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- All Subjects: Environmental science
- Creators: Grimm, Nancy
- Creators: Herckes, Pierre
Description
The prevalence and unique properties of airborne nanoparticles have raised concerns regarding their potential adverse health effects. Despite their significance, the understanding of nanoparticle generation, transport, and exposure remains incomplete. This study first aimed to assess nanoparticle exposure in indoor workplace environments, in the semiconductor manufacturing industry. On-site observations during tool preventive maintenance revealed a significant release of particles smaller than 30 nm, which subsequent instrumental analysis confirmed as predominantly composed of transition metals. Although the measured mass concentration levels did not exceed current federal limits, it prompted concerns regarding how well filter-based air sampling methods would capture the particles for exposure assessment and how well common personal protective equipment would protect from exposure. To address these concerns, this study evaluated the capture efficiency of filters and masks. When challenged by aerosolized engineered nanomaterials, common filters used in industrial hygiene sampling exhibited capture efficiencies of over 60%. Filtering Facepiece Respirators, such as the N95 mask, exhibited a capture efficiency of over 98%. In contrast, simple surgical masks showed a capture efficiency of approximately 70%. The experiments showed that face velocity and ambient humidity influence capture performance and mostly identified the critical role of mask and particle surface charge in capturing nanoparticles. Masks with higher surface potential exhibited higher capture efficiency towards nanoparticles. Eliminating their surface charge resulted in a significantly diminished capture efficiency, up to 43%. Finally, this study characterized outdoor nanoparticle concentrations in the Phoenix metropolitan area, revealing typical concentrations on the order of 10^4 #/cm3 consistent with other urban environments. During the North American monsoon season, in dust storms, with elevated number concentrations of large particles, particularly in the size range of 1-10 μm, the number concentration of nanoparticles in the size range of 30-100 nm was substantially lower by approximately 55%. These findings provide valuable insights for future assessments of nanoparticle exposure risks and filter capture mechanisms associated with airborne nanoparticles.
ContributorsZhang, Zhaobo (Author) / Herckes, Pierre (Thesis advisor) / Westerhoff, Paul (Committee member) / Shock, Everett (Committee member) / Fraser, Matthew (Committee member) / Arizona State University (Publisher)
Created2023
Description
Climate change is one of the most pressing issues facing humanity, and cities are likely to experience many of the most dangerous effects of climate change. One way that cities aim to adapt to become more resilient to climate change is through the provision of locally produced ecosystem services: the benefits that people get from nature. In cities, these ecosystem services are provided by diverse forms of urban ecological infrastructure (UEI): all parts of a city that include ecological structure and function. While there is a growing body of research touting the multifunctionality of UEI and an increasing number of cities implementing UEI plans, there remain important gaps in understanding how UEI features perform at providing ecosystem services and how the local social-ecological-technological context affects the efficacy of UEI solutions. Inspired by the need for cities to adapt to become more resilient to climate change, this dissertation takes an interdisciplinary approach to understand how diverse UEI features and their ecosystem services are perceived, provided, and prioritized for current and future climate resilience. The second chapter explores how a diverse group of local actors in Valdivia, Chile perceives the city’s urban wetlands and identifies common trade-offs in the perceived importance of different ecosystem services from the wetlands. The third chapter demonstrates species-level differences and trade-offs between common street trees in Phoenix, Arizona in their ability to provide the ecosystem services of both local climate regulation and stormwater regulation. The fourth chapter compares how participatory scenarios from nine cities across the United States and Latin America vary in the degree to which they incorporate UEI and ecosystem services into future visions. The fifth chapter returns focus to Phoenix and illustrates dominant perspectives on the prioritization of ecosystem services for achieving climate resilience and how those priorities change across temporal scales. The dissertation concludes with a synthesis of the previous chapters and suggestions for future urban ecosystem services research. Combined, this dissertation advances understanding of ecosystem services from UEI and highlights the importance of considering trade-offs among UEI features in order help achieve more just, verdant, and resilient urban futures.
ContributorsElser, Stephen Robert (Author) / Grimm, Nancy (Thesis advisor) / Berbés-Blázquez, Marta (Committee member) / Cook, Elizabeth (Committee member) / McPhillips, Lauren (Committee member) / York, Abigail (Committee member) / Arizona State University (Publisher)
Created2022
Description
Terrestrial ecosystems are critical to human welfare and regulating Earth’s life support systems but many gaps in our knowledge remain regarding how terrestrial plant communities respond to changes in climate or human actions. I used field experiments distributed across three dryland ecosystems in North America to evaluate the consequences of changing precipitation and physical disturbance on plant community structure and function. Evidence from experiments and observational work exploring both plant community composition and ecological processes suggest that physical disturbance and precipitation reductions can reduce the diversity and function of these dryland ecosystems. Specifically, I found that aboveground net primary productivity could be reduced in an interactive manner when precipitation reductions and physical disturbance co-occur, and that within sites, this reduction in productivity was greater when growing-season precipitation was low. Further, I found that these dryland plant communities, commonly dominated by highly drought-resistant shrubs and perennial grasses, were not capable of compensating for the absence of these dominant shrubs and perennial grasses when they were removed by disturbance, and that precipitation reductions (as predicted to occur from anthropogenic climate change) exacerbate these gaps. Collectively, the results of the field experiment suggest that current management paradigms of maintaining cover and structure of native perennial plants in dryland systems are well founded and may be especially important as climate variability increases over time. Evaluating how these best management practices take place in the real world is an important extension of fundamental ecological research. To address the research-management gap in the context of dryland ecosystems in the western US, I used a set of environmental management plans and remotely sensed data to investigate how ecosystem services in drylands are accounted for, both as a supply from the land base and as a demand from stakeholders. Focusing on a less-investigated land base in the United States–areas owned and managed by the Department of Defense–I explored how ecosystem services are produced by this unique land management arrangement even if they are not explicitly managed for under current management schemes. My findings support a growing body of evidence that Department of Defense lands represent a valuable conservation opportunity, both for biodiversity and ecosystem services, if management regimes fully integrate the ecosystem services concept.
ContributorsJordan, Samuel (Author) / Grimm, Nancy (Thesis advisor) / Reed, Sasha (Committee member) / Wu, Jianguo (Committee member) / Throop, Heather (Committee member) / Arizona State University (Publisher)
Created2024
Description
Pollen allergies are common in the United States, especially in Arizona. In addition to more people experiencing allergies, the allergies themselves are worse, with people reporting more severe and longer lasting symptoms, after moving to Arizona. Potential reasons behind this include a longer blooming season in the state, a lack of rain to wash out pollen from the atmosphere, and compounding factors of poor air quality. One significant contributor to poor air quality are high ozone levels in urban areas like Phoenix. The goal of this study is to determine if ozone and pollen interact in a way that changes pollen physically or chemically. Ragweed pollen was placed in a chamber and exposed to low, medium, and high levels of ozone for 6-72 hours corresponding to different exposure doses. Exposed and non-exposed pollen was analyzed for physical changes in the pollen grain using scanning electron microscopy (SEM). Chemical changes were investigated using Fourier Transform Infrared Spectroscopy (FT-IR). Finally, exposed and non-exposed pollen was analyzed for changes in lipid profiles using gas chromatography mass spectrometry (GC/MS). SEM analysis found that when ragweed pollen is exposed to high ozone levels (60-100 ppm, > 48 hours), pollen grains become damaged. The same exposure level results in chemical changes in the pollen that are detectable by FT-IR. A higher ozone dose results in worse physical damage and increased changes in the lipid profile. Future research should study a wider ranges of exposure doses and relate the physicochemical changes to differences in immune response.
ContributorsKing, Lily (Author) / Herckes, Pierre (Thesis advisor) / Fraser, Matthew (Committee member) / Levitus, Marcia (Committee member) / Arizona State University (Publisher)
Created2024
Description
Functioning freshwater ecosystems are widely recognized as a planetary boundary for the continued human inhabitation of our planet, but little is known about the tradeoffs at the nexus of food, energy and water. In this dissertation I explored the effects of hydrologic variability in the Lower Mekong Basin (LMB) on rice production and functional structure of fish catches. I then examined the tradeoffs at the intersection of fish and rice harvest as a function of hydrologic variability and modeled production under novel engineered hydrologic scenarios. I modeled rice production using a Multivariate Autoregressive State Space (MARSS) model and mechanistically tested for the effect of saline intrusion. I found rice production to be heterogeneously affected by hydrology; in saline afflicted areas, floods had a positive effect size on production, whereas in non-saline afflicted areas, floods had a negative effect size on production. To address hydrologic filtering of the functional structure of fish catches, I collected thousands of specimens from over 100 LMB species in collaboration with Cambodia’s Inland Fisheries Research and Development institute and the Royal University of Agriculture. LMB fishes comprise a large portion of the 1,200 known species in the basin and have historically provided a substantial amount of animal protein to 60 million people in the region. Using an RLQ, co-inertia analysis, I found four functionally relevant morphological trats that were significantly associated with hydrologic variation—mouth position, maxillary length, relative body depth, and relative head depth. These traits are associated with many of the threated species in the LMB, which make up a large portion of the 1200 known species in the basin and have historically provided a substantial amount of animal protein to 60 million people in the region. To examine the tradeoffs within food systems, I used MARSS maximum likelihood estimation to forecast fish and rice production throughout the LMB under different hydrologic scenarios. I end my dissertation with an opinion piece on NexGen Mekong Scientists, a program I started in 2020 with funding from the United States Department of State.
ContributorsHolway, Joseph Henry (Author) / Sabo, John (Thesis advisor) / Grimm, Nancy (Committee member) / Holtgrieve, Gordon (Committee member) / Winemiller, Kirk (Committee member) / Hanemann, Michael (Committee member) / Arizona State University (Publisher)
Created2024
Description
Microplastics, plastics smaller than 5 mm, are an emerging concern worldwide due to their potential adverse effects on the environment and human health. Microplastics have the potential to biomagnify through the food chain, and are prone to adsorbing organic pollutants and heavy metals. Therefore, there is an urgent need to assess the extent of microplastic contamination in different environments. The occurrence of microplastics in the atmosphere of Tempe, AZ was investigated and results show concentrations as high as 1.1 microplastics/m3. The most abundant identified polymer was polyvinyl chloride. However, chemical characterization is fraught with challenges, with a majority of microplastics remaining chemically unidentified. Laboratory experiments simulating weathering of microplastics revealed that Raman spectra of microplastics change over time due to weathering processes. This work also studied the spatial variation of microplastics in soil in Phoenix and the surrounding areas of the Sonoran Desert, and microplastic abundances ranged from 122 to 1299 microplastics/kg with no clear trends between different locations, and substantial total deposition of microplastics occurring in the same location with resuspension and redistribution of deposited microplastics likely contributing to unclear spatial trends. Temporal variation of soil microplastics from 2005 to 2015 show a systematic increase in the abundance of microplastics. Polyethylene was prominent in all soil samples.
Further, recreational surface waters were investigated as a potential source of microplastics in aquatic environments. The temporal variation of microplastics in the Salt River, AZ over the course of one day depicted an increase of 8 times in microplastic concentration at peak activity time of 16:00 hr compared to 8:00 hr. Concurrently, microplastic concentrations in surface water samples from apartment community swimming pools in Tempe, AZ depicted substantial variability with concentrations as high as 254,574 MPs/m3. Polyester and Polyamide fibers were prevalent in surface water samples, indicating a release from synthetic fabrics. Finally, a method for distinguishing tire wear microplastics from soot in ambient aerosol samples was developed using Programmed Thermal Analysis, that allows for the quantification of Elemental Carbon. The method was successfully applied on urban aerosol samples with results depicting substantial fractions of tire wear in urban atmospheric environments.
ContributorsChandrakanthan, Kanchana (Author) / Herckes, Pierre (Thesis advisor) / Fraser, Matthew (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2024
Description
Spatial and temporal patterns of biodiversity are shaped, in part, by the resources available to biota, the efficiency of resource transfer through the food web, and variation in environmental conditions. Stream and riparian zones are dynamic systems connected through reciprocal resource exchange and shaped by floods, droughts, and long-term patterns in the quantity, timing, and variability of streamflow (flow regime). The interdependent nature of the stream-riparian ecosystem defies the scope of any single discipline, requiring novel approaches to untangle the controls on ecological processes. In this dissertation, I explored multiple mechanisms through which streamflow and energy flow pathways maintain the community and trophic dynamics of desert stream and riparian food webs. I conducted seasonal sampling of Arizona streams on a gradient of flow regime variability to capture fluctuations in aquatic communities and ecosystem production. I found that flow regime shapes fish community structure and the trajectory of community response following short-term flow events by constraining the life history traits of communities, which fluctuate in prevalence following discrete events. Streamflow may additionally constrain the efficiency of energy flow from primary producers to consumers. I estimated annual food web efficiency and found that efficiency decreased with higher temperature and more variable flow regime. Surprisingly, fish production was not related to the rate of aquatic primary production. To understand the origin of resources supporting aquatic and riparian food webs, I studied the contribution of aquatic and terrestrial primary production to consumers in both habitats. I demonstrated that emergent insects “recycled” terrestrial primary production back to the riparian zone, reducing the proportion of aquatic primary production in emergent insect biomass and riparian predator diet. To expand the concept of stream and riparian zones as an integrated ecosystem connected by resource cycling through the food web, I introduced a quantitative framework describing reciprocal interconnections across spatial boundaries and demonstrated strong aquatic-riparian interdependencies along an Arizona river. In this dissertation, I develop a novel perspective on the stream-riparian ecosystem as an intertwined food web, which may be vulnerable to unforeseen impacts of global change if not considered in the context of streamflow and resource dynamics.
ContributorsBaruch, Ethan Max (Author) / Sabo, John (Thesis advisor) / Bateman, Heather (Committee member) / Cease, Arianne (Committee member) / Grimm, Nancy (Committee member) / Arizona State University (Publisher)
Created2021
Assessing the Response of Macroinvertebrate Communities to River Flow Dynamics in the Sonoran Desert
Description
Climate change is causing hydrologic intensification globally by increasing both the frequency and magnitude of floods and droughts. While environmental variation is a key regulator at all levels of ecological organization, such changes to the hydrological cycle that are beyond the normal range of variability can have strong impacts on stream and riparian ecosystems within sensitive landscapes, such as the American Southwest. The main objective of this study was to investigate how anomalous hydrologic variability influences macroinvertebrate communities in desert streams. I studied seasonal changes in aquatic macroinvertebrate abundances in eleven streams that encompass a hydrologic gradient across Arizona’s Sonoran Desert. This analysis was coupled with the quantification and assessment of stochastic hydrology to determine influences of flow regimes and discrete events on invertebrate community composition. I found high community variability within sites, illustrated by seasonal measures of beta diversity and nonmetric multidimensional scaling (NMDS) plots. I observed notable patterns of NMDS data points when invertebrate abundances were summarized by summer versus winter surveys. These results suggest that there is a difference within the communities between summer and winter seasons, irrespective of differences in site hydroclimate. Estimates of beta diversity were the best metric for summarizing and comparing diversity among sites, compared to richness difference and replacement. Seasonal measures of beta diversity either increased, decreased, or stayed constant across the study period, further demonstrating the high variation within and among study sites. Regime shifts, summarized by regime shift frequency (RSF) and mean net annual anomaly (NAA), and anomalous events, summarized by the power of blue noise (Maximum Blue Noise), were the best predictors of macroinvertebrate diversity, and thus should be more widely applied to ecological data. These results suggest that future studies of community composition in freshwater systems should focus on understanding the cause of variation in biodiversity gradients. This study highlights the importance of considering both flow regimes and discrete anomalous events when studying spatial and temporal variation in stream communities.
ContributorsSainz, Ruby (Author) / Sabo, John L (Thesis advisor) / Grimm, Nancy (Committee member) / Stampoulis, Dimitrios (Committee member) / Arizona State University (Publisher)
Created2021