The aim of our study was to evaluate surficial sediments from two selected Ethiopian Rift Valley aquatic environments – Lake Awassa and Koka Reservoir, for the occurrence of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). The total concentration of target compounds resulted several times higher in the lake (270.39 pg/g dry weight than in the reservoir (63.17 pg/g d.w.). Similarly, concentrations measured as WHO-Toxic Equivalent (WHO-TEQ) were 23.78 pg TEQ/g d.w. and 4.03 pg TEQ/g d.w., respectively.
Obtained results, in reference to the Canadian Sediment Quality Guidelines, exceed the limit of 0.85 pg TEQ/g d.w. in both lake and reservoir, as well as probable effect level (PEL) of 21.5 pg TEQ/g d.w. in lake sediment, and thus represent high pollution levels of analyzed samples.