This study investigates the mechanical properties of A500-C steel round hollow structural sections through tension testing of coupons cut from tubes with various radii and thicknesses. Testing was conducted following ASTM A370 standards to evaluate relationships between carbon equivalent, strength ratios, and ductility. The carbon equivalent was determined using the International Institute of Welding equation with chemical compositions obtained from mill certifications. Strength ratios that were analyzed include measured tensile-to-yield strength, measured-to-mill certification values, and measured-to-nominal values, with comparisons to the ratios prescribed for design in the American Institute of Steel Construction Seismic Provision. The results indicate that most strength ratios and ductility metrics showed no significant correlation with HSS thickness or carbon equivalent. However, some trends were observed. Negative correlations were found between the ratio of measured to nominal ultimate strength and thickness, the measured tensile-to-yield strength ratio and thickness, the ratio of measured to mill-certification yield strength and carbon equivalent, and the ratio of measured to nominal yield strength and carbon equivalent. A positive correlation was observed between the measured tensile-to-yield strength ratio and carbon equivalent. These findings help provide insight into the variability of A500-C steel properties and their dependence on chemical composition and wall thickness, with potential implications for design assumptions in the structural design code.

Understanding how temperature varies across space and through time is fundamental to hydrologic and ecological study. Modeling within these fields requires realistic near-surface temperature reconstructions to accurately represent site-specific processes. In complex terrain, these representations rely on understanding how temperature varies with elevation and topography. On average globally, temperature decreases with elevation at about 6.5°C per km, termed the lapse rate. However, numerous studies have shown that commonly used models of lapse rate perform poorly in complex terrain, and spatial patterns of temperature vary in response to diurnal and seasonal patterns, topography, and synoptic conditions. Notably, cold air pooling (CAP; the accumulation of sinking cold air in poorly drained topographic features) is a dominant influence on night-time temperatures in mountain terrain, resulting in valley bottoms cooling significantly more than mid-slope elevations. However, the literature has yet to explore whether CAP significantly impacts snowpack development and subsequent spring melt patterns. By leveraging a dense network of temperature sensors and terrain analysis, this study aims to (1) implement and optimize an automated algorithm for mapping CAP in the well-studied East River watershed (Colorado), (2) develop a regional temperature model that accurately captures local variability and spatial patterns of CAP, and (3) integrate these temperatures into a hydrologic model to assess their impacts on snow distributions and melt. Findings will provide insight into local temperature structures relevant to ongoing ecological and hydrologic research in the region, and ultimately inform hydrologic modeling practices in mountain environments worldwide where CAP remains largely overlooked. 

6PPD-Quinone (6PPD-Q) is a toxic transformation product of the tire rubber additive, 6PPD, that has been identified as the primary cause of Coho Salmon (Oncorhynchus kisutch) mortality in watersheds impacted by roadway runoff. Recent studies have focused on quantifying the lethal concentration of 6PPD-Q, identifying the major sources, and predicting the environmental release from rubber products. Organic chemical release from solids is typically evaluated with solvent extraction where organic solvent and solid are contacted, releasing the leachable chemicals for measurement. However, different solvents and methods introduce inconsistencies in leaching data from different laboratories. This study evaluates the impact of solvent choice on 6PPD-Q extraction from crumb rubber. I will quantify 6PPD-Q concentrations in methanol, ethyl acetate, or acetone during storage after rubber extractions. Determining the best solvent for 6PPD-Q that promotes the most recovery and stability is essential for data quality. After this study, desorption and resorption rates of 6PPD-Q onto various crumb rubbers will be measured.  These studies aim to improve study design for leaching assessments and enhance our understanding of the persistence and mobility of 6PPD-Q in the environment.

Restoration practices are crucial to the sustainable management of city parks, constructed wetlands, and natural ecosystems that have been disturbed or invaded. Oftentimes, restoration sites have some level of disturbance, such as soil contaminants in urban parks. Therefore, selecting plants for restoration comes with a list of considerations based on the goal and scale of the restoration project. Commonly, plants transplanted into these disturbed or polluted environments experience shock from transplanting stress, making finding solutions that increase restoration planting success invaluable to these practices. Soil fungi and bacteria have potential to boost the success of these efforts through their synergistic interactions with each other and plants. These microorganisms have high potential for use as biofertilizers in place of conventional nitrogen- and phosphorus-based fertilizers, which both have negative environmental impacts, including greenhouse gas emissions and water contamination. We hypothesize that by enriching plants by encasing these beneficial bacteria and fungi in alginate-based hydrogel beads, both plant biomass and overall fitness would improve. Further, this improved fitness has the potential to increase post-transplantation survival rates for plants used in restoration and/or phytoremediation regimes. To determine the effect of hydrogel biofertilizers on early stage development and transplant success in a contaminated restoration site, we are examining the response of blanketflower (Gaillardia aristata) to our novel biofertilizer. This plant is rapid-growing, used in restoration, and is drought-tolerant. Therefore, we are pursuing two questions: 1) How does our mixed-consortium hydrogel impact early development of these plants in greenhouse conditions; and 2) Does transplant survivability increase when planted in contaminated soils? Based on previous studies showing the strong efficacy of hydrogel-encapsulated biofertilizers, we predict that plants treated with biofertilizers will have better outcomes (improved early-stage growth and higher survival rates post-transplant) due to their supplemented nutrient accessibility and accelerated growth and development in early adolescence.

Bridges serve as critical lifelines after seismic events, and closures or rerouting due to earthquake damage can significantly impact the communities that they serve. To reduce bridge damage during an earthquake, nickel-titanium (NiTi) shape memory alloy (SMAs) reinforcement have been proposed. The self-centering and energy dissipation capabilities of NiTi SMA can be used to reduce residual displacements and inhibit critical damage states. However, the high cost of NiTi SMAs necessitates their selective placement in the most structurally efficient locations, requiring coupling with conventional low-carbon steel reinforcement. This coupling of dissimilar metals introduces potential long-term durability and performance concerns, particularly in chloride-rich environments from de-icing salts or marine exposure. These concerns are especially relevant to the Seattle region, where the first U.S. bridge utilizing SMA reinforcement was constructed in 2016. This study aims to characterize the corrosion-induced degradation in reinforced concrete infrastructure incorporating coupled NiTi SMA and steel reinforcement. To investigate the effect of the anode-to-cathode ratio, the exposed area of the steel was varied while keeping the exposed area of NiTi SMA constant. For each anode-to-cathode ratio, three cells were prepared: two half-cells with only steel or NiTi specimens and one coupled cell connecting both materials. All specimens were immersed in a simulated pore concrete solution for 18 days, after which 3% wt NaCl was introduced. After another 18 days, this concentration was increased to 10 wt% NaCl. Electrochemical techniques—including linear polarization resistance, cyclic polarization resistance, and zero-resistance ammetry—were used to evaluate the corrosion behavior of the steel specimens. Results indicate that coupling NiTi and mild steel alters the corrosion response of steel and provides insights into the long-term durability of structures reinforced with coupled NiTi and steel reinforcements.

Anaerobic digestion is a biological method of treating wastewater. Waste, such as food scraps, oils, and manure, is converted to acetate among other biodegradable organic matter in the absence of oxygen. Acetate is converted to biogas later in the digestion process, which may be captured as a renewable energy source. This study aims to determine how different dosages of substrate affect biomethane generation of anaerobic archaic culture. To explore this hypothesis, six serum bottles are filled with 30 milliliters of material from anaerobic. They are then injected with different acetate dosages. To determine the methane generation rates, gas from the headspace of each bottle was injected into a Gas Chromatography Flame Ionization Detector (GC-FID) instrument that detected the concentration of methane. Three measurements for each bottle were taken at one-hour intervals for five runs and are averaged in the results. The GC-FID rendered a graph between time and methane concentration from these measurements. The results of this study will help improve the understanding of anaerobic digester activity in response to different acetate concentrations, which is critical in establishing stable, large-scale digestion operations. 

Given the pressing challenges of climate change caused by human interference in natural systems, the civil engineering industry must adopt more sustainable solutions. One approach is the use of supplementary cementitious materials (SCMs), as cement production is a major source of CO₂ emissions. This ongoing study investigates the use of zeolite as an SCM in pervious concrete. During the summer of 2024, over a dozen pervious concrete specimens were cast with 0%, 25%, and 50% zeolite powder replacing traditional Portland cement. Zeolite, a naturally occurring mineral formed from volcanic eruptions millions of years ago, has been shown to adsorb pollutants and, when used as an SCM, can reduce CO₂ emissions from cement production and potentially increase the material's levels of strength. To assess the impact of zeolite on the mechanical and hydraulic properties of pervious concrete, tests on compressive strength, porosity, and permeability shall be conducted during the Winter 2025 and early Spring 2025 quarters. Results will be shared as laboratory tests are conducted and data is analyzed. The filtration capacity of pervious concrete for different types of pollutants, both with and without zeolite, is a key focus for future phases of this research project.

Mountain snow is an important source of freshwater for forest and meadow ecosystems. However, extreme events such as heat waves and low snowpack pose a significant threat to the availability of these essential resources. Current technology for detecting snow coverage from satellite imagery is limited due to insufficient image quality, especially in forests and meadows. To address this, we developed a Python package that improves access to a machine learning-based snow coverage detector at meter-scale resolution. Built upon research by Yang et al., 2023, this package integrates machine learning models to generate snow coverage masks from Planet satellite imagery. The package includes five core components to assist researchers in leveraging this technology: data searching and downloading from Planet's satellite imagery, custom training and fine-tuning of random forest models for snow coverage detection, prediction of snow-covered areas using the model, and geometry simplification for defining areas of interest. Other features include pre-trained models and sample datasets for quick and efficient implementation. By consolidating their research into a Python package, we aim to improve accessibility to software and research for those seeking to track mountain snow coverage and its environmental impact. Ultimately, our goal is to empower researchers to accelerate progress in understanding spatial patterns of snow in forests and mountain meadows. Additionally, we aim to support resource managers in more effectively tracking snow distribution across complex terrain.

Anaerobic digestion is a biological process that converts waste into biomethane, a renewable energy source. Acetate conversion is the last step of anaerobic digestion and is the most likely to fail in methane production. Understanding the microorganisms responsible for this process, and the conditions they thrive in, can help to increase success of that final step. Previous studies have concluded that changing the acetate feeding conditions of a digester will select for different microbial species. Starting with established lab-scale acetate-fed digesters, this study aimed to identify the present species through DNA extraction and sequencing. Samples were extracted over the course of a week from digesters that varied in feeding schedule. Statistical analysis of the DNA sequences was then completed to determine the diversity in archaeal and bacterial species, and the richness of those species. The variance between digesters was visualized using Principal Coordinate Analysis (PCoA). This data confirmed that digesters operated under different feeding conditions establish different microbial communities. Next steps will include comparing the community composition to acetate consumption kinetics. These results will help advance the understanding of conditions required to ensure stabilized biomethane energy production from anaerobic digestion.