Study On Grass And Microbe Combined Remediation On Uranium Contaminated Soil

In recent years, bioremediation has become a focus in environmental remediation. To sum up, we can strengthen the repair efficiency and shorten repair period by establishment of plant and microbial remediation system. In order to build a joint uranium-contaminated soil remediation system and filtrate advantages grass combined with dominant microorganism., the paper have conducted the following studies:(1) Filtering grasses in seed germination conditions: Through the germination rate, germination and vigor index of the 24 species of grasses seed germination experiments which were under the uranium stress, the dominant material was screened out. Results show that the Sorghum sudanense(Piper) Stapf, Lolium multiflorum Lamk, Lolium perenne L, Phleum pratense L, Dactylis glomerata L, Medicago sativa L, Phleum pratense L. are advantageous seed.(2) Analysing the growth and enrichment of dominant grasses: With soil culture experiment under uranium stress of grasses in better germination condition, this paper filtrated advantageous raw material of pasture for restoration by the analysis of growth indexes and accumulation ability. Analysis shows that the dominant grasses in different levels of uranium-contaminated soil can be selected for ecological restoration, low concentrations of pollution may use Lolium perenne L; high concentrations of pollution using Lolium perenne L, Lolium multiflorum Lamk. Comprehensive consideration of Lolium perenne L is better than the other grassess to various degrees, with its growth, thick roots developed in uranium pollution of soil.(3)The combination of microorganisms: The orthogonal combination experiment studied the symbiotics seffect offive strains, such as Citrobacter Werkman and Gillen, Bacillus mucitaginosus, Bacillus subtilis, Bacillus thuringiensis, Bacillus cereus, under the stress of 50 mg/L uranium and researched the secretive capability of combination of bacterial IAA, ACC deaminase and siderophore. This analysis resulted in 5 kinds of combination with good symbiotic effect and strong uranium resistance ability. According to the plant growth promoting indexes of secreting IAA and ACC deaminase and siderophore, this study selected combination of number 2, number 10 and number 12 to be the advantageous microorganism which have the opportunity to apply in Combined Bioremediation.(4) Plant microbial remediation: Match the advantageous grass combined with the advantageous microorganisms, detection of pasture growth and enrichment indicator found mix 2, mix 12 have a strong prmoting effect on biomass and enrichment capacity of three kinds grasses. To sum up, depending on the pollution level using different combinations of systems to complete the repair work, Lolium perenne L-3rd microbial remediation system used for treatment of high concentration of uranium-contaminated soil; Lolium multiflorum Lamk-3rd microbial remediation system used for treatment of low concentration uranium-contaminated soil.(5) Effect of cutting intensity on growth and accumulation: This paper used of different cutting intensities on pasture stubble, contrasting he biomass and accumulation of uranium under different treatments. Results showed that clipping intensity directly determined the secondary growth of grasses, and second harvest amount of uranium enrichment was not lower than the initial cutting; Severe clipping intensity(1th), seriously hampering the completion of its photosynthesis, has influence on the secondary growth, and the accumulation of uranium was low, thus it was not suitable to be applied related to the other two scenarios which were more repressive; Medium cutting intensities(2nd) without affecting grasses under normal growth conditions, has effectively promotied the uranium-enrichment capacity of Lolium perenne L, and also reached the maximum accumulation of uranium. It can be practical applied to uranium-contaminated soil treatment.To sum up, we can use Lolium perenne L with concentrations of mumber 3 into microbial remediation of high uranium-contaminated soil; using Lolium multiflorum Lamk. with concentrations of mumber 3 into low concentrations uranium contaminated soil; together with moderate clipping intensity can increase repair effectiveness. The study provided theoretical basis for uranium contaminated soil bioremediation and exploration of new materials.