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Evaluation of ground‐based black carbon measurements by filter‐based photometers at two Arctic sites
Author(s) -
Sinha P. R.,
Kondo Y.,
Koike M.,
Ogren J. A.,
Jefferson A.,
Barrett T. E.,
Sheesley R. J.,
Ohata S.,
Moteki N.,
Coe H.,
Liu D.,
Irwin M.,
Tunved P.,
Quinn P. K.,
Zhao Y.
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd025843
Subject(s) - aerosol , soot , carbon black , arctic , absorption (acoustics) , chemistry , particle (ecology) , environmental science , analytical chemistry (journal) , atmospheric sciences , environmental chemistry , physics , oceanography , optics , organic chemistry , combustion , geology , natural rubber
Long‐term measurements of the light absorption coefficient ( b abs ) obtained with a particle soot absorption photometer (PSAP), b abs (PSAP), have been previously reported for Barrow, Alaska, and Ny‐Ålesund, Spitsbergen, in the Arctic. However, the effects on b abs of other aerosol chemical species coexisting with black carbon (BC) have not been critically evaluated. Furthermore, different mass absorption cross section (MAC) values have been used to convert b abs to BC mass concentration ( M BC = b abs /MAC). We used a continuous soot monitoring system (COSMOS), which uses a heated inlet to remove volatile aerosol compounds, to measure b abs ( b abs (COSMOS)) at these sites during 2012–2015. Field measurements and laboratory experiments have suggested that b abs (COSMOS) is affected by about 9% on average by sea‐salt aerosols. M BC values derived by COSMOS ( M BC (COSMOS)) using a MAC value obtained by our previous studies agreed to within 9% with elemental carbon concentrations at Barrow measured over 11 months. b abs (PSAP) was higher than b abs (COSMOS), by 22% at Barrow (PM 1 ) and by 43% at Ny‐Ålesund (PM 10 ), presumably due to the contribution of volatile aerosol species to b abs (PSAP). Using b abs (COSMOS) as a reference, we derived M BC (PSAP) from b abs (PSAP) measured since 1998. We also established the seasonal variations of M BC at these sites. Seasonally averaged M BC (PSAP) decreased at a rate of about 0.55 ± 0.30 ng m −3 yr −1 . We also compared M BC (COSMOS) and scaled M BC (PSAP) values with previously reported data and evaluated the degree of inconsistency in the previous data.