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Modeling Perspectives on the Environmental Legacy of Human and Natural Mercury Releases
No full textMercury (Hg) is a naturally occurring heavy metal that has been mined and used by humans since antiquity. Exposure to Hg, particularly its organic form (methylmercury) poses health risks for humans and wildlife globally. This thesis quantitatively explores the natural biogeochemical Hg cycle and the extent of the perturbation from human activity.
Chapter 1 focuses on the natural Hg cycle. Volcanism is the largest natural source of Hg to the biosphere. However, past Hg emission estimates have varied by three orders of magnitude. Here, we present an updated central estimate and interquartile range (232 Mg a−1; IQR: 170 - 336 Mg a−1) for modern volcanic Hg emissions based on advances in satellite remote sensing of sulfur dioxide (SO2) and an improved method for considering uncertainty in Hg:SO2 emissions ratios. Atmospheric modeling shows the influence of volcanic Hg on surface atmospheric concentrations in the extratropical Northern Hemisphere is 1.8 times higher than in the Southern Hemisphere. Spatiotemporal variability in volcanic Hg emissions may obscure atmospheric trends forced by anthropogenic emissions at some locations. This should be considered when selecting monitoring sites to inform global regulatory actions. Volcanic emission estimates from this work suggest the pre-anthropogenic global atmospheric Hg reservoir was 580 Mg, 7-fold lower than in 2015 (4000 Mg).
Chapter 2 focuses on the future anthropogenic perturbation to the global mercury cycle. Mercury (Hg) is a naturally occurring element that has been greatly enriched in the environment by human activities like mining and fossil fuel combustion. Despite commonalities in some carbon dioxide (CO2) and Hg emission sources, the implications of long-range climate scenarios for anthropogenic Hg emissions have yet to be explored. Here, we present comprehensive projections of anthropogenic Hg emissions up to 2300 and evaluate impacts on global atmospheric Hg deposition. Projections are based on four Shared Socioeconomic Pathways (SSPs) ranging from sustainable reductions in resource and energy intensity to rapid economic growth driven by abundant fossil fuel exploitation. There is a greater than two-fold difference in cumulative anthropogenic Hg emissions between the lower-bound (110 Gg) and upper-bound (235 Gg) scenarios. Hg releases to land and water are approximately six times those of direct emissions to air (600 - 1470 Gg). At their peak, anthropogenic Hg emissions reach 2200 - 2600 Mg a−1 sometime between 2010 (baseline) and 2030, depending on the SSP scenario. Coal combustion is the largest determinant of differences in Hg emissions among scenarios. Decoupling of Hg and CO2 emission sources occurs under low- to mid-range scenarios, though contributions from artisanal and small-scale gold mining remain uncertain. Future Hg emissions may have lower gaseous elemental Hg (Hg0) and higher divalent Hg (HgII), resulting in a higher fraction of locally sourced Hg deposition. Projected reemissions of previously deposited anthropogenic Hg follow a similar temporal trajectory to primary emissions, amplifying the benefits of primary Hg emission reductions under the most stringent mitigation scenarios.
Chapter 3 explores the cumulative impact of historical and future Hg releases on the global cycle. Humans have intentionally mined and released Hg from the Earth’s lithosphere over millennia. Here, we synthesize past, present, and future anthropogenic releases of Hg and explore its fate using a global geochemical box model. Future growth trajectories are based on the Shared Socioeconomic Pathways (SSPs). Results suggest that the upper bound for future anthropogenic Hg releases (SSP5-8.5) between 2010 and 2300 (1.7 Tg) could surpass historical anthropogenic releases over the past half millennium (1.5 Tg). In contrast, lower bound releases (SSP1-2.6; 0.7 Tg) highlight substantial effects of mitigation. We estimate that cumulative future (2010 - 2300) Hg releases from coal combustion will be ∼12 times higher under SSP5-8.5 than under SSP1-2.6. Observational constraints on global modeling suggest that most Hg released to land and water prior to 2010 remains sequestered at contaminated sites. Substantial oceanic enrichment by anthropogenic Hg (270%) has been driven mainly by atmospheric emissions, which totaled 0.36 Tg between antiquity and 2010. In the future, about 6-times more Hg is expected to be released to land and water than to the atmosphere. This pattern of Hg releases may result in localized Hg contamination issues but is unlikely to substantially impact Hg pollution in the ocean unless legacy Hg waste pools are mobilized by climate change. Modeling results suggest that by 2100 atmospheric Hg concentrations will be similar to present levels if society follows SSP5-8.5. Declines in the surface ocean (-19%) and atmosphere (-45%) are expected under SSP1-2.6, emphasizing the benefits of stringent regulatory controls on future Hg releases.
The chapters presented in this work: (1) leverage satellite observations to reduce uncertainty in natural Hg emissions, (2) quantify the drivers of future anthropogenic Hg emissions, and (3) provide a framework for combining simple and complex models to gain new insight into the environmental fate of Hg following release. Together, these studies advance understanding of the key sources of Hg, the processes mediating its redistribution, and the timescales of its removal.Engineering and Applied Sciences - Engineering Science
Peeking Through the Iron Curtain: How Finnish Television Influenced Politics and Culture in Soviet Estonia
No full textThis paper examines the causal impact of accidental exposure to Finnish television on politi cal attitudes and voting behavior in Soviet Estonia. To isolate the effect of Western media on post-independence parliamentary election outcomes I exploit a unique natural experiment: differential access to Finnish television determined by geographic features. Combining novel data on broadcast signal strength with municipal-level voting outcomes in the pre- and post- Soviet periods, I adopt three complementary empirical methods: fixed-effects weighted least squares, a difference-in-differences event study, and a regression discontinuity design. The results reveal that exposure to Finnish television increased vote shares for parties that promoted democratic values, a market economy, fiscal conservatism, business incentives, welfare policies, and civil rights, and decreased support for parties endorsing marxist ideologies and the need for strong central authority. Mechanism analyses using archival records and survey data indicate that (i) Finnish television had a particularly strong impact on younger audiences, and (ii) the shift in voting behavior was driven primarily by Western entertainment content rather than explicitly political programming. This highlights the power of non-political media as a compelling vehicle for democratic soft power, capable of driving significant political change even in authoritarian regimes.Applied Mathematic
Exploring the Role of Physical and Virtual Manipulatives in Elementary Mixed Fractions Learning
No full textUnderstanding how different types of manipulatives influence children’s learning of mixed fractions can provide insight into effective instructional strategies and inform educational interventions. While both physical and virtual manipulatives are widely used in mathematics education, research comparing their relative effectiveness—particularly in relation to sequencing and retention—is still limited (Moyer-Packenham & Westenskow, 2013; Westenskow, 2013).
The present study investigated whether sequencing physical and virtual manipulatives across two weeks influences children’s ability to identify, compare, and add mixed fractions. Twenty children were assigned to one of four groups: two groups used the same manipulative type across both weeks (physical or virtual), while the remaining two groups switched manipulative types between weeks. Pre- and post-tests were administered in Weeks 1 and 2 to assess performance across the three mixed fraction skills and to evaluate the effects of sequencing and retention.
Although results were not statistically significant, descriptive analyses indicated that all groups improved in all skill areas using manipulatives. Non-sequencing groups generally achieving greater learning gains, while groups using virtual manipulatives demonstrated higher retention from Week 1 to Week 2.
This study contributes to the growing literature on manipulative-based learning and highlights the need for further research on how sequencing and manipulative type affect children’s acquisition and retention of mathematical concepts.Extension Studie
Bridging the Gap Between Imagined and Plausible Futures for Refugees: What Students Wish Their Teachers Knew
No full textThere is a gap between the futures that refugee young people imagine will be possible through their education and the plausible futures in exile, where opportunities are truncated by social, economic, and political exclusions. Our study examines how education can narrow this gap. Through interviews with Syrian students in Lebanon, we document fixed and malleable elements of education that refugee students identify as bridging their current education and their futures. Students experience the structures and content of schooling in Lebanon as both exclusionary and immutable, yet their teachers use what we call relational pedagogies rooted in predictability, explaining, fairness, and care to support students' learning and navigation toward future opportunities. While our research focuses on refugees, it has conceptual implications for educators and school systems in other settings where teachers support their marginalized students to make sense of disconnects between what they imagine is possible through school and their future opportunities.Version of Recor
“Beam Me a Book, Scotty” Virtual Access Rooms under Section 108 of the Copyright Act
No full textMany library and archive reading rooms mandate in-person visits, but this requirement often restricts access rather than enhancing it. Such limitations can be viewed as ableist, classist, and fundamentally at odds with the purpose of copyright, which is to “promote the progress of science and useful arts.” Libraries have historically been at the forefront of providing new modes of access by adopting new technologies to facilitate broader and easier access to preserved works. Unfortunately, these efforts have been hindered by restrictive interpretations of the rights granted to libraries under Section 108 of the Copyright Act—specifically, the notion that providing access to preserved works in digital formats violates the Act. This interpretation is unfounded. This paper launches the concept of Virtual Access Rooms (VARs) that are not only permissible under a proper reading of Section 108 but are also essential to the modern library’s mission. Knowledge should not be confined to physical spaces, and access to preserved works should not be contingent upon a patron's ability to visit such spaces. There is no legitimate basis for denying access to these works through physical location requirements. The solution offered in this paper is both straightforward and aligned with an accurate reading of the language of the section. It requires no amendments or updates. The language Congress chose in drafting Section 108 in the Copyright Act empowers libraries and archives to provide remote access to their collections via VARs because: (1) libraries and archives do not make digital works “available to the public” when they enable regulated, mitigated access for researchers and other approved patrons; and (2) in offering remote access, libraries and archives do not make such works available “outside the premises” of their institutions.Author's Origina
