文摘
In Taiwan, the main technologies currently adopted regarding the remediation of soil polluted by heavy metals include blending and dilution, soil acid washing, as well as soil removal and replacement. The blending and dilution method is often used for farmland with deeper soil and a lower concentration of pollutants. The standard procedure for such remediation is easy to establish and implement, and therefore more favorable in terms of cost and time control. Nevertheless, during the process, not all parts of the soil can be fully mixed, which causes the failure of soil improvement. Soil acid washing is generally applied to farmland with high pollutant concentrations by using nitric acid, hydrochloric acid, and citric acid for oxidation reduction and complexation processes in the farmland. It can reduce concentration levels of heavy metals in the soil in a short period of time, and the acid solution can be recycled to lower the overall costs after the remediation. However, such a method could alter soil pH value, which leads to a certain level of damage to farmland and infertility. Soil removal and replacement excavates soil with high concentrations of heavy metal pollutants, and replaces it with clean soil. But such a method is more expensive in a sense that clean soil needs to be purchased, and waste soil needs to be purified. Consequently, sunflowers are selected for phytoremediation in this study. By integrating a plant growth hormone, GA3, as well as environmentally friendly and bio-degradable chelating agent, EDDS, this study aims to improve the effectiveness of the heavy metal contamination remediation via phytoremediation, thereby achieving environmental sustainability.
