[An Incoherent Broadband Optical Cavity Spectroscopy for Measuring Weak Absorption Cross Section of Sulfur Dioxide].

As a highly sensitive detection technology, incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) have successfully measured a variety of trace gases. According to the principle of cavity enhanced absorption spectroscopy, if the accurate concentration of the target gas, the curve of the mirror reflectance, effective absorption path length, the light intensity of the absorbing gas and non-absorbing gas are known, the absorption cross section of the absorption gas can be measured. The accurate measurements of absorption cross section are necessary for satellite retrievals of atmospheric trace gases and the atmospheric research. This paper describes an incoherent broadband cavity enhanced absorption spectroscopy(IBBCEAS) instrument with 365 nm LED as the light source for measuring absorption cross section of SO2 from 357 to 385 nm which is arising from the spin-forbidden a ³B1--X¹A1 transition. In comparison to the literature absorption cross section of SO2, and correlation coefficient r is 0.997 3. The result shows the potential of the IBBCEAS system for measuring weak absorption cross section.

[The Detection of Atmospheric HONO and NO2 with Fiber Coupling Long-Path Differential Optical Absorption Spectroscopy System].

A new type of fiber coupling Long-Path Differential Optical Absorption Spectroscopy System(LP-DOAS) based on schmidt - cassegrain telescope was introduced in detail in this paper and it was applied to the accurate measurement of the actual atmospheric HONO and NO2. This measuring system simplified the structure of traditional LP-DOAS system, combining with the design of optical fiber coupling.It made full use of the telescope primary mirror's effective area. The effects of the offset, dark current and telescope stray light to the new LP-DOAS system were discussed in this paper; On a clear day, the ratio between telescope stray light and the optical intensities was less than 1%. To verify the accurate of the new LP-DOAS system, the atmospheric NO2 were simultaneously measured with the new LP-DOAS system and traditional LP-DOAS system. The correlation coefficient R2 was up to 0.968. The observation of atmospheric HONO was carried out by using the fiber coupling LP-DOAS in Gucheng, Hebei Province, China, and the detection limit (2σ) of HONO and NO2 was 84.2 and 144.6 ppt , respectively, with 2 490 m path length and the average time resolution of about 30 s. In the whole measurement in Gucheng, the maximum of HONO and NO2 were 3.2 and 37.8 ppb, respectively, and the minimum were both under the detection limits; the ratio of HONO/NO2 at night was calculated.

[Cruise Observation of SO2, NO2 and Benzene with Mobile Portable DOAS in the Industrial Park].

The self-developed portable DOAS instrument based on differential optical absorption spectroscopy(DOAS) and composed of optical fiber spectrograph and multiple-pass cell was introduced. The standard gases of SO2 and NO2 were employed to test the accuracy and stability of the system, and then cruise observation of SO2, NO2 and benzene was carried out using the system in Tongling industrial park. During the entire period, the polluted gases showed high concentrations near the contaminated areas and the maximum concentrations of SO2, NO2 and benzene were 5 023.2, 2 195.2 and 162.5 µg·m-3, respectively. With 12.6 m optical path, the detection limits of SO2, NO2 and benzene were 67.0, 169.9, 30.6 µg·m-3, respectively. The portable DOAS system provides a convenient and effective technique for industrial park about emergency and supervisory monitoring and evaluation of gas leakage and fugitive emissions of gaseous pollutants.