First report of geochemical fractionation distribution, bioavailability and risk assessment of potentially toxic inorganic elements in sediments of coral reef Islands of the Persian Gulf, Iran

Abstract

Metal contamination is a serious environmental concern in the Middle East. Herein, geochemical fractionation distribution and potential sources of thirteen metals (Fe, Al, Mn, Zn, Cu, Co, Cr, Ni, V, As, Hg, Pb and Cd) were investigated in sediments from ten coral reef Islands in the Persian Gulf, Iran. To properly assess availability and mobility of elements, enrichment factor (EF), pollution load index (PLI), pollution index (PI), contamination index (CI), sediment pollution index (SPI) and ecological risk assessment were provided. Sediment grain size showed an outstanding role in controlling the levels of potentially toxic inorganic elements (PTIEs). The highest values of total organic matter (TOM) were detected in Kharg and Lavan Islands. Different metals fractionation distribution was found across sites. As was noticed in carbonate (F₂), exchangeable (F₁), Fe-Mn oxy-hydroxide (F₃), organic (F₄) and residual (F₅) fractions, Hg primarily associated with F₂ and F₁, whereas Pb and Cd with F₂, followed by F₁, F₃, F₅ and F₄. Conversely, Ni and V accumulated in F₁, suggesting their high mobility and bioavailability, and thus environmental risk to aquatic biota. All metals (except Al, Fe and As) had geological and anthropogenic sources. Based on modified risk assessment analysis, the sediments from Kharg, Lavan, Siri and Lark Islands showed medium adverse effects. Overall, results from this study corroborate that petroleum industry is the main source of pollution of PTIEs in the Persian Gulf, and offer a scientific basis for monitoring and preventing metal pollution in the environment.

Keywords: Bioavailability index; Coral reef sediment; Ecological risk assessment; Fractionation; Persian Gulf; Potentially toxic inorganic elements (PTIEs).