| Eutrophication of water lead to cyanobacterial bloom phenomenon has become a global environmentalproblems.cyanobacterial bloom can damage water environmental ecological balance, cause the industryand agriculture production and living water difficult, serious impact on economic development and peoplelife. at present, cyanobacterial bloom management by the chemical measures and biological measuresrespectively exist the secondary pollution and effective slow、controllable disadvantages and so on. moreand more research into the effects fast and relative environmental of physical measures. low intensityultrasonic control algae is one of physical alga methods，people pay more attention to it at home andabroad in recent years, there is no high strength ultrasonic energy dissipation, also there is no securityproblem as high strength ultrasound, it has deeply research and development prospects in the control ofcyanobacterial bloom.The study on low intensity ultrasonic under the condition of different Settingseffect、control alga mechanism、aquatic ecological safety and outdoor applications control alga growt ofrelevant test research, aims to establish a low price and high efficient cyanobacterial bloom treatmenttechnology to provide the scientific basis.Indoor experiment choose the microcystis aeruginosa which is one of the common blue-green algae, thestudy found that low intensity ultrasound in different function conditions (algae growth phase, algal cellconcentration, pH, temperature, and the second ultrasound) inhibit microcystis aeruginosa effect showed:cell concentration and pH have no notable influence on the ultrasonic inhibiting algal(p>0.05),but algaegrowth phase、water temperature and ultrasonic times have notable influence on ultrasonic inhibitingmicrocystis aeruginosa(p<0.05).The effect of algae inhibition of15℃、20℃and25℃are better than30℃and35℃,40℃high temperature that is against the algae growth without ultrasonic;The algaeinhibition effect of lag phase、stationary phase and senescence phase are better than logarithmic phase;There-ultrasonic can effective prolong the time of remainder algal recovery,stability the algae inhibition effect.at the same time, the test found that low intensity ultrasonic can significantly reduce the rate ofphotosynthesis liberate oxygen, the third day for the same period only70.55%compared with controlgroup (p<0.05), at5days there is a slightly elevated. experiment have shown that there is a significantimpact to algae cell of chlorophyll (Chla) content, superoxide dismutase (SOD) liveness, catalase (CAT)liveness and ATP enzyme liveness by low intensity ultrasonic. after5days Chla content inside cells frominitial298.09mg/g declined to175.95mg/g, decreased by40.97%(p<0.05), but control group have no significant differences with the starting; after1day the liveness of superoxide dismutase (SOD) ultrasoundgroup was32.65%higher than the control group (p<0.05), at the second and the third day SOD liveness oftwo groups of basic quite, but to the fifith day,ultrasound group is27.39%lower than the control group(p<0.05);when catalase (CAT) liveness is the highest,ultrasound group than in the control group3.5timeshigher in the same period (p<0.01), the three kinds of ATP enzyme (Na+K+-ATPase, Mg+-ATPase,Ca+-ATPase) also have a significant influence on the liveness, at the first day,3kinds of ATP enzymeliveness reached the highest value, the fourth and fifth day continuous down slowly, but always higher thanthe same period control group and the initial value;cell membrane permeability is also significantlyincreased, and the first day is64.81%higher than the control group at the same period (p<0.05).transmission electron microscopy images showed, ultrasound caused microcystis aeuginrosa ultrastructuralsignificant damaged, after ultrasound the algal cells’ strong pervious to light areas onsists of air vesiclesignificantly reduced, the thylakoid piece layer from clearly state to disorder fuzzy state gradually,at5thday appeared plasmolysis phenomenon,nuclear area performance for extremely disorders, cells form alsoappeared obviously shrinks phenomenon,but still keep cells integrity..aquatic biological safety test showedthat the low intensity ultrasound for8days had significant inhibitory effect on two kinds of microcystisaeuginrosa (p<0.05), compared with initial value, the two groups algae biomass by ultrasonic treatmentwere reduced89.01%and83.05%respectively; there was no significant effect to life activities of onekind of zooplankton(D magna), two kinds of aquatic plants(Common duckweed, Alopecurus pratensis L),three kinds of aquatic animals(Bellamya aeruginosa, Procambarus clarkia, crucian carp)by low intensityultrasound, showed the excellent security,but the effect of chronic nfluence needs further research.Outdoor application experiment(33d) showed that low intensity ultrasound can significantly improvetransparency and remove Chla, ultrasonic coverage area was significantly better than the control area for along time, at the end the Chla concentration of ultrasonic area only44.62%for the control area (p<0.05).from the time of the second sampling until experiment over, TP and TN concentration in the waters of theultrasonic cover were always lower than the controlled area, compared with the control area, the waters ofthe ultrasonic cover when the lowest amounted to only14.46%(p<0.05),44.59%(p <0.05)of the controlarea, showed that low intensity ultrasonic can reduce water TN, TP concentration. low intensity ultrasoundhave certain influence on the phytoplankton community structure, at the middle and late time, thedominant species ratio as scenedesmus、chlorella were increased, but microcystis is the most significantdecline. |
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