Arsenic fractionation in sediments and speciation in muscles of fish, Chrysichthys nigrodigitatus from a contaminated tropical Lagoon, Nigeria.

This study assesses arsenic (As) fractionation in sediments and speciation in muscle tissues of Bagrid catfish, Chrysichthys nigrodigitatus from Lagos Lagoon, southwest Nigeria to determine risks to ecological receptors and humans. Residual As was the predominant geochemical fraction (86.2%) in sediments. Arsenite [As (III)] concentrations which ranged from 0.06 to 0.53 mg kg-1 in catfish muscle tissue, accounting for 25.9% of total As was the dominant species. Less toxic dimethylarsinic acid (DMA) which varied between 0.06 and 0.27 mg kg-1 made up to 10.8% of total As in catfish muscle tissue. Estimated human average daily intake (ADI) of As as As (III) and DMA were 1.35 × 10-4 and 0.62 × 10-4 mg kg-1 BW with corresponding hazard quotients (HQs) of 0.45 and 0.21, respectively, indicate no apparent health hazard to adult consumers. The incremental lifetime cancer risks (ILCR) of 0.78 × 10-3 for total As, 0.20 × 10-3 for As (III), and 0.93 × 10-3 for DMA, for adults from the consumption of catfish is slightly higher than the US EPA threshold and indicates moderate carcinogenic risk. Furthermore, 12.5% bioavailable fraction of As in sediment and relatively higher levels of As (III) in fish tissues has ecological and public health implications.

Iron, manganese, cadmium, chromium, zinc and arsenic groundwater contents of Agbor and Owa communities of Nigeria.

Iron, manganese, zinc, cadmium, and chromium heavy metals and arsenic contents of groundwater in area and surrounding environment, of Ika land in the Delta state, Nigeria was studied. Groundwater without any treatment is the predominant source of drinking water by inhabitants of these communities. However, the quality of this water source is not immediately known, raising questions of its safety. Results of a regional composite of groundwater obtained, shows high iron (27%) and zinc (36%) contents in Boji-Boji Agbor area, manganese (31%) was highest in Boji-Boji Owa. Alihame recorded the lowest value of zinc (8%), while manganese was lowest in Agbor Obi area (12%). Arsenic, cadmium, and chromium were below detection limit in all the sample sites. Correlational matrix analysis revealed no significant relationships between metal types studied. Analyses of chronic daily dose intake (CDI), and hazard index were all very low. A hazard index of 0.01 was obtained. One-way ANOVA show significant statistical difference in the mean concentrations of the heavy metals for the different sample sites, which indicate that different sites contribute differently to the mean concentrations of the groundwater in the study area. Four conclusions are drawn from this study. Indications are that the heavy metals present in the Nigerian aquifer are very much below the maximum concentration levels and guideline values of national and WHO standards. Secondly, there is a heavier load of these metals in the city centre than in the suburbs; with Boji-Boji area Agbor/Owa urban areas accounting for 27 and 20 percent of load respectively. Thirdly, the below detection limit results for some of the metal ions and the very low concentrations of those detected are pointers to the absence of industrial activities and mining. Finally, the groundwater in the study area is considered to be generally safe with respect to the contaminants studied and results posted for the composite samples. Inhabitants are therefore under no illusion of immediate or remote health challenges with regards to the heavy metals analyzed. More individual sampling, however, is recommended.