Distribution, source and pollution assessment of heavy metals in surface sediments of Qinzhou bay, Guangxi

In order to systematically study the distribution, source and potential ecological risks of heavy metals (HMS) in surface sediments of Qinzhou bay in Guangxi, In 2019 and 2020, 116 surface sediment samples were collected in Qinzhou bay, the concentrations of 7 kinds of HMS were measured, the status of HMS pollution was evaluated by Geo-accumulation index (I_geo) and pollution load index (PLI), the possible ecological risk was analyzed by potential ecological risk index (E_RI) method, and the source of HMS was discussed by enrichment factor (EF) and UNMIX model. The results showed that the average concentration of As in surface sediments of Qinzhou bay is (10.18±4.61) μg/g, Cd is (0.17 ±0.13) μg/g, Cr is (44.28±23.56) μg /g, Cu is (18.53 ±10.75) μg/g, Ni is (23.38±11.11) μg/g, Pb is (24.76±12.75) μg/g, Zn is (62.66±27.32) μg/g, which was relatively lower than that in the sediments of other areas, and it was decreased compared with the previous study in Qinzhou bay, except for Cd. The concentration of Cd was relatively increased. The I_geo and PLI showed that Cd was at a high pollution level and was the main element affecting PLI. The heavily polluted areas were mainly located near the coast of Fangcheng port. The E_RI also showed that Cd was at a medium risk level. The EF showed the characteristics of significant anthropogenic impact of HMs. The UNMIX model identified three potential pollution sources. Source 1 represents the ore combustion source dominated by Ni, source 2 represents the discharge source of hull coating and aquaculture wastewater, and source 3 represents the source of industrial pollution and natural weathering of rocks near the coast of Fangcheng port.