Isan assessment of heavy metals in water, sediments, and fauna of selected areas along the kenyan coastline

Abstract

Every year millions of tones of industrial wastes and municipal sewage are dumped into the world oceans as rivers carrying agricultural wastes discharge their waters into the ocean. The Mombasa inshore (Kilindini and Portreiz) waters and Sabaki/Malindi bay complex are characterized by rapid urbanization, industrial activities including shipping, agriculture and tourism. As a result, the coastal fauna, sediments and sea water are polluted with heavy metals, raw sewage and organochlorine pesticides. Heavy metals such as Cadmium (Cd), Copper (Cu), Chromium (Cr), Lead (Pb), Iron (Fe), Manganese (Mn), Mercury (Hg), and Zinc (Zn) have threshold limits (USEPA) above which they are toxic. The aim of this study was to assess the levels of heavy metals Cd, Cu, Cr, Fe, Mn, Hg and Zn at selected areas along the Kenyan Coastline. The analysis was done, during the dry and wet seasons. The levels of the heavy metals were determined using Atomic Absorption spectro-photometry flameless Atomic Absorption Spectrophotometry (Mercury cold vapour) and Energy Dispersive X-ray fluorescence. The levels of the metals were as follows: In sediments Hg: nd, Cr: nd, Cu: 9.912- 40.412-μg/g, Fe: 3,195.667-35,435.981 μg/g, Mn: 135.467-228.780 μg/g, Zn: 54.700 -181.725 μg/g. Biota: Hg: nd, Cr: nd, Cu: 43.963-229843 μg/g, Mn: 29.770-486.611 μg/g, Fe: 379.853-35,277.752 μg/g, Zn: 99.476-872.852 μg/g, Cd: nd, Pb: 135.407-833.111 μg/g. Sea water: Cr: 0.015-0.026 μg/ml, Fe: 0.062-16.524 μg/ml, Cu: 0.010-0.033 μg/ml, Zn: 0.028-0.066 μg/ml, Pb: 0.006-0.010 μg/ml. Cd and Hg levels were not detected in seawater, sediments, and fauna while Cr was not detected in sediments and fauna but had levels above USEPA guidelines at sites at Kilindini, at Malindi Bay and at Sabaki estuary. Cu had levels above USEPA guideline at Sabaki in the water and in sediments at most sites. Pb levels were above USEPA guidelines at most sites of the Kenyan Coastline while Zn levels indicated moderate pollution in seawater, sediments and fauna. These findings indicated that sea water sediments and fauna from the Kenyan Coastline are moderately polluted with Cu, Pb and Zn according to USEPA guidelines. It is recommended that regular assessments of pollution levels be done and measures be put in place to prevent increased pollution of the Kenyan Coastline.