Contamination and Ecological Risk Assessment of Heavy Metal in the Sediment of Turag River, Bangladesh: An Index Analysis Approach

Abstract

Encroachment, disposal of untreated domestic and industrial wastewater and dumping of solid wastes have degraded the overall quality of the river Turag, which is located in Dhaka—the Capital City of Bangladesh. The present study investigated the extent of pollution of sediments of this river and analyzed the regional variability for the concentrations of Cr, Pb, Zn, Cu and Cd—all of concern because of their potential toxicity, using atomic absorption spectrophotometer. As per US EPA sediment quality guideline, metal concentrations ranged between Cd: 0.00 - 0.80, Cr: 32.00 - 75.50, Cu: 46.30 - 60.00, Pb: 28.30 - 36.40, and Zn: 94.60 - 190.10 mg/kg in the Turag river sediments. Cr, Cu, Zn belongs to moderately to highly polluted, Pb and Cd belongs to not polluted for Turag river. The heavy metals contamination in the sediments were also evaluated by applying Index of geo-accumulation (Igeo), contamination factor (Cf), pollution load index (PLI) etc. Toxicity characteristics leaching procedure (TCLP) test (US EPA 1311) for sediment samples have been performed also for metals (Pb, Cd, Cr, Cu and Zn) to determine the readily toxicity level of heavy metals. Sieve analysis of sediment performed in this study to determine the physical characteristic of sediment samples. The metal concentrations are well below the regulated level as per US EPA. This index can be complemented with the contamination index, which allows more site-specific and accurate information on contaminant levels. If the aim of work on contamination evaluation is to assess the overall contamination of a study area, the indices are highly appropriate.