Study On The Correlation Of N, P Nutrients And Algae Growth

Water eutrophication is the plankton fulminate proliferation phenomenon caused by excessive content of N,P nutrient elements in lakes or reservoirs. In recent years, eutrophication was gradually increased in major waters of China, which leading to pollution of water bodies and the phenomenon of human poisoning. Nitrogen and phosphorus are the most important controlling factors causing the proliferation of algae. The relationship between algae biomass and N,P is causing more and more people’s attention and becoming a hot research topic in the field of environmental science all over the world.In this paper, two dominant algae in Yellow River Diversion reservoir (Chlorella vulgans, Pseudomonas microcystin) were selected as experimental subjects to train in laboratory. The experiment of the relationship between algae biomass and N,P was studied from the following aspects:the type of nitrogen source, the concentration of N and P, N:P. Crafts of acetone-ultrasound method to extract the chlorophyll a were also optimized in the experiment. Algae biomass was determined by optical density method and chlorophyll a method. The main results of the paper are as follows:1.Chlorella vulgaris was selected as the research object and the optimum acetone ultrasonic extraction method suitable for freshwater algae was got in this paper. The results showed that the optimum extraction steps for chlorophyll a are as follows:with90%acetone as extraction agent, by ultrasonic extraction for30min at21°C,225W power,6000r/min speed centrifuged for9min, stirring, then repeat the ultrasound, centrifugation step.2. NaNO3, KNO3, NaNO2, NH4CI, urea and glycine were selected as nitrogen source for the study of environment. Results found that there were significant differences in the growth of Chlorella vulgaris and Microcyslis aerngrnosa, and KNO;, was the best nitrogen for growth of both two kinds of algae. While soil extract or manure extract was used alternative to NaNO3 of the BG11medium, there was a certain role in promoting growth of both Chlorella vulgaris and Pseudomonas microcvstin, and the effect of the manure extract was more obvious.3.Under conditions of NaNO3and K2HPO4respectively as nitrogen and phosphorus sources, the appropriate concentrations of nitrogen and phosphorus suitable for the growth for the two algae were obtained. For Chlorella vulgaris, it can be adapted to the lower N, but very difficult to survive in the environment of the lack of P, so P is the limiting factor for its growth. In addition, Chlorella vulgaris has optimum N concentration of500mg/L, the optimum P concentration of15.6mg/L, the optimum nitrogen to phosphorus ratio of16:1. For Microcystis aeruginosa, the suitable concentration of nitrogen and phosphorus is relatively wide. In general, it is suitable for growing in the high N and low P environment; it has the optimum N concentration of250mg/L, the optimum P concentration of62.5mg/L, the most suitable nitrogen to phosphorus ratio of50:1.4.While optical density method and chlorophyll-a method were used to measure Algae biomass, the optical density (OD680) and chlorophyll a concentration has good positive correlation in the logarithmic phase of growth of algae.