| Traditional heavy metal treatment process is not suitable for polluted soil, because it dramatically destroys property of soil. Phytoremediation is a cost-effective technology. It provides multi-benefits including high efficiency, low investment, cheap operational fee, easy management, simply operation and so on. It is adapt to developing country. At present the pivot task is to find and develop the hyperaccumulator and accumulate plant, and these plants must have sound heredity. The study is based on the phytoremediation theory, according to the phytormediation and compound pollution research of cad-polluted soil, finding cadmium enrichment plant that has large biomass. This study researches cadmium accumulation capacity of plant, the distribution of cad in plant tissue, the growth of plant influenced by cadmium, and the effect of accumulation under compound pollution, and the impact of Zn to growth of Phytolacca acinosa Roxb. and Cd sorption. This will supply basic theory and technological measure of using this plant to treat cad-polluted soil.Through field investigation and sampling of Zhuzhou smelt factory, it finds that Phytolacca acinosa Roxb can has heavier concentration of cadmium, and finding concentration of Cd in above-ground tissue >that of down-ground tissue. The principle of selecting plant: indigenous extensive, large-biomass, economic-value or esthetically pleasing-value. In light of it, this experiment uses Phytolacca acinosa Roxb., Canna generalis., Lycopus lucidus Turcz. .Lycopus lucidus Turcz of pot-planting experiment. The results show:(1)Cadmium inhibits plant growing obviously, and this impact getting more serious with concentration of Cd growing in soil. Due to different plant having different physiological characteristic, different plant has different critical concentration and different impact. At this experiment, the restraint impact to Lycopus lucidus Turcz is the least, and the most serious is Canna generalis.. In addition, it confirms that Cd can stimulate plant growth with certain low cadmium concentration, for instance Smg.kg-1.For some plants, adverse effect on growth of plant will more serious with time, and increase of biomass reduces with time. Therefore, it can consider to shortening the growth period of plant that can harvest several times a year. It not only can improve the dry material, but also can reduce the disadvantage influence of cadmium and increase removal amount of heavy metal.(2) Phytolacca acinosa Roxb. can grow at any Cd concentration within this experiment. The maximal Cd concentration of above ground tissue is up to 482.25mg,kg-1. Applying Phytolacca acinosa Roxb.to treat 200mg.kg-1 Cd polluted soil, it can get 3.5kg.ha-1 Cd per year. Due to high Cd concentration in plant tissue, we can incinerate root and above ground tissue to reclaim Cd, and this can bring economical benefit. The optimal growth period of Phytolacca acinosa Roxb. is three months, it can be harvesting twice a year.(3) Mirabilis jalapa. also has strong accumulation capability of cadmium, approach to the standard of hyperaccumulator. It has strong endurance with Cd, especially with high cad concentration it has good domestication capability, keeps relatively high biomass. There is positive relationship between accumulated concentration of above ground tissue and Cd concentration in soil.(4) In light of the equation that concentration of Cd multiplies biomass equal to the total removed from soil, coefficient absorption capacity is putted forward based on the absorption coefficient and transformation coefficient. The coefficient is the ratio of the total of heavy metal absorbed in the above-ground tissue to the concentration in soil per unit area at given growthperiod. Plant can be judged whether it is hyperaccumulator with this coefficient. This study, the critical concentration of coefficient absorption capacity is 4.2t.ha-1. The new coefficient expands the conventional definition of hyperaccumulator. It can judge some plant as hyperaccumulator, which does not meet en... |
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