Identification of the sources and migration of antimony in karst terraces via Sb stable isotopes

The provenance and migration pathways of antimony (Sb) in karst terraced soils remain poorly constrained. This study employs Sb isotopic compositions (ε¹²³Sb values ranging from -1.91ε to 4.55ε), major-trace element geochemistry, and mass balance modeling to quantitatively resolve Sb input fluxes and translocation mechanisms in typical Guizhou karst terrace systems. The results demonstrate that approximately 67 % of the soil Sb is derived from limestone weathering, with 27 % and 6 % attributable to wet deposition and dry deposition, respectively. Within the 0-0.59 m soil layer, the Sb isotopic composition is relatively heavier (1.96ε-3.18ε), which is likely influenced by atmospheric deposition and organic matter adsorption. Within the 0.59-8.7 m soil layer, the Sb isotopic composition becomes lighter (0.17ε-2.45ε), which is attributed to the preferential adsorption of lighter Sb isotopes by iron oxides and manganese oxides. Within the 8.7 m valley bottom layer, leaching drives the migration of heavier isotopes toward the valley bottom, resulting in the heaviest Sb isotopic composition in this layer (with a maximum value of 4.55ε).