Trace metals analysis of soil and edible plant leaves from abandoned municipal waste dumpsite in Owerri, Imo state, Nigeria

Municipal refuse may increase heavy metal concentration in soil, even at low levels, and their resulting long-term cumulative health effects are among the leading health concerns all over the world. In this study, we investigated the concentration of heavy metals in soils and edible plant leaves grown in an abandoned dumpsite along Akachi road in Owerri municipality. The soil samples were collected at each plot using a soil Auger at the depth of 0-10 cm. Leaves of dominant edible plant species were selected and collected from each sample plot. The samples were dried in an oven with forced air at 40 °C, milled to fine powder, then digested with 10 ml concentrated HNO₃ and 5 ml concentrated HClO₄ and were analyzed for Cr, Cu, Fe, Mn, Al, and Zn, using an H183200 MultiParameter Bench Photometer. Result showed that metals in the sampled soils included (in order of quantity) Cr: 150-280 >Fe: 116.50-203 >Cu: 12.4-18.8 >Mn: 0-20 >Al: 0.08-0.16 >Zn: 0-1.4 mg kg^-1 Dw. Moreover, levels of metals in the edible plant leaves are in the order of: Zn>Fe>Cu>Al>Mn>Cr. Zn content, in particular, was higher than FAO/WHO recommended limits. Still, application of Pollution Load Index and Ecological risk models showed that the area is unpolluted and safe for use. Daily Metal Intake estimates indicated that zinc is mostly consumed from the plant species. The trends in Transfer Factor for the heavy metal in vegetable samples studied were in order: Zn>Al>Cu>Mn>Fe>Cr. Therefore, abandoned solid waste dumpsites contained significant concentrations of heavy metals which are later absorbed and accumulated by plants growing it.