Abstract
Abstract. An instrument based on 20 m open-path incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) was established at the Jülich SAPHIR chamber in spring 2011. The setup was optimized for the detection of HONO and NO2 in the near-UV region 352–386 nm, utilizing a bright hot-spot Xe-arc lamp and a UV-enhanced charge-coupled device (CCD) detector. A 2σ detection limit of 26 pptv for HONO and 76 pptv for NO2 was achieved for an integration time of 1 min. Methacrolein (MACR) was also detected at mixing ratios below 5 ppbv with an estimated 2σ detection limit of 340 pptv for the same integration time. The IBBCEAS instrument's performance for HONO and NO2 detection was compared to that of extractive wet techniques, long-path absorption photometry (LOPAP), and chemiluminescence spectrometry (CLS) NOx detection, respectively. For the combined data sets an overall good agreement for both trend and absolute mixing ratios was observed between IBBCEAS and these established instruments at SAPHIR. Correlation coefficients r for HONO range from 0.930 to 0.994 and for NO2 from 0.937 to 0.992. For the single measurement of MACR r=0.981 is found in comparison to proton-transfer-reaction mass spectrometry (PTRMS).
Highlights
Photolysis of nitrous acid (HONO + hν(λ < 400 nm) → OH + NO) leads to the formation of the most important daytime oxidant in the atmosphere, the hydroxyl radical (OH)
The experiments presented here supplement a campaign on the Formal Intercomparison of Observations of Nitrous Acid (FIONA) (Ródenas et al, 2013), where instruments for the quantification of HONO were compared at the EUPHORE simulation chambers in Valencia (Spain) in May 2009
Measurements of time-dependent mixing ratios of HONO, NO2, and MACR using open-path incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) were taken during summer and autumn 2011 and compared with those utilizing long-path absorption photometry (LOPAP), chemiluminescence spectrometry (CLS), and proton-transferreaction mass spectrometry (PTRMS), respectively
Summary
Photolysis of nitrous acid (HONO + hν(λ < 400 nm) → OH + NO) leads to the formation of the most important daytime oxidant in the atmosphere, the hydroxyl radical (OH). MACR is of interest as an “interfering species”, which is naturally formed together with methyl vinyl ketone (MVK, called butenone) (Pierotti et al, 1990) as a secondary atmospheric product after the reaction of isoprene with OH (Fehsenfeld et al, 1992) Both MACR and MVK are important factors in the oxidation chemistry of biogenically emitted species such as isoprene and can lead to the formation of ozone and/or secondary organic aerosol (Wennberg et al, 2018). The data are respectively compared with results from different instruments at SAPHIR: (a) a LOPAP system (HONO), (b) a standardized chemiluminescence detector (NO2), and (c) a proton-transfer reaction mass spectrometer (PTRMS) (MACR). The experiments presented here supplement a campaign on the Formal Intercomparison of Observations of Nitrous Acid (FIONA) (Ródenas et al, 2013), where instruments for the quantification of HONO were compared at the EUPHORE simulation chambers in Valencia (Spain) in May 2009
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