Development And Optimization Of The Atmospheric Concentrations Of Sulfur Dioxide Uv Fluorescence Analyzer

With the development of economic, environment pollution becomes more and more serious. It is important to protect and improve our environment, improving our environment depends on monitoring environment, one reflects levels of our surroundings,the other accumulates a lot of datas to evaluate our surroundings, one of major pollutants, sulfur dioxide, has done great harm to our environment , so it is more and more necessary to operate an continuous monitoring for pollution by sulfur dioxide, but most of monitoring systems foratmospheric , including sulfur dioxide , have imported for along time in our country , such situation do no good to national environment protection technology and environmental protection industry, we should develop our environment protection technology including detection of sulfur dioxide in air. Among all methods for detecting sulfur dioxide, ultraviolet fluorescence method is popular in many countries,including our country, and also is promoted by Word Health Organization. In the great support of Guangzhou Environment Protection Administration, we start the theories and technique studies on ultraviolet fluorescence for detecting sulfur dioxide in air based on photon counting method. The achievements include:(1) In theory, we conclude single wavelength excitating fluorescence detection theory and multiple excitation wavelength fluorescence detection theory. The results present the later can improve the fluorescence intensity and the fluorescence response of sulfur dioxide.(2) We analyse the peculiarity of fluorescence cell to affect detecting sulfur dioxide in air, such as, radius of cell, length of cell, intersect dimension of fluorescence .On the base ofthat , we design fluorescence of cell,cone that reduces others light, loop that stabilize gas current to detract fluctuation of gas current. The performance of the cell is improved .(3) Filter methods are analysed .diffraction grating filter method is adopted in the place of interference filter.Spectral transmission of diffraction grating filter at 214nm is about 50%, its band breadth is 5nm.(4) Zero gas set and system of setuping gas are designed, wich is helpful for the following experimentation.(5) Many factors having an effect on system' s performance arestudied, by adjustment of light path, the background counts reduce from 110010cps to 2890cps.(6) The experimental system is designed. The results show the photon counts is linear to the concentration of sulfur dioxide from 0 to 40 ppm in volume. The detector response is linear from 0 to 40 ppm, the response of S02fluorescence signal is 0. 5 counts/ppb. s, and the detection limit is about Ippb with an integrarion time of tow minutes, about 0. 5ppb with an intergration time of 300s.(7) Gas pressure having an effect on measurement is studied. The results show SO2 fluorescence signal and the response of SO2 rises with pressure rising. Flux of mixing gas to cell having an effect on measurement is studied.the diffent of flux affect on measurement . the results show it is best at 1000ml/min total flux.(8) Repetition and stability of system are studied, the results show that drift of system is 3% at diffent time.