Se predominantly exists in the residual and strongly organic-bound fractions. The readily available fraction comprised only 4.92% of the total Se, indicating low to moderate bioavailability. A strong positive correlation was identified between the residual fraction and total soil Se, while the carbonate-bound and strongly organic-bound fractions showed high correlation with organic matter content. The average bioavailable Se concentration was found to be 0.074 mg/kg, corresponding to an availability rate of 11.35%. Bioavailable Se content positively correlated with total Se and soil pH but exhibited a weak relationship with organic matter. Major crops, including wheat, maize, sweet potato, millet, and rapeseed, were found to be enriched with Se, with enrichment levels ranging from moderate to strong. The study area is endowed with substantial Se resources, and no heavy metal contamination was detected in the soils or crops. These findings provide a scientific basis for optimizing agricultural practices and developing a sustainable Se-enriched industry in the region.
WANG et al. (Thu,) studied this question.