Study On The Discipline Of Algal Fluorescence Response To Heavy Metal Toxicity

The effectiveness evaluation of water environment has become the urgent needs of society, biological toxicity as water ecological evaluation index of pollutants can quickly concluded by the biological efficiency under the coexistence. Biological toxicity test is a kind of indispensable assistant method which be used to Predicte and control chemical pollution. Because it can response the joint toxicity role of compound pollutants in waste water comprehensively, and it can describe the compositive toxicity to biological population which done by the polluted water intuitive. The chlorophyll fluorescerce is considered the best probe to research photosynthesis. The photosynthesis of microalgae occupies the core status of cell metabolism. So there have prospects to detection toxicity which belonds to heavy metals by chlorophyll fluorescence, because it has advantages of quickly and sensitively.After Literature retrieval, the author selected three strains microalgae for experiment, there are Scenedesmus obliquus, Chlorella pyrenoidosa, Microcystis aeruginosa. Cd2+, Hg2+, Cu2+, Zn2+ four types of typical metals for the Stress testing. The Concentration of metals designed as 0.004μmol·L-1,0.01μmol·L-1,0.02μmol·L-1,0.21μmol·L-1,2.09μmol·L-1,20.9μmol·L-1. We can add some heavy metal solution to the culture solution, when the testing micoalgae growth to logarithmic growth, and its value of OD more than 0.3.First, we do the experiment about the growth and photosynthetic pigment influence of three strains microalgae by Cd2+, Hg2+, Cu2+, Zn2+ four types of typical metals Stressed. The results show that, the toxicity of four kinds of heavy metals to three strains microalgae as follows. The toxic effects to Scenedesmus obliquus is Hg2+>Cd2+>Cu2+>Zn2+; the toxic effects to Chlorella pyrenoidos is Cd2+>Cu2+>Zn2+>Hg2+; the toxic effects to Microcystis aeruginosa is Cu2+>Hg2+>Zn2+>Cd2+. In order of patience with toxic heavy metals by three strains microalgae as follows. Hg2+:Chlorella pyrenoidosa> Microcystis aeruginosa> Scenedesmus obliquus; Cu2+:Scenedesmus obliquus> Chlorella pyrenoidosa> Microcystis aeruginosa; Zn2+:Scenedesmus obliquus > Microcystis aeruginosa> Chlorella pyrenoidosa.Then the author do the experiment about the Chlorophyll fluorescence response with four types of typical metals Stressed. Get a conclusion:the response of Chlorophyll fluorescence sex of algae striking by metals Stressed. The results of experiment showed that the fluorescence affect of Microalgae by heavy metal significantly. Photosynthesis restrained seriously on account of prolonging stress concentration and time. Fluorescence stress experiment results obtained with algae growth inhibition and photosynthetic pigment is basically the same influence of trend, proof by fluorescence value change, use toxic heavy metals responses can algae fluorescence response characteristics testing heavy metal concentration stress is feasible.The experiment of determining sensitive algae to test the fluorescence value change in 20 minutes With two minutes frequency. Finally determined fluorescence heavy metal sensitive algae is Scenedesmus obliquus. HgCl2 as a typical toxicity representative material, analyzed the different time linear relationship between HgCl2 solution concentration and algae fluorescence value change. Determine the 16 minutes for testing the stable time, according to the algae fluorescence value for the difference and corresponding HgCl2 concentration initially established a water quality toxicity assessment level.