This study assessed the levels and distribution of selected persistent organic pollutants (POPs) in water of River Niger. The selected POPs of interest were organochlorine pesticides (OCPs). Fifteen representative sites along River Niger: three each from Gurara River (tributary) in Niger State, Lokoja (confluence) in Kogi State, Onitsha in Anambra State, Brass and Nicolas Rivers (tributaries) in Bayelsa State were selected for sampling quarterly over a 24-month period. A total of 240 surface and bottom water samples were collected using Van Dorn water sampler in the eight quarters of 2008-2009. At the Delta locations where tidal effects take place, high- and low-tide water samples were taken as compared to surface and bottom at the River Niger locations. For sample extraction, EPA method 3510c was employed with slight modifications. Certified reference standards from Accustandards USA was used for the instrument calibration and quantification of OCPs. The extracted samples were subjected to gas chromatography (GC/ECD) for identification/quantification. And Shimadzu GCMS QP2010 was used for confirmation. Chlordane, endosulfan, endrin and DDT metabolites were very prominent in the water samples, compared to HCH, dieldrin, and isomers which occurred at lower concentrations. The sequence in the concentration of the organochlorine pesticides were ∑chlordane > ∑DDT > ∑endosulfan > ∑endrine > ∑dieldrin > ∑HCH. The highest concentration of ∑OCPs in water samples of River Niger, 1138.0 ± 246.7 ng/L, with range 560.8-1629 ng/L was detected at Onitsha location, while the lowest concentration, 292.6 ± 74.9, with range 181-443.0 ng/L was detected at Nicolas River. Levels of OCPs in a larger percentage of the samples exceeded guidelines and therefore hold potential harmful effects on benthic fauna, fish, and man. Abstraction of water from the River for drinking water treatment should be discouraged. Because of the potential danger, this presents, continuous monitoring of the water body and if possible remediation, determination of the sources of the POPs is therefore very necessary.

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) were more dominant than the incineration sources (34.9 ± 3.82 to 75.5 ± 65.2 ng L). 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.

Background.Anthropogenic polychlorinated biphenyls (PCBs) in aquatic environments poses human and ecological health risks in Nigeria.Objectives.This study determined the concentrations of PCBs in brackish water fish in the River Niger to assess the contamination status of fish consumed by the local population.Methods.The sampled fish species included Drepane africana, Mochokus niloticus, Chrysichthys nigrodigitatus, Pristipoma jubelini, Vomer septapinis, Pseudotolithus senegalensis, Mugil cephalus, Pseudotolithus elongatus, Sphyraena piscatorum and Lutjanus goreensis, purchased from landing sites. Six fish from each species were sampled, for a total of 60 samples. Twenty-seven (27) PCB congeners, #8, #18 #28, #44, #52, #60, #77, #81, #101, #105, #114, #118, #123, #126, #128, #138, #153, #156, #157, #167, #169, #170, #180, #185, #189, #195, and #206 were screened in the fish samples using standard methods. The PCBs were identified and quantified using gas chromatography (GC) (Hewlett Packard GC 5890 series 11 with electron capture detector). Confirmation was performed using Shimadzu GCMS QP2010.Results.The sum of the National Oceanic and Atmospheric Administration Agency (ΣNOAA) PCBs occurred at the highest concentration of 1830.0±484.0 μg/kg detected in Vomer septapinis, and the lowest in Pseudotolithus senegalensis, with a mean concentration of 795±169.3 μg/kg. The concentration of dioxin-like (DL) PCBs was highest in Pristipoma jubelini (992.0±88.6 μg/kg) and lowest (285.6±81.5 μg/kg) in Drepane africana. The highest mean concentration (418.±177.6 μg/kg) of International Council for the Exploration of the Seas-7 (ICES-7) PCBs was observed in Vomer septapinis. The heavier ICES-7 congeners PCB-138, PCB-153, and PCB-180 occurred at higher concentrations compared to the lighter molecular weight ICES-7: PCB-28, PCB-52, and PCB-101. The European Union (EU) marker PCB limit of 335 μg/kg was exceeded in all the brackish water fishes with the exception of Mochokus niloticus, Pristipoma jubelini and Pseudotolithus senegalensis.Discussion.The total level of PCBs in the brackish fish samples was relatively high at >1000 μg/kg (above the World Health Organization (WHO) and Food and Agriculture Organization of the United Nations (FAO) guideline of 1000 μg/kg fresh weight). The EU guideline value for fish (220 μg/kg fresh weight) was exceeded in about 80% of the brackish fish samples studied.Conclusions.Consumption of fish from the River Niger may expose humans to polychlorinated biphenyls. In addition, since contamination of the fish samples is an indication of river contamination, river water quality is of great concern and there is a need for additional PCB data on water quality to be distributed to the community, followed by mitigation measures.Competing interests.The authors declare no competing financial interests.

ResearchBackground. Pollution in aquatic ecosystems is a serious environmental concern. There is a great need for constant assessment and monitoring of hazardous substances, particularly in aquatic environments in developing countries, as rivers are media with easy trans-boundary transport of chemical substances. Objectives. The present study assessed the occurrence and distribution of organochlorine pesticides (OCPs) in the sediments of the Niger River, Nigeria. Methods. A total of 120 samples of sediment were collected from 15 locations along the river using Van Veen grab. The Environmental Protection Agency (USEPA) 3570 method with slight modification was used for sample preparation. Organochlorine pesticides were analyzed using Hewlett Packard 5890 series II gas chromatography with electron capture detector. Confirmation of OCPs was performed using a gas chromatograph/mass spectrometer (Shimadzu QP2010) and capillary column type HP1MS (30 m x 0.25 um x 0.25 mm id). Results. The highest concentration of ∑OCPs in the sediment samples of the River Niger (5023±1596 µg/kg, 4672-7009 µg/kg) was detected in a location at Onitsha, while the lowest concentration (1570±204.5, 1214-1820 µg/kg) was detected in a location at the Nicolas River. Discussion. High values of ∑OCPs (>2000 µg/kg) were detected in all of the locations except in three locations where lower levels were detected. The ∑OCPs were higher during the dry season compared to the rainy season. This may be because the resident time of the sediment transported was higher during the dry season compared to the rainy season, which is characterized by storms, high current, and bottom scour. The chlordane concentration ranged between 24.4 and 134.1 μg/kg dry weight (dw) in locations Nicolas 14 and Lokoja 5; and the Probable Effect Concentration guidelines were exceeded. Dieldrin was detected at very low levels in most of the locations and ranged from 5.67 to 70.3 μg/kg dw in locations Onitsha 9 and 8; and the Probable Effect Concentration guideline was only exceeded in location Onitsha 8; however, the Toxic Effect Concentration guideline was exceeded at all of the locations. Dichlorodiphenyldichloroethane (DDD) was not detected in location Lokoja 6 or 7, and Onitsha 8 and 9, although the concentration in all other locations exceeded the guidelines. Dichlorodiphenyldichloroethylene (DDE) concentrations exceeded the guidelines except in location Nicolas 13. Conclusions. Due to the environmental/human risk and potential danger of the elevated levels of OCPs, there is a need for continuous monitoring of the Niger River. Competing Interests. The authors declare no competing financial interests.

Investigation of the levels of organochlorine pesticides (OCPs) in fish samples was carried out to assess the contamination status of Niger River. Ten different brackish water species of fish (6 samples for each, making a total of 60) were purchased from landing sites at the Delta area of Niger River. These were Drapane africana, Mochokus niloticus, Chrysichthys nigrodigitatus, Pristipoma jubelini, Vomer septapinis, Pseudotolithus senegalensis, Mugil cephalus, Pseudotolithus elongatus, Sphyraena piscatorum, and Lutjanus goreensis. OCPs were determined using standard methods. Certified reference standards from Accustandard USA were used for the instrument calibration and quantification of OCPs. Twenty OCPs, namely, α-HCH, β-HCH, γ-HCH, δ-HCH, endrin, endrin aldehyde, endrin ketone, heptachlor, heptachlor epoxide, aldrin, dieldrin, endosulfan I, endosulfan II, endosulfan sulfate, methoxychlor, α-chlordane, γ-chlordane, DDE, DDT, and DDT, were identified/quantified using Gas Chromatography (GC) (Hewlett Packard GC 5890 series 11 with electron capture detector). Confirmation was done using Shimadzu GCMS QP2010. The highest concentration of ∑OCPs in the brackish fish samples of the Niger River, 4302±2066 µg/kg fresh weight, with a range of 2237-6368 µg/kg, was detected in Drapane africana, while the lowest concentration, 2320±876.4, with a range of 1006-3288 µg/kg, was found in Mochokus niloticus. The concentration of total OCP compounds varied markedly amongst the different fish species. The guideline value of 2000 µg/kg fresh weight by WHO/FAO was exceeded and therefore implied potential harmful effects on humans. Since contamination of the fish samples was an indication of contamination of the river, the quality of the water for public water supply should be of concern; and therefore further monitoring is suggested.