Heavy metal contamination in water, sediments, and fauna of selected areas along the Kenyan coastline

Abstract

Abstract. Mwatsahu SH, Wanjau R, Tole M, Munga D. 2020. Heavy metal contamination in water, sediments, and fauna of selected areas along the Kenyan coastline. Ocean Life 4: 37-47. Every year millions of tons of industrial waste and municipal sewage are dumped into the world’s oceans as rivers carrying agricultural wastes discharge their waters into the ocean. The Mombasa inshore (Kilindini and Portreiz) waters and Sabaki/Malindi bay, Kenyan coastline, complex are characterized by rapid urbanization and industrial activities, including shipping, agriculture, and tourism. As a result, the coastal fauna, sediments, and seawater 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 in 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 vapor), 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. In contrast, Cr was not detected in sediments and fauna but had levels above USEPA guidelines at Kilindini, Malindi Bay, and Sabaki estuary sites. Cu had levels above USEPA guidelines at Sabaki in the water and 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 seawater 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 put in place to prevent increased pollution of the Kenyan Coastline.