Open Path Incoherent Broadband Cavity Enhanced Absorption Spectrometer for in situ measurement of nitrogen oxides, iodine oxide, and glyoxal in the atmosphere

In this work we report a compact, low-cost instrument based on Open Path – Incoherent BroadBand Cavity Enhanced Absorption Spectroscopy (OP-IBBCEAS) at 445 nm for the detection of iodine oxide (IO), nitrogen oxide (NO2) and glyoxal (CHOCHO) in the atmosphere. We provide a comparison between OP-IBBCEAS and the closed-path setup on which our instrument is based, previously described in Barbero et al. (2020). The OP system achieved a noise-equivalent absorption sensitivity (NEAS) of 5.7×10-10 cm-1Hz-1/2 per spectral element, only 3 times higher than the closed-path system. Automated performance of regular measurements without absorbance ensures good long-term accuracy of the system. The OP-IBBCEAS is robust and simple to install in the field, allowing quantitative measurements of NO2, CHOCHO, and IO with precisions of ±150, ±150, and ±7 ppt (pmol mol−1, 2σ) in 50 s of measurement.