Spatial Distribution and Potential Risks of Mercury in Surficial Sediments of the Kenyan Waters of Lake Victoria

Abstract

Mercury is among the potentially harmful elements of concern globally, with known toxicity and potential for bio-magnification in aquatic food webs.In Lake Victoria, initial sediment core total Hg data has been provided, but THg distribution in Nyanza gulf are not well known, despite the available data from Napoleon gulf, Uganda, and its reported occurrences around gold mining areas. Surficial lake sediments were collected in 2012 and 2010 (from 26 and 24 sites respectively) from the Kenyan portion of Lake Victoria (East Africa) and the sedimentary characteristics and THg contents determined. The detectable THg concentrations had a spatial mean (±standard deviation) of 167±21ng/g dry weight. Surficial sediments contained high organic matter contents, which were positively correlated to THg. The sediments enrichment factors ranged from 0.4 to 33.8 showing anthropogenic effects although levels measured were similar to those found in other lakes. An assessment of the potential ecological effects for bottom dwelling organisms was made based on the mercury concentrations. There is need of continued awareness creation on improved waste management and treatment technologies, and the use of better techniques in Au mineral processing.

Keywords: Lake Victoria, Mercury concentration, Nyanza gulf, Sediment quality, Surficial sediments