Study On The Engineering-plant Combined Remediational Technology Of Contaminated Farmland Soil By Heavy Metal In Mining Area

Research about remediation of contaminated soil by heavy metal attracts more and more attention with the unceasing deepening of industrial progress, increasing seriousness of contamination of heavy metal and its harm. Through analyzing the content of mercury, cadmium and chromium, different fertility index in soil before and after different remediational measure, and determining biological indicators and content of mercury, cadmium and chromium in ground/underground part in different phase of wheat and ryegrass, this paper discusses the theory and removal efficiency towards heavy metal of engineeringplant(crop) remediation technology as new agricultural mode of producing while remediating, then analyzes and compares the economic and environmental benefit of engineering-plant combined remediation technology, and finally screens the best composite mode towards heavy metal in mining area, which provide theoretical basis and technical reference for the reclamation and utilization of farmland soil in mining area, taking mercury, cadmium and chromium in soil as reaearch project and farmland nearby goldfield of Tongguan in Shaanxi province as test site. The main findings are as following:1. Engineering treatment significantly decrease the content of mercury, cadmium and chromium in soil, and there is a significant difference between diverse processing. The reducing amplitude of mercury, cadmium and chromium respectively are 17%, 27% and 29%, which is depending on the treatment of 40cm-turned soil, while the effect of treatment of 80cm-turned soil is the best and the reducing amplitude of mercury, cadmium and chromium respectively are 26.7%, 35.2%, and 37.1%.2. The enrichment coefficient of wheat/ryegrass towards mercury, cadmium and chromium are all less 1, which indicates that both crops have no features of enrichment plant. However, the enrichment coefficient of the underground part of wheat/ryegrass towards cadmium respectively reach 1.06 and 0.74, and the enrichment coefficient of the ground part respectively reach 0.39 and 0.43. Considering the high biomass, both crops are feasible as phytoremediation of cadmium.3. The repairing effect of engineering-plant combined remediation towards mercury, cadmium and chromium in soil is significant. The measure of 80cm-turned soil+wheat combined remediation has the best effect and results show that the decreasing amplitude of mercury, cadmium and chromium respectively are 61.4%, 61.1% and 66.7%, besides, the content of cadmium and chromium have lied in clean level.4. The output per mu of 80cm-turned soil+wheat combined remediation is higher than other treatment of wheat/ryegrass, and reaches 518.4kg which is in accordance with theoretical output per mu of Wenmai 19.5. Compared with the control, the content of cadmium in grain of treatment of 80 cmturned soil+wheat combined remediation has reduced from alert level to clean level. Therefore, in the view of wheat as the main economic crops of northern area, applying soilturnded+crops combined remediation technology is promising.