Spatial distribution, sources, and ecological risk assessment of heavy metals in Lianyungang coastal sediments of China

Heavy metals are the primary pollutants in surface sediments of coastal area, and they can affect aquatic organisms and human health through accumulation and release into the environment. To investigate the spatial distribution, sources, and ecological hazards of heavy metals, this study analyzed the data on the contents of heavy metals in surface sediments of coastal areas in Lianyungang. The results indicate that significant spatial differences exist in the distribution of these metals. The average contents of As, Cd, Cr, Ni, Pb, and Zn were 5.6, 0.53, 41.4, 21.2, 12.4, and 49.6 mg/kg, respectively. Only the average value of Cd exceeded the background value, while the others were all lower than their respective background values. The ecological risk index of individual elements ranked from high to low is as follows: Cd > As > Ni > Pb > Cr > Zn. Additionally, the comprehensive ecological hazard index suggests that the ecological risk of the coastal sediments in Lianyungang is generally at a low to moderate level, with Cd being the major contributor. Numerous analyses show that Cr, Ni, and Zn mainly stem from industrial wastewater discharge, As and Cd mainly originate from agricultural and aquaculture activities, and Pb mainly comes from port traffic and atmospheric deposition.