Ecological risk assessment of heavy metals after dredging in Mogan Lake, Turkey

Abstract

The lake management strategy of sediment dredging (removal) is periodically undertaken in shallow, eutrophic Mogan Lake, an important recreation area. This study aims to use certain indices - enrichment index (EF), contamination/pollution index (CF), degree of contamination (Cd), pollution load index (PLI), geoaccumulation index (Igeo), potential ecological risk index (Eri), integrated ecological risk index (PER), and mean probable effect concentration quotient (mPEC-Q) - to evaluate the state of sediment pollution in the lake after dredging. With this in mind, after dredging was completed, two stations in the littoral zone were selected. Station I was located especially where it would be reached by wastewater from mineral processing facilities and domestic areas; and Station II, where it would be reached by residential and agricultural wastewater. Surface sediment samples were taken repeatedly in May and November 2020 using a sediment grabber. According to the study findings, a) Among the heavy metals studied (Hg, As, Cd, Cr, Pb, Ni, Cu, and Zn), Cu, As, and Cd were found to have the highest enrichment and contamination indices; b) The pollution load index (PLI) values (1.30-2.26) suggest heavy metal pollution in the sediment, and the geoaccumulation index (Igeo) values show intensive Pb contamination at both stations in both months; c) In terms of potential ecological risk index (Eri), Cd was found to have a significant level of ecological risk index; d) The integrated risk index (PER) indicates that all heavy metals in the lake were present at moderate ecological risk levels. Ni and As were metals that had negative biological effects. The results indicate that a) Dredging is not a very effective tool for reducing pollution in the sediment; and b) As long as anthropogenic pollutants continue to enter the lake basin, sediment heavy metal levels should be routinely monitored, particularly those with ecological and biological effects on the sediment: Cu, Cd, Pb, Ni and As. It is predicted that the findings of this study will contribute to the sediment-focused monitoring efforts of organizations and local governments.