| Popis: |
The mini-topography and leaching conditions significantly affect the spatial distribution of selenium (Se) in the local environment. However, the driving factors controlling Se distribution have not been well addressed. In this paper, taking Yutangba, a village known for human selenosis in China, as an example, we demonstrate how topographic factors comprehensively influence the spatial distribution of Se in soils and plants. In the scenarios of slope ≤25°, the correlations among slope and soil/extractable/plant Se are significantly negative, whereas they become weak or unclear when the slope is 25°, which suggests that 25° of slope is a critical transition boundary. Similar observations are further verified by the soil erosion modulus (SEM) and surface runoff intensity index (SRI), indicating that Se transport via soil erosion is limited and accounts for 11.2-17% of the soil Se, while surface runoff plays a dominant role in the Se distribution, accounting for 83-88.1%. Soil extractable Se is negatively correlated with SRI (Pearson r = -0.871 at slope25°), showing that the migration capacity of Se is higher at steep terrain and indirectly controlled by topography through soil erosion and surface runoff. The positive relationship between plant Se and soil/extractable Se demonstrates that topography can influence plant Se through soil Se bioavailability. Abnormally local Se enrichment observed at the elevated steep hillside (25°) in northwest Yutangba primarily resulted from the weathering of Se-rich rocks. These observations confirm that the topographic slope gradient influences the transport and spatial distribution of soil Se, implying that topography should be considered when we study the spatial distribution of soil Se at the regional scale, especially for the Se-poor belt in China. |
Full Text from ScienceDirect