Abstract
This study was designed to investigate the possible variation in bioaccumulation of heavy metals (lead, cadmium, zinc, cobalt, chromium, nickel, and manganese) in the tissue of harvested Oreochromis niloticus (tilapia) and the associated fungi from vials treated with soil from e-waste dumpsite and soil without e-waste. E-waste is electronic waste which contains valuable metals as well as potential environmental contaminants. The heavy metals in soil and fish samples were determined using flame atomic absorption spectrophotometer (AAS) after homogeneity and digestion of samples. The associated fungi were identified using standard microbiological methods. The genera of the associated fungi were: Penicillium, Candida, Articulospora, Aspergillus, Aspergillus, Aspergillus, Rhizopus, Mucor, Zoopage, Varicosporium and Rhodoturula. The quantity of fungi isolated from each pollution treatments showed that the number of fungi were inversely proportional to the quantity of e-waste soil pollution and directly proportional to the quantity of soil without e-waste pollution. The occurrence of the fungi species revealed that the untreated (control) vial had the highest occurrence (191) while the lowest occurrence (103) occurred in the vial polluted with the highest quantity of soil from e-waste dumpsite. The pH and the biochemical oxygen demand (BOD) of the vials were significantly affected by the pollutions. Variations were also observed in the bioaccumulation of the heavy metals by Oreochromis niloticus. Cadmium (0.01 mg/kg) and nickel (0.02 - 0.08 mg/kg) were the least recorded metal in the tissue of the fish while cobalt was not detected after the five weeks period. The sequence of the heavy metals concentrations in Oreochromis niloticus tissue samples was Zn > Mn > Pb > Cr > Ni > Cd > Co. The accumulation of the metals in the fish tissue were, however, lower than the international maximum guidelines, except for manganese (0.29 - 3.13 mg/kg) that exceeded the 0.01 - 0.05 mg/kg threshold levels for manganese by Federal Environmental Protection Agency (FEPA). Protecting the environments from toxic metals is necessary, hence a need for public awareness on the dangers of these toxic metals and law for proper disposal of e-waste.
Highlights
Electronic waste (e-waste) includes an increasing range of electronic appliances from large household appliances, such as refrigerators, air-conditioners, cell phones, stereo systems and consumable electronic items to computers discarded by their users [1]
A total of eleven different fungi species were isolated from the e-waste soil sample, soil without e-waste sample and polluted fish vials, nine of which (Aspergillus niger, Aspergillus flavus, Articulospora inflata, Zoopagenitospora, Varicosporiumelodeae, Penicillium sp., Rhodoturula sp., Rhizopus stolonifer, and Mucormucedo) had been isolated from crude oil polluted environment, other polluted areas, gastrointestinal tract and agricultural soil
Fungal colony count from each polluted vial showed that the quantity of fungi was inversely proportional to the quantity of e-waste soil pollution and directly proportional to the quantity of soil without e-waste pollution (Figure 1), indicating possible suppressing effect of the pollution on fungal growth in these vials [25]
Summary
Electronic waste (e-waste) includes an increasing range of electronic appliances from large household appliances, such as refrigerators, air-conditioners, cell phones, stereo systems and consumable electronic items to computers discarded by their users [1]. When a river in China received discharged waste water from a nearby e-waste processing plant, the organisms in the river had increased heavy metals concentrations in their tissues [11] Such pollution put living organisms at risk of heavy metal toxicity and human inhabitants relying on such water are at risk. This e-waste dumpsite is close to Lagos lagoon Run offs from this e-waste dumpsite can reach the lagoon, thereby increasing the concentrations of heavy metals released to the lagoon water. This will expose both the micro and macro organisms (including man) to heavy metal toxicity. The results in this research are geared towards raising public awareness on the danger of improper disposal of e-waste and to provide baseline data on e-waste pollution of aquatic environment
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