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- Genre: Masters Thesis
Description
Phosphorus (P), an essential element for life, is becoming increasingly scarce, and its global management presents a serious challenge. As urban environments dominate the landscape, we need to elucidate how P cycles in urban ecosystems to better understand how cities contribute to — and provide opportunities to solve — problems of P management. The goal of my research was to increase our understanding of urban P cycling in the context of urban resource management through analysis of existing ecological and socio-economic data supplemented with expert interviews in order to facilitate a transition to sustainable P management. Study objectives were to: I) Quantify and map P stocks and flows in the Phoenix metropolitan area and analyze the drivers of spatial distribution and dynamics of P flows; II) examine changes in P-flow dynamics at the urban agricultural interface (UAI), and the drivers of those changes, between 1978 and 2008; III) compare the UAI's average annual P budget to the global agricultural P budget; and IV) explore opportunities for more sustainable P management in Phoenix. Results showed that Phoenix is a sink for P, and that agriculture played a primary role in the dynamics of P cycling. Internal P dynamics at the UAI shifted over the 30-year study period, with alfalfa replacing cotton as the main locus of agricultural P cycling. Results also suggest that the extent of P recycling in Phoenix is proportionally larger than comparable estimates available at the global scale due to the biophysical characteristics of the region and the proximity of various land uses. Uncertainty remains about the effectiveness of current recycling strategies and about best management strategies for the future because we do not have sufficient data to use as basis for evaluation and decision-making. By working in collaboration with practitioners, researchers can overcome some of these data limitations to develop a deeper understanding of the complexities of P dynamics and the range of options available to sustainably manage P. There is also a need to better connect P management with that of other resources, notably water and other nutrients, in order to sustainably manage cities.
ContributorsMetson, Genevieve (Author) / Childers, Daniel (Thesis advisor) / Aggarwal, Rimjhim (Thesis advisor) / Redman, Charles (Committee member) / Arizona State University (Publisher)
Created2011
Description
Plastics are an emerging issue in aquatic ecosystems due to their slow degradation and ability to fragment into smaller more mobile parts. Concluding this process, plastics <5mm are categorized as Microplastics, MPs. Currently, the majority of MP studies bring attention to marine pollution and the impacts that follow. However, it remains a high priority to understand how MPs move through urban aquatic environments, and the impacts this may have for surrounding urban ecosystems. Little is known about how MPs move through tertiary treated wastewater plants, such as constructed wetlands, and how much, if any, remain trapped in abiotic and biotic material such as soil or plant life, respectively. An analysis of MP distribution using Tres Rios, a tertiary wastewater treatment wetland, as the study site may help to shed light on the source-occurrences of MPs. Microplastics extraction was performed on soil, plant, and water samples that were collected along major access points within the system with emphasis on inflow and outflow. The inflow of the wetland receives between 246-398 MPs/L vs the outflow of 90-199 MPs/L. Tres Rios soil concentrations ranged between 1,017-10,100 per kg and 133-700 MPs per kg in sampled vegetation throughout the wetland. The distribution of soil and vegetation samples differed throughout Tres Rios, as soil sampled exhibited higher quantities towards inflow site and vegetation MP occurrences were increased throughout the middle of the system. Additionally, this study aimed to determine if seasonality impacted the concentration of plastics seen throughout the system. There was no evidence that suggested seasonal variations were occurring in any sample type. Atmospheric deposition fluxes of microplastics were considered as a potential additional influx but even at the measured 1510 MP m-2 day-1 they were small compared to the water influx. Overall, the results suggest that the Tres Rios wetland removed 55% of the microplastics it receives and hence performs a substantial ecosystem service.
ContributorsCisco, Jordan (Author) / Green, Douglas (Thesis advisor) / Herckes, Pierre (Thesis advisor) / Childers, Daniel (Committee member) / Arizona State University (Publisher)
Created2023