Invisible face of COVID-19 pandemic on the freshwater environment: An impact assessment on the sediment quality of a cross boundary river basin in Turkey

In the current research, the impact of the COVID-19 lockdown period on sediment quality of the Meriç-Ergene River Basin was evaluated by determining the potentially toxic elements (PTEs) in sediment samples collected from 25 sampling points in the basin. Also some important ecological indicators including potential ecological risk index (PERI), contamination factor (CF), pollution load index (PLI), biological risk index (BRI), and geo-accumulation index (I_geo) and some important statistical indicators including the Pearson correlation index (PCI), factor analysis (FA), and cluster analysis (CA) were applied to collected data. Levels of all the investigated PTEs in sediment of the basin show significant differences between the pre-lockdown and lockdown periods. The PTE contents have considerably decreased by 12.8%–45.4% during the lockdown period. Similarly, the results of applied sediment quality risk assessment indices showed significant improvement and the values have decreased by 22.4%–35.8%. In the lockdown period, reduction of industrial activities or limited production at many industrial facilities located in the basin reduced the amount of effluent, leading to significant improvement in sediment quality.