Intellectual merit: The PI proposes to conduct a series of laboratory-based experiments aimed at revealing the photochemical mechanisms controlling peroxide (HOOH) formation and destruction in the photoactive surface snow pack and ice. Some of these experiments require snow samples from the field to be obtained through collaborative connections to funded field programs. The experiments follow on similar previously funded studies. One of the more notable findings of earlier work established that HOOH rather than nitrate photolysis is the dominant source of hydroxyl radicals (.OH) on snow grains. It was shown that while nitrate absorbed more sunlight, its quantum yield for .OH is about 200-fold less than that of HOOH. Thus HOOH can be calculated to have about 9-fold higher rate constant of photolysis than nitrate during typical Antarctic summer snow pack conditions. This is relevant because atmospheric oxidants such as .OH, HOOH and ozone (O3) determine the fate of many airborne pollutants and HOOH preserved in ice cores is purported to record the oxidative capacity of the atmosphere. While a reasonable understanding of physical transfer of HOOH has been established, photochemical processes have not. The focused experiments are designed to 1) address whether rates of HOOH photolysis differ in surficial "quasi-liquid" layers from those in the solid matrix 2) examine how HOOH interacts with organic compounds 3) learn whether lignin-derived organics and iron-carboxylates contribute to HOOH photoformation under a range of conditions 4) determine rates of HOOH photoformation on Antarctic snow and 5) evaluate the importance of the firn air as a source of HO2. that could recombine and form HOOH on snow grains. The overarching goal is to characterize pathways for photochemical production and destruction of HOOH on snow grains as a contribution to improving knowledge of the budget of this important species in snow. A steady state model published by others will be modified to address this goal.
Broader impacts: An extensive education and outreach plan is presented that will include the training of a postdoc and an identified Ph.D. student (Jon Bower) and multiple undergraduates. The Ph.D. student did his undergraduate training at the University of Alaska Southeast (Juneau), which is an EPSCoR Institution (9000 students: 16% are Native American). It is planned to capitalize on the experience and ties of Jon to set up a connection between UC Davis and UAS that involves a UAS undergraduate internship to UCD each summer. That student would be involved in existing support programs at UCD. One or two of the UCD participants would travel to Juneau each year to interact with students and faculty in a number of ways. The objective is to contribute meaningful lectures to courses, to transmit the importance of polar regions in global change, and to encourage the interest the interest of the student body in further studies of science. The latter will encompass participation in an existing program to reach and retain low-income or first generation college students with the goal of increasing their participation in undergraduate and graduate study. This program will also serve as a potential source of summer students. Public presentations on global change and snow and ice chemistry will be given in Juneau at the established Evening at the Egan and Pacific Rim Forum both of which are free and emphasize diverse community involvement. The PI expects to continue to mentor students and integrate research related information into his graduate and undergraduate courses as a continuation of broader impacts extending from his NSF CAREER Award in 1997.
