Peroxynitric acid (HO&lt;sub&gt;2&lt;/sub&gt;NO&lt;sub&gt;2&lt;/sub&gt;) measurements during the UBWOS 2013 and 2014 studies using iodide ion chemical ionization mass spectrometry

Abstract. In this paper laboratory work is documented establishing iodide ion chemical ionization mass spectrometry (I- CIMS) as a sensitive method for the unambiguous detection of peroxynitric acid (HO2NO2; PNA). A dynamic calibration source for HO2NO2, HO2, and HONO was developed and calibrated using a novel total NOy cavity ring-down spectroscopy (CaRDS) detector. Photochemical sources of these species were used for the calibration and validation of the I- CIMS instrument for detection of HO2NO2. Ambient observations of HO2NO2 using I- CIMS during the 2013 and 2014 Uintah Basin Wintertime Ozone Study (UBWOS) are presented. Strong inversions leading to a build-up of many primary and secondary pollutants as well as low temperatures drove daytime HO2NO2 as high as 1.5 ppbv during the 2013 study. A comparison of HO2NO2 observations to mixing ratios predicted using a chemical box model describing an ozone formation event observed during the 2013 wintertime shows agreement in the daily maxima HO2NO2 mixing ratio, but a differences of several hours in the timing of the observed maxima. Observations of vertical gradients suggest that the ground snow surface potentially serves as both a net sink and source of HO2NO2 depending on the time of day. Sensitivity tests using a chemical box model indicate that the lifetime of HO2NO2 with respect to deposition has a non-negligible impact on ozone production rates on the order of 10 %.

Download Full-text

Peroxynitric acid (HO2NO2) measurements during the UBWOS 2013 and 2014 studies using iodide ion chemical ionization mass spectrometry

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-3629-2015 ◽

2015 ◽

Vol 15 (3) ◽

pp. 3629-3666

Author(s):

P. R. Veres ◽

J. M. Roberts ◽

R. J. Wild ◽

P. M. Edwards ◽

S. S. Brown ◽

...

Keyword(s):

Mass Spectrometry ◽

Detection Limit ◽

Chemical Ionization ◽

Box Model ◽

Ionization Mass Spectrometry ◽

Chemical Ionization Mass Spectrometry ◽

Ionization Mass ◽

Peroxynitric Acid ◽

Iodide Ion ◽

Cluster Ion

Abstract. Laboratory work is reported here establishing iodide ion chemical ionization mass spectrometry (I− CIMS) as a sensitive method for the unambiguous detection of peroxynitric acid (HO2NO2, PNA). A~dynamic calibration source for HO2NO2, HO2, and HONO was developed and calibrated using a~novel total NOy detector (NOy CaRDS). Photochemical sources of these species were used for the calibration and validation of the I− CIMS instrument for detection of HO2NO2. A dual inlet system was developed to determine differences in the instrument response when using a heated inlet dissociator (150 °C) and a "cold" room-temperature inlet. HO2NO2 was detected as I-HO2− (m/z 160), NO3− (m/z 62) and I-HO2NO2− (m/z 206). The I− CIMS normalized sensitivity to peroxynitric acid was 2.0 Hz pptv−1 with a detection limit (3σ) of 40 pptv via detection of the I-HO2− (m/z 160) cluster ion using an inlet dissociator at a temperature of 150 °C. Alternatively, PNA was detected via I− CIMS with a cold inlet at both the NO3− (m/z 62) and I-HO2NO2− (m/z 206) ions with normalized detection sensitivities of 144 and 0.4 Hz pptv−1 respectively. The cold inlet sensitivity of iodide CIMS towards the detection of HO2 radicals, also via detection at the I-HO2− cluster ion, a potential HO2NO2 interference, was approximately 2.6 Hz pptv−1 with an instrumental detection limit (3σ) of 20 pptv. Ambient observations of HO2NO2 using I− CIMS were made during the 2013 and 2014 Uintah Basin Wintertime Ozone Study (UBWOS) are presented. Strong inversions leading to a build-up of many primary and secondary pollutants as well as low temperatures drove daytime HO2NO2 as high as 1.5 ppbv during the 2013 study. A comparison of HO2NO2 observations to mixing ratios predicted using a chemical box model describing an ozone formation event observed during the 2013 wintertime shows agreement in the daily maxima HO2NO2 mixing ratio, but a significant difference os several hours in the timing of the observed maxima. Observations of vertical gradients suggest that the ground snow surface potentially serves as both a net sink and source of HO2NO2 depending on time of day. Sensitivity tests using a chemical box model indicate that the lifetime of HO2NO2 with respect to deposition has a non-negligible impact on ozone production rates on the order of 10%.

Download Full-text