Application of antimony stable isotopes in revealing the source and migration of Sb in rivers

Antimony (Sb), a potentially carcinogenic metalloid and contaminant of emerging concern, has garnered widespread attention worldwide because of its environmental pollution. Rivers represent critical pathways for the transport and cycling of Sb contamination. However, the sources and transport pathways of Sb in water and sediment remain poorly understood and difficult to quantify. This knowledge gap significantly hinders an in-depth understanding of the environmental behavior and pollution control of Sb in rivers. This study selected two rivers affected by typical Sb pollution sources to systematically quantify the origins and transport pathways of Sb within these rivers. These results indicate that Sb-containing wastes (smelting slag and tailings) are the primary source of Sb in river water. Dissolved Sb enters rivers mainly through surface runoff (45.7-54.1 %) and groundwater seepage (45.9-54.3 %), with surface runoff becoming the dominant pathway during the wet season (59.3-75.3 %). The Sb in sediments near pollution sources is influenced mainly by the dissolved Sb in river water. In the downstream areas of pollution sources, the enrichment of Sb in sediments is derived from eroded Sb-containing wastes (18.0-52.8 %) and contaminated soils (47.2-82.0 %). Prioritizing the management of weathering and erosion of Sb-containing waste and contaminated soils, particularly by controlling the transport of dissolved and particulate Sb via surface runoff, can significantly mitigate Sb pollution in rivers. For the first time, by coupling the isotopic signatures and fractionation mechanisms of Sb in both water and sediment, this study elucidates the sources and migration processes of Sb contamination in rivers. This study provides an innovative framework for the quantitative tracing of riverine Sb pollution and advances the scientific understanding of the surficial environmental behavior of Sb.