This paper is the result of oceanic geological survey engineering.

Objective The heavy metal contents in the Xiamen Bay have been greatly changed due to the ecological management in the bay and the port construction in Xiamen City. Identifying the distributions, evolution, and sources of heavy metals in the bay is significant for the prevention and control of heavy metal pollution, as well as ecological risk management.

Methods This study determined the contents of seven heavy metals in 87 surface samples from bottom sediments in the Xiamen Bay and the Jiulong River estuary, investigated the distributions and the degrees of enrichment of these heavy metals, and quantitatively analyzed the primary sources of these heavy metals using factor analysis and principal component analysis.

Results The western Xiamen Bay displays the highest average mass contents of heavy metals Cu (26.37 mg/kg), Zn (122.58 mg/kg), and Cr (57.25 mg/kg). In contrast, the Jiulong River estuary exhibits the highest contents of Pb (48.03 mg/kg), Cd (0.25 mg/kg), Hg (0.085 mg/kg), and As (9.35 mg/kg). Based on the indices of Class I sediments specified in GB 18668−2002 Marine sediment quality, Cu in the western Xiamen Bay exhibits the highest over−limit ratio of up to 25%, followed by Zn (20.69%) in the Jiulong River. In the Xiamen Bay, the enrichment coefficients of heavy metals decrease in the order of Cu (1.01), Cr (0.99), Cd (0.70), Zn (0.64), Pb (0.63), As (0.48), Hg (0.33), indicating that Cu is moderately enriched, Cr approximate to their background values, and Hg is severely enriched.

Conclusions The potential sources of the seven heavy metals in the Xiamen Bay include mine smelting, the weathering of natural parent rocks, the discharge of agricultural and domestic sewage, and fossil fuel combustion, which account for 36.16%, 22.03%, 21.98%, and 19.83%, respectively. Among these heavy metals, Cu, Zn, Cd, and Cr originate primarily from mine smelting, As from fuel combustion (85.76%) and agricultural non−point source pollution (14.16%), and Pb and Hg principally from the weathering of parent rocks. Zones with moderate and high ecological risks induced by heavy metals in sediments are concentrated in the Jiulong River estuary and the Xiamen Harbor.