Leachate Characterization, Pollution Load Assessment, and Waste Management Infrastructure Policy for an Unregulated Open Dumpsite in a Tropical Peri-Urban Environment: Evidence from Benin City, Nigeria

The leachate resulting from improperly managed and unregulated open dumpsites acts as a proximate and immediate link between waste accumulation and resultant groundwater and soil contamination; however, it has received relatively little attention in terms of analytical studies within the Nigerian environmental literature compared to the resultant endpoints of contamination. This study seeks to provide a comprehensive characterization and pollution load assessment of the leachate from the Upper Ekehuan/Asoro open dumpsite in Ovia North-East LGA, Edo State, Nigeria, with a focus on two leachate samples obtained from active zones of seepage within the site, employing the Pollution Load Index and Nemerow Pollution Index models. The results showed that the leachate was of extreme pollution potential with Iron concentrations of 66.65–103.85 mg/L or 67–104 times over the WHO limits; Nickel concentrations of 4.73–7.37 mg/L or 237–369 times over the WHO limits; Cadmium concentrations of 0.87–0.93 mg/L or 174–186 times over the WHO limits; and Hexavalent Chromium concentrations of 1.98–3.08 mg/L or 40–62 times over the WHO limits. The PLI value ranged from 62.4 to 94.7, indicating that both leachate samples fall within the 'Extremely Polluted' category. Comparatively, this study found that the leachate from this site compares favorably with the most polluted leachate from landfill sites across Africa. A conceptual model of a Source-Pathway-Receptor relationship was employed to illustrate the pathway of contamination resulting from the leachate. This study concludes that no investment in soil and groundwater remediation will be effective if the pathway of leachate contamination and infiltration is not first addressed and halted. This study also offers policy recommendations to NESREA, the Federal Ministry of Environment, and the SWMA of Edo State.

leachate characterization, pollution load index, Nemerow pollution index, source-pathway-receptor model, waste management hierarchy, dumpsite remediation, open dumpsite, Nigeria

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