Evaluation of Uranium mine tailing remediation by amending land soil and invading native plant species

Abstract

Properties of the mine waste represented the toxic nature to human health and may pose numerous risks to the local environment. Although the recorded radioactivity level in these tailings is very low, but to avoid any long term effect of these tailings on the atmosphere as well as native living things, the tailings need to cover with soil. This reduces gamma radiation and radon emission levels. However, to consolidate the radioactivity and remediate the contaminants in the tailings on a sustainable basis, the area needs to be revegetated by candidate plants. Remediation of heavy metal-contaminated sites using plants presents a promising alternative to current methodologies. Therefore, the study was to evaluate the ex-situ phyto-remediation of uranium mine tailing ponds by amending with land soil followed by invading to grow predominant native plant species. Three volumes of the pot culture experiment were carried out i.e. additions of land soil to mine tailing at 0, 50, and 100 percent by volume with four abundance plant species of S. spontaneous (terrestrial), P. vittata (fern) and T. latifolia and C. compressus (aquatic species) were selected in the study. After appropriate preparation U, Mn, Fe, V, Ni, Cu and Zn which were the major contaminants and the pH and EC in soil fractions and also growth parameters in plant materials were analyzed at five stage intervals in the duration of four months. The addition of soil was found significant change in pH to alleviate the toxic effects that heavy metals have on plant health, hence the enhanced growth and survivability was reached. Even while redistributing metals to a less available form, during the remediation the plant species have the capabilities to accumulate substantial amount of toxic metals. The metal concentrations in the plants were found in the order Fe50.92 > Mn7.22 > Zn0.94 > Cu0.92 > Ni0.65 > V0.18 > U0.07 and accumulated in the order Zn0.021 > Cu0.019 > Mn0.014 > Ni0.013 > U0.002 > V0.001 > Fe0.001. The results of the study indicate that C. compressus and S. spontanium were found to be the candidate species for Phyto-remediation (i.e. either accumulation and non-accumulation or consolidation respectively) of contaminants in soil amended Uranium mine tailings. For maximum accumulation, C. compressus harvesting need to be done at after the fourth month of plantation and for consolidation, S. spontanium plantation was greatly recommended. It also confirms that the land soil could be the best amendment for remediation of abandoned mine waste.

"Mercury Uptake and Translocation by Indigenous Plants "

“…The increase in pH with an increase in treatment period was attributed to the 'alkalizing' effect of soils. 25 The Electrical conductivity at initial was found to be low at 20 th day followed by a 40 th day and drastically increased with the increase of time period 60 th day; this may be because of the increased concentrations of mercury salts (HgCl2) in the soil. Similar results have been reported in uranium mine tailing remediation by native plant species.…”

“…Similar results have been reported in uranium mine tailing remediation by native plant species. 25 The mobility, bioavailability, ecological and toxicological effects of mercury are strongly dependent on its chemical speciation. 33 The organic matter, Phosphate and nitrate content were also analyzed which support the plant growth and helps in mobility of metals.…”

“…Below and above ground parts were separated, weighed and dried in an oven at 110 o C for 2 hours for measuring dry weight. 25 Dried plant samples were ground into a fine powder and stored in a polythene bags for mercury analysis. Each individual plant height was measured during the experiment.…”