| Nowdays,the organic pollution in farmland soil is serious problem in some areas in China.These organic pollutants could affect the safety of agricultural products and bunman health through soil-plant system.Thus,it is essential to remedy the organic contaminated soils to improve the quality of soil environment and ensure agricultural safety.Surfactant enhanced remediation(SER)is one of the most potential remediation technology of organic-contaminated soil.In this study,the effects of anionic-nonionic mixed sufactants on root exudates of plants were analyzed,the effects of artificial root exudate components in facilitating the degradation of pyrene in soil were studied,and the mechanisms of PAHs removal by anionic-nonionic sufactants-ryegrass were explored.(1)The anionic-nonionic mixed sufactants(SDBS-Tween 80)could affect the compositions and concentrations of root exudates of ryegrass,alfalfa and pennisetum hydridum.SDBS-Tween 80 significantly promoted the secretion of the exudates of ryegrass at the ratio of 1:1,the concentrations of ribofuranose,oxalic acid,and threonine were 1.95-fold,1.45-fold and 1.49-fold of control treatment,respectively.(2)The artificial root exudate components could promote the degradation of pyrene through increasing the concentration of dehydrogenase and enhancing the abundance of degrading bacteria.Carbohydrate and organic acid treatments significant increased the concentration of dehydrogenase,and the removal rate of pyrene was significantly correlated with the trends of dehydrogenase(p<0.01).Carbohydrate and organic acid treatments increased abundance of degrading bacteria(Mycobacterium).A significant correlation was observed between the abundance of degrading bacteria and the removal of pyrene in soil(p<0.01).(3)The mechanism of SDBS-Tween 80-ryegrass enhanced the removal of phenanthrene and pyrene from soil was explored.When SDBS-Tween 80 was added at the ratio of 1:1(mol/mol),the removal of pyrene in soil was significantly improved,the transformation of pyrene from the bound and residual fractions to bioavailable fractions was promoted,and the abundance of degrading bacteria,phenanthrene and pyrene degradation related genes,and the concentrations of dehydrogenase were increased.The removal rate of pyrene was significantly correlated with phenanthrene and pyrene degradation related genes,and the concentrations of dehydrogenase(p<0.05).The increased of degradation genes was the main reason of promotion of removal of pyrene. |
