Persistent organic pollutants in sediment of a tropical river: the case of N’djili River in Kinshasa (Democratic Republic of the Congo)

Abstract

Abstract Surface sediments collected in several areas along the N’djili River, in the Kinshasa Province, Democratic Republic of the Congo, were analyzed for persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine, polycyclic aromatic hydrocarbons (PAHs), and also organophosphorus and pyrethroid (PYR) pesticides. High values of POPs were determined in the DIGUE area of the river reaching 710 µg kg −1 for ∑ 12 PCBs, 397 µg kg −1 for ∑ 6 DDTs, 1138 µg kg −1 for ∑ 16 PAHs, and 23 µg kg −1 for ∑ 6 PBDEs. Regarding toxic effects on aquatic biota, the Total PCBs (∑ 7 × 4.3 ) were above the Threshold Effect Level (TEL) value of 34.1 μg kg −1 and above the Probable Effect Level (PEL) value of 277 μg kg −1 in most sampling sites. ∑ 16 PAHs values were, in general, below the TEL value of 610 μg kg −1 , but with exceptions for several sampling sites where values exceeded the TEL value. The ∑ 6 DDTs in all sampling sites were higher than both TEL and PEL values of 6.15 and 20.03 μg kg −1 , respectively. These values above TEL and PEL indicate potential adverse effects on benthic organisms. In general, the ratio values of (DDD + DDE)/DDT were higher than 0.5 reflecting past DDT use mostly, and Fluo/(Fluo + Pyr), IDP/(IDP + BghiP) and BaA/(BaA + Chry) ratios indicated several PAHs origins including petrogenic and pyrolytic sources, petroleum, grass, wood and coal combustion. Globally, the results of this research showed high contamination of N´djili River sediments by a plethora of organic pollutants and at toxic levels to the aquatic biota. Furthermore, the river water quality might be not suitable for human consumption.