In:
Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 101, No. D2 ( 1996-02-20), p. 4413-4423
Abstract:
We measured aerosol methanesulfonic acid (MSA), Cl − , NO 3 − , SO 4 = , Na + , and NH 4 + concentrations and size distributions and gaseous ammonia and nitric acid concentrations from Santa Maria, Azores during the Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange (ASTEX/MAGE) experiment in June 1992. We also sampled some of these species in the free troposphere and marine boundary layer (MBL) from the National Center for Atmospheric Research's (NCAR's) Electra aircraft and at the surface from the R/V Oceanus . In relatively clean Atlantic marine air masses the mean (and standard error of the mean) observed MSA concentrations (27 ± 2 parts per trillion molar mixing ratio, ppt) were smaller than in continental polluted air masses (36 ± 6 ppt), reflecting either longer aerosol lifetimes in air with higher cloud condensation nuclei (CCN) concentrations or more active photochemical production in polluted air. Mean NH 4 + /non‐sea‐salt (nss) SO 4 = molar ratios in marine and continental air masses were 0.65 ± 0.05 and 1.3 ± 0.2, respectively, indicating that continental sulfate was neutralized by ammonia to a greater extent than marine sulfate was. Most of the NH 4 + and nss SO 4 = was contained in submicrometer modes; Na + , Cl − , and NO 3 − were in supermicron modes; and MSA showed bimodal behavior, with major and minor peaks at 0.3–0.4 μm and 1.5 μm, respectively. The molar ratio NH 4 + /nss SO 4 = relative to size confirms that most ammonia vapor condensed on submicron nss SO 4 = . The average dry deposition fluxes for aerosol nss SO 4 = , MSA, NH 4 + and NO 3 − during ASTEX/MAGE were 1.49, 0.09, 0.18, and 3.25 μmol m −2 d −1 , respectively.
Type of Medium:
Online Resource
ISSN:
0148-0227
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
1996
detail.hit.zdb_id:
161666-3
SSG:
16,13
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