HR: 1340h
AN: A53B-1148    [Abstracts]
TI: A Solid-Phase Chemical Actinometer for Snowpack Solar Irradiation Measurements
AU: * Rowland, G A
EM: glenn.rowland@villanova.edu
AF: Department of Chemistry, Villanova University, 800 Lancaster Ave., Villanova, PA 19085, United States
AU: Grannas, A M
EM: amanda.grannas@villanova.edu
AF: Department of Chemistry, Villanova University, 800 Lancaster Ave., Villanova, PA 19085, United States
AB: Research over the past decade has established the importance of polar snow as a medium for chemical processing of atmospheric species; recent laboratory studies have demonstrated the photochemical transformation of anthropogenic organic contaminants in frozen water matrices. In order to investigate the role of snow photochemistry under environmental conditions, field researchers need methods for determining the intensity of light available at the surface and also penetrating the snowpack as a function of depth. While theoretical models exist for light penetration, they rely on a number of parameters relating to the formation and history of the snowpack that field researchers are unlikely to have knowledge of; this makes direct in-situ measurements desirable. Conventional liquid-phase actinometers are of limited use in polar environments where low ambient temperatures may interfere with diffusion-controlled processes - the freezing of aqueous solutions being an extreme case - resulting in varying quantum yields. A solid-phase actinometer system based on the well-studied photoisomerization of o-nitrobenzaldehyde (oNB) has been developed as an alternative device for the measurement of solar UV light intensity. Sample films consisting of oNB incorporated in a polymethylmethacrylate matrix are exposed to light and the extent of oNB loss from the film's surface is determined by ATR-IR spectroscopy. Films are rugged enough to allow deployment in environments that are impractical to access with bulkier electronic instruments, and small enough to allow precise placement and positioning without disturbing the bulk of the snowpack under consideration. Trial measurements made in late- thaw snowpacks near Barrow, Alaska in June 2007 demonstrate the usefulness of this technique for determining relative light intensity as a function of snowpack depth. The technique could readily be extended to other environments where solar irradiance cannot readily be measured by instrumental approaches.
DE: 0394 Instruments and techniques
DE: 0736 Snow (1827, 1863)
DE: 0794 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting