Polychlorinated biphenyls (PCBs) in the sediments of the River Chenab, Pakistan

Abstract

Polychlorinated biphenyl (PCBs, sum of 31 congeners) concentrations (ng g−1 dry weight) in sediments collected from the River Chenab during two years of monitoring ranged from 9.33 to 129.45 in winter and from 12.55 to 144.23 in summer. Levels of PCBs in sediments from the feeding tributaries were relatively greater. Sediments from the mainstream sites were dominated by tetra-CBs and penta-CBs, while hepta-CBs and octa-CBs were predominant in industrial and urban sites near tributaries. Factor analysis based on principal component analysis (FA/PCA) and correlation analysis suggested surface run-off from surrounding agricultural soils, direct discharge of industrial and municipal effluents without prior treatment into the aquatic ecosystem, and atmospheric deposition as the main sources of PCB contamination. Risk assessment was carried out by comparing the results with established sediment quality guidelines; PCB concentrations in 35% of sediments exceeded effect range low (ELR) and threshold effect level (TEL) values, however, none of sediments showed PCB concentrations greater than the effect range median (ERM) and probable effect level (PEL) with the exception of site S-20 (144.23 ng g−1, dry weight), which showed values higher than ERL and TEL.