Contamination and ecological risk of heavy metals in Al-Uqair coastal sediments, Saudi Arabia

The level of heavy metal contamination and ecological risk, as well as the sources of contamination, of 35 sediments from the Al-Uqair coast, Saudi Arabia, were determined via inductively coupled plasma mass spectrometry. The average concentrations (dry weight) were highest for Fe (8091.51 mu g/g), followed by Al (1816.60), As (14.99), Cu (11.27), Zn (7.62), Pb (3.88), Mn (3.82), Cr (3.67), Hg (2.40), Se (0.68), Ni (0.57), Cd (0.07), and Sb (0.06). The average TOC and heavy metal values, except Hg and As, were much lower than many coastal sediments elsewhere. The sediments had moderate-to-high heavy metal pollution, especially with high Hg contamination and substantial Se and As enrichment. Moreover, the sediments were at a high ecological risk for Hg, As, and Cd, moderate risk for Cu, and no-to-low risk for Pb, Zn, Ni, Cr, and Sb. Hg, Cd, Cr, As, Se, Cu, Sb, Pb, Ni, and Zn were likely from lithogenic and anthropogenic sources, including rock weathering, agricultural runoff, and untreated domestic sewage. However, Al, Fe, and Mn were naturally derived.