Volume 4 Issue 3
Authors: Luke Ikechukwu Mamah; Kizito Ejiro Aweto
Abstract: A resistivity investigation was carried out in order to provide information on the subsurface layers and characterization of the protective capacity of overburden units to groundwater in Egbeleku, a community where a proposed landfill will be sited by Shell Petroleum Development Company. Fifteen vertical electrical soundings (VES) using the Schlumberger electrode configuration and one azimuthal resistivity sounding (ARS) were carried out. Results of the resistivity survey indicated mainly four geoelectric layers; top soil, clayey sand/sandy clay, clay and sand. The fourth layer constitute the groundwater aquifer which was determined to be confined by the third ubiquitous layer constituted by clays with thickness varying from 11.0 – 42.2 m and sandy clay/clayey sand of about 30.2 – 44.0 m thick. The longitudinal conductance map showed that the area has moderate to good protective capacity as a result of the thick clay, sandy clay and clayey sand protecting the groundwater in the aquifer. The location of the landfill site is in the region of groundwater discharge rather than a recharge region as indicated by azimuthal resistivity sounding and groundwater head contour map which showed that groundwater flow direction is SW – NE towards the proposed landfill area. Hence, the groundwater in this area is sufficiently protected.
Keywords: Contaminants; Protective Layers; Landfill; Leachates; Residence Time; Geoelectric Horizon
Authors: Haji Mwevura
Abstract: This paper reports the level of persistent of organic pollutants (POPs) from locally made antifouling agent (Sifa) in Zanzibar. A total of 9 samples of the antifouling agent prepared from decayed mixture of blubber and liver of common bottlenose (Tursiops truncates) dolphins were analysed for a wide range of acid stable organohalogen compounds. Organochlorine pesticides mostly DDT metabolites and methoxylated brominated diphenyl ethers were found well above the detection limits. The levels of DDTs measured in this study were highly dominated by p,p’-DDE reflecting the effect of metabolism due to the decay process. The concentrations of two MeO-BDEs found in this study showed significant correlation (R2= 0.952) indicating that they originate from the same source and they have same stability to microbial degradation. Pollutants of industrial origin, such as polychlorinated biphenyls (PCBs) were not detected showing that the sampled areas are free from persistent industrial pollutants. The results indicate that users of local antifouling agent are exposed to aged chlorinated contaminants though the levels have no detrimental effects on their health. On the contrary, HCHs were found in trace levels in fresh samples of dolphin liver, indicating their relatively low persistence compared to DDTs.
Keywords: Local antifouling; methoxylated brominated diphenyl ethers; organohalogen; Persistent Organic Pollutants (POPs); Sifa