Phytoextraction has been suggested as a viable alternative to traditional restoration practices for heavy metal-contaminated soils (e.g., soil removal and disposal in land fill areas, or co-processing in cement), in view of the lower costs and lower environmental impact. Juvenile and mature plants proved a high accumulation potential and a 3 week growth period was observed as a sufficient time period to remove more than 80% of Cd, Pb, and Zn. The risk element translocation into aerial parts decreased with increased time. The bioconcentration factor was approximately 2-5 times higher for juvenile plants than mature plants for all treatments as well as for both parts (leaves and roots). In comparison to control, citric acid mobilised 71%, 181%, and 112% of Cd, Pb, and Zn while tartaric acid mobilised 70%, 155%, and 135% of Cd, Pb, and Zn respectively. The results revealed that citric and tartaric acids mobilised the highest amount of all risk elements. ![]() In addition, the bioaccumulation of Cd, Pb, and Zn, in water lettuce (Pistia stratiotes L.) will be studied as they affect the biomass in the rhizofiltration process. The aim of this study was to investigate the efficiency of organic acids in soil by conducting flushing experiments to enhance the mobility of Cd, Pb, and Zn from soil to solution. The use of natural chelates to enhance risk element mobility combined with rhizofiltration by free floating macrophytes have not been thoroughly studied in recent years. LMWOA mobilized Pb and Cu from iron oxides, but such an increase in solubility was not high enough to affect phytoextraction. Zn was remobilized from the organic matter fraction through LMWOA application into the water soluble and exchangeable fractions. Zinc and Cu were retained mostly in the organic matter fraction. In general, low molecular weight organic acids (LMWOA) application increased the metal concentrations in the water soluble and exchangeable fractions. Neither citric acid nor gallic acid was efficient for metals phytoextraction. ![]() Soil samples were sequentially extracted and soil solution metal concentrations assessed. The organic acids were added as follows: 5 mmol kg-1 in the 28th cultivation day two doses of 5 mmol kg-1 at the 28th and 31st day and three applications at the same rate at the 28th, 31st, and 34th day of velvet bean cultivation. ![]() This work was carried out to compare the effectiveness of multiple applications of citric and gallic acids on the availability in soil and accumulation of Cd, Pb, Cu, and Zn by velvet bean (Stizolobium aterrimum) plants. Natural organic acids have been proposed to enhance phytoextraction due to their higher biodegradability, but they can also be a drawback for efficient phytoextraction. However, the most successful chelants tested so far are synthetic agents that barely degrade in soil, increasing the metal leaching risks. Chelate-assisted phytoextraction of heavy metals is a promising approach to clean up polluted soils.
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