title: An ecotoxicological approach to assessing the impact of tanning industry effluent on river health.
abstract: A study was conducted to investigate the sediment health and water quality of the River Sagana, Kenya, as impacted by the local tanning industry. Chemical analysis identified the main chemical pollutants (pentachlorophenols and chromium) while a bioassay addressed pollutant bioavailability. The bioassay, exploiting the luminescence response of a lux marked bacterial biosensor, was coupled to a dehydrogenase and Dapnia magna test to determine toxicity effects on sediments. Results highlighted the toxicity of the tannery effluent to the sediments at the point of discharge (64% of control bioluminescence) with gradual improvement downstream. There was a significant increase in dehydrogenase downstream, with the enzyme activity attaining a peak at 600 m, also indicating a gradual reduction of toxicity. Biological oxygen demand (19.56 mg L(-1)) dissolved oxygen (3.97 mg L(-1)) and high lethal dose value (85%) of D. magna also confirmed an initial stress at the point of discharge and recovery downstream. Optical density of surface water demonstrated an increase in suspended particulates and colour after the discharge point, eventually decreasing beyond 400 m. In conclusion, the study highlighted the importance of understanding the biogeochemistry of river systems impacted by industries discharging effluent into them and the invaluable role of a biosensor-based ecotoxicological approach to address effluent hazards, particularly in relation to river sediments.
authors.affiliation: School of Biological Sciences, Plant and Soil Sciences, University of Aberdeen, St. Machar Drive, Cruickshank Building, Aberdeen, AB24 3UU, UK. m_mwinyi@hotmail.co.uk
authors.forename: Mwinyikione
authors.initials: M
authors.lastname: Mwinyihija
authors.forename: Andy
authors.initials: A
authors.lastname: Meharg
authors.forename: Julian
authors.initials: J
authors.lastname: Dawson
authors.forename: Norval J C
authors.initials: NJ
authors.lastname: Strachan
authors.forename: Ken
authors.initials: K
authors.lastname: Killham
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D015374:Biosensing Techniques; D003621:Daphnia / Q000187:drug effects; D004784:Environmental Monitoring; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019015:Geologic Sediments / Q000032:analysis; D007220:Industrial Waste; D007630:Kenya; D007928:Lethal Dose 50; D049449:Luminescence; D019216:Metals, Heavy / Q000032:analysis / Q000633:toxicity; D010088:Oxidoreductases / Q000378:metabolism; D045483:Rivers; D013633:Tanning; D013778:Tetrazolium Salts / Q000378:metabolism; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D007220:Industrial Waste; D019216:Metals, Heavy; D013778:Tetrazolium Salts; D014874:Water Pollutants, Chemical; C013574:iodonitrotetrazolium; D010088:Oxidoreductases