Tea Saponin Enhanced Lolium Multiflorum In The Remediation Of Pyrene-cadmium Contaminated Soils And Morphological Transformation Mechanism Of Pollutants

It is an effective method that biosurfactants enhanced plant in the remediation of heavy metals and organic matter, and it is promising in the remediation of contaminated soils. However, little is known about its comprehensive mechanisms involved. A view of biosurfactants enhanced plant remediation with the transformation of different pollutants fractions was chosen in this paper. And also to improve the bioaccessible fraction of pollutants in this study. Four kinds of surfactants were chosen in the remediation of pyrene(PY) and cadmium(Cd) polluted soil. Through the simulation environment, tea saponin(TS) at 40 mg kg-1 was the best choice to enhance Lolium multiflorum in the remediation of single and combined contaminated soils. It was studied that the solubilization effect of surfactants on pyrene and Cd, the morphological transformation of different fractions of pollutants, mutual effect of single and combined pollutants, the enrichment effect of Cd and the degradation effect of pyrene by Lolium multiflorum, the catalase activity(CAT) and the peroxidase activity(POD) of plant, soil microorganism activity, the dehydrogenase activity(DHA) and the polyphenol oxidase activity(PPO) of soil, the micromorphology of Lolium multiflorum’s leaves and roots. The main results are:(1) TS at 40 mg L-1 was chosen among four kinds of surfactants to do the later remediation experiment. The solubilization effect of pyrene and Cd was promoted by TS. The morphology of Cd was transformed from Fe-Mn oxides and associated to carbonates fractions to exchangeable fraction with adding TS. The morphology of pyrene was transformed from associated fraction to bioaccessible fraction with adding TS. The solubilization of pyrene was promoted in the presence of Cd in pyrene-Cd contaminated soil. The solubilization of Cd was hindered in the presence of pyrene in pyrene-Cd contaminated soil.(2) There was a little stress effect of pollutants on the seed germination. But it had no significant effect on seed germination. The biomass of Lolium multiflorum could be increased by the addition of TS at 40 mg L-1. The addition of TS could promote the enrichment of Cd and the degradation of pyrene. It could increase the CAT and POD in the plant, also the DHA and PPO in the soil. It could enhance the resistance of plants and the protection mechanism of plant. The accessible fraction of pollutants and the enzyme activity were improved by the addition of TS. Thus, the enrichment and degradation effect of pollutants was promoted by the plant and microorganism remediation. And the process of remediation was accelerated by the addition of TS. Roots were the main part of accumulation of pyrene and Cd. There was migration effect of Cd from upper soils to lower soils.(3) The micromorphology of Lolium multiflorum roots and leaves were watched by SEM after TS enhanced remediation. When the plant was stressed by the pollutants, it would produce defense mechanism by discharging some white particles, folding the leaves or producing tuber to protect the basic physical characteristics of plant. The addition of TS could activate the pollutants and accelerate the process of phytoremediation. As a kind of biodegradable surfactant, a very good application prospect will be given by TS on the remediation of heavy metals and organic pollutions.The mechanisms resolved in the TS enhancing Lolium multiflorum remediation of pyrene and Cd and the micromorphology transformation of pollutants were investigated. These results might provide support for the development and utilization of TS enhancing plant remediation technology.