| This paper studied in the laboratory the impact of physical and chemical factors such as different illumination, temperature and pH on the growth of Microcystis aeruginosa. It was also studied the impact of different elements:nitrogen, phosphorus, iron, calcium, magnesium and other elements on the growth of Microcystis aeruginosa.the Experimental results show that:(1) When the nutritive elements are sufficient, the longer and the greater strength of illumination is,the faster Microcystis aeruginosa grows.it is also one of the reseans that Algal blooms is usually occurred in summer when illumination is sufficient.(2) compared with the growth curve of the Microcystis aeruginosa in 5℃,15℃,25℃and 40℃,it can be found that temperature has a great impact in the growth of Microcystis aeruginosa. In low temperature, Microcystis aeruginosa is in a dormant state. When the temperature reaches to 40℃, a large number of Microcystis aeruginosan is dead. In 15-25℃range, the growth rate of Microcystis aeruginosa is elevated along with the temperature enhanced.(3) Microcystis aeruginosa grow the best in the neutral pH,but it has a certain adaptability of the change of pH. However, if the pH is less than 4.5 or higher than 10.5, Microcystis aeruginosa can't grow, and most of it is dead.(4) Nitrogen has the very important influence to the growth of Microcystis aeruginos. Microcystis aeruginosa can get nitrogen for its growth from air by biological nitrogen fixation. But If Microcystis aeruginosa has a high growth and reproduction, the nitrogen must be absorbed from the water. Microcystis aeruginosa grows well in the water of nitrate nitrogen, ammonium nitrogen or organic nitrogen. If other condition is good,with the increase of nitrogen in the water, Microcystis aeruginosa grows faster, and ultimately lead to algal blooms.(5) phosphorus is one of the main limiting nutrient for the growth of Microcystis aeruginosa. When there is no phosphorus in the water, Microcystis aeruginosa can not live. If other element is enough, with the increase of phosphorus in water, the Microcystis aeruginosa grows faster.(6) When the Fe3+ was less than 50μg/L, the proliferation of Microcystis aeruginosa proliferation was inhibited, and it grows slowly; when the Fe3+ concentrations was higher than 50μg/L, the Microcystis aeruginosa cells grows faster, when the concentration of Fe3+ was higher than 1000μg/L, the growth of Microcystis aeruginosa was significant at first, but Microcystis aeruginosa's growth entered the decline phase very quickly.(7) Calcium is an necessary element for the growth of Microcystis aeruginosa. In the water of low calcium, Microcystis aeruginosa grows slowly. However, because calcium is a high quantity element in the earth, and usually in water it is not lack When the algae bloom is happen, quicklime can effectively mitigate Microcystis aeruginosa, beacaue quicklime produce lime hydroxide ions in the water, which is bad for the growth of Microcystis aeruginosa. Only the high content of the calcium in water can not affect the growth and reproduction of Microcystis aeruginosa.(8) Magnesium is a necessary element for the growth of Microcystis aeruginosa. low magnesium conditions, Microcystis aeruginosa can not grow well. But the nature water is rich of magnesium, and it will not be a lack element of Microcystis aeruginosa. When Magnesium, ammonium and phosphate is in the water, it will be form magnesium ammonium phosphate,but because Microcystis aeruginosa is need the three elements lowly, so adding magnesium chloride to reduce two main elements- nitrogen and phosphorus in water, in order to preventing the occurrence of algal blooms is not feasible. Therefore, the nitrogen and phosphorus removal must be completed before the water let to natural water. |
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