Distribution and enrichment of trace metallic elements in the sediments of the Kaswa/Mahagi thermal waters of (North-East of the Democratic Republic of the Congo)

Abstract

Sediments contamination by trace metals constitutes one of the major problems in aquatic environments worldwide. This work aimed to study the distribution and evaluate the level of contamination of trace metallic trace elements (TMEs) in the sediments of the thermal waters of Kaswa/Mahagi in the North-East of the Democratic Republic of Congo. The indexes and statistics method allowed the assessment of sediment quality. Six surface sediment samples, collected in January and April 2022, were analysed using the FAAS Perkin Elmer brand-Analyst 400 spectrometer. The TMEs identified were lead (Pb), copper (Cu), zinc (Zn), manganese (Mn), chromium (Cr), cadmium Cd) and nickel (Ni), the abundance being Mn>Zn>Pb>Fe> Cu>Cr>Ni>Cd. The concentrations of Cd (0.83±0.14 μg/g) and Pb (43.22±5.76 μg/g) were beyond the standards considered. The geo-accumulation index (Igeo) and enrichment factor (EF) showed moderate pollution of the sediments and serious enrichment in Cd (2<Igeo<3, 10<EF<25), enrichment of anthropogenic origin (FE>1.5). The sites were unpolluted to slightly polluted and moderately enriched in Pb, Cu and Zn (Igeo<1, 1<FE<3). Polymetallic toxicity revealed a considerable degree of contamination (12<DC<24) and a progressive deterioration of sediment quality (Pollution load index-PLI>1) in all sites.