Effect of coal mine soil contamination on the elemental uptake and distribution in two edible Amaranthus species, A. dubius and A. hybridus

The impact of coal mine dump contaminated soil on the elemental uptake by two edible plants, namely, Amaranthus dubius (red herbs) and Amaranthus hybridus (green herbs), was studied by investigating their response and ability to tolerate and accumulate varying levels of elements in their roots and shoots. The vegetation was grown on varying amounts of contaminated soil, viz. 0%, 5%, 15%, 25% w/w using coal mine dump soil. The soil was analyzed for soil pH, cation exchange capacity (CEC), soil organic matter (SOM), moisture content, and selected heavy metals. The distribution of six metals, namely, Pb, Cd, Hg, Ni, Mn, and Fe, in roots, stem, and leaves of the plants was determined in two stages of growth after 5 weeks and 10 weeks. All soil and plant samples were microwave digested and subjected to heavy metal analysis using the ICP-OES, GFAAS, and CVAAS. The pH of the coal mine dump contaminated soil decreased with an increase in contamination. Both the SOM and CEC values decreased, which increases the availability of elements, by providing more binding sites in the soil. Relatively, the red herbs had higher elemental concentrations than the green herbs. Both plants recorded high manganese accumulation. No mercury was detected in the soils or plants.