Near-real time infrared observations of acidic sulfates in /open quotes/clean/close quotes/ air at Mauna Loa, Hawaii
Sulfuric acid and its partially or completely neutralized salts with ammonia are believed to result from the oxidation of sulfur dioxide in cloud water and in other heterogeneous media present in the atmosphere. Due to the natural abundance of ammonia and the ubiquitous presence of sulfur in the atmosphere, (NH/sub 4/)/sub 2/SO/sub 4/ is commonly the dominant chemical species in the ambient aerosol. The amounts of ammonium sulfates are expected to be very low in areas far removed from anthropogenic emissions of sulfur dioxide. The chemical composition of submicrometer aerosol particles was determined at the Mauna Loa Observatory (MLO) on Mauna Loa in Hawaii during an eight-day period in August 1986. The MLO site was selected for this measurement because it is the only ground-based aerosol observatory in the remote Pacific Ocean that allows extended sampling of aerosols in the free troposphere. Measurements were made using an attenuated total internal reflection (ATR) impactor system. The impactor collects size-fractionated submicrometer particles for analysis by ATR infrared spectroscopy. The collected samples were analyzed using an on-site Perkin Elmer dispersive infrared spectrophotometer. Infrared absorption spectra (4000 to 250 cm/sup /minus/1/) of the samples were obtained within minutes after the ATR substrates were removed from the impactor. Absorbances were measured for sulfate, nitrate, and ammonium. Acidic sulfate showed infrared absorbances at 600 cm/sup /minus/1/ and 1210 cm/sup /minus/1/ in addition. Results showed that ammonium sulfate was the dominant chemical species in the submicrometer particles. Over half of the nearly 40 samples collected showed an acidic sulfate component. Consecutive samples were found to change from completely neutralized ammonium sulfate to acidic ammonium sulfates in a two-hour time interval. 5 refs., 1 tab.
- Research Organization:
- Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 5120615
- Report Number(s):
- CONF-8806123-1; ON: DE88010047
- Country of Publication:
- United States
- Language:
- English
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54 ENVIRONMENTAL SCIENCES
ABSORPTION
AEROSOLS
AIR
AMMONIA
CHALCOGENIDES
CHEMICAL REACTIONS
CLOUDS
COLLOIDS
DAILY VARIATIONS
DISPERSIONS
FEDERAL REGION IX
FLUIDS
GASES
HAWAII
HYDRIDES
HYDROGEN COMPOUNDS
INFRARED SPECTRA
MEASURING INSTRUMENTS
NITRATES
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NORTH AMERICA
OXIDATION
OXIDES
OXYGEN COMPOUNDS
SAMPLING
SOLS
SPECTRA
SULFATES
SULFUR COMPOUNDS
SULFUR DIOXIDE
SULFUR OXIDES
USA
VARIATIONS
WATER