Ozone absorbance monitor

Atmospheric and remote-sensing appHcations of uv—vis spectroscopy have been reviewed (157,158). Many volatile organics absorb in the near-uv, and the vapors exhibit rovibronic stmcture suitable for identification and quantification if interferences can be avoided. Especially suitable for uv monitoring are the strong Huggins (300—370 nm) and Hartley (210—300 nm) bands of O other inorganics such as NO2 and SO2 have been successfully analyzed at kilometer distances (see Ozone). 

To date, direct UV absorption sensing has been used mainly in environmental applications to monitor pollutants in the atmosphere such as ozone and NO (Wu et al. 2006), hydrocarbons, and volatile organic compounds (VOCs) (Lin et al. 2004). Fiber optic UV systems for gas and vapor analysis have been reviewed by Eckhardt et al. (2007). The strong absorbance of vapors and gases in the UV region is advantageous and has resulted in a compact detection system of good accuracy. 

Environmental scientists can monitor the pollutant gases in the air using an instrumental technique called infrared spectroscopy (see Chapter 18, page 241). It works quickly and accurately to monitor pollutants, including nitrogen dioxide, sulfur dioxide, carbon monoxide and carbon dioxide, as well as more than a hundred VOCs and low-level ozone. The scientists can use the characteristic wavelengths of infrared radiation absorbed by the molecules of the pollutants to identify them. They can also analyse the intensity of the absorptions to find the concentration of each pollutant present in a sample. Monitored over a period of time, the scientists provide useful information on the effectiveness of pollution control measures introduced locally and on a global level. 

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