The concentration distribution and biohazard assessment of heavy metal elements in surface sediments from the continental shelf of Hainan Island

Highlights: • First study to report the spatial distribution of heavy metals in CSHI. • CSHI does not face significant heavy metal pollution. • Negligible biological toxicity caused by Cu, Pb, and Zn in the surface sediments • Ni and Cr in the CSHI can pose potential biological hazards. The level of heavy metals (Cr, Co, Ni, Cu, Zn, and Pb) and Al₂O₃ were quantified in 140 surface sediment samples from the continental shelf of Hainan Island (CSHI). The mean heavy metal concentration in the decreasing order was: Cr > Zn > Pb > Ni > Cu > Co. Although heavy metals were locally enriched in the CSHI, the overall pollution level was relatively low. The biohazard assessment results of the mean effects range-median quotient (M-ERM-Q) and hazard quotient (HQ) for a single metal element (Cu, Pb, Zn) in the surface sediments showed that the exposure to individual heavy metals posed a low health risk. However, the biohazard assessment of multiple metals was higher than the single metals. Particular attention should be paid to the potential biological hazard from Cr and Ni in the CSHI.