The sources of bioavailable toxic metals in sediments regulated their aggregated form, environmental responses and health risk-a case study in Liujiang River Basin, China

Abstract

Bioavailable toxic metals (BTMs) predominantly stem from anthropogenic emissions, but their emission inventory remain unspecified. Considering the regulation of toxic metals (TMs) forms, variations in BTMs input linked to sources likely result from specific TM forms. To test this, we identified BTMs sources in Liujiang River Basin sediments, focusing on their aggregation and risk based on varying TMs forms. The findings indicated BTMs ratios decreased in the order as follows: Cd > Pb > Zn > Cu > As > Cr > Hg. PMF identified BTMs sourced from industrial, agricultural, and mining emissions with ratio of 43.2%, 36.7% and 20.2%, respectively. The correspondences between the correlation coefficients of TMs forms and the sources proportions suggested reducible forms were predominantly present in industrial BTMs, whereas residual and carbonate-bound forms were less abundant in mining and agricultural BTMs, respectively. Additionally, the correspondence between correlations of environmental parameters and the sources proportions confirmed different responses of industrial, agricultural and mining BTMs for Eh, for OM and Mz and for pH, TDS and EC, respectively. HI values, generally within 1, suggested the absence of non-carcinogenic risks. Conversely, TCR values, frequently exceeded 10⁻⁶, highlighted a significant carcinogenic risk, particularly for children. Considering industrial BTMs contributed most to both HI and TCR values, frequent aeration in sediments, particularly for industrial zones, will effectively alleviate the aggregation of BTMs in Liujiang River Basin. This study confirmed TMs forms in discharged wastewater are tightly related to BTMs aggregations, therefore, strengthening their monitoring is essential.