Effect of the uranium contamination on soil enzyme activities and microbial functional diversity

To investigate the effect of uranium on soil microbiology, the soils were treated with different concentratons (0, 10, 20, 50, 100, 150 mg · kg^-1) of uranium, and the soil enzyme activity and microbial functional diversity were measured. The Shannon, Simpson and McIntosh diversity indices fell by increase in uranium concentration and microbial activity decreased in soil against the control group under the uranium treatment in Biolog-ECO microplate analysis. Uranium treatment decreased the ability of microorganisms to utilize six carbon sources. The average well color development (AWCD) of Phenolic acid was only 19.98% of the control group. In the control groups, microorganisms showed the highest ability to utilize carbon sources of amines;in the 10 mg uranium · kg^-1 treatment group, microorganisms showed the highest ability to utilize carbon sources of polymers; in the 50, 100 and 150 mg uranium · kg^-1 treatment groups, microorganisms had the highest ability to utilize carbon sources of carboxylic acids. Enzyme activity analysis showed that with the increase of uranium concentration, the activities of alkaline phosphatase and aryl sulfatase decreased. Whereas activity of nitrite reductase showed fluctuation of simultaneous, increase and then decrease. Highly polluted soil by uranium concentration inhibited cellulose activity. Enzymatic activity was strongly inhibited due to uranium stress at the 30th day. The order of enzymatic sensitivity by uranium was aryl sulfatase > alkaline phosphatase > nitrite reductase > cellulase. Therefore, the carbon utilization of soil microorganisms was significantly inhibited by uranium pollution and aryl sulfatase could be used as indicators for the evaluation of uranium-contaminated soils. The results of this study provide a theoretical basis for evaluating and remediating ecological environments polluted by uranium. (authors)