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Assessment of solid waste and dumpsite leachate and topsoil

Dumpsite leachate contains different hazardous substances, some of which threaten the environment. In this study, municipal solid waste, dumpsite leachate and topsoil from seven different dumpsites in Lagos and Ibadan, Nigeria were analysed using standard methods. The parameters analysed in the composite leachate samples collected are pH, solids, alkalinity, chloride, nitrate, sulfate, phosphate, biochemical oxygen demand, chemical oxygen demand turbidity, heavy metals (e.g. Zn, Pb, Co, Ni, Cd) and some persistent organic pollutants (e.g. polyaromatic hydrocarbons [PAHs] and polychlorinated biphenyls [PCBs]). Total organic carbon, heavy metals (e.g. Zn, Pb, Co, Ni, Cd) and organic pollutants (e.g. PAHs, PCBs) were analysed in the dumpsite topsoil and the control samples. The samples for heavy metal determination were digested using concentrated nitric acid and the digestate was analysed using atomic absorption spectrometry, whereas organic pollutants were extracted using cold extraction and quantified by gas chromatography-mass spectrometry (GC-MS). The study revealed that dumpsites in Ibadan have ∼90% domestic and 10% industrial waste, whereas the figures for Lagos are 80% and 20%, respectively. In the leachate samples, concentrations of PAHs and PCBs ranged from 0.85 to 1.47 mg/L and 0.01 to 0.08 mg/L, respectively; the values were 0.94–2.79 mg/kg and 10.0–412 μg/kg in the topsoil. If not properly managed, dumpsite leachate can seep into groundwater and surface water via run-off, and can have adverse effects on human health and the entire ecosystem.