EDTA, Water-extractable Lead and Bioavailability of Lead in Soils/Tailings: The Effects of Zeolite and Beringite Amendment

Field experiment was conducted in the Teaching and Research Farm of Enugu State University of Science and Technology in 2015 cropping season to evaluate the effectiveness of phytoremediation as a tool for cleaning up soils contaminated with diesel (AGO). The experimental design was split-plot in a Randomized Complete Block Design (RCBD) with two soil amendments (petroleum contaminated soil and petroleum uncontaminated soil) for main plots and eight plants [Soy bean (Glycine max), cowpea (Vigna unguiculata), groundnut (Arachis hypogaea), African yam bean (Sphenostylis stenocarpa), vetiver grass (Chrysopogon zizanioides), maize (Zea mays), carpet grass (Axonopus fissifolius) and spear grass (Heteropogon contortus)] consisted sub plots. Soil samples were collected before the application of petroleum and at 90 days after planting. The influence of petroleum contamination on the physical properties of the soil at 90 days after planting revealed that the soils with petroleum amendment were higher in bulk density (1.49 g cm-3) and lower in hydraulic conductivity (8.22 k cm-3 hr-1) than the uncontaminated ones. Petroleum treated soil contained lower total porosity value (43.75%) and moisture content (9.80%) than the uncontaminated soil. Soils without petroleum amendment contained more levels of total nitrogen, exchangeable sodium, exchangeable magnesium, base saturation and available phosphorus than the contaminated soils. Petroleum treated soil contained more concentration of carbon, organic matter, exchangeable calcium and cation exchange capacity than the uncontaminated soil. Cultivation of soy beans is recommended on petroleum contaminated soils, since the analyses of soil samples taken at 90 days after planting, showed that the soy beans suppressed the bulk density and increased the available potassium, exchangeable calcium and exchangeable magnesium of the soil for optimum soil fertility replenishment for crop production.