Intercomparison of IBBCEAS, NitroMAC and FTIR for HONO, NO 2 and HCHO measurements during the reaction of NO 2 with H 2 O vapor in the atmospheric simulation chamber of CESAM

Abstract. We report on applications of ultraviolet light emitted diode based incoherent broadband cavity enhanced absorption spectroscopy (UV-LED-IBBCEAS) technique for optical monitoring of HONO, NO2 and CH2O in a simulation chamber. Performance intercomparison of the UV-LED-IBBCEAS with a wet chemistry-based NitroMAC sensor and a FTIR spectrometer has been carried out on real time simultaneous measurement of HONO, NO2 and CH2O concentrations during the reaction of NO2 with H2O vapor in the CESAM atmospheric simulation chamber. 1-σ (SNR = 1) detection limits of 200 pptv for NO2, 100 pptv for HONO and 5 ppbv for CH2O over 120 s were found for the UV-LED-IBBCEAS measurement. On the contrary to many set-ups where cavities are installed outside the simulation chamber, we describe here an original in-situ permanent installation. The intercomparison results demonstrate that IBBCEAS is a very well suitable technique for in situ simultaneous measurements of multiple chemically reactive species with high sensitivity and high precision even if the absorption bands of these species are overlapped. It offers excellent capacity to non-invasive optical monitoring of chemical reaction without any perturbation. For the application to simulation chamber, it has the advantage to provide a spatially integrated measurement across the reactor and hence to avoid point sampling related artefact.