Response Of Soil Microbes To In Situ Leaching Model Of Ionic Rare Earth

For the current prosperity of rare earth mining and smelting, waste water and large quantities of waste residue have been discharged to environment. Consequently, the accumulation of rare earth in earth has big potential influences to soil environment, particularly soil environment in mining areas. Therefore knowledge of biological effects of rare earth in soil has become a necessary; At same time, looking for ways to recycle rare earth and control the pollution of rare earth are needed urgently. In the present work, systematic study of biological effects of Yttrium on soil microorganism (bacteria, fungi, actinomyces) and soil enzyme activity has been carried out, also these effects when Yttrium under the stress of (NH4)SO4. And a strain of microorganism has been isolated from soil to adsorb Yttrium ion, and the adsorption character has also been studied. Through modern analysis techniques, the determination of concentration of rare earth element and the enzyme activity have been completed.(1) Through the study of biological effects on soil microorganism, it has found that Y3+has stimulative effect on bacteria, fungi and actinomyces at low concentration and the maximum stimulation ratio of bacteria is16.8%, of fungi is32.1%, of actinomyces is41.8%. while had inhibitory effect at high concentration, the critical concentrations were about1000mg/kg、500mg/kg、500mg/kg. Similarly, suitable concentrations of (NH4)2SO4in soil has timulative effect on bacteria, fungi and actinomyces and these most suitable concentration of (NH4)2SO4are100mg/kg,200mg/kg,100mg/kg, while (NH4)2SO4has inhibitory effect at high concentration. Under the stress of low concentration of (NH4)2SO4, low concentration of Y can increase the stimulative effect of (NH4)2SO4on bacteria, fungi and actinomyces, but while had inhibitory effect at high concentration of Y. Under the stress of high concentration of (NH4)2SO4, low concentration of Y can reduce the inhibitory effect of (NH4)2SO3on bacteria, fungi and actinomyces, high concentration of Y can increase inhibitory effect of (NH4)2SO4on bacteria, fungi and actinomyces.(2) Through the study of biological effects on soil enzyme activity, it has found that Y3+had only inhibitory effect on catalase and the inhibitory effect was more obvious at low concentration, had stimulative effect on protease at low concentration and the maximum stimulation ratio is54.8%while had inhibitory effect at high concentration and the maximum inhibition ratio is23.3%, and the critical concentration was about1000mg/kg, while had no significant effect on urease.(NH4)2SO4has stimulative effect on catalase at low concentration(50-100mg/kg) and inhibitory effect at high concentration, while (NH4)2SO4shows inhibitory effect on both protease and urease. Under the stress of (NH4)2SO4, low concentration of Y can reduce the stimulative effect of on catalase and reduce the inhibitory effect of (NH4)2SO4on protease and urease, high concentration of Y can also reduce the stimulative effect of (NH4)2SO4on catalase and increase the inhibitory effect of (NH4)2SO4on protease and urease. Under the high concentration of (NH4)2SO4, low concentration of Y can increase the inhibitory effect of (NH4)2SO4on catalase and reduce the inhibitory effect of (NH4)2SO4on protease and urease, high concentration of Y can increase the the inhibitory effect of (NH4)2SO4on catalase, protease and urease.(3) Through the adsorption character study, it has found that the adsorption time, the pH, adsorption temperature, biomass concentration and concentration of rare earth are the important factors for the biosorption of the rare earth. The biosorption of Y3+is a fast process, the most suitable pH is6, the adsorption temperature should be30℃, the biomass concentration should been chosen according to the requirement.