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Airborne Acid May Help Soot Turn Into Cloud Seeds

Date:
March 28, 2009
Source:
American Geophysical Union
Summary:
Carbon soot aerosols from combustion of fossil fuels and forest fires directly influence the Earth-atmosphere heat balance by absorbing sunlight. Fresh soot particles repel water and hence have little effect on properties and lifetimes of clouds. As soot particles age, they are thought to undergo a weathering process that allows them to absorb water, potentially transforming particles into cloud condensation nuclei.
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Carbon soot aerosols from combustion of fossil fuels and forest fires directly influence the Earth-atmosphere heat balance by absorbing sunlight. Fresh soot particles repel water and hence have little effect on properties and lifetimes of clouds.

As soot particles age, they are thought to undergo a weathering process that allows them to absorb water, potentially transforming particles into cloud condensation nuclei.

To learn more about how soot develops an affinity for water, Khalizov et al. examine the properties of soot aerosols exposed to gaseous sulfuric acid. They find that although fresh soot does not change below water saturation, soot particles exposed to sulfuric acid increase in mass when relative humidity rises because the acid-coated soot absorbs water.

An increase in particle mass is often accompanied by a decrease in size, suggesting that conventional measurement methods based on particle size may underestimate the impact of soot aging on clouds.

Because sulfuric acid, a pollutant and the driving agent in acid rain, is increasing in the atmosphere due to industrial activities, the authors expect that this mechanism of water absorption by acid-coated soot significantly influences cloud formation.

The findings are reported in the Journal of Geophysical Research-Atmospheres.

The authors include: Alexei F. Khalizov, Renyi Zhang, Dan Zhang, and Huaxin Xue: Department of Atmospheric sciences, Texas A&M University, College Station, Texas, U.S.A.; Joakim Pagels: Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, U.S.A.; also at Division of Ergonomics and Aerosol Technology, Faculty of Engineering, Lund University, Lund, Sweden; Peter H. McMurry: Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, U.S.A.


Story Source:

The above post is reprinted from materials provided by American Geophysical Union. Note: Materials may be edited for content and length.


Journal Reference:

  1. Khalizov et al. Formation of highly hygroscopic soot aerosols upon internal mixing with sulfuric acid vapor. Journal of Geophysical Research, 2009; 114 (d5): D05208 DOI: 10.1029/2008JD010595

Cite This Page:

American Geophysical Union. "Airborne Acid May Help Soot Turn Into Cloud Seeds." ScienceDaily. ScienceDaily, 28 March 2009. <www.sciencedaily.com/releases/2009/03/090325155535.htm>.
American Geophysical Union. (2009, March 28). Airborne Acid May Help Soot Turn Into Cloud Seeds. ScienceDaily. Retrieved August 28, 2015 from www.sciencedaily.com/releases/2009/03/090325155535.htm
American Geophysical Union. "Airborne Acid May Help Soot Turn Into Cloud Seeds." ScienceDaily. www.sciencedaily.com/releases/2009/03/090325155535.htm (accessed August 28, 2015).

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