Effects Of Uranium And Associated Heavy Metals On Hyperaccumulator Plants Rhizosphere Soil Enzyme Activity

This paper aims at biological treatment technology of radioactive contamination. Experimental material were Amaranthus retroflexus L.,Abelmoschus esculentus L.,Bidens pilosa L.,Brassica juncea L. The effects of uranium and associated heavy metals on hyperaccumulator plants rhizosphere soil enzyme activity are studied by pot tests. The changes of rhizosphere soil and non rhizosphere soil enzyme of Bidens pilosa L. is discussed. The paper is order to elect the key enzyme indexes for evaluating radioactive and associated heavy metals pollution,and provide the reference basis for studying on the mechanism of radioactive and associated heavy metals pollution of bioremediation.Main results are as follows:(1)Comparing of the rhizosphere soil enzyme activity of emaranthus retroflexus L.,Abelmoschus esculentus L.,Bidens pilosa L.,Brassica juncea L. under uranium and associated heavy metals pollution, the results are follows: Urease can reflect the pollution intensity of U, Mn,Hg. Phosphatase can reflect the pollution intensity of As.The pearson correlations of the rhizosphere soil phosphatase activity of Abelmoschus esculentus L.,Bidens pilosa L.,Brassica juncea L. with As is-0.996**,-0.935*,-0.974**. Invertase can reflect the pollution intensity of Hg. The pearson correlations of the rhizosphere soil invertase activity of the four plants with Hg is-0.894*,-0.913*,-0.926*,-0.817*. Dehydrogenase can reflect the pollution intensity of U and Hg. The last pearson correlations of the rhizosphere soil dehydrogenase activity with U and Hg is-0.948**、-0.961**.(2)The order of the rhizosphere soil urease activities is Brassica juncea L.>Abelmoschus esculentus L.>Bidens pilosa L.>Amaranthus retroflexus L.. The highest value of soil phosphatase activity is Amaranthus rhizosphere, and the remaining did not change significantly.(3)When Bidens pilosa L. under the single and the complex heavy metal stress, the order that the increase of soil enzyme activities is phosphatase > dehydrogenase > invertase >urease. Under the complex heavy metal stress, the rhizosphere soil enzyme activities is higher than the non-rhizosphere soil enzyme activities. And invertase can uesd as an important indicator enzyme complex pollution intensity of U, Cd, Pb, As.(4)Under the uranium and associated heavy metals stress, the Bidens pilosa L. height and overground parts dry weight have decrease significant, and inhibition effect increased with increasing concentration. But the Bidens pilosa L. underground parts dry weight when low concentration stress treatment is heavier than it when high concentration stress treatment. U, Cd, Pb and As stress make the Bidens pilosa L. underground parts dry weight decreased. The largest inhibition rate of each is 51.12%, 31.58%, 29.62 % and 31.17%. In the some range concentration of U 、 Cd 、 Pb 、 As, the Bidens pilosa L. intensity of photosynthesis, chlorophyll fluorescence parameters and chlorophyll have not significant impact. And the toxic effect of the Bidens pilosa L. photosynthesis of U, Cd stress is larger than Pb, As stress.