環境分析化学ジャーナル

Seasonal Variation of the Physicochemical and Bacteriological Quality of Water from Five Rural Catchment Areas of Lake Victoria Basin in Kenya

Abstract

Ouma SO, Ngeranwa JN, Juma KK and Mburu DN

Seasonal and regional variation of the physicochemical and bacteriological characteristics of 180 water samples collected from five fish landing beaches of Luanda Rombo, Dunga, Marengo, Osieko and Usoma in the Lake Victoria Basin of Kenya was investigated. Colour, chloride, TSS, TDS, zinc, mercury and nitrates were all below the maximum permissible but other parameters were above limits. Pathogenic bacteria isolated were Escherichea coli (69.6%), Salmonella spp (18.5%), Shigella spp (6.5%) and Vibrio cholerae (5.4%). Dunga site was the most polluted and that water from catchment areas closer to urban areas was more contaminated. Seasonal variation showed that pH, colour, turbidity, TSS, BOD, phosphate, nitrates and coliforms were significantly high (p<0.001) in the wet season. In the dry season temperature, EC, TDS, heavy metals, chloride and ammonia were significantly high (p<0.001). The high level of pollutants in wet season was due to storm water run offs carrying a higher load of contaminants while in dry season it is likely due to the increased solubility of ions as a consequence of the elevated water temperature and low pH. High loads of contaminants in water could pose immediate and long term public health concerns to unsuspecting water users especially due to the pathogenic coliforms, nutrients, algae and heavy metals. Therefore, proper policies regarding protection of the Lake Victoria environmental integrity are required and stiff measures should be taken to discourage law breakers.