外源稀土Ce^(3+)对紫背浮萍光合作用和水体富营养化的影响

Influence of Exogenous Ce^(3+) on Photosynthesis of Spirodela polyrhiza and Water Eutrophication

随着稀土的大量开采、冶炼和应用,导致稀土元素正逐渐由岩石圈向水圈和生物圈转移,由此对水环境很可能造成类同重金属的环境负面效应。基于适量稀土对植物生长的促进作用,以四川境内较为常见且易引起水体富营养化的紫背浮萍为研究对象,运用室内受控实验,观测不同浓度稀土Ce3+对紫背浮萍光合作用的影响,并对紫背浮萍鲜重以及培养液进行了15 d的监测。结果表明较低浓度Ce3+(0.30,0.60 mg.L-1)能提高紫背浮萍叶绿素a的含量和碳酸酐酶活性,促进植物的光合作用,其鲜重均高于空白样(P<0.05),并随着时间推移,培养液中DO含量逐渐下降,COD含量则显示出上升趋势;而较高浓度Ce3+(1.50,3.00 mg.L-1)条件下,紫背浮萍叶绿素a和碳酸酐酶活性明显降低,鲜重低于空白样,光合作用下降,植物生长受到抑制。研究结果可知,水域中适量浓度Ce3+(0～0.60 mg.L-1)可提高水生植物光合作用,加快新陈代谢,进而使水质恶化,促进水体富营养化的发生。

With the development of rare earth（RE） industry,a mass of RE have been transferred from lithosphere to hydrosphere and biosphere,which may cause negative effects which are similar to heavy metals on water environment.In view of the fact that the moderate rare earth elements（REE） can promote the growth of plants,Spirodela polyrhiza,which is common in Sichuan Province and easy to cause the eutrophication,was selected for research.The controlled experiment was used for the observation of the influence of different Ce^3＋ concentration on the photosynthesis of Spirodela polyrhiza and quality of nutrient solution.The results showed that,under low Ce^3＋ concentrations（0.30 and 0.60 mg·L^-1）,the chlorophyll a（Chl.a） content,carbonic anhydrase activity and photosynthetic rate of Spirodela polyrhiza could be increased,meanwhile,the fresh weights were higher than that of the blank（P0.05）,DO content in nutrient solution decreased and COD increased as time prolonged.However,the chlorophyll a（Chl.a） content,carbonic anhydrase activity,photosynthetic rate and fresh weight under high Ce^3＋ concentrations（1.50,3.00 mg·L^-1） were lower than those of the blank,the growth of Spirodela polyrhiza was inhibited.The results indicated,that the moderate REE cerium（0~0.60 mg·L^-1） could boost the photosynthesis and metabolism of Spirodela polyrhiza,and thereby caused the water quality deterioration and water eutrophication.