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Organic carbon-mineral interactions with implications on water reuse and carbon cycling
No full textSoil organic carbon (OC)-mineral associations play an important role in regulating the fate and transport of pollutants in soils, biogeochemical cycles of carbon, as well as response to climate change. With the reuse of reclaimed water for agriculture as a promising strategy for the sustainable management of water resources, residual trace organic pollutants in reclaimed water can exert potential risks to human health. Predictive modeling about how the organic pollutants (including ionizable organic compounds) behave at the soil OC-mineral-water interface can help determine the environmental risks of water reuse for agriculture. Molecular-level understanding of OC-mineral associations, i.e., identification of the chemical structures of organic ligands occurring in soil environment, can shed light on not only predicting the plant uptake of organic pollutants for water reuse but also carbon stability in soil environment under dynamic climate. This study aims to: 1) develop a screening model for estimating the environmental risks of organic pollutants in reclaimed water for agricultural irrigation accounting for the sorption of pollutants by soil OC-mineral complexes; 2) identify the chemical nature of unknown organic ligands in soils derived from degradation of plant macromolecules (lignin). The fate of five different pharmaceuticals and personal care products (PPCPs) was predicted in agricultural grazing farms irrigated with reclaimed wastewater by our developed model. The degradation rate constant of the PPCPs was found to be a critical factor regulating the concentration of compounds in soil and plants. Without considering the sorption of organic pollutants by organic matter and minerals in the soil environment, the environmental risks of widely occurring pollutants can be overestimated. The model was developed to simulate the pH-dependent speciation and fate of ionizable PPCPs (iPPCPs) in soils and their plant uptake during the application of reclaimed wastewater to agricultural soils. Assuming sorption only for neutral compounds on soil organic carbon led to a miscalculation of iPPCP concentrations in plant tissues by up to one and a half orders of magnitude. Overall, the results demonstrated the importance of considering pH and speciation of iPPCPs when simulating their fate in the soil-plant system and plant uptake. To identify the organic ligands, a method that combined high-performance liquid chromatography (HPLC) with high-resolution Orbitrap mass spectrometry (HRMS), screening for Fe isotopologues, and metabolomic analysis was utilized. Lignin-derived model compounds (such as caffeic acid, coumaric acid, vanillin, and cinnamic acid)) were used to validate and optimize the protocol before applying the protocol to identify the chemical structure of unknown organic ligands generated from microbial degradation of lignin by Pseudomonas putida. Fe complexes and corresponding apo-ligands were determined by isotopic pattern matching, accurately predicting the molecular formula, identifying the apo-ligands with MS/MS data, and predicting the structure of organic ligands utilizing the MS/MS peaks. Library search based on the MS results also uncovered additional organic ligands as well as molecular networking analysis grouped apo-ligands and complexes with similar chemical natures in the same clusters which helped to identify further interesting compounds. The approach has the potential to be employed in a wider array of complex environmental samples to discover compounds that possess significant potential for binding with Fe-containing as well as other soil minerals
Exploring the plant communities of historical greenstrip seedings containing forage kochia (Bassia prostrata) across northern Nevada
Get PDFIn 1985, a roadside program of planting fire-resistant species to help slow wildfire spread on rangelands called “greenstripping” was initiated in Idaho by the Bureau of Land Management (BLM). Originally, most greenstrips were seeded with introduced grass species. However, by the 1990s, an introduced semi-shrub cultivar, forage kochia (Bassia prostrata), became a preferred species for these plantings due to its competitive interference with cheatgrass (Bromus tectorum), low stature, forage production, and its ability to resprout after fire. Forage kochia has been seeded on over 1.5 million acres by the BLM in four states (Idaho, Oregon, Utah, and Nevada) with Nevada exceeding them all in acreage and number of projects. However, little research has been done to examine the current condition and status of these greenstrips, especially in Nevada. Therefore, I surveyed fourteen historical (1992-2011) greenstrip plantings that included forage kochia across northern Nevada within a variety of Ecological Sites (ESs) to ask: 1) Do historically seeded forage kochia greenstrips in Nevada still meet the BLM criteria for a successfully seeded greenstrip? 2) Has the density of the forage kochia seeding changed in these greenstrips, since last monitoring? 3) How does current forage kochia cover differ by seeding year and among different ES within the same seeding year? 4) Are there differences in plant diversity and richness that are related to ESs? 5) Do cover groups (forage kochia, bare ground, cheatgrass, perennial forbs, native grasses, seeded grasses, invasive annual forbs, shrubs, litter, and rock) differ between ES and/or by individual greenstrip? Overall, I found low abundance of forage kochia. None was encountered in the majority (8) of the greenstrips or in two seeding years (1999 and 2001). Even where forage kochia remained, none of these greenstrips maintained the densities expected of a successful greenstrip seeding. The highest cover of forage kochia was found in the oldest seeding (30 years), suggesting it can establish self-perpetuating populations in Nevada even though its density had declined since seeding in all but one ES. Neither ES nor precipitation was useful at predicting the success of forage kochia in these greenstrips, and there was high variability in forage kochia cover in greenstrips within the same ES (unless otherwise explained by low seeding rate), even in the same seeding year. In contrast, seeded nonnative grasses and native forbs were affected by ES and precipitation. Otherwise, cover groups varied across greenstrips without a clear pattern. Plant communities on the greenstrips were low in species diversity and richness while evenness suggested most were not dominated by a single species. Taken together, my results illustrate 1) the low seeding success of forage kochia in these historically-planted fuel breaks over the long term, 2) these greenstrips are no longer serving as intended fuel breaks across northern Nevada, and 3) there is a high degree of variation in current site condition among greenstrips. Better monitoring is needed to understand how to seed and maintain successful fuel breaks using forage kochia across Nevada
Biogeochemistry in changing Sierra Nevada ecosystems
Get PDFForest and meadow ecosystems of the Sierra Nevada are experiencing change on varied temporal and spatial scales that may influence biogeochemical and ecosystem function. Repeated high severity fire within a relatively short time frame (10 �" 20 y) is a major driver of change in mixed-conifer forests, a dominant cover type of the northern Sierra Nevada and southern Cascades. Repeated high severity fire can lead to long-term forest conversion to montane chaparral, representing a “press” or long-term, continuous effect on mixed-conifer forests.Chapter 1 explores the potential soil biogeochemical impacts of multiple severe fires with short fire return intervals on forest soil using existing disturbance frameworks. This conceptual paper includes an empirical analysis of the reburn trends throughout the Sierra Nevada and Modoc (encompassing the neighboring southern Cascades) bioregions of California and a review of extant literature exploring this press effect on aboveground ecosystem components. Lastly, Chapter 1 poses a series of hypotheses on press effects to belowground ecosystem components. Our hypotheses were: 1) reduced recovery time between fire events will prevent the soil microbiome from returning to pre-fire conditions, leading to long-term changes in the microbial community; 2) reduced recovery time between fire events will prevent plant carbon (C) inputs from returning to pre-fire conditions, hindering soil organic matter (SOM) recovery; 3) particulate organic matter (POM) is more likely to experience continued decline with successive burning until a lower limit is reached than mineral-associated organic matter (MAOM); and 4): less aboveground biomass with repeated burning will produce smaller post-fire inorganic nitrogen (IN) pulses through ash deposition in each fire event, with the potential to influence ecosystem-level nitrogen (N) dynamics. Chapter 2 is an empirical study that addresses some of the hypotheses of Chapter 1 by comparing soil biogeochemical properties of a series of sites that have burned either once or twice in the past 20 years. We found that certain aspects of biogeochemistry, including inorganic N content and cycling and heterotrophic respiration (Rh), were affected by repeated burning while other aspects, including soil carbon C and N storage in soil organic matter fractions, do not. Chapter 2 also includes a burn table experiment to identify if soils from sites of varied burn history respond differently to an additional fire event, though the effects of the experiment were limited. Chapter 3 focuses on montane meadows, which are commonly degraded following past land use practices. As such, the main driver of change in montane meadows is currently hydrologic restoration aimed at restoring the ecosystem properties lost in degradation. Hydrologic restoration has been shown to increase soil C inputs from vegetation and increase soil C stocks. Chapter 3 aims to identify changes in soil C stability, or resistance to loss through time, with time since restoration. We found three lines of evidence that indicate soil C stability in montane meadows increases with restoration age: increased soil C storage in MAOM which has a longer residence time than that of POM, decreased susceptibility of MAOM-C to decomposition across the temperature manipulation experiment, and limited signs of MAOM utilization through stable isotope analyses. Overall, this dissertation identifies the resistance and resilience of forest and meadow soils to change and highlights soil as a persistent reservoir of ecosystem C and N
Using Large Language Models in the Experimental Analysis of Persuasion and Bias
Get PDFThe United States of America currently faces high levels of political polarization, which has resulted in political violence including the events of January 6th, 2021. Traditional cable news networks such as FOX and MSNBC are in part responsible for this worsening polarization among American citizens. As America faces rising political tension in the 2024 election cycle, Artificial Intelligence-powered products such as Large Language Models may have the potential to pour fuel on the fire. This study uses the Relational Frame Theory of language and cognition to conceptualize how media content may contribute to polarization, and what the role of AI may be in the future of polarizing content. This study consisted of two experiments. Experiment 1 scraped transcripts from ABC, FOX, and MSNBC along with asking ChatGPT (an LLM developed by OpenAI) to produce monologues mimicking the hosts of popular shows on this network. These Real or AI transcripts were then compared using the Linguistic Inquiry and Word Count (LIWC) tool and the Inflexitext program to visually compare and contrast the linguistic elements used across these sources of media content. Experiment 2 consisted of a two by two ANOVA and ANCOVA to assess the main and interaction effects of media outlet (FOX or MSNBC) and monologue type (Real or AI) on a sample of 250 participants. The results of this experiment indicated that MSNBC monologues are perceived as more persuasive (p < .001) and credible (p < .001) than FOX monologues, and FOX monologues were viewed as more polarizing (p < .001). Additionally, MSNBC AI monologues were significantly more persuasive than MSNBC Real monologues (p < .05), indicating that LLMs may be capable of providing text that is more persuasive than real writers in some contexts. Implications for polarization in America are discussed
A Study on Magmatic Diversity: Determining the Evolution and Petrogenesis of Eocene Magmatism at Swales Mountain, NV
Get PDFModern volcanic systems are commonly not static but change through time as magmas are added from below and tapped during eruption. From the Eocene to Miocene, the Great Basin underwent a magmatic episode tied to slab rollback of the Farallon plate. Swales Mountain, Nevada, hosts a complex shallow to mid-crustal Eocene magmatic system (39.5-35.5 Ma) that, due to Basin and Range extension, are exhumed and exposed today at the Earth surface. This study provides an updated 1:5,000 geologic map, new U-Pb zircon ages, amphibole barometry, Sr-Nd-Pb isotopic data and whole rock major and trace element geochemistry to explore the temporal, spatial, and petrologic evolution of the Swales Mountain magmatic system over its ~4 Ma activity. The six calc-alkaline, high-K, intrusive and subvolcanic units range from 56 to 76 wt% SiO2. Three texturally and compositionally distinct plutons ranging 0.5-2 km in width are exposed in different parts of the plumbing system. In between, various dikes, sills, and breccias interact with Paleozoic sedimentary units. A variety of mixing textures with mafic material have been observed in the plutonic units, indicating contemporaneous existence of distinct magmas in the Swales Mountain system. Swales Mountain is ~17 km northeast of the Carlin Trend allowing the Swales intrusions to be a potential heat and fluid source leading to Carlin-type mineralization.Results indicate that Swales Mountain had at least two episodes of magmatism: the first being a smaller event lasting ~100 ka generating the Eastern Swales quartz monzodiorite at a relatively shallow depth, and the second event lasting ~ 3.1 Myr producing the Central Swales quartz monzonite, Southern Swales monzogranite, dacite porphyry, and rhyolite. Basaltic andesite dikes intrude the dacite porphyry and rhyolite. I speculate that the Swales magmatic system came from a lithospheric mantle source that experienced upper crustal assimilation and homogenization. Small compositionally diverse systems, such as Swales Mountain, may potentially be used to explore how initial crustal magmatism integrates mantle material over time
Use of Nanotechnology as a Phenomena to Motivate Secondary Students’ Understanding of Proportions and Atomic Composition and Scale
No full textMany students in secondary grade levels struggle with proportional reasoning. Calisici (2018) found that 48 percent of students were unable to solve a multiplication problem involving fractions. Furthermore, many students struggle with complex Chemistry topics due to the difficulty many students have visualizing the microscopic scale. “3D visualization media effectively improved students’ critical thinking skills and scientific attitude (Astuti et al, 2020).” In another study done in Turkey, students were asked to draw static and dynamic models of an Oxygen atom. The study concludes, “Therefore, it could be suggested that generating animations as a modeling activity helps learners to improve their mental models of the atom. (Akaygun, 2016). ”Thus, this study aims to address these misconceptions using a STEM Integration approach. A paper by Roehrig et al (2021) looked at creating a framework for STEM integration. The paper gave 7 key characteristics for integrating STEM, “(a) focus on real-world problems, (b) centrality of engineering, (c) context integration, (d) content integration, (e) STEM practices, (f) twenty-first century skills, and (g) informing students about STEM careers (Roehrig et al 2021).” This study examines how students understanding of proportions and atomic composition and scale develop throughout a week-long summer camp using Nanotechnology as the driving phenomena. Implications of this integrated STEM approach as well as students conceptual understanding is then examined and discussed
Toward Terabit-per-second Networks: Developing Data Transfer Solutions for Next-Generation Research Networks
Get PDFResearch networks provide high-speed wide-area network connectivity between research and education institutions to facilitate large-scale data transfers. However, scalability issues of legacy transfer applications (e.g., scp and FTP) and their extensions (e.g., GridFTP and rsync) hinder the effective utilization of these networks. In this dissertation, we propose online optimization algorithms to tune the degree of parallelism for file transfers to maximize transfer throughput while keeping system overhead at a minimum. First, we introduce Falcon that utilizes game theory-inspired novel utility function to evaluate the performance of various parallelism levels such that competing transfers are guaranteed to converge to a fair and stable solution. We assessed the performance of Falcon in isolated and production high-speed networks and found that it can discover optimal transfer parallelism in as little as 20 seconds and outperform the state-of-the-art solutions by more than 2x. On the other hand, Falcon uses the same level of parallelism for network and I/O operations which may result in increased system overhead and unfair resource allocation. To address this issue, we developed modular file transfer architecture, Marlin, that separates I/O and network operations so that parallelism can be independently adjusted for each component. Marlin adopts online gradient descent algorithm to swiftly search the solution space and find the optimal level of parallelism for read, transfer, and write operations. Experimental results collected under various network settings show that Marlin can identify and use a minimum parallelism level for each component, reducing system overhead (e.g., low CPU usage and I/O contention) and improving fairness among competing transfers
Pushed to the Limit: Chinese Environmental Governance and the 1998 China Floods
No full textThe 1998 China floods were the negative culmination of decades of Chinese Communist Party environmental policy, first under Mao and then under Deng, which removed the overflow capability of local river systems through land reclamation and deforestation. This disaster had the effect of shifting how the Chinese government viewed environmental governance as they came to recognize that environmental degradation could pose a threat to the stability of their regime as it had to those of the Qing and earlier dynasties. This was a significant change in governmental thinking as combating environmental degradation became a major state priority. However, the logic and approaches used by the Chinese government to counter this threat have a lot of similarities to those used before 1998. They are still highly reliant on ecologically damaging solutions like dams and electric vehicles to counter the effects of environmental degradation and still employ aggressive top-down campaigns to enact environmental enforcement