Study On The Inhibitory Effect Of Iron And Silicon On Dominant Algae In Urban River

River is an important part of a city,not only carries the basic functions of providing shipping,leisure tourism and beautification of the city,but also carries the special function of regulating the city's climate and ecological environment.However,the rapid development of urban economy and the overexploitation of water resources have caused great pressure on city's water ecosystem environment,which has been degraded and its self-purification capacity has decreased.When water eutrophication occurs in the river flowing through the city,algae multiply and breed,the water quality in the urban river becomes worse and ecological functions are lost,which seriously affects the health of the city and the physical and mental health of the residents.According to the current research,it is generally believed that the algal blooms in general water are mainly caused by nitrogen and phosphorus.When these two elements are in excess,eutrophication occurs rapidly in the water.Some trace elements,such as iron and silicon,are also closely related to the physiology and biochemistry of algae.In recent years,Japan has adopted a new type of solid material with slow release of iron and silicon,which has been tested in sea areas and rivers.The results showed that it improved water quality and effectively inhibited algal blooms.However,the mechanism of regulating iron and silicon nutrients to inhibit algal blooms in rivers is still not comprehensive,and the dominant algae in different water are not only the same,and the effect needs to be further verified by experiments.In this study,the water quality and dominant algal species along the river were monitored and analyzed based on the urban river course in an area of Suzhou that needed to accommodate tailwater of sewage plant.The results showed that in the water where algal blooms occurred,Cyanophyta were the dominant algae and Anabaena were the dominant species.The response of Anabaena cells to iron and silicon treatment was investigated in the laboratory.The results showed that:(1)The optimal inhibitory concentration of iron on Anabaena was high concentration of 100 mg/L and low concentration of 0.01 mg/L,both of which inhibited the production of chlorophyll a and cell contents of Anabaena cells,while high concentration of iron(100 mg/L)also inhibited the cell proliferation of Anabaena cells;(2)Silicon at concentrations of 100 mg/L,10mg/L and 1mg/L inhibited cell proliferation and cell content generation,but had no effect on cell volume and chlorophyll a content;(3)For the urban river water in which Anabaena is the dominant species,the iron concentration in the water body should be reduced to 0.01mg/L or the high concentration of iron should be released artificially to regulate the iron content in the river so as to avoid promoting the breeding of Anabaena due to the appropriate iron content.In addition to regulating dominant algae,silicon can also inhibit Anabaena.Therefore,in theory,it is feasible to use the technology of releasing iron and silicon to inhibit the breeding of Anabaena in river.