Photochemical Formation and Destruction of Hydrogen Peroxide on Antarctic Snow Gains

知识价值：PI建议进行一系列基于实验室的实验，旨在揭示光活性表面积雪和冰中控制过氧化氢（HOOH）形成和破坏的光化学机制。其中一些实验需要通过与资助的实地项目的合作关系获得实地的雪样。这些实验是在之前资助的类似研究的基础上进行的。早期工作的一个更值得注意的发现是，HOOH而不是硝酸盐光解作用是雪颗粒上羟基自由基（. oh）的主要来源。结果表明，虽然硝酸盐吸收了更多的阳光，但其量子产率为。氢氧根比氢氧根少约200倍。因此，在典型的南极夏季积雪条件下，可以计算出HOOH的光解速率常数比硝酸盐高约9倍。这是相关的，因为大气氧化剂，如。OH， HOOH和臭氧（O3）决定了许多空气中污染物的命运，保存在冰芯中的HOOH据称记录了大气的氧化能力。虽然对HOOH的物理转移已经有了合理的理解，但光化学过程还没有。重点实验的目的是：1)研究表面“准液体”层中HOOH光解速率与固体基质中的HOOH光解速率是否不同；2)研究HOOH如何与有机化合物相互作用；3)了解木质素衍生有机物和铁羧酸盐是否在一系列条件下促进HOOH光解速率；4)确定南极雪中HOOH光解速率；5)评估大气作为HO2来源的重要性。可以在雪粒上重新组合并形成HOOH。总体目标是表征雪颗粒上HOOH光化学产生和破坏的途径，以提高对雪中这一重要物种预算的认识。其他人发表的稳态模型将被修改以实现这一目标。更广泛的影响：提出了一个广泛的教育和推广计划，包括培养一名博士后和一名确定的博士生（Jon Bower）和多名本科生。这位博士生在阿拉斯加东南大学（朱诺）完成了他的本科训练，这是一个EPSCoR机构（9000名学生：16%是印第安人）。计划利用乔恩的经验和关系，在加州大学戴维斯分校和UAS之间建立联系，其中包括每年夏天在UCD进行UAS本科生实习。该学生将参与UCD现有的支持项目。每年都会有一到两名UCD参与者前往朱诺，以多种方式与学生和教师进行互动。其目标是为课程提供有意义的讲座，传达极地地区在全球变化中的重要性，并鼓励学生对进一步研究科学的兴趣。后者将包括参与一个现有的项目，以吸引和留住低收入或第一代大学生，目标是增加他们在本科和研究生学习中的参与度。这个项目也将成为暑期学生的潜在来源。关于全球变化和冰雪化学的公开演讲将在朱诺举行的伊根和环太平洋论坛的既定晚会上进行，这两个论坛都是免费的，强调社区的多样化参与。PI希望继续指导学生，并将研究相关信息整合到他的研究生和本科课程中，作为1997年获得美国国家科学基金会职业奖后更广泛影响的延续。

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.