| Recently-rising Chelate-induced Phytoremediation shows good application prospects in practice because of its clear advantages in governance of heavy metal contamination, which can further improve the extraction and restoration efficiency of plants to heavy metals. On the other hand, Loliurn perenne L annual monocotyledon Poaceae, as a plant of mining ecological restoration, having features of relatively large biomass, strong regeneration capacity, easy planting, strong capacity of heavy metal accumulation and so on, becomes a hotspot in recent researches as a common plant of water-soil conservation in mining area due to its well-developed root system. On this basis, this thesis takes the lead-zinc contaminated soil from Hanyuan County in Ya'an City as the matrix, with Loliurn perenne L., an accumulator as the experiment plant, EDTA, DTPA and critic acid being the exogenous additives for pot experiments by stages. The activation effect of chelating agents above to the elements in soil is determined firstly to further research the influences of chelating agents in different concentrations as well as combinations thereof on lead-zinc extractions of accumulator plants and on the nutrient balance of accumulator plants; furthermore, preliminary analysis and evaluation are implemented for the chelate-induced technical feasibility and environmental risk. The experimental results show that:1) Different types of chelating agents have an activation effect on each element in soil. But the effect of the mixture in each group is better than the activated effect of single application. The most obvious effect comes to the mixture reagent of DTPA and EDTA (each 5mmol/L) which measures up to an extraordinarily significant level.2) All various chelating agents and mixtures there of have no greater impact on the pH value of soil.3) Different concentrations of DTPA and EDTA mixed reagent have different influences on growth conditions of plants. Except the high concentration, the rest treatment has increased the total biomass of plants as well as the aboveground biomass, specifically D3E3 (DTPA 2mmol/L, EDTA 2mmol/L can better promote the growth of plants, reaching the extraordinarily significant level.4) The addition of DTPA and EDTA mixed reagents in different concentrations has enhanced the plant uptake of lead and zinc, and each treatment has reached a significant level. In addition, with the exception of high concentration, with the increase of chelating agent concentration, plant uptake of lead and zinc also increases, and the transfer coefficient also increases. However, in case of high concentration, plants reduce the uptake of lead and zinc with the increase in concentrations of chelating agents.5) In this study, the selected chelating agents and combinations thereof have increased the aboveground plant absorption of lead and zinc, an increase of the aboveground part of the lead and zinc enrichment factor.6) For lead and zinc, DTPA and EDTA treatment of the mixed reagent concentration is in significantly positive correlation with the amounts of lead and zinc absorbed by plants.7) Different concentrations of DTPA and EDTA mixed reagents promote the absorptions of nutrient elements in plants, with a significant influence on the absorption of N, P and K nutrients.8) A combination of EDTA and DTPA can also promote the absorption of grass-rich vegetation to various nutrients (calcium and magnesium) with low concentration.9) The imposition of different chelating agents has potential secondary pollution to the environment especially to soil and water; in particular, single application of organic chelating agents with high concentration increases the risk of secondary pollution to the environment as well as endangers soil fertility loss significantly.
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