| Eutrophication leads to excessive proliferation of algae and releases microcystin(MC)-based multiple toxins，which are serious harm to human health and drinking watersafety. Existing methods using for Microcystin test were almostly completed in lab. Thesemethods were time-force consuming, high cost and not suitable for on-time monitoring thedrinking water crisis caused by Microcystin. Recently, concentration of chlorophyll-a wasconsidered as a reliable characterization of algal biomass, and fluorescence spectrum wasused as one kind of technical means to characterize the composition and concentration ofDOM(Dissolved Organic Matter， DOM). Both detecting methods were continuous,automatic and on line. Therefore, the dynamic law of MC-LR concentration changing withthe Chlorophyll-a concentration and intensity of specific wavelengthes of fluorescencesignals at different periods of Microcystis aeruginosa growth have been studied, in order toget the theory basis for indirectly estimating on the concentration of Microcystin.At first, Microcystic aeruginosaa was cultivated in BG-11medium and nature waterfor100days under the same environmental conditions. the dynamic relevance betweenMC-LR concentration and the Chlorophyll-a concentration has been analysed.The resultsshow: Microcystic aeruginosaa cultivated in both culture mediums show similar dynamiclaw in different growth phrases, chlorophyll-a concentration and Microcystisn-LRconcentration were positively correlated in the logarithmic period, negatively correlated inthe stabilization period and chlorophyll-a concentration reduced while Microcystisn-LRconcentration first increased, then decreased in the decline period. Linear fitting ofchlorophyll-a concentration and Microcystisn-LR concentration in the logarithmic periodand decline period was made, and linear correlation coefficient was>0.8. MC-LRconcentration in water can be estimated approximatly by chlorophyll-a concentration.Secondly, this article explores some of the environmental factors such as temperature,light intensity and nutrients how to affect on Microcystis aeruginosa growth and toxinproduction. The results show: the optimum tempratures for Microcysis. aeraginos growthand toxin producing was20℃and25℃respectively, the best light intensity was100μmol/m2/s and phosphorus was a restriction factor. When N/P>16:1, increasing theconcentration of phosphorus can significantly accelerate the speed of algal growth andtoxins releasing, while N/P＜16:1, continuously increasing the concentration ofphosphorus, the speed of algal growth and toxins releasing were not significantly changed. Finally, the dynamic law and correlation between extracellular MC-LR concentration and fluorescence signals of culture in different growth phrases have been studied, the results show: Three features fluorescent signals were obvious in the fluorescent spectrum of culture water. There are fluorescence signal A（protein-like substance）, signal X（marine humic-like acid） and signal C（fulvic-like substance）. Allthe three fluorescence signals intensity and MC-LR concentration were normalized by chlorophyll-a concentration. In the decline phase, the normalized fluorescence signals(A,X,C) and normalized MC-LR concentration show good linear correlation. Linear correlation coefficient was0.76,0.64,0.6respectively.All in all, extracellular MC-LR concentration, the Chlorophyll-a concentration andintensity of fluorescence signals of culture water at different periods of Microcystisaeruginosa growth show a certain extent dynamic relevance. Therefore, the Chlorophyll-aconcentration and intensity of fluorescence signals of culture water have the protential toindirectly estimate the MC-LR concentration in water. It will offer a new thougth forreseach on the rapid, on-line monitoring instruments of toxins pollution in water. |
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