Systematic Assessment of Bottomland Resources Influenced by Waste Disposal

Abstract

In Ile-Oluji, Nigeria, issues with waste disposal brought on by population growth have resulted in contamination of the bottomland resources that sustain humankind. Random soil samples were taken from a solid dumpsite and its adjacent closed bottomland at depths of 0–15, 15–30, and 30–75 cm and analyzed in the laboratory. Soil texture, soil moisture content (MC), porosity, bulk density, pH, electrical conductivity (EC), organic carbon (OC), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) were measured. Also examined was the concentration of heavy metals such as lead (Pb), cadmium (Cd), arsenic (As), nickel (Ni), chromium (Cr), and manganese (Mn) in the samples. Soil moisture content (MC), porosity, bulk density, pH, and electrical conductivity (EC) ranged from 8.52 to 16.08%, 30.14 to 51.19%, 1.16 to 1.46 g/cm3, 6.98 to 7.58, and 299.82 to 432.61 μS/cm, respectively. The concentrations of nutrients and heavy metals (OC, K, Ca, Mg, and Na) and (Pb, Cd, As, Ni, Cr, and Mn) in the soil samples collected from the solid waste dumpsite and bottomland ranged respectively from 2.13–3.10%,, 3.98–6.57, 5.08–8.11, 5.41–7.11, and 0.98–2.61 Cmol/kg, and 6.83– 29.04, 0.00–0.35, 0.41–3.92, 0.89–3.46, 0.00–0.63, and 13.74–74.38 mg/kg. The highest concentrations of nutrients and heavy metals were found in the soil sample collected from the solid waste dumpsite between 0 and 15 cm of soil depth, and it was closely followed by the sample obtained from the bottomland at the same soil depth compared to other locations. The concentration of heavy metals did not exceed the limits established by the World Health Organization (WHO) and the Food and Agricultural Organization (FAO), but persistent dumping of waste in the area may eventually increase the concentration of heavy metals beyond the acceptable limit. There is a need for the locals to be aware that the growing of crops on dumpsites and closed adjacent bottomland due to its fertility status could result in the uptake of heavy metals and eventually end up in human or animal bodies. A measure to avoid dumping waste close to the bottomland should be put in place by ensuring the immediate construction of a standard environmental sanitary dumpsite in combination with the waste recycling strategy in the study area.