A cavity-enhanced differential optical absorption spectroscopy instrument for measurement of BrO, HCHO, HONO and O 3.

Abstract

The chemistry of the troposphere and specifically the global tropospheric ozone bud-get is affected by reactive halogen compounds like BrO or ClO. Bromine monoxide (BrO) plays an important role in the processes of ozone destruction, disturbance of NO x and HO x chemistry, oxidation of DMS, and the deposition of elementary mercury. 5 In the troposphere BrO has been detected in polar regions, at salt lakes, in volcanic plumes, and in the marine boundary layer. For a better understanding of these pro-cesses instruments with high spatial resolution and high sensitivity are necessary. A Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) instrument was designed and applied. For the first time, such an instrument uses an UV-LED in the 10 UV-wavelength range (325–365 nm) to identify BrO. In laboratory studies at the Atmo-spheric Chemistry Research Laboratory, University of Bayreuth, Germany, BrO, as well as HONO, HCHO, O 3 , and O 4 , could be reliable determined at detection limits (for five minutes integration time) of 20 ppt for BrO, 9.1 ppb for HCHO, 970 ppt for HONO, and 91 ppb for O 3 , respectively. The best detection limits for BrO (11 ppt), HCHO (5.1 ppb), 15 HONO (490 ppt), and O 3 (59 ppb) were achieved for integration times of 81 min or less.