| As an important part of people’s livelihood construction, the Chinese government pay more attention to control air pollution. In order to control two kinds of main pollution gases in the atmosphere, based on ultraviolet spectroscopy, two continuous monitoring systems for sulfur dioxide and elemental mercury are demonstrated to real-time monitor their concentrations in this paper, respectively.A compact and low-cost ultraviolet light-emitting diode (UV-LED) with center wavelength of 295 nm and high light density was used to measure the concentration of sulfur dioxide, which has a strong structured absorption band in the ultraviolet region around 300 nm. Differential optical absorption spectroscopy (DOAS) was used to determine the concentration of sulfur dioxide. A sensitivity of about 0.15 ppm·m was achieved in 1-s integration time, enabling real-time monitoring of sulfur dioxide.A continuous monitoring system for elemental mercury concentrations is demonstrated. Two low-cost multi-mode diode lasers (MDL), with central wavelengths around 682 nm and 404 nm, are used as light sources to generate ultraviolet light of 253.7 nm through sum-frequency generation. Correlation spectroscopy (COSPEC) is employed to guarantee measurement accuracy. Data processing algorithms (including derivation spectroscopy and multiple-linear-regression) are used to retrieve the data of mercury concentration. Allan variance is used to analyze a sensitivity of 0.15μg/m3 can be achieved in 10-s integration time. Experimental results show that the present system has great potential for industrial applications in the future. |
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