Abstract
In this study, elemental abundances of As, Cd, Cr, Co, Cu, Pb, and Zn in the 30 composite sediment samples from Jamuna River, Bangladesh were measured by atomic absorption spectrophotometer to assess their contamination level, toxicity, and ecological risks in both summer and winter season. In the summer season, mean concentrations of As, Cd, Cr, Co, Cu, Pb, and Zn in sediment samples were 2.82, 1.13, 25.30, 8.63, 22.01, 4.58, and 68.82 mg/kg, respectively. In the winter season, mean concentrations of As, Cd, Cr, Co, Cu, Pb, and Zn were 3.83, 1.48, 43.22, 13.86, 35.63, 8.48, and 100.27 mg/kg, respectively. The mean concentrations of all elements were found lower than the sediment quality guidelines values of probable effect level (PEL), effect range medium (ERM), and toxic effect thresholds (TET) in both seasons. There was a significant variation in elemental concentrations between wet and dry seasons and also between upstream and downstream sites (P < 0.05). Principal component analysis showed Zn, Cr, and Pb; As and Cu; and Cd and Co might have originated from the same geogenic source. The pollution evaluation indices showed consistent outcomes of almost no pollution for As, Cr, Co, Cu, Pb, and Zn, but moderately to strongly polluted for Cd in all seasons. The contamination level of elements follows the decreasing order of Cd > Zn > Cu > As > Co > Cr > Pb for both seasons. The elemental toxicity in the sediments follows the order of Cd > Cr > Zn > As > Cu > Pb, with a very high risk for Cd while a minimal risk for other elements. The ecological threats of the toxic elements were found moderate to very high. Therefore, the findings of our study concluded that the ecological condition of the Jamuna River posed a considerable risk for human health and living organisms.