Heavy Metal And Organochlorine Pollutants In Tissues Of Marine Fauna Along The Coast Of Mombasa Island - Kenya

ABSTRACT

Marine pollution is increasingly becoming a problem along the Kenyan coast. ' I 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 X-ray Fluorescene (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% of the certified values (Appendix Ill). For statistical analysis, regression analysis was used to calculate the concentration of samples 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 p~0.05, unless otherwise stated. Tukey's studentized range test was used to separete the means when ANOVA indicated significant differences. Marine animals used for the study were chosen from molluscs, echinoderms, crustaceans and chordates sampled mainly along the xiii 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 of animals 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 (0.227 ± 0.026 ppm). Lindane which was found in 64% of all the animals studied, ranged from the detection limit (0.01 ppm) - 0.561 ppm. Marine fauna sampled near the Mombasa showground (English Point) contained higher than average (4.25±0.37 ppm against a mean value of 2.295±0.22 ppm) levels of the heavy metals studied. Pesticide concentration had a similar pattern with a level of 0.383±0.039 ppm against a mean value of 0.235±0.039 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 (4.07±0.25 ppm and 0.242±0.01 ppm respectively). The highest concentration of lead (14.80 ± 0.42 ppm), recorded in this study was found in Crassostrea sp. sampled from Vanga. Cadmium registered a concentration of 3.49 ± 0.31 ppm in Uca vocans collected from Mbaraki. The same species registered the highest concentration of lindane ( 0.561±0.5 ppm).