Rapid development of industry and unceasing emergence of factories lead to an increased soil pollution and make it an urgent and rigorous environmental issue worldwide. During which, one of the most serious problems is metal pollution due to the growing risk of heavy metal uptake by human and livestock. Copper is an essential element for all organisms at low concentrations, while it is toxic when absorbed excessively. The normal concentration of copper in plant tissues is 5-20 mg/kg, and the toxicity effects are likely to occur if it exceeds the upper limit. During recent decades, in comparison with physical and chemical remediation, phytoremediation had been reported to be more effective, non-intrusive and less expensive. All these characteristics together with the aesthetically pleasing feature make it the most socially approved technology to remediate polluted soil. Ornamental plant has become a novel source of phytoremediation species due to their multi-functions: pollution monitoring and control as well as landscaping. Extensive studies of the tolerance and accumulation of heavy metal by plants underpinned their utilizations in the restoration of heavy metal contaminated soil. Phytoextraction, a form of phytoremediation, is one example of applying plants to remove contaminants from soil by concentrating them in the havrvestable parts and based on the hyper-accumulation capacity of heavy metal by certain species. To improve metal enrichment of plants, chelators could be used as activators of metal to facilitate the procedure of plants to absorb available metal. Citric acid (CA), a natural metal chelator, is a kind of low-molecular-weight organic acids (LMWOAs). And ethylenediaminetetraacetic acid (EDTA) is a representative kind of artificially synthesized metal chelators. Recently, numerous articles focused on the researches about activation of heavy metal by chelators.
This paper explored the effects of CA and EDTA on the growth of Chlorophytum comosum, a type of ornamental plants, in copper-contaminated soil by pot-planting. The experiments included effects of CA and EDTA on content of available copper in soil, copper enrichment, morphological indicators, biomass, some physiological indexes and activities of antioxidant enzymes of C. comosum. The results showed that, the relationship, between influence of CA and EDTA on copper enrichment of C. comosum and capability of them on activating copper in soil, was a significantly positive correlation. CA could effectively improve the ability on copper absorption of C. comosum through activating copper in soil, and the best concentration was 5mmol/L. However, higher metal enrichment inhibited the growth of plants, so the morphological indicators and biomass of C. comosum both showed a crosscurrent to the trend of copper enrichment uner treatments of CA. The influence of EDTA on copper enrichment of C. comosum was less intensively, and the effects on growth of C. comosum was also not significant. In contrast, the effects of CA on growth of C. comosum in copper-contaminated soil was superior to EDTA, which provided theoretical foundation and scientific basis for widely applying CA and EDTA in phytoremediation.