Risk elements contamination in the riverbed sediments of the Xiangjiang River, China: a review

This review provides comprehensive insight into the issue of risk elements in the river basin, i.e. to mean, their origin, distribution and future fate research and ecological environment management in the Xiangjiang River, China. A widespread Cd anomaly was observed across the area. Between 1983 and 2020, risk elements Cd, Pb, Zn, Cu and Mn in sediments from Yongzhou to Xiangyin were consistently elevated with significant spatial variability. In contrast, risk elements Ni, Cr, Th, Sc, V, Ba, Co and U demonstrated relatively uniform distribution patterns. Metals Cd, Zn, Cu, Mn and Pb were primarily derived from anthropogenic sources, whereas Ni, Cr, Th, Sc, V, Ba, Co and U originated mainly from parent rock weathering. Geo accumulation index (I_Geo) assessment revealed moderate to severe contamination degree (I_Geo > 1) for Cd, Cu, Zn, Mn and Pb in sediments. Lead isotope tracing in sediments revealed a binary mixing model for Pb in the mid-lower Xiangjiang River sediment, comprising both anthropogenic and natural sources. Cd in middle-lower reach sediments is mainly hosted in exchangeable and carbonate fractions (24%-75%); whereas Pb and Zn are predominantly associated with Fe-Mn oxides (27%-61%); and Cu shows a strong affinity for organic matter. Xiangyin and Changsha section Cd, Cu, Zn, Pb concentrations followed a pattern of initial decrease from 1980s to 2025; the similar trends might exist in other area, but lacks robust scientific evidence currently.