INTRODUCTION-MARINE AEROSOL

Roger J. CHENG-ASRC UALBANY SUNYA

纽约州立大学，大气科学研究中心郑均华研究员主持的科研项目
 

The generation of maritime cloud condensation nuclei (CCN) through the ejection of jet and film droplets from bursting whitecap-produced bubbles on the ocean surface has been well documented. The processes involved in the transformation (evaporation and crystallization) of these liquid droplets into their solid form under varying conditions, however, has not previously attracted much attention from researchers. A set of laboratory investigations and field observations of the characteristics, both physical and chemical, of sea water droplets during phase change in a controlled environment has revealed the following startling and very significant phenomena:

           
  • 1, Ejection of micro-size aerosols from the crystallizing droplet.
  • 2, Formation of hollow sphere of sea-salt particles.
  • 3, Shell structure of chlorides (MgCl/2 and KC1) on the surface of
  • the ejected aerosols and sea-salt particles
   

 

The DISCOVERY of HOLLOW SEA-SALT AEROSOL

  • Roger J. CHENG ASRC UALBANY SUNYA

  • 纽约州立大学，大气科学研究中心郑均华研究员主持的科研项目

 
  • SHELL STRUCTURED MARINE AEROSOL:
  • A LABORATORY OBSERVATION
  • 纽约州立大学，大气科学研究中心郑均华研究员主持的科研项目

  • Roger J. CHENG ASRC UALBANY

  • Atmospheric Sciences Research Center
  • State University of New York

Laboratory investigation revealed that a shell structure of chlorides (MgCl/2 and KCl) is always present on the surface of marine aerosol. Close examination by a polarizing microscope of an individual seawater droplet has resulted in the following observations: Evaporation of water increased the salt concentration. At first, a thin layer of brine formed at the surface of the evaporating droplet; this was followed by clearly sequential precipitations of numerous microcystals of sulfates (CaSO4, MgSO4), and by a crust of many relatively larger cubic NaCI crystals correspondent with their individual solubility and concentrations.

During this process solution of chlorides (MgCl/2, KCl) mixed with microciystals of sulfates or NaCl were situated beneath the surface of the droplet. Finally, a seasalt particle with chloride film on the surface was formed. The shell structure of chlorides film present on the surface of the marine aerosol confirmed via optical and scanning electron microscopy is of extreme importance to understanding the fundamental nucleation processes in the atmosphere.

A chloride film presents a highly hygroscopic surface and was found to initiate the condensation of water in an environment with RH as low as 40%. Sodium chloride (NaCI) crystals, on the other hand play only a minor role in initiating condensation (RH 75%) for cloud droplets formation in the atmosphere.

    • To be presented at the Annual Meeting of the American Association
    • for Aerosol Research (AAAR),
    • Oak Brook, ILL. October 11-15, 1993

 

 

The MICRO-WORLD in the ATMOSPHERE
纽约州立大学，大气科学研究中心郑均华研究员主持的科研项目

REFERENCES

  • 1. "The Formation of Hollow Sea-Salt Particles from the Evaporation of Drops of Seawater"

  • ATMOSPHERIC RESEARCH,

  • Vol. 22, No. 1. June 1988 (Cheng, Blanchard & Cipriano).

  • 2. "The Generation of Secondary Marine Aerosols: The Crystallization of Seawater Droplets"

  • A. LECTURE NOTES IN PHYSICS, 309, Atmospheric Aerosols and Nucleation,

  • Ed: P.E Wagner and G. Vail, Springer-Verlag. 1988.

  • B. International Conference on Atmospheric Aerosols and Nucleation,

  • Vienna, Austria. August 22-27, 1988

  • 3. "Sulfate Aerosols Generation in the Marine Atmosphere:

  • The Evaporation of SeawaterDroplets"

  • International Conference on Global and Regional Environmental Atmospheric Chemistry,

  • Beijing, China. May 1989.

  • 4. "A New Mechanism for the Generation of High Sulfate Enriched Aerosols

  • in the Marine Atmosphere"

  • 9th World Clean Air Congress, Montreal, Quebec, Canada. 1992.

  • 5. "Shell Structured Marine Aerosol: A Laboratory Observation"

  • Annual Meeting of American Association for Aerosol Research,

  • Oak Brook, Illinois. October 11-15, 1993.

  • 6. "On the Phenomenon of Nuclei Enhancement During the Evaporative Stage of a Cloud"

  • ATMOSPHERIC RESEARCH, Vol. 47, No. 48, 1998. ( DeFelice and Cheng )

CITATIONS:

    A. "AN INTRODUCTION TO METEOROLOGICAL INSTRUMENTATION

  • AND MEASUREMENT"

  • By Dr.Thomas P. DeFelice, Prentice Hall, 1998.

  • B. "A Wind Tunnel Study on the Drop-to-Particle Conversion"

  • JOURNAL of AEROSOL SCIENCES, Vol.23, No.3, 1992.

  • (Confirmation by Dr. Pruppacher's term at Institute of Atmospheric Physics, Germany)

  • C. "MICROPHYSICS OF CLOUDS AND PRECIPITATION".

  • By Dr. Pruppacher and Dr. Klett, Second Revised and Enlarged Edition.

  • Kluwer Academic Publishers, 1997

  • D. " Microscopic Investigation of Marine Aerosol "

  • ALBANY-Fall 1996-University at Albany Magazine.

 
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