The goal of this CAREER project is to study the cycling and photochemistry of persistent organic pollutants in snow and ice. The research will concentrate on atmosphere-cryosphere interactions of organic pollutants and photochemical transformations of pollutants occurring in snow and ice. Laboratory and field studies will be conducted to probe photochemical processes that may degrade organic compounds, and to address the environmental impact of such processes. Irradiation experiments will be conducted in the laboratory to elucidate the degradation mechanisms and products. Both direct and indirect photochemical pathways will be studied, along with other variables such as wavelength, pH, temperature, and snow grain size. Photochemistry experiments will be conducted in the Arctic (Barrow, Alaska) to determine if the chemistry observed in the laboratory also occurs under natural conditions. Organic pollutants in air, snow and ice will be measured in the field in an effort to better understand air/snow/ice partitioning processes.
This project will help to educate undergraduate and master's students (via participation in active laboratory and field research) and K-12 students and the general public (via outreach efforts). Curriculum development activities will be aimed at students in grades 9-12, particularly in urban school districts with high minority populations. The project will also involve outreach to native Alaskan Inupiat Eskimos in Barrow. The PI will mentor a post-doctoral researcher, with the goal of recruiting someone interested in continuing his or her career at a predominantly undergraduate institution. Efforts will be made to recruit underrepresented minorities into the research and outreach activities. Assessment of undergraduate research and the Grade 9-12 curriculum will also be performed.
Scientific Merit: Snow and ice cover a seasonal maximum of 40% of Earth’s land surfaces, and several percent of the world’s oceans. This snow and ice has traditionally been viewed only as a physical barrier to chemical and heat fluxes from the underlying land or water, or as a reservoir ("sink") of atmospheric species that deposit with (or onto) the snow/ice. In the past decade the research community has discovered very active chemistry occurring in snow and ice, particularly processes induced by sunlight (photochemistry). Snow and ice can no longer be viewed as merely a "cap" to emissions or a physical sink for atmospheric species, and this revelation has resulted in a new field of research related to snow/ice photochemistry. The main goal of this project was to better understand how snow/ice photochemistry could impact the fate of man-made (anthropogenic) pollutants that can be transported to polar regions, and to better understand the fundamental chemistry occurring in snow/ice. Pollutants such as industrial chemicals and pesticides used in lower latitudes can be transported to the Arctic, sometimes in significant quantities. These pollutants can accumulate in wildlife and may pose a health threat to the indigenous Arctic people who rely on both terrestrial and marine wildlife as food sources. As such, it is important to understand the fate of these pollutants under Arctic conditions. We have conducted field-based studies in Barrow, Alaska to investigate the photochemical fate of anthropogenic pollutants. We showed that significant photochemical degradation of certain pesticides occurs in snow/ice. The reaction rates depend on temperature, depth of the snow within the snowpack, and whether the predominant phase of the sample is ice or liquid water. We found that natural materials present in the snow (specifically, dissolved organic matter that could originate from plant matter, microbial activity, etc.) participates in the chemistry. In an attempt to characterize the concentration and nature of organic materials present in natural snow and ice samples, we measured a variety of organochlorine compounds in sea water, snow, brine, and frost flowers (ice crystals that form over re-freezing open leads in the Arctic Ocean). Our results indicate that certain contaminants are concentrated from sea water into brine and frost flowers as they form. Through controlled lab studies, we have been able to use chemical reactions that are well characterized in liquid water to investigate how reaction rates and mechanisms may change when that water is frozen. Significant rate enhancements for chemical reactions can occur when a sample is frozen, due to the concentration of chemicals into microscopic liquid-like layers of water that form on and within ice. We also investigated the role of natural organic matter in snow/ice photochemistry. When sunlight interacts with natural organic matter, highly reactive products can form (such as hydroxyl radical, singlet oxygen, and excited-state organic matter). These reactive products can do further chemistry within the snow/ice, such as react with anthropogenic pollutants that are also present. We found that natural organic matter (and the reactive products it generates in sunlight) plays a critical role in the fate of pollutants. The reactivity is dependent on the concentration of the organic matter (more natural organic matter leads to faster degradation of the pollutant) and on temperature (reaction rates are faster at colder temperatures). We have also quantified the role of OH radical and singlet oxygen chemistry and have found that both play a role in pollutant degradation. Broader Impacts: Our study has helped lay the foundation for future studies of natural organic matter chemistry and cycling in polar regions. This work represents the first investigation of natural organic matter chemistry in snow/ice and the role it plays in the fate of anthropogenic pollutants. The results indicate that natural organic matter plays an important role in ice photochemical processes and in the fate of pollutants in snow/ice. Our study was the first to report the use of natural Arctic snow samples in pollutant degradation studies under environmental conditions and has shed light on important snowpack components that play a role in the chemistry occurring. Although this work focused on Arctic regions (due to the potential impact of pollutant accumulation in the Arctic food chain), similar chemistry likely occurs at mid-latitudes also. This project contributed to the education and training of 10 undergraduate student researchers, 7 master’s student researchers, and a post-doctoral teaching/research fellow. We have worked with a local high school teacher (who accompanied the research group to Alaska for fieldwork) and developed curricular materials related to environmental chemistry. We developed a continuing research project with the juniors and seniors at the high school, studying iron dynamics in a local watershed. High school students participated in teleconferences with research group members working in Alaska and were able to interact with local indigenous people from the Barrow area during the remotely broadcast classroom sessions.
