Deng Xiaorong*

Chongqing Normal University

Abstract：

Soil Se content and speciation critically affect agricultural safety and human health, yet their regulation by lithology and land use remains unclear. This study reveals that the total Se (TSe) content decreases progressively from older to younger geological strata. Crystalline free iron oxides (Fec) showed significant positive correlations with soil TSe, organic-bound Se (ORG-Se), and residual-Se (RES-Se). Nevertheless, amorphous free iron oxides (Feo) were significantly positively correlated with bioavailable Se (ASe). Under the same land-use type, surface soils in carbonate-rich areas exhibited higher concentrations of TSe, ASe, Fe/Mn oxide-bound Se (FMO-Se), ORG-Se, and RES-Se compared to those in clastic rock regions. The concentrations of soil Se speciation exhibited a gradual decrease from surface to deeper layers in clastic rock regions, whereas Se levels remained stable initially before showing a sharp decline with depth in carbonate rock areas. The above analysis demonstrates that the magnitude and direction of land use effects on soil Se content and speciation are constrained by parent rock lithology. These findings therefore could provide a basis for regulating Se bioavailability for landuse under different lithologies.

Key Words：

Selenium; Carbonate rocks; Clastic rocks; soil; land use change