Polychlorinated biphenyls (PCBs) in River Niger, Nigeria: Occurrence, distribution and composition profiles

Contamination of rivers with persistent organic pollutants (POPs) is an issue of current global concern. Polychlorinated biphenyls (PCBs) are POPs with origin from commercial, incineration and industrial sources. Hence, there is a need for monitoring their occurrence and distribution in the environment. This study assessed the occurrence, distribution and composition profiles of PCBs in River Niger, Nigeria. Surface and bottom water samples were collected in consecutive quarters for a period of 2 years, covering the beginning and end of the rainy seasons and the dry seasons, from five locations (Gurara, Lokoja, Onitsha, Brass and Nicolas) along River Niger. A total of 240 water samples were collected using a Van Dorn water sampler. EPA method 3510c was used with slight modifications for sample preparation and analysis. The PCBs were analysed using a Hewlett Packard GC 5890 Series 11 with electron capture detection, and confirmation was made using a Shimadzu GCMS QP2010. The higher molecular weight marker PCBs (∑CB 138, 153 and 180) were more dominant than the lighter homologues (∑CB 28, 52 and 101), while commercial sources Co-PCBs (80.8 ± 61.7 to 288.3 ± 102.0 ng L^-1) were more dominant than the incineration sources (34.9 ± 3.82 to 75.5 ± 65.2 ng L^-1). The POPs load in River Niger water varied in both time and space. In surface water of the River Niger, ∑PCBs were higher during the rainy season, as a result of storm run-off from land-based sources. In the Brass and Nicolas Rivers during the dry season, the ∑PCBs were higher during low tide. There was no noticeable pattern during the rainy season. It may be concluded from this study that the water of River Niger is not good for human consumption or abstraction of water from the river for drinking water treatment.