Comment on amt-2021-432

doi:10.5194/amt-2021-432-rc1

Abstract

Abstract. We present a comparison of fast-response instruments installed onboard the NASA DC-8 aircraft that measured nitrogen oxides (NO and NO2), nitrous acid (HONO), total reactive odd nitrogen (measured both as the total (NOy) and from the sum of individually measured species (Î£NOy)), and carbon monoxide (CO) in the troposphere during the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign. By targeting smoke from summertime wildfires, prescribed fires, and agricultural burns across the continental United States, FIREX-AQ provided a unique opportunity to investigate measurement accuracy in concentrated plumes where hundreds of species coexist. Here, we compare NO measurements by chemiluminescence (CL) and laser-induced fluorescence (LIF); NO2 measurements by CL, LIF, and cavity-enhanced spectroscopy (CES); HONO measurements by CES and iodide-adduct chemical ionization mass spectrometry (CIMS); and CO measurements by tunable diode laser absorption spectrometry (TDLAS) and integrated cavity output spectroscopy (ICOS). Additionally, total NOy measurements using the CL instrument were compared with Î£NOy (=âNOâ+âNO2â+âHONOâ+ânitric acid (HNO3)â+âacyl peroxy nitrates (APNs)â+âsubmicrometer particulate nitrate (pNO3)). Other NOy species were not included in Î£NOy as they either contributed minimally to it (e.g., C1âC5 alkyl nitrates, nitryl chloride (ClNO2), dinitrogen pentoxide (N2O5)) or were not measured during FIREX-AQ (e.g., higher oxidized alkyl nitrates, nitrate (NO3), non-acyl peroxynitrates, coarse-mode aerosol nitrate). The aircraft instrument intercomparisons demonstrate the following points: (1)Â NO measurements by CL and LIF agreed well within instrument uncertainties but with potentially reduced time response for the CL instrument; (2)Â NO2 measurements by LIF and CES agreed well within instrument uncertainties, but CL NO2 was on average 10â% higher; (3)Â CES and CIMS HONO measurements were highly correlated in each fire plume transect, but the correlation slope of CES vs. CIMS for all 1âHz data during FIREX-AQ was 1.8, which we attribute to a reduction in the CIMS sensitivity to HONO in high-temperature environments; (4)Â NOy budget closure was demonstrated for all flights within the combined instrument uncertainties of 25â%. However, we used a fluid dynamic flow model to estimate that average pNO3 sampling fraction through the NOy inlet in smoke was variable from one flight to another and ranged between 0.36 and 0.99, meaning that approximately 0â%â24â% on average of the total measured NOy in smoke may have been unaccounted for and may be due to unmeasured species such as organic nitrates; (5)Â CO measurements by ICOS and TDLAS agreed well within combined instrument uncertainties, but with a systematic offset that averaged 2.87âppbv; and (6)Â integrating smoke plumes followed by fitting the integrated values of each plume improved the correlation between independent measurements.

Highlights

IntroductionBiomass burning (BB) can take multiple forms (e.g., wildfires, prescribed fires, agricultural burns, grass fires, peat fires) and accounts for a large fraction of global carbon emissions with consequences for climate (Bowman et al, 2009; van der Werf et al, 2010, 2017) and biogeochemical cycles (Crutzen & Andreae, 2016)
Biomass burning (BB) can take multiple forms and accounts for a large fraction of global carbon emissions with consequences for climate (Bowman et al, 2009; van der Werf et al, 2010, 2017) and biogeochemical cycles (Crutzen & Andreae, 2016)
In this paper we present a comparison of Nitric oxide (NO), NO2, HONO, NOy and carbon monoxide (CO) measurements, which are compounds of major interest for fire-related science, air quality and climate

Summary

Introduction

Biomass burning (BB) can take multiple forms (e.g., wildfires, prescribed fires, agricultural burns, grass fires, peat fires) and accounts for a large fraction of global carbon emissions with consequences for climate (Bowman et al, 2009; van der Werf et al, 2010, 2017) and biogeochemical cycles (Crutzen & Andreae, 2016). BB contributes substantially to the atmospheric burden of trace gases and aerosols (Andreae, 2019), causing poor air quality on regional to continental scales (Jaffe et al, 2020; O’Dell et al, 2019; Wotawa, 2000) and posing a major threat to public health (Johnston et al, 2012, 2021). While agricultural burns are usually smaller and less intense than wildfires or prescribed fires, they occur more frequently and throughout the whole year, and can significantly impact local air quality (Dennis et al, 2002; McCarty, 2011)

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