Seasonal distributions and risk assessment of polychlorinated biphenyls (PCBs) in the surficial sediments from the Turag River, Dhaka, Bangladesh

Abstract

Polychlorinated biphenyls (PCBs) were determined in sediment samples collected from the Turag River, Dhaka city, Bangladesh. This river provides critical ecological services to agriculture, industry, and transportation. However, it is one of the most polluted rivers surrounding the capital city. This study analyzed six PCB congeners (PCB 10, PCB 28, PCB 52, PCB 138, PCB 153, and PCB 180) by GC-ECD at 9 sampling sites in two different seasons. The total concentrations of PCBs in studied samples varied from 344 to 0.217 ng/g dw and 10.6 to 1.68 ng/g dw in Monsoon-season and Dry-season, respectively. The paramount contributor-congener to the total PCBs was PCB 180, and it was found at all the study sites. The ecological risk assessment indicated a high potential risk in the Monsoon-season ([Formula: see text]= 277) and low potential risk in the Dry-season ([Formula: see text]= 25.7). Sediment quality guideline quotients (SQGQs) showed that PCBs in the Monsoon-season would cause "no" or "moderate" biological effects on organisms at every site except site-5 (S5) (high biological effects), while no adverse ecotoxicological effect was observed in the Dry-season. Considering both probable effect level (PEL) and threshold effect level (TEL), the new sediment quality guideline quotient (NSQGQ) showed that in the Dry-season PCB contamination would cause "moderate" biological effects. At the same time, in the Monsoon-season, the findings remained consistent with the findings of SQGQ. This study looked at the PCB contamination scenario in the Turag River sediments for the first time and allowed for a comparison with other rivers worldwide.

Keywords: Ecological risk assessment; GC-ECD; Occurrence of PCBs; River sediment; Sediment quality guideline quotients.