Prevalence and sources of polychlorinated biphenyls in the atmospheric environment of Lake Victoria, East Africa

Abstract

The large surface area of Lake Victoria (about 68,800 km²) makes it vulnerable to high atmospheric deposition of chemical pollutants. We present measurements of polychlorinated biphenyls (PCBs) from the lake's atmospheric environment. High volume air (24 h) samples were collected within the northern Lake Victoria watershed in Uganda over two periods; 1999-2004 [at Kakira (KAK) and Entebbe (EBB)] and 2008-2010 (at EBB only). Precipitation samples were also collected monthly during the 2008-2010 period at EBB. Analysis for PCBs was done using GC-μECD in a dual column approach. The ranges of ΣPCB concentrations in the KAK air samples were 154-462 pg m^-3 (KAK 1999-2000), 26.7-226 pg m^-3 (KAK 2003-2004), 27.0-186 pg m^-3 (EBB 2003), 46.8-174 pg m^-3 (EBB 2004), 19.2-128 pg m^-3 (EBB 2008), 45.8-237 pg m^-3 (EBB 2009) and 65.6-244 pg m^-3 (EBB 2010). The di-, tri-, tetra- and penta-PCBs were predominant in air sample sets while the tetra- and penta-PCBs were predominant in precipitation samples. The mean flux of ΣPCBs in the precipitation samples was 26.9 ng m^-2 (range of 14.8-41.5 and median of 27.5). Concentrations at EBB were lower than those reported elsewhere for urban sites in the East and Central African region. Multivariate analysis and analysis of air mass movements suggested influence of combustion sources on the PCB profiles from the region, especially, from the major East African urbanized regions.

Keywords: Atmospheric deposition; East Africa; Lake Victoria; Persistent organic pollutants; Polychlorinated biphenyls.