Making a Place for the Next Generation of Geoscientists

Early-career scientists from the AGU Mentoring Network discuss how the global pandemic has exacerbated long-standing issues with the availability of positions in and the diversity of the geosciences.</jats:p

The fate of sediment, wood and organic carbon eroded during an extreme flood, Colorado Front Range, USA

Identifying and quantifying the dominant processes of erosion and tracking the fate of sediment, wood, and carbon eroded during floods is important for understanding channel response to floods, downstream sediment and carbon loading, and the influence of extreme events on landscapes and the terrestrial carbon cycle. We quantify sediment, wood, and organic carbon (OC) from source to local sink following an extreme flood in the tectonically quiescent, semi-arid Colorado (USA) Front Range. Erosion of >500,000 m3 or as much as ~115 yr of weathering products occurred through landsliding and channel erosion during September 2013 flooding. More than half of the eroded sediment was deposited at the inlet and delta of a water supply reservoir, resulting in the equivalent of 100 yr of reservoir sedimentation and 2% loss in water storage capacity. The flood discharged 28 Mg C/km2, producing an event OC flux equivalent to humid, tectonically active areas. Post-flood remobilization resulted in a further ~100 yr of reservoir sedimentation plus export of an additional 1.3 Mg C/km2 of wood, demonstrating the ongoing impact of the flood on reservoir capacity and carbon cycling. Pronounced channel widening during the flood created accommodation space for 40% of flood sediment and storage of wood and eroded carbon. We conclude that confined channels, normally dismissed as transport reaches, can store and export substantial amounts of flood constituents

Luminescence Dating Without Sand Lenses: an Application of Osl to Coarse-grained Alluvial Fan Deposits of the Lost River Range, Idaho, USA

Optically stimulated luminescence (OSL) dating is increasingly used to estimate the age of fluvial deposits. A significant limitation, however, has been that conventional techniques of sampling and dose rate estimation are suitable only for thick (\u3e60 cm) layers consisting of sand size or finer grains. Application of OSL dating to deposits lacking such layers remains a significant challenge. Alluvial fans along the western front of the Lost River Range in east-central Idaho, USA are one example. Deposits are typically pebble to cobble sheetflood gravels with a sandy matrix but thin to absent sand lenses. As a result, the majority of samples for this project were collected by excavating matrix material from gravelly deposits under light-safe tarps or at night. To examine the contributions of different grain-size fractions to calculated dose-rates, multiple grain-size fractions were analyzed using ICP–MS, high resolution gamma spectrometry and XRF. Dose rates from bulk sediment samples were 0.4–40% (mean of 18%) lower than dose-rate estimates from the sand-size fractions alone, illustrating the importance of representative sampling for dose rate determination. We attribute the difference to the low dose-rate contribution from radio-nuclide poor carbonate pebbles and cobbles that occur disproportionately in clast sizes larger than sand. Where possible, dose rates were based on bulk sediment samples since they integrate the dose-rate contribution from all grain sizes. Equivalent dose distributions showed little evidence for partial bleaching. However, many samples had significant kurtosis and/or overdispersion, possibly due to grain-size related microdosimetry effects, accumulation of pedogenic carbonate or post-depositional sediment mixing. Our OSL age estimates range from 4 to 120 ka, preserve stratigraphic and geomorphic order, and show good agreement with independent ages from tephra correlation and U-series dating of pedogenic carbonate. Furthermore, multiple samples from the same deposit produced ages in good agreement. This study demonstrates that with modified sampling methods and careful consideration of the dose rate, OSL dating can be successfully applied to coarse-grained deposits of climatic and tectonic significance that may be difficult to date by other methods

Impact of a Randomized Campus/Community Trial to Prevent High-Risk Drinking Among College Students

High-risk drinking by college students continues to pose a significant threat to public health. Despite increasing evidence of the contribution of community-level and campus-level environmental factors to high risk drinking, there have been few rigorous tests of interventions that focus on changing these interlinked environments. The Study to Prevent Alcohol Related Consequences (SPARC) assessed the efficacy of a comprehensive intervention using a community organizing approach to implement environmental strategies in and around college campuses. The goal of SPARC was to reduce high-risk drinking and alcohol-related consequences among college students

The natural wood regime in rivers

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Impact of a Randomized Campus/Community Trial to Prevent High-Risk Drinking Among College Students

BACKGROUND: High-risk drinking by college students continues to pose a significant threat to public health. Despite increasing evidence of the contribution of community-level and campus-level environmental factors to high risk drinking, there have been few rigorous tests of interventions that focus on changing these interlinked environments. The Study to Prevent Alcohol Related Consequences (SPARC) assessed the efficacy of a comprehensive intervention using a community organizing approach to implement environmental strategies in and around college campuses. The goal of SPARC was to reduce high-risk drinking and alcohol-related consequences among college students. METHODS: Ten universities in North Carolina were randomized to an Intervention or Comparison condition. Each Intervention school was assigned a campus/community organizer. The organizer worked to form a campus-community coalition, which developed and implemented a strategic plan to use environmental strategies to reduce high-risk drinking and its consequences. The intervention was implemented over a period of 3 years. Primary outcome measures were assessed using a web-based survey of students. Measures of high-risk drinking included number of days alcohol was consumed, number of days of binge drinking, and greatest number of drinks consumed (all in the past 30 days); and number of days one gets drunk in a typical week. Measures of alcohol-related consequences included indices of moderate consequences due to one’s own drinking, severe consequences due to one’s own drinking, interpersonal consequences due to others’ drinking, and community consequences due to others’ drinking (all using a past 30-day timeframe). Measure of alcohol-related injuries included (1) experiencing alcohol-related injuries and (2) alcohol-related injuries caused to others. RESULTS: We found significant decreases in the Intervention group compared to the Comparison group in severe consequences due to students’ own drinking and alcohol-related injuries caused to others. In secondary analyses, higher levels of implementation of the intervention were associated with reductions in interpersonal consequences due to others’ drinking and alcohol-related injuries caused to others. CONCLUSIONS: A community organizing approach promoting implementation of environmental interventions can significantly affect high-risk drinking and its consequences among college students

The role of intracellular calcium phosphate in osteoblast-mediated bone apatite formation

Mineralization is a ubiquitous process in the animal kingdom and is fundamental to human development and health. Dysfunctional or aberrant mineralization leads to a variety of medical problems, and so an understanding of these processes is essential to their mitigation. Osteoblasts create the nano-composite structure of bone by secreting a collagenous extracellular matrix (ECM) on which apatite crystals subsequently form. However, despite their requisite function in building bone and decades of observations describing intracellular calcium phosphate, the precise role osteoblasts play in mediating bone apatite formation remains largely unknown. To better understand the relationship between intracellular and extracellular mineralization, we combined a sample-preparation method that simultaneously preserved mineral, ions, and ECM with nano-analytical electron microscopy techniques to examine osteoblasts in an in vitro model of bone formation. We identified calcium phosphate both within osteoblast mitochondrial granules and intracellular vesicles that transported material to the ECM. Moreover, we observed calcium-containing vesicles conjoining mitochondria, which also contained calcium, suggesting a storage and transport mechanism. Our observations further highlight the important relationship between intracellular calcium phosphate in osteoblasts and their role in mineralizing the ECM. These observations may have important implications in deciphering both how normal bone forms and in understanding pathological mineralization