Effect and mechanism of microbial-Lolium perenne L.combined remediation on radioactively contaminated soil
Pot experiments were conducted to study the effects of the addition of Bacillus subtilis,Gillus niger,and Mortierella alpina(0,5,10,20,and 40 mL;bacterial concentrations were 0,2 × 105,4 × 105,8 × 105,and 1.6 × 106 CFU/g)on the growth characteristics,enrichment and transfer ability to uranium and thorium,physical and chemical properties of the rhizosphere,and the distribution of uranium and thorium in Lolium perenne.The results showed that addition of a small amount of B.subtilis(5 mL)significantly promoted L.perenne L growth,greatly enhanced uranium and thorium enrichment and transfer ability in L.perenne,and substantially boosted the proportion of exchangeable uranium and thorium in the soil.Fourier transform infrared spectroscopy(FTIR)results showed that the addition of a small amount of B.subtilis(5 mL)promoted the synthesis of amino-,carboxyl-,and methyl groups in plants,as well as the combination of carboxyl groups with metal ions such as U and Th in plants.This promoted plant growth,absorption,and enrichment of uranium and thorium,consistent with the growth,absorption,and transfer of uranium and thorium in L.perenne.Transmission electron microscopy(TEM)and energy-dispersive × ray spectroscopy(EDS)results showed that uranium and thorium were uniformly distributed in L.perenne when 5 mL B.subtilis or 10 mL Aspergillus niger was added.No additional reagents were used in this experiment except for the strain to establish a sustainable,low-carbon,accessible,and reliable approach for the treatment of radioactively contaminated soil.Adding B.subtilis at a concentration of 2 × 105 CFU/g to the soil significantly improved the enrichment ability of uranium and thorium nuclides and enhanced the soil remediation effect.
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