PCDD/F and Dioxin-Like PCB Determinations in Mtoni Estuarine Sediments (Tanzania) Using the Chemically Activated Luciferase Gene Expression (CALUX) Bioassay

Sediments from Mtoni estuary and 2 tributaries in Tanzania, were screened for polychlorinated-p-dibenzodioxins, -dibenzofurans (PCDD/F) and dioxin-like PCBs (dl-PCB) using the chemically activated luciferase gene expression (CALUX) bioassay approach. PCDD/Fs expressed as bio analytical equivalence (BEQ) values ranged from 5.7 plus or minus 1.4 pg to 39.9 plus or minus 5.8 pg BEQ/g sediment in the wet season and from 14.1 plus or minus 2.0 pg to 32.8 plus or minus 4.7 pg BEQ/g sediment in the dry season, with higher levels were observed in Kizinga river and stations close to the mouth of that river. A third sampling campaign, including stations in the downstream estuary, confirmed the enhanced levels in the Kizinga river (maximum of 400 pg-BEQ/g) and also showed that a clear decreasing concentration gradient in the downstream direction exists. It cannot be excluded that the levels of these pollutants in the sediments of the Mtoni estuary pose a threat to the local biological community.