Multielement analysis in sediments of the River Buriganga (Bangladesh): potential ecological risk assessment

Sediments collected from the River Buriganga were analyzed by using ICP-MS for spatial (site-to-site) and seasonal variations of a large number of elements, as many as 48. Out of these elements, 15 elements were given more attention because of their detrimental effects on human health and aquatic lives. These 15 elements are V, Cr, Mn, Ni, Cu, Zn, As, Se, Mo, Cd, Ba, Hg, Pb, Bi and U, and their mean concentrations were 7.51 ± 2.25, 39.70 ± 18.84, 37.58 ± 3.13, 6.39 ± 0.96, 14.07 ± 15.93, 36.73 ± 34.38, 0.18 ± 0.12, 1.07 ± 0.05, 0.40 ± 0.09, 0.21 ± 0.02, 20.80 ± 2.21, 0.016 ± 0.001, 10.41 ± 13.61, 0.33 ± 0.02 and 0.45 ± 0.09 mg/kg in monsoon, respectively; the mean concentrations in winter were 8.66 ± 2.77, 41.45 ± 15.88, 39.06 ± 2.72, 7.14 ± 1.11, 15.93 ± 18.38, 40.71 ± 37.33, 0.21 ± 0.13, 1.19 ± 0.05, 0.44 ± 0.11, 0.23 ± 0.03, 23.09 ± 2.63, 0.018 ± 0.001, 11.40 ± 15.09, 0.36 ± 0.02 and 0.50 ± 0.11 mg/kg, respectively. These results indicate that concentrations of the studied elements were almost the same in both the seasons. However, the concentrations were slightly higher in winter than those in monsoon with respect to spatial variation. The higher concentrations of Cr in both the seasons were due to direct discharge of tanning effluents for a long time. Values of contamination factor (Cf), degree of contamination (Cd), pollution load index and ecological risk potential (RI) factors for the selected toxic elements, i.e., Cr, Mn, Zn, Cu, Pb, Ni, Cd, As, Hg in the surface sediments, indicated that the contamination status in the studied area was low. The low contamination level may be due to steps taken by the authorities to prevent direct discharge of industrial effluents in the River Buriganga in the recent years.