Thermochromism of Model Organic Aerosol Matter
Abstract
Laboratory experiments show that the optical absorptivity of model organic matter is not an intrinsic property, but a strong function of relative humidity, temperature, and insolation. Suites of representative polyfunctional C_(x)H_(y)O_(z) oligomers in water develop intense visible absorptions upon addition of inert electrolytes. The resulting mixtures reach mass absorption cross sections σ(532 nm) ~ 0.1 m^(2)/gC in a few hours, absorb up to 9 times more solar radiation than the starting material, can be half-bleached by noon sunlight in ~ 1 h, and can be repeatedly recycled without carbon loss. Visible absorptions red-shift and evolve increasingly faster in subsequent thermal aging cycles. Thermochromism and its strong direct dependences on ionic strength and temperature are ascribed to the dehydration of >CH−C(OH)< groups into >C═C< unsaturations by a polar E1 mechanism, and bleaching to photoinduced retrohydration. These transformations are deemed to underlie the daily cycles of aerosol absorption observed in the field, and may introduce a key feedback in the earth's radiative balance.
Additional Information
© 2010 American Chemical Society. Received Date: October 26, 2009; accepted Date: December 2, 2009; Published on Web Date: December 09, 2009. This project was financially supported by the National Science Foundation (ATM-0714329). A.G.R. acknowledges financial support from the Swiss National Science Foundation (PBL2-110274).Attached Files
Supplemental Material - jz900186e_si_001.pdf
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Additional details
- Eprint ID
- 18450
- Resolver ID
- CaltechAUTHORS:20100526-092341428
- NSF
- ATM-0714329
- Swiss National Science Foundation (SNSF)
- PBL2-110274
- Created
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2010-05-27Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field