The Study On The Surfactant Enhanced Remediation Of Cd And As Polluted Soil By Ramie

Phytoremediation is a low-cost,green method for remediating heavy metal pollution in soil.Heavy metals in soil can be activated by surfactants to further enhance the absorption capacity of plants.This study aimed to remediate the Cd and As combined contaminated soil in Hunan Province.The activities of heavy metals in the soil were enhanced by three different types of surfactants after applying Sophorae resin（SL）,triton-100（TX-100）and sodium dodecyl sulfate（SDS）to the potted soil.and the remediation effect of Ramie on Cd and As contaminated soil was studied.The effects of different ratio of surfactants on Physiological Indexes of ramie were determined by pot experiment.Secondly,the effects of surfactants on the accumulation and migration of Cd and As were discussed by analyzing the contents of Cd and As in Ramie root,stem,leaf and rhizosphere soil.Finally,the contents of Cd and As in potted soil at different depths were determined to clarify the vertical transport behavior of Cd and As under different surfactant treatments.The main conclusions are as follows:（1）To analyze the related plant indicators of ramie through pot experiment,it could be seen that the application of SL and SDS will significantly reduce the biomass of ramie.The biomass first increased and then decreased with the increase of TX-100 concentration,and the phenomenon of low promotion and high suppression appears.The root vigor of ramie showed a decreasing trend with the increase of the amount of SL.With the increase of the concentration of TX-100,the root vigor first was increased and then decreased.There was no significant difference in root activity under different dosage of SDS.The analysis of MDA content in ramie leaves showed that both TX-100 and SDS would stress the growth of ramie,while the application of biosurfactant SL had no significant effect on ramie MDA.The activity of POD and CAT increased first and then decreased with the increase of the concentration of SL,TX-100 and SDS,while the activity of SOD showed a downward trend.The activity of antioxidant enzymes in Ramie can be increased by adding appropriate amount of surfactant,which is conducive to eliminating free radicals such as reactive oxygen species,so as to deal with the harm of Cd and As pollution..（2）The accumulation of Cd and As in Ramie could be promoted by SL,TX-100 and SDS.SL promoted ramie roots and stems to absorb Cd and As best,and TX-100 promoted ramie stems and leaves to absorb Cd and As best.The addition of surfactants could reduce the content of Cd and As in rhizosphere soil.The biomass of ramie was the largest under low-level TX-100 treatment(4 mmol kg^-1),and the effect of enriching Cd and As was the best.The cumulative amount of accumulation of Cd per plant of ramie was SL>TX-100>SDS,and the cumulative amount of accumulation of As was TX-100>SDS>SL..（3）The transport behavior of Cd and As in soil under different concentrations of three surfactants showed that Cd was enriched in the middle and lower layer of soil,and As was enriched in the middle layer of soil.The accumulation of Cd and As in the middle layer of soil where the roots are located is due to the accumulation of Cd and As by ramie roots.Ramie root has stronger traction effect on As.The results showed that 4 mmolkg^-1 TX-100 and 2 mmolkg^-1 SL treatments could enhance the remediation effect of Ramie on Cd and As combined contaminated soil.The results of the study can make ramie enrich more Cd and As in soil,and remove Cd and As in soil to the maximum extent,without damaging the normal physiological growth of ramie.