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

Authors :
L. Zeng
A. P. Sullivan
R. A. Washenfelder
J. Dibb
E. Scheuer
T. L. Campos
J. M. Katich
E. Levin
M. A. Robinson
R. J. Weber
Source :
Atmospheric Measurement Techniques, Vol 14, Pp 6357-6378 (2021)
Publication Year :
2021
Publisher :
Copernicus Publications, 2021.

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.

Details

Language :
English
ISSN :
18671381 and 18678548
Volume :
14
Database :
Directory of Open Access Journals
Journal :
Atmospheric Measurement Techniques
Publication Type :
Academic Journal
Accession number :
edsdoj.238586161c754018abf149efdd02ecb9
Document Type :
article
Full Text :
https://doi.org/10.5194/amt-14-6357-2021