 |
| Titel |
Latitudinal variation in the multiphase chemical processing of inorganic halogens and related species over the eastern North and South Atlantic Oceans |
| VerfasserIn |
W. C. Keene, M. S. Long, A. A. P. Pszenny, R. Sander, J. R. Maben, A. J. Wall, T. L. O'Halloran, A. Kerkweg, E. V. Fischer, O. Schrems |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 19 ; Nr. 9, no. 19 (2009-10-02), S.7361-7385 |
| Datensatznummer |
250007665
|
| Publikation (Nr.) |
 copernicus.org/acp-9-7361-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| Volatile inorganic and size-resolved particulate Cl- and Br-species were
measured in near-surface air over a broad range of conditions within four
distinct regimes (European – EURO, North African – N-AFR, the
Intertropical Convergence Zone – ITCZ, and South Atlantic – S-ATL) along a
latitudinal gradient from 51° N to 18° S through the eastern Atlantic Ocean.
Median dry-deposition fluxes of sea salt, oxidized N, and oxidized
non-sea-salt S varied by factors of 25, 17, and 9, respectively, among the
regimes. Sea-salt production was the primary source for inorganic
Cl and Br. Acidification and dechlorination of sea salt primarily by
HNO3 sustained HCl mixing ratios ranging from medians of 82 (ITCZ) to
682 (EURO) pmol mol−1. Median aerosol pHs inferred from HCl phase
partitioning with super-μm size fractions ranged from ~3.0 for
EURO to ~4.5 for ITCZ. Because SO2 solubility over this pH range
was low, S(IV) oxidation by hypohalous acids was unimportant under most
conditions. Simulations with a detailed multiphase box model indicated that
BrCl photolysis and ClO + NO were the major sources for atomic Cl in all
regimes. Simulated midday concentrations of Cl atoms ranged from 2.1×104 to
7.8×104 cm−3 in the ITCZ and N-AFR regimes, respectively. Measured
particulate Br− (median enrichment factor = 0.25) was greater and
volatile inorganic Br less than simulated values, suggesting that the halogen
activation mechanism in the model overestimated Br-radical production and
processing. Reaction with atomic Br was an important sink for modeled
O3 (5% in EURO to 46% in N-AFR). Formation of halogen nitrates
accelerated the oxidation of NOx (NO + NO2) primarily via
hydrolysis reactions involving S aerosol. Relative to simulations with no
halogens, lower NOx coupled with direct reactions involving halogens
yielded lower steady state mixing ratios of OH (20% to 54%) and
O3 (22% to 62%) and lower midday ratios of OH:HO2 (3% to
32%) in all regimes. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|