Heavy metal and organochlorine pollutants in tissues of marine fauna along the coast of Mombasa Island, Kenya
Kipkosgei, Bor Samuel
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Marine pollution is increasingly becoming a problem along the Kenyan coast. Heavy metals and organochlorine pollutants have the potential to damage the delicate marine ecosystem with the result that the country's important foreign exchange earner - tourism - could seriously be affected. This study aimed at assessing the levels of cadmium, lead, copper, zinc, manganese, iron and titanium using Energy Dispersive Z-ray Fluorescence (EDXRF) and Atomic Absorption Spectroscopy (AAS) in selected marine fauna. It further assessed the levels of lindane, aldrin, dieldrin, endosulfan (a-, B-), DDT and its metabolites using Gas-Liquid Chromatographic (GLC) techniques. Certified reference material (Mussel Tissue, MA-M-2/TM, IAEA) was analyzed by, both AAS and EDXRF techniques, for quality assurance and control. The two methods are in good agreement and the results are within 10 per cent of the certifies values (Appendix III). For statistical analysis, regression analysis was used to calculate the concentration of saples and relationship between pollutant concentrations. Some of the calculations refer to the dry weight of soft tissues. One-way analysis of variance (ANOVA) was applied with the aid of a computer programme to investigate the differences in pollutant concentrations between animal samples and between locations. The level of statistical significance was set at p0.05, unless otherwise stated. Turkey's studentized range test was used to separate the means when ANOVA indicated significant differences. Marine animals used for the study were chosen form molluscs, echinoderms, crustaceans and chordates sampled mainly along the Coast of Mombasa Island. Some samples were also collected from Vanga in the South coast, Nyali Beach and Marine Park in the north. The four groups were all found to have accumulated heavy metals and pesticides to some considerable extent. Concentrations of lead and cadmium ranged from 3.68 - 5.70 ppm and 0.47 - 1.45 ppm respectively. Pesticide levels were, however, relatively low (0.2270.37 ppm). Lindane which was found in 64% of all the animals studied, ranged from the detection limit (0.01ppm) - 0.561ppm. Marine fauna sampled near the Mombasa showground (English Point) contained higher than average (4.250.37ppmagainst a mean value of 2.2950.22 ppm) levels of the heavy metals studies. Pesticide concentration had a similar pattern with a level of 0.3830.039 ppm against a mean value of 0.2350.039 ppm. Vanga was another place where marine animals were found to have accumulated the heavy metals and pesticides to a significant (p = 0.0481) extent (4.070.25 ppm and 0.2420.01 ppm respectively). The highest concentration of lead (14.800.42 ppm), recorded in this study was found in Crassostrea sp. sampled from Vanga. Cadmium registered a concentration of 3.490.31 ppm in Uca vocans collected from Mbaraki. The same species registered the highest concentration of lindane (0.5610.5 ppm). Although this study has confirmed that marine fauna from the Kenyan Coast have accumulated both the heavy metals and pesticides studied, the levels are generally low compared to the results from a similar study by Windom (1991). However, unless the pollutants are monitored continuously, the levels are set to increase, with serious implications.
- MST-Zoological Sciences