HR: 0800h
AN: A21C-0879    [Abstracts]
TI: Light Absorbance of Melted Arctic and Antarctic Snow
AU: * Robles, T
EM: rarobles@ucdavis.edu
AF: University of California, Davis, One Shields Ave, Davis, CA 95616
AB: Photochemical reactions in polar snowpacks can have large effects on both the composition of the snow as well as emissions into the overlying atmosphere. While we generally understand some of the important photochemistry in snow (such as the photolysis of nitrate and hydrogen peroxide), much remains to be discovered. For example, there have been no measurements of the total light absorption of dissolved chromophores in polar snow. These measurements are important because they would indicate whether significant amounts of chromophores other than NO3- and HOOH are present in the snow and, therefore, whether significant amounts of other photochemistry could be occurring. However, to date these measurements have not been made because snow from these regions is so pristine that its light absorbance is below the detection limit of cuvette-based spectrophotometers. To overcome this challenge, we have designed and built a Teflon liquid core waveguide spectrophotometer that has an optical pathlength of more than 100 cm. Because the absorbance of a sample is directly proportional to its pathlength, our system amplifies the absorption signal of polar snow samples enough that they can be quantified. Using this system we have quantified the absorbance spectra of filtered, melted snow samples from Summit, Greenland and from the Antarctic. Our results show that although chromophores like nitrate and hydrogen peroxide are important, there is also a significant percentage of light absorption coming from other, currently unknown, species. We will discuss the absorbance spectra from these samples as well as how absorbance varies diurnally and as a function of depth in the snowpack.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0394 Instruments and techniques
DE: 0770 Properties
DE: 0794 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005