Browsing by Author "Henkelmann, Bernhard"
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Item Dioxin-like PCBs and PCDD/Fs in surface sediments near the shore of Winam Gulf, Lake Victoria(Elsevier, 2015) Omwoma, Solomon; Lalah, Joseph O; Virani, Munir; Schramm, Karl-Werner; Henkelmann, BernhardWinam Gulf of Lake Victoria is considered to be contaminated with toxic chemicals emanating from anthropogenic activities, especially near large industrial towns such as Kisumu. This has recently caused concerns about its water quality and impact on aquatic organisms and human beings. This study was justified by the need to generate baseline concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in surface sediment from selected sites in the lake and determine the influence of activities on their concentrations and potential risks to fish-eating birds living near the lake. Surface sediments (<30 cm) from three different fish landing beaches, located 200 m from the shore of Winam Gulf of Lake Victoria near Kisumu city, Homa Bay and Mbita (control) towns, were analysed. The total mean concentrations (in pg g−1 dry wt) were found to range from 17.4–812 (Σdl-PCBs), 36.6–813 (ΣPCDDs) and 1.45–46.4 (ΣPCDFs). The calculated Toxic Equivalents (TEQWHO(2005)) ranged from 0.001–0.43 (Σdl-PCBs) and 0.09–31 (ΣPCDD/Fs). The fish landing beaches at Kisumu city were found to be contaminated with respect to dl-PCBs and dioxins, followed by Homa Bay and Mbita. The relatively high levels of octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) influenced the TEQ and the ΣPCDFs/ΣPCDDs ratios indicated chemical processes as partial sources of the dioxins. The levels of contaminants obtained in this study showed potential exposure to aquatic organisms and fish eating birds through food chain transferItem Regioselective Synthesis of a Branched Isomer of Nonylphenol, 4-(3′,6′-Dimethyl-3′-heptyl)phenol, and Determination of its Important Environmental Properties(2001) Lalah, Joseph O; Schramm, Karl-Werner; Lenoir, Dieter; Henkelmann, Bernhard; Hertkorn, Norbert; Kettrup, Antonius; Günther, KlausA method for the synthesis of a pure nonylphenol isomer, 4-(3′,6′-dimethyl-3′-heptyl)phenol, by Friedel–Crafts reaction between anisole and 3-bromo-3,6-dimethylheptane that gives a 47.3 % overall yield is reported. The reactions were followed by GC-MS, and the chemical structures are in agreement with the NMR and IR spectra. The log Kow value for this compound, its water solubility, vapor pressure, and Henry's Law constant were also determined. These physicochemical properties were required for prediction of the compound's behavior in aquatic ecosystems.