DISTRIBUTION AND RISK ASSESSMENT OF TRACE ELEMENTS IN SEDIMENT CORES FROM A COASTAL WATERSHED: AN EXAMPLE FROM THE LIAN RIVER, SOUTH CHINA

The Lian river catchment hold one of the largest e-waste recycling centers in the world between 1995 and 2015. Valuable elements were extracted and much of the residues were discarded into the Lian watershed. These practices may have released toxic trace elements to water bodies nearby, as it has been reported for flame retardants in the area before. Therefore, our aim was to evaluate the distribution, potential risks and sources of 7 trace metals (Cr, Ni, Cu, Zn, As, Cd and Pb) known to be linked to these effluents in the Lian river. Sediments cores from 5 sites from the upper to the lower reaches of the river were collected. The total concentrations of trace metals were determined by means of a digestion with HNO₃-HF followed by measurement with an ICP-MS. The results showed that the sediments of the river were significantly polluted by Cr (18.32–83.73 mg/kg), Ni (6.45–50.6 mg/kg), Cu (9.36–531.5 mg/kg), Zn (38.57–441.9 mg/kg), Cd (0.209–1.135 mg/kg) and Pb (54.02–492.8 mg/kg). The pollution load index showed values higher than 4 in the middle section and between 2 and 3 in the lower sections of the study area. Source identification based on principal components analysis showed strong positive correlations among al metals except of Cd, that showed a different behavior, suggesting industrial pollution for the formers and agriculture pollution for the latter.