Assessing sediment and water quality issues in expanding African wetlands: the case of the Mara River, Tanzania.

Climatological influences and catchment pressures have altered the natural energy regime in the lower Mara River in Tanzania, creating conditions favourable for sedimentation. Wetland growth in the lower Mara River is investigated through particle size analyses and high resolution micro-XRF screening of sediment cores from the area. Geochemical profiling indicates that the Mara wetlands serve as an important trap for contaminated sediments originating the North Mara Gold Mine complex. Heavy metals and arsenic (As) appear to be reasonably well bound in alluvial stores of the wetlands but selected elements (e.g. Cr) may become progressively mobile over time. Human activity in the catchment presents risks to the biodiversity of the wetland area, and also to its ability to buffer Lake Victoria by assimilating pollutants. Changes to the hydrological regime of the Mara wetlands could reverse the patterns of sedimentation and adversely affect water and sediment quality in Lake Victoria. Furthermore, the study highlights a deficit of data relating to sediment sources, deposition patterns and associated contamination, which must be understood before effective management strategies on sediment and contaminants can be applied. [ABSTRACT FROM PUBLISHER]