Study On Phytoremediation Of Cu-contaminated Soils Using Zea Mays Induced By CO₂

Soil is one of the most important natural resources that people depend on. With the development of economy and the progress of society, the problem of soil contaminated by heavy metals has increasingly become the focus of attention, and its decontamination has become a difficulty that academic study. Remediation of soil by conventional engineering techniques often cost much money and likely to cause much disturbance to the environment and secondary pollution. More importantly, it often results in destruction of the soil structure and degradation of soil fertility. Phytoremediation is an emerging technology of pollution control. It has many advantages, such as low cost, less disturbance to the environment, higher aesthetic value of the environment and the psychological ability of the public, easy to be accepted by community. But how to increase the plants biomass, shorten the cycle and improve the efficiency becomes a bottleneck problem that limits phytoremediation technology. To overcome these limitations, it is necessary to develop new methods and techniques of phytoremediation. In this paper, carbon dioxide fertilization technique is applied to the field of phytoremediation. Using homemade close CO2 chambers, the effects of copper stress and CO2 enriching on the biomass, photosynthesis, copper uptake by the Zea mays grown in soil or nutrient solutions containing different copper concentrations were studied. It can provide scientific experimental data for phytoremediation, and further enrich phytoremediation theories. Following results were obtained:Compared with the control,the Zea mays had less plant height and leaf area under the copper stress. With copper concentrations from 0 to 400ppm, the inhibition was more obvious. High concentrations of copper obviously decreased the Fv/Fm value and Yield value of Zea mays seedling's leaves; Fm' value had less obvious differences, but also showed decreasing trends; Photochemical quenching factor qP had little difference. But NPQ value demonstrated increasing trend. This may be the Zea mays self-protection mechanism under copper stress conditions.It was found that enriching CO2 promoted growth and development of Zea mays. It was also observed in our experiments that increasing CO2 concentration can shorten phenophase. For copper control, the anthesis of Zea mays exposed to CO2 concentrations of 1000ppm is ahead, respectively as compared to 350ppm. Enriching CO2 can enhance the Zea mays'ability of resisting copper and pests. Also, it can increase plant height, leaf area, leaf numbers and dry weight. The values of Fv/Fm, yield and Fm under the condition of high atmospheric CO2 concentration (1000ppm) were improved. So it increased the efficiency of photosynthesis of Zea mays. Significant increases in copper accumulation by Zea mays occurred with CO2 fertilization. But enriching CO2 did not make Zea mays hyperaccumulate copper.