Combining single and complex indices of pollution with grain size trend analysis of surficial sediments in Edremit Gulf, western Turkey

Pollution risk assessment of heavy metals (Pb, Cr, Cu, Ni, Zn, As) in sediment samples from 68 locations in the Gulf of Edremit, western Turkey, was performed using single and complex indices of pollution assessment approaches. The pollution indices used in the sediment analyses included pollution load index, contamination factor, contamination degree for individual metals, geoaccumulation index (Igeo), enrichment factors, toxic risk index, modified pollution index, frequency of adverse biological effects (TEL-PEL), percent incidence of biological effects (ERL-ERM), and total risk quotients. Results indicated a low degree of contamination for the entire surveyed area except moderate contamination factor for arsenic using single indices. Enrichment factors and geoaccumulation indices indicated moderate to significant enrichment and uncontaminated to moderately contaminated both for arsenic (As) and lead (Pb), respectively. According to the results of ecological risk assessment based on TELs and PELs, the adverse biological effects of heavy metals on aquatic organisms; are for As, Cr, Ni frequently, Cu and Pb occasionally, and Zn rare. The toxic risk index values displayed low to considerably toxic risk for the entire Gulf and calculated toxic risk index results showed that arsenic accounted for most of the entire sediment toxicity. Transport patterns of sediment grain size trend analyses were correlated with the results of pollution assessment models. Transport trends are compatible with the sources of lithogenic, anthropogenic, mining activities and wastewater treatment/ geothermal originated arsenic.