Effects Of Heavy Metals And Microorganism Fertilizer On Phytoremediation Of Uranium Polluted Soil

In order to provide the basis for the application and popularization of plant- microbial remediation technology, the interaction effects of uranium and heavy metal and the function of microbial fertilizer in the phytoremediation process by Cichorium intybus L. were studied in pot culture. Soil was treated at twice:(1) The uranium concentration gradients were 0, 50, 100 and 150 mg·kg-1, mixed with cadmium, lead, mercury, nickel and chromium respectively, whose concentration settings include the concentration of 0, low concentration(1 times of the background concentration) and high concentration(5 times of the background concentration). The co ntrol treatment was added nothing but tap-water.(2) When test(1) ended, 200 times EM bacteria liquid was added into the soil treated with uranium, nickel and cadmium separately and uranium mixed with nickel and cadmium respectively. Sowing, growth manage ment and the index determined in the two tests were the same. The results showed that:(1) Coexistence of uranium and cadmium had certain harm to the chicory germination, and cadmium strengthened the inhibiting action of uranium on chicory growth. In high concentrations of uranium contaminated soil, lead or mercury or nickel strengthened the inhibitory effect of uranium on the growth of chicory seedlings, but relieved the impacts of uranium on chicory regenerated plantlets growing taller, meanwhile promoted the biomass increasing of regenerated plantlets jointly with uranium. Most of the plants growing in the soil contained chromium died, which mean chromium was the most toxic to chicory. Lead of mercury or nickel could lighten the damage of high concentration uranium on chicory to a certain extent, mainly for when U concentration was 150 mg·kg-1, compared with separate uranium contamination, combined pollution of some heavy metal and uranium resulted in net photosynthetic rate increasing, Fo decreasing, Fv/Fm and Fm increasing.(2) In high concentration of uranium contaminated soil appropriate concentration of cadmium or lead or mercury or nickel ions was helpful to chicory absorbing and accumulating uranium, among which the promoting effect of lead was the largest and nickel the minimum, moreover, cadmium was in favor of the transfer of uranium from root to shoot. In lead or nickel or cadmium polluted soil, the existence of uranium inhibited chicory absorbing the three kinds of heavy metal. In addition, high concentration of uranium(150 mg·kg-1) played a negative role in transportation of cadmium in chicory, but contributed to increasing the shoot to root ratio of nickel or lead.(3) Under uranium alone stress and combined stress of high concentration uranium and cadmium, addition of effective microorganisms(EM) fertilizer aggravated harm to chicory, resulting in lower net photosynthetic rate(Pn) and Fv/Fm. However, EM bacterial manure improved peroxidase(POD) activity and superoxide dismutase(SOD) activity of chicory leaf, indicating the reducing of damage to cell membrane. Besides, EM bacterial manure could enhance tolerance of chicory under combined stress of uranium and nickel.(4) In low concentration of uranium contaminated soil, EM bacterial manure had negative influence on uranium absorption by chicory, but made positive contribution to increasing the transfer efficiency of uranium from chicory root to shoot. In high concentration of uranium contaminated soil, however, EM bacterial manure went against uranium absorption and transfer by chicory when concentration of nickel or cadmium existed, but was helpful to uranium absorption when low concentration of nickel existed. Besides, EM bacterial manure could hinder chicory absorbing nickel, but helped to increase the transfer efficiency from root to above-ground organs. Meanwhile, EM bacterial manure was helpful to the absorption of cadmium by chicory under high concentration of cadmium alone stress and combined stress together with high concentration of uranium.In conclusion, in high concentration of uranium polluted soil, the presence of a certain concentration of heavy metal reduced stress on plant. Heavy metal inhibited plant from accumulating uranium in low or moderate concentration of uranium contaminated soil, but was conducive to plant accumulating uranium in high concentration of uranium contaminated soil. Microorganism fertilizer wasn’t conducive to the absorption of uranium by plant, and yet increased the transfer efficiency of uranium from root to shoot.