Heavy Metals and Organic Pollutants in Sediments of Dar es Salaam Harbour Prior to Dredging in 1999

Heavy metals and organic contaminants were analysed in the sediments of the inner area of the Dar es Salaam harbour. Complementary analytical parameters, such as, the organic carbon content and the silt/clay fraction of the sediments showed good positive correlation (r = 0.64). Stations that had high content of fine grain material in the sediment also indicated relatively high level of organic carbon and pollutants. The Florida criteria (MacDonald 1993) for assessment of pollution of tropical marine sediments was adopted in oredr to evaluate the extent of pollution in Dar es Salaam harbour sediments. The Florida criteria is one of the established references for sediment quality assessment. Heavy metals that had concentrations above the Florida no effect level were chromium, copper, lead, mercury and zinc. Mercury exceeded the Florida no effect level (0.1 mgkg-1) at 18 of 22 sampling stations, but the Florida probable effect level (1.4 mgkg-1) was not closely reached at any station. Lead and chromium exceeded the Florida no effect level (21 mgkg-1and 33 mgkg-1respectively) at 15 stations. Copper and zinc exceeded the Florida no effect level (28 mgkg-1and 68 mgkg-1respectively) at 12 and 16 stations respectively. Levels of pollutants in the study area were generally lower than in the sediments of some major harbours of the world.