Effects of iron and phosphorus on Microcystis physiological reactions.

OBJECTIVE: To observe the effects of iron and phosphorus on Microcystis physiological reactions. METHODS: The experimental conditions were chosen as the light dark cycles of 16 h 8 h, 12 h 12 h, and 8 h 16 h. The cell change of morphology and life history, cell number, cell color, and cell area of Microcystis were analyzed quantitatively. According to the resource competition and Monod equation, Microcystis kinetics of phosphorus and iron were also examined. RESULTS: The longer light time caused more special cell division, slower growth rate, and easier change of bigger cell area. The color of alga was changed from green to brown. Ks and micromax of phosphorus absorption were 0.0352 mircomol x L(-l) and 0.493 d(-1), respectively. Those of iron absorption were 0.00323 micromol x L(-1) and 0.483 d(-1). CONCLUSION: Microcystis bloom is more dominant than other algae.

Visible light induced photodegradation of organic pollutants on nitrogen and fluorine co-doped TiO2 photocatalyst.

The nitrogen and fluorine co-doped TiO2 polycrystalline powder was synthesized by calcinations of the hydrolysis product of tetrabutyl titanate with ammonium fluoride. Nitrogen and fluorine co-doping causes the absorption edge of TiO2 to shift to a lower energy region. The photocatalytic activity of co-doped TiO2 with anatase phases was found to be 2.4 times higher than that of the commercial TiO2 photocatalyst Degussa P25 for phenol decomposition under visible light irradiation. The co-doped TiO2 powders only contain anatase phases even at 1000 degrees C. Apparently, ammonium fluoride added retarded phase transformation of the TiO2 powders from anatase to rutile. The substitutional fluorine and interstitial nitrogen atoms in co-doped TiO2 polycrystalline powder were responsible for the vis light response and caused the absorption edge of TiO2 to shift to a lower energy region.

Effects of nutrients on Microcystis growth more easily forming bloom.

Different nutrient media experimentally were N, P and Fe-limited conditions and a serial of diluted BG11 media. The cell change of morphology and life history, cell number, cell color and cell area of Microcystis were analyzed quantitatively. First, the effects of nitrogen, phosphorus and iron depletion were distinctively different. Phosphorus and iron depletion caused more special division cells, slowly growth increasing, the easier change of bigger cell area. Second, the nitrogen and iron depletion could make the color of alga from green to brown. Finally, according to the resource competition and Monod equation, Microcystis kinetics of phosphorus and iron were also examined. K(s) and micro(max) of phosphorus absorption were 0.0352 micromol/L, 0.493 d(-1) respectively; iron absorption: 0.00323 micromol/L, 0.483 d(-1). In a word, some evidences of the Microcystis bloom dominance in certain nutrient conditions were indicated in the experiments. The dominances were determined as the reviving under the adverse circumstances through the special division, the various nitrogen resources, and the lower kinetics of phosphorus and iron than that of most of other algae. The conclusions provided the scientific basis for preventing and managing Microcystis bloom in freshwater.