Spatial distribution, environmental risk and sources of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in surface sediments-northwest of Persian Gulf

In the current study, environmental risk, potential sources and spatial distribution of heavy metals and polycyclic aromatic hydrocarbons (PAHs) were investigated in the sediments of Musa Estuary, the largest Estuary in the Persian Gulf. A total of 68 surface sediment samples were collected and analyzed for heavy metals and PAH concentration using inductively coupled plasma mass spectrometry (ICP-MS) and High-Performance Liquid Chromatography (HPLC). Enrichment factor (EF) and ecological risk (E) calculation revealed the highest contamination and risk for Hg, mostly due to the activity of a petrochemical complex in the area. Also, most samples showed a mean probable effect level (PEL) quotient of 0.51-1.50, and a probable 49% toxicity. Pearson's correlation coefficient and principal component analysis (PCA) indicated the same (anthropogenic) origin for Cu, Hg, Pb and Zn. Five-six ring PAHs are dominant in sediments, and most studied compounds showed higher concentrations than their effect range low (ERL) and effect range median (ERM). Moreover, the highest toxic equivalent (TEQ) and ecological risk were observed in the main treatment lagoon. PAH diagnostic ratios and PCA revealed both petrogenic and pyrogenic sources for these compounds, and calculated mass inventory (I) values indicated a relatively high potential of the sediments (0.2-12.28 tons) for contaminating the marine environment. The results indicated that the wastewater treatment has good efficiency in reducing contaminant levels, as Mann-Whitney U test results showed a significant difference in Ni, Cr, Hg and Sigma PAH concentration between treatment lagoons and estuarine sediments.