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| Titel |
Real-time measurements of ammonia, acidic trace gases and water-soluble inorganic aerosol species at a rural site in the Amazon Basin |
| VerfasserIn |
I. Trebs, F. X. Meixner, J. Slanina, R. Otjes, P. Jongejan, M. O. Andreae |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 4 ; Nr. 4, no. 4 (2004-06-28), S.967-987 |
| Datensatznummer |
250001833
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| Publikation (Nr.) |
 copernicus.org/acp-4-967-2004.pdf |
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| Zusammenfassung |
| We measured the mixing ratios of ammonia (NH3), nitric acid
(HNO3), nitrous acid (HONO), hydrochloric acid (HCl), sulfur dioxide
(SO2 and the corresponding water-soluble inorganic aerosol species,
ammonium (NH4+), nitrate (NO3-), nitrite
(NO2-), chloride (Cl- and sulfate (SO42-), and
their diel and seasonal variations at a pasture site in the Amazon Basin
(Rondônia, Brazil). This study was conducted within the framework of
LBA-SMOCC (Large Scale Biosphere Atmosphere Experiment in Amazonia -
Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass Burning Perturb Global and Regional Climate).
Sampling was performed from 12
September to 14 November 2002, extending from the dry season (extensive
biomass burning activity), through the transition period to the wet season
(background conditions). Measurements were made continuously using a
wet-annular denuder (WAD) in combination with a Steam-Jet Aerosol Collector
(SJAC) followed by suitable on-line analysis. A detailed description and
verification of the inlet system for simultaneous sampling of soluble gases
and aerosol compounds is presented. Overall measurement uncertainties of the
ambient mixing ratios usually remained below 15%. The limit of detection
(LOD) was determined for each single data point measured during the field
experiment. Median LOD values (3σ-definition) were ≤0.015ppb for
acidic trace gases and aerosol anions and ≤0.118ppb for NH3 and aerosol
NH4+. Mixing ratios of acidic trace gases remained below 1ppb
throughout the measurement period, while NH3 levels were an order of
magnitude higher. Accordingly, mixing ratios of NH4+ exceeded
those of other inorganic aerosol contributors by a factor of 4 to 10. During
the wet season, mixing ratios decreased by nearly a factor of 3 for all
compounds compared to those observed when intensive biomass burning took
place. Additionally, N-containing gas and aerosol species featured
pronounced diel variations. This is attributed to strong relative humidity
and temperature variations between day and night as well as to changing
photochemistry and stability conditions of the planetary boundary layer.
HONO exhibited a characteristic diel cycle with high mixing ratios at
nighttime and was not completely depleted by photolysis during daylight
hours. |
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