Effects Of Endogenous Rare Earth And Ammonia Nitrogen On Plant Enzyme Activity And Soil Nitrogen Form Transformation

Under the irregular mining of rare earth mining areas and diffusion of pollutants in rare earth mining areas,the combined pollution of rare earth elements and ammonium nitrogen has become one of the environmental problems in China.In this paper,the common wild plants and common crops in the rare earth mining area were taken as research objects.Using the combination of mining area survey and pot experiment method determine the rare earth elements in mining soil,the rare earth elements and ammonium nitrogen in different tissues of common plants in mining area,the nitrate reductase?NR?,peroxidase?POD?and malondialdehyde?MDA?activities in leaves of maize,soybean and pepper and the contents of ammonium nitrogen?NH₄⁺-N?and nitrate nitrogen?NO₃^--N?in the upper,middle and lower layers of rhizosphere and non-rhizosphere soils.The response of plants under endogenous rare earth element-ammonium nitrogen combined pollution and the transformation of nitrides by endogenous rare earth elements were studied.The results show:?1?The combined pollution of high concentration of endogenous rare earths and nitrides would reduce the types and quantity of vegetation in the mining area.The endogenous rare earths in the soil of the mining area promoted the accumulation of ammonium nitrogen in the Dicranopteris dichotoma,but there was no significant correlation between the content of endogenous rare earth and the content of ammonia nitrogen in the tissues of Dicranopteris dichotoma.The common plants in Long nan rare earth mining area had high enrichment of light rare earth elements.Among them,Dicranopteris dichotoma and Uganda were rich in rare earth,especially for the enrichment of alfalfa.The mining of rare earth mining areas would increase the distribution of heavy rare earths in the soil surface layer,such as reducing the distribution of strontium and strontium in the soil surface.The mining area was characterized by a rich of yttrium elements,but a loss of europium elements.?2?The effects of endogenous rare earth and nitride composite pollution on the enzyme activities of corn,soybean and pepper were significant.High concentration of?NH₄?₂SO₄ inhibited the POD activity of pepper leaves,and the POD activity of soybean leaves was less affected by the change of ammonium sulfate concentration.The addition of 3 mg/kg of endogenous rare earth elements could enhance the POD activity of soybean and maize leaves but decrease the activity of POD in pepper leaves.Low concentration of endogenous rare earth elements reduced the degree of membrane lipid peroxidation in soybean leaves.Under the action of endogenous rare earth,?NH₄?₂SO₄ had a low inhibition and high promotion effect on the MDA content in maize and pepper leaves.The addition of low concentrations of endogenous rare earth elements could promote NR activity in soybean leaves and enhance the resistance of maize to?NH₄?₂SO₄,but inhibit the NR activity of pepper leaves.High concentration of endogenous rare earth and high concentration of ammonium sulfate would reduce the germination rate of corn seeds.Therefore,in the later restoration of the mining area,it is considered to first use the rare earth enriched plants to reduce the damage of the soil environment in the mining area,and then introduce other surviving plants to repair the soil.?3?Under the combined pollution of endogenous rare earth and nitride,it could promote the conversion of NH₄⁺-N to other nitrides in the rhizosphere environment of corn,soybean and pepper crops.Adding low concentration of endogenous rare earth elements would increase the content of NO₃^--N in rhizosphere soil.High concentration of endogenous rare earth would inhibit the conversion of NH₄⁺-N to NO₃^--N,but at the same time promote the transformation of NH₄⁺-N to other nitrides.