Photochemical Formation and Destruction of Hydrogen Peroxide on Antarctic Snow Gains

南极积雪中过氧化氢的光化学形成和破坏

• 批准号: 0636985
• 负责人: Cort Anastasio
• 金额: $ 36.61万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0636985&HistoricalAwards=false
• 关键词: Photochemical; Formation; Destruction; Hydrogen; Peroxide

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.

智力优点：PI建议进行一系列以实验室为基础的实验，旨在揭示控制光活性表面积雪和冰中过氧化物（HOOH）形成和破坏的光化学机制。 其中一些实验需要通过与受资助的实地项目的合作联系获得实地雪样。 这些实验是在以前资助的类似研究的基础上进行的。 早期工作中一个更值得注意的发现是，HOOH而不是硝酸盐光解是雪粒上羟基自由基（.OH）的主要来源。 结果表明，虽然硝酸盐吸收更多的阳光，但它对.OH的量子产率比HOOH小约200倍。 因此，可以计算出，在典型的南极夏季积雪条件下，HOOH的光解速率常数比硝酸盐高出约9倍。 这是相关的，因为大气氧化剂，如OH，HOOH和臭氧（O3）决定了许多空气污染物的命运，保存在冰芯中的HOOH据称可以记录大气的氧化能力。 虽然已经建立了对HOOH物理转移的合理理解，但光化学过程还没有。 重点实验的目的是：1）解决表面“准液体”层中HOOH光解速率是否与固体基质中的HOOH光解速率不同; 2）研究HOOH如何与有机化合物相互作用; 3）了解木质素衍生的有机物和铁羧酸盐是否有助于HOOH在一系列条件下的光生成; 4）确定南极雪上HOOH光生成速率; 5）评估积雪空气作为HO 2来源的重要性。可以在雪粒上重组形成HOOH 总体目标是表征雪颗粒上HOOH的光化学产生和破坏途径，以促进对雪中这一重要物种的预算的了解。 其他人发表的稳态模型将被修改，以解决这个目标。更广泛的影响：提出了一个广泛的教育和推广计划，将包括博士后和确定的博士学位的培训。学生（乔恩鲍尔）和多名本科生。 的博士一名学生在阿拉斯加东南大学（朱诺）进行了本科培训，这是一个EPSCoR机构（9000名学生：16%是美洲土著人）。 计划利用乔恩的经验和联系，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UAS本科生实习到UCD。 该学生将参与UCD现有的支持计划。 每年都会有一两名UCD参与者前往朱诺，以多种方式与学生和教师互动。 目的是为课程提供有意义的讲座，传播极地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。 后者将包括参与现有的方案，以达到和留住低收入或第一代大学生，以增加他们在本科和研究生学习的参与目标。 该计划也将作为夏季学生的潜在来源。 将在朱诺的埃根和环太平洋论坛上举行的既定晚会上就全球变化和冰雪化学问题发表公开演讲，这两个论坛都是免费的，并强调不同社区的参与。 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NSF职业奖延伸的更广泛影响的延续。