TY - JOUR
T1 - Black carbon over Mexico
T2 - The effect of atmospheric transport on mixing state, mass absorption cross-section, and BC/CO ratios
AU - Subramanian, R.
AU - Kok, G. L.
AU - Baumgardner, D.
AU - Clarke, A.
AU - Shinozuka, Y.
AU - Campos, T. L.
AU - Heizer, C. G.
AU - Stephens, B. B.
AU - De Foy, B.
AU - Voss, P. B.
AU - Zaveri, R. A.
PY - 2010
Y1 - 2010
N2 - A single particle soot photometer (SP2) was operated on the NCAR C-130 during the MIRAGE campaign (part of MILAGRO), sampling black carbon (BC) over Mexico. The highest BC concentrations were measured over Mexico City (sometimes as much as 2μg/m3) and over hillfires to the south of the city. The age of plumes outside of Mexico City was determined using a combination of HYSPLIT trajectories, WRF-FLEXPART modeling and CMET balloon tracks. As expected, older, diluted air masses had lower BC concentrations. A comparison of carbon monoxide (CO) and BC suggests a CO background of around 65 ppbv, and a background-corrected BC/COnet ratio of 2.89±0.89 (ng/m 3-STP)/ppbv (average ± standard deviation). This ratio is similar for fresh emissions over Mexico City, as well as for aged airmasses. Comparison of light absorption measured with a particle soot absorption photometer (PSAP) and the SP2 BC suggests a BC mass-normalized absorption cross-section (MAC) of 10.9±2.1m2/g at 660 nm (or 13.1m 3/g @ 550 nm, assuming MAC is inversely dependent on wavelength). This appears independent of aging and similar to the expected absorption cross-section for aged BC, but values, particularly in fresh emissions, could be biased high due to instrument artifacts. SP2-derived BC coating indicators show a prominent thinly-coated BC mode over the Mexico City Metropolitan Area (MCMA), while older air masses show both thinly-coated and thickly-coated BC. Some 2-day-old plumes do not show a prominent thicklycoated BC mode, possibly due to preferential wet scavenging of the likely-hydrophilic thickly-coated BC.
AB - A single particle soot photometer (SP2) was operated on the NCAR C-130 during the MIRAGE campaign (part of MILAGRO), sampling black carbon (BC) over Mexico. The highest BC concentrations were measured over Mexico City (sometimes as much as 2μg/m3) and over hillfires to the south of the city. The age of plumes outside of Mexico City was determined using a combination of HYSPLIT trajectories, WRF-FLEXPART modeling and CMET balloon tracks. As expected, older, diluted air masses had lower BC concentrations. A comparison of carbon monoxide (CO) and BC suggests a CO background of around 65 ppbv, and a background-corrected BC/COnet ratio of 2.89±0.89 (ng/m 3-STP)/ppbv (average ± standard deviation). This ratio is similar for fresh emissions over Mexico City, as well as for aged airmasses. Comparison of light absorption measured with a particle soot absorption photometer (PSAP) and the SP2 BC suggests a BC mass-normalized absorption cross-section (MAC) of 10.9±2.1m2/g at 660 nm (or 13.1m 3/g @ 550 nm, assuming MAC is inversely dependent on wavelength). This appears independent of aging and similar to the expected absorption cross-section for aged BC, but values, particularly in fresh emissions, could be biased high due to instrument artifacts. SP2-derived BC coating indicators show a prominent thinly-coated BC mode over the Mexico City Metropolitan Area (MCMA), while older air masses show both thinly-coated and thickly-coated BC. Some 2-day-old plumes do not show a prominent thicklycoated BC mode, possibly due to preferential wet scavenging of the likely-hydrophilic thickly-coated BC.
UR - https://www.scopus.com/pages/publications/84860390378
U2 - 10.5194/acp-10-219-2010
DO - 10.5194/acp-10-219-2010
M3 - Article
AN - SCOPUS:84860390378
SN - 1680-7316
VL - 10
SP - 219
EP - 237
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 1
ER -