Environmental Assessment of Sediment Quality for the Main Outfall Drain and Al-Sanaf Marsh

Abstract

This study evaluated the sediment quality of the Main Outfall Drain River in Thi-qar Government by measuring (Mn, Ni, Pb, Fe, Cr, Zn, Cd and Cu) in the sediments. Samples were collected at 4 locations between the summer of 2021 and the winter of 2022, and the results revealed that the heavy metal dominance in the Main Outfall Drain and Al-Sanaf Marsh was in the order of Fe> Mn> Ni> Zn> Cr> Pb>Cu>Cd. Among these sedimentary contaminants, Fe has the highest level in sediments. Two indices were used: sediment quality criteria (QSm) and pollution index (PI). All sites were in the third class of QSm (a possible hazard for aquatic life) because QSm> 0.5. The lowest value is recorded in site 4, and the highest value is located in site 3. The results of PI of Zn and Cu show no effected by pollution to slightly affected in all sites, Cr exhibits the same pattern as Zn and Cu except for site 3 was moderately affected in winter, while Pb caused moderate pollution effect in all sites, except site 2 and site 3 which were slightly affected in winter. Mn, Cd and Fe were seriously affected by pollution in all sites. Pollution index values of most metals (except Fe and Cr) were higher in summer than in winter, probably due to the observed dilution of the metals with anthropogenic origin by rain, leading to lower values in winter. At the same time, Fe and Cr were higher in winter than in summer due to being mostly of terrestrial origin, derived from runoff of the nearby soil by rain. The results show that the sediments of the main outfall drain suffer from large quantities of heavy metals, mainly from site 3, which may be due to receiving industrial effluent, sewage and irrigation water from the governorates through which it passes.