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Observations of aerosols over Southern California coastal waters

Hidy, G. M. and Mueller, P. K. and Wang, H. H. and Karney, J. and Twiss, S. and Imada, M. and Alcocer, A. (1974) Observations of aerosols over Southern California coastal waters. Journal of Applied Meteorology, 13 (1). pp. 96-107. ISSN 0894-8763. doi:10.1175/1520-0450(1974)013<0096:OOAOSC>2.0.CO;2.

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To characterize the background aerosol in air off the California coast, observations of suspended particles were made in the summer and fall of 1970 on San Nicolas Island (SNI), located about 130 km west-south-west of Los Angeles. Measurements of the physical and chemical properties of aerosols showed that the particles are a complex mixture of material from marine and continental origins. The Aitken nuclei population averaged 2400 cm−3, while the particles >0.5 μm diameter averaged 20–100 cm−3. The average total mass concentration of aerosol evaluated from 22 samples was 29.8 μg m−3, but the refined fraction defined as particles ~< 3.5 μm diameter was 40% of this level. The averages of the chemical analysis of 13 samples revealed that 11% of the aerosol sampled at a 200 m height above the ocean was sea salt, while approximately 20% evidently was soil dust, as indicated by silicates. Over 25% of the suspended material was found to be sulfate, nitrate or ammonium, which are constituents believed to be produced primarily from gaseous transformation reactions in the atmosphere. More than 20% of the sampled material was volatile in nature and is believed to be partly water. The ratio for the average chlorine to sodium concentrations from the analysis of 13 different samples was 2.4 compared with 1.8 for sea water. This high ratio supports other limited results for unpolluted air from offshore sources taken in this geographical region. The anomaly is believed to be linked with chemical reactions transforming gaseous chlorine compounds into condensed material. Comparison was made between the aerosol sampled on San Nicolas Island and the “natural” background contribution of the Los Angeles smog aerosol, as estimated elsewhere assuming contributions solely from sea salt and soil dust. The calculated background and the composition of the SNI aerosol were qualitatively similar, with the principal differences showing in Ca, Zn, SO4− and NO3−. Further comparison with aerosol analyzed from Pasadena illustrated the major contribution of localized pollution to the chemical properties of the particles, particularly in the concentrations of Mu, Ca, Br, Fe, Pb, SO4− and NO3−.

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URLURL TypeDescription 10.1175/1520-0450(1974)013<0096:OOAOSC>2.0.CO;2DOIUNSPECIFIED
Additional Information:© 1974 American Meteorological Society. Manuscript received May 24, 1973, in final form October 10, 1973. We are grateful for the use of several instruments supplied by Prof. Friedlander at the California Institute of Technology. The cooperation and help from the U.S. Navy operations on San Nicolas Island are very much appreciated. Thanks go to S. Heisler, Duane Lea, G. Mathews, D. Fleming, W.W. Ho, T. Cahill J. Jaklevie, M. Haik, I. Sharenbock, J. Wesolowski, T. Belsky, L. Pierce, B. Appel, and K. Bell for their part in helping us make the observations and obtain the extensive analyses required of the data.
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11616
Deposited By: Tony Diaz
Deposited On:17 Sep 2008 05:12
Last Modified:08 Nov 2021 22:01

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