Preprints
https://doi.org/10.5194/amt-2021-131
https://doi.org/10.5194/amt-2021-131

  17 May 2021

17 May 2021

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Assessment of online water-soluble brown carbon measuring systems for aircraft sampling

Linghan Zeng1, Amy P. Sullivan2, Rebecca A. Washenfelder3, Jack Dibb4, Eric Scheuer4, Teresa L. Campos5, Joseph M. Katich3,6, Ezra Levin2,7, Michael A. Robinson3,6,8, and Rodney J. Weber1 Linghan Zeng et al.
  • 1School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
  • 2Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA
  • 3Chemical Sciences Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
  • 4College of Engineering and Physical Sciences, University of New Hampshire, Durham, New Hampshire, USA
  • 5Atmospheric Chemistry Observations and Modelling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
  • 6Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
  • 7Handix Scientific, Boulder, CO, USA
  • 8Department of Chemistry, University of Colorado Boulder, Boulder, Colorado, USA

Abstract. Brown carbon (BrC) consists of particulate organic species that preferentially absorb light at visible and ultraviolet wavelengths. Ambient studies show that as a component of aerosol particles, BrC affects photochemical reaction rates and regional to global climate. Some organic chromophores are especially toxic linking BrC to adverse health effects. The lack of direct measurements of BrC has limited our understanding of its prevalence, sources, evolution, and impacts. We describe the first direct, online measurements of water-soluble BrC on research aircraft by three separate instruments. Each instrument measured light absorption over a broad wavelength range using a liquid waveguide capillary cell (LWCC) and grating spectrometer, with particles collected into water by a Particle-into-Liquid Sampler (CSU PILS-LWCC and NOAA PILS-LWCC) or a mist chamber (MC-LWCC). The instruments were deployed on the NSF C-130 aircraft during WE-CAN 2018 as well as the NASA DC-8 and the NOAA Twin Otter aircraft during FIREX-AQ 2019, where they sampled fresh and moderately aged wildfire plumes. Here, we describe the instruments, calibrations, data analysis, and corrections for baseline drift and hysteresis. Detection limits (3σ) at 365 nm were 1.53 Mm−1 (MC-LWCC; 2.5 min sampling time), 0.89 Mm−1 (CSU PILS-LWCC; 30 s sampling time), and 0.03 Mm−1 (NOAA PILS-LWCC; 30 s sampling time). Measurement uncertainties were 28 % (MC-LWCC), 12 % (CSU PILS-LWCC), and 11 % (NOAA PILS-LWCC). The MC-LWCC system agreed well with offline measurements from filter samples, with a slope of 0.91 and R2 = 0.89. Overall, these instruments provide soluble BrC measurements with specificity and geographical coverage that is unavailable by other methods, but their sensitivity and time resolution can be challenging for aircraft studies where large and rapid changes in BrC concentrations may be encountered.

Linghan Zeng et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of manuscript amt-2021-131', Anonymous Referee #1, 03 Aug 2021
  • RC2: 'Comment on amt-2021-131', Anonymous Referee #2, 05 Aug 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of manuscript amt-2021-131', Anonymous Referee #1, 03 Aug 2021
  • RC2: 'Comment on amt-2021-131', Anonymous Referee #2, 05 Aug 2021

Linghan Zeng et al.

Linghan Zeng et al.

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Short summary
Three online systems for measuring water-soluble brown carbon are compared. A mist chamber and two different particle-into-liquid samplers were deployed on separate research aircraft targeting wildfires and followed a similar detection method using a long path liquid waveguide with a spectrometer to measure the light absorption from 300 to 700 nm. Detection limits, signal hysteresis and other sampling issues are compared, and further improvements of these liquid-based systems are provided.