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Recent Submissions
Assessment of a foundational machine-learned potential for energy ranking of molecular crystal polymorphs
(Royal Society of Chemistry, 2025-05-19) Nickerson, Cameron J.; Johnson, Erin R.
Sustaining Soil Organic Carbon and Soil Health in Intensively Tilled Short Crop Rotations
(2025-05-29) Lavergne, Stéphanie; No; Doctor of Philosophy; Department of Plant, Food and Environmental Sciences; Received; Meagan E. Schipanski; Yes; Andrew M. Hammermeister; David L. Burton; Derek H. Lynch; Caroline Halde
Soils in Canada are under degradation due to the intensification of agricultural systems. Intensive field crop rotations are characterized by low crop diversity and crop residues, and high tillage frequency and external nutrient inputs. However, the impact of these intensive short rotations on soil health, earthworm communities, and soil organic carbon (SOC) has been little investigated and is the focus of this thesis. A field survey was conducted over three years on eleven organic grain farms in Québec, Canada, to assess the impact of short crop rotations without forages (corn [Zea mays L.] -soybean [Glycine max (L.) Merr.] – small grain) on the earthworm community and soil health. Earthworm abundance and richness were generally low in both fields and field margins, with earthworm communities in cropped fields primarily dominated by endogeic species. Our findings suggest that long-term manure application, along with frequent use of cover crops, plus inversion tillage favours endogeic species in these systems. In contrast anecic and epigeic species increased under winter cereals. Legacy (prior three years) management practices were characterized using indices for crop diversity (CDI), soil tillage intensity rating (STIR) and organic amendment use (OAI). In-season management indices, in particular CDI (increased by cover crops and winter crops) and STIR, varied across crop fields and had a greater effect on soil health outcomes. A replicated potato (Solanum tuberculum L.) experiment in Prince Edward Island, Canada, compared the impact of contrasting three-year rotations including one full season cover crop on SOC dynamics and distribution. Treatments failed to differ in soil profile (0-45cm) SOC. Our results indicate that, carbon (C) inputs from full season cover crops were insufficient to offset SOC loss due to high tillage intensity in these rotations, affecting both topsoil and subsoil SOC stocks. Overall, this research has shown that reducing tillage intensity by increasing crop diversity was the main driver of earthworm community diversity and soil health. Rotations that enhance C inputs, such as via winter cover crops and cash crops residues, could buffer the earthworm community, and soil health and SOC, against the impacts of greater tillage intensity in short rotation cropping systems.
FUNCTIONALIZING GOLD NANOPARTICLES WITH A DNA APTAMER FOR BIOSENSING 25-HYDROXYVITAMIN D3
(2025-05-29) Hansson, Benjamin; Not Applicable; Master of Science; Department of Physics & Atmospheric Science; Not Applicable; n/a; Not Applicable; Laurent Kreplak; Alan Fine; Kimberley Hall; Kevin Hewitt
Vitamin D influences over 400 processes in the human body and its deficiency is associated with several diseases such as uterine fibroids. Accessible point-of-need tools are required to detect 25-hydroxyvitamin D3 (25(OH)D3), a Vitamin D biomarker. This thesis investigated conjugation methods for the specific, yet structurally complex 25(OH)D3 aptamer, VDBA14, to gold nanoparticles (AuNPs), common biosensor transducers. Initial approaches using salt-aging, low pH, and freeze conjugation, evaluated with UV-Vis, fluorescence, and salt stability assays, were ineffective due to poor aptamer conjugation and the resulting AuNP aggregation. A promising development was the inclusion of an 18atom hexa-ethyleneglycol spacer between the aptamer and disulphide linker. Freeze conjugation of the modified aptamer improved AuNP stability, with conjugation confirmed by UV-Vis redshift and DNA FT-IR bands. Future experiments are required to demonstrate conjugation without destabilizing AuNPs. This work represents a foundation for functionalizing AuNPs with VDBA14, and the first step towards point-of-need 25(OH)D3 biosensors.
Student Perceptions of Sanitary Products Sustainability in Studley Campus Washrooms at Dalhousie University
(2025-04) Jacobi, Aurora; Sun, Bocong; Lavergne, Dana; MacLeod, Em; Hunt, Natasha
Restroom products play a crucial role in social sustainability, they also pose challenges to sustainable development by negatively impacting the environment (Pejčić & Vranjanac, 2016). The environmental consequences include the generation of significant waste, which can lead to environmental degradation (Pejčić & Vranjanac, 2016). Products such as toilet paper, paper towels, and menstrual products have been particularly controversial due to their single-use nature (Brito, 2023; Aujla et al., 2024). When discarded, toilet paper and paper towels become insoluble pollutants because of their material composition (Wang et al., 2023; Ingwersen et al., 2016). This study explores the sustainability of restroom products (soap, toilet paper, paper towels, and menstrual products) used on Dalhousie University’s Studley campus, focusing on student perceptions of these products and their environmental impacts. While essential for public health and hygiene, these products contribute significantly to environmental degradation, creating waste and affecting water and soil quality. Despite their importance in everyday life, the sustainability of products has been largely overlooked in university sustainability policies. To investigate these perceptions, an anonymous survey was distributed to undergraduate and graduate students on the Studley Campus, focused on their thoughts and understanding on key sustainability criteria such as biodegradability, recycled content, and plastic-free packaging when it comes to different restroom products. A total of 89 responses were received over a ten-day period, but only 81 replies were analyzed due to eight incomplete responses. Chi-squared and T-tests were performed to compare perceptions across different environmental and sustainability focused programs against non-environmental and sustainability focused programs. The findings revealed a gap in student knowledge regarding the environmental impact of restroom products. In addition, it indicated that students are interested in more sustainable alternatives. This research provides valuable insights for Dalhousie University to refine its sustainability policies and practices, offering opportunities to improve waste management, procurement strategies, and overall environmental stewardship. By better understanding student demands, this study contributes to ongoing efforts to align university operations with sustainability goals and environmental responsibility.
Keywords: Sustainability, Hygiene Products, Soap, Paper Towels, Toilet Paper, Dalhousie University, Perspectives, Environmental Impact, Menstrual Products, Restrooms
Quantifying Cigarette Butt Waste on Dalhousie University’s Studley Campus: A Spatial Analysis of Hotspots via Location and Ground-Type Patterns
(2025-04) Maynard, Gabrielle; Glover, Sophie; Kisseljov, Roman; Ottenbreit-Born, Petra; Sparling, Kate
The abundance of cigarette butt litter present on Dalhousie University’s Studley Campus, resulting from continued smoking creates a barrier to achieving the university's goal of maintaining a smoke-free campus. Physical counts of littered cigarette butts were conducted to quantify cigarette butt pollution on the two campuses and create a visual representation of the data using heatmaps generated using ArcGIS Pro. A total of 13,816 cigarette butts were recorded across 749 surveyed locations. Kruskal-Wallis and Post Hoc Dunn’s tests were used to assess the significance of the distribution of cigarette butts, as well as their associated ground and location types. Cigarette butt accumulation varied by ground type: 65.77% of cigarette butts were found on natural surfaces, 17.44% on artificial surfaces, and 16.79% of cigarette butts were found in areas with both artificial and natural ground types. Additionally, accumulation of cigarette butts varied by location type: the largest quantities were recorded near sidewalks (25.11%), parking lots (21.56%), and educational buildings (21.06%). Notable high-density areas were observed: 676 outside of an administration building, 607 found outside of a library and 485 cigarette butts outside of a residence building, which are visible on the heatmap and illustrated in accompanying figures. The mean cigarette butt count per square meter was 18.45 with a standard deviation of 50.36. Results of the Kruskal-Wallis tests show a significant difference in cigarette butt counts across ground types (p = 0.028) and between location types (p < 0.001). The results of the Post Hoc Dunn’s tests indicate a greater accumulation of cigarette butts on sidewalks and natural ground types. The findings of this study demonstrate that smoking persists despite campus guidelines. However, the results can be used to help inform Dalhousie’s waste management practices and policy enforcement, contributing to a healthier and cleaner environment on Studley Campus.
Keywords: Cigarette Butt, Cellulose Acetate, University, Leaching, Second-Hand Smoke, Smoke-Free Policy, Hotspots, GIS (Geographic Information Systems), Litter Audit, Displacement Effect.
Quantifying Carbon Dioxide Emission Equivalence from Dalhousie Undergraduates’ Air Travel During the 2024/2025 Academic Year Study
(2025-04) Bendzsa, Liam; Gysel, Jake; Healey, Nyah; Lazo, Lorena; Schwartz, Jaime
Aviation accounts for 4-5% of global Greenhouse Gas (GHG) emissions. With only 15% of Dalhousie University's undergraduate student body being from Nova Scotia, several students partake in extraneous (Section 3.2) flying over the fall and winter study breaks. This study was conducted to estimate the quantity of carbon dioxide equivalent (CO2 eq) emissions produced by Dalhousie undergraduate students based in Studley campus who took part in air travel during the either the fall or winter 2024/2025 study breaks. Quantitative data on student flight paths and qualitative data on perceptions on air travel were gathered through online survey, wherein a sample of 378 eligible students responded. Calculations determined that approximately 9,206.40 tonnes (t) of CO2 eq were emitted by the extraneous study break flights of Dalhousie undergraduate students, based on Studley campus, during the 2024/2025 academic year. Results from this survey disclosed that the added CO2 eq emissions from one (1) student air travel round-trip (Section 3.2) during study breaks amounted to a 6.33% increase from the Canadian average, representing a difference between 17.7 and 18.8 t of CO2 eq emitted by a person in a year. Comparisons were also made to the 1.5 t of CO2 eq target level of emissions per person required to the Paris Agreement goal of keeping warming below 1.5 degrees Celsius (°C ) and achieving carbon neutrality by 2050 (Kreil, 2021). These added emissions were calculated for the
38.1% of respondents who took flights during either or both fall and winter study breaks using a weighted average. Flight destination and consequent distance was also analyzed as a variable of this study. These factors were compared to respondents’ level of concern around CO2 eq resulting from air travel. The results determined that students flew to a multitude of different cities across Canada and the world, with Toronto being the most common stop, where 215 students reported landing (Figure 2). This is in part due to the volume of layovers that take place at Toronto Pearson International Airport. The qualitative data gathered from the survey reflected that the majority of respondents do not consider the CO2 eq emissions of air travel as a factor impacting their decision to fly. Instead, flight cost, local activities, and obligations were reasons why
students chose to stay local during study breaks. This signifies that Dalhousie should take these factors into consideration, along with the large CO2 eq expenditure of students flying over study breaks and attempt to find ways to incentivize students to remain in Halifax over their Fall and Winter study breaks to reduce overall CO2 eq emissions.