HR: 14:00h
AN: A43F-02 INVITED [Abstracts]
TI: A Tale of Two Oxidants: Hydroxyl Radical and Singlet Molecular Oxygen on Ice
AU: * Anastasio, C
EM: canastasio@ucdavis.edu
AF: Department of Land, Air & Water Resources, University of California - Davis, One Shields
Ave., Davis, CA 95616-8627, United States
AU: Bower, J P
EM: jpbower@ucdavis.edu
AF: Department of Land, Air & Water Resources, University of California - Davis, One Shields
Ave., Davis, CA 95616-8627, United States
AU: McKellar, S R
EM: srmckellar@gmail.com
AF: Department of Land, Air & Water Resources, University of California - Davis, One Shields
Ave., Davis, CA 95616-8627, United States
AU: Chu, L
EM: lchu@ucdavis.edu
AF: Department of Land, Air & Water Resources, University of California - Davis, One Shields
Ave., Davis, CA 95616-8627, United States
AB:
The lifetimes for most compounds in the troposphere are determined by reactions with oxidants such as the
hydroxyl radical (OH). This paradigm likely also holds true for many trace contaminants on snow and ice,
especially organic species. However, we cannot currently estimate the lifetimes of these frozen contaminants
because we do not know the steady-state concentrations of OH or other oxidants in/on snow or ice. To address
this gap, we are currently working to measure the concentrations of OH and singlet molecular oxygen
(1O2*), another potentially important oxidant, in illuminated ice samples prepared from laboratory
solutions as well as polar snows.
Our results show some surprising differences between the photochemistries of OH and 1O2* on ice.
In the case of hydroxyl radical, the steady-state concentration in an illuminated ice sample is very similar to the
value in an illuminated aqueous solution made from the same sample. In contrast, the behavior of
1O2* is very different between ice and solution for the same sample: steady-state concentrations
in/on the ice are several orders of magnitude larger than in solution. We will discuss how these behaviors in
oxidant concentrations likely reflect differences in the oxidant kinetics (i.e., rates of formation and lifetimes)
between ice and solution. Based on our measured steady-state concentrations, reactions with OH will be an
important sink for relatively recalcitrant contaminants in snow, while 1O2* might be a very rapid sink
for electron-rich compounds in snow, such as phenols, alkenes, and polycyclic aromatic hydrocarbons.
DE: 0365 Troposphere: composition and chemistry
DE: 0736 Snow (1827, 1863)
DE: 0738 Ice (1863)
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting