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- All Subjects: Nitrogen
- Creators: Blair, Antonio
DescriptionThis project focuses on how best management practices impact the phosphorus and nitrogen concentrations in water bodies all across the United States. Both chemical and biological indicators were analyzed.
ContributorsBaker, Kayla (Author) / Blair, Antonio (Co-author) / Kumar, Saurav (Thesis director) / Johnson, Abbey (Committee member) / Weiss, Josh (Committee member) / Barrett, The Honors College (Contributor) / School of Sustainable Engineering & Built Envirnmt (Contributor)
Created2024-05
Description
Best Management Practices (BMPs) are often designed to restore the water quality of impaired waterbodies. They are expensive to install and maintain and often have limited post-installation analysis. There is a gap in our knowledge of the long-term real-world efficiency of such systems as their dynamics are complex and poorly understood, and we have very limited data about these systems. We looked at water quality changes pre- and post-BMP implementation from sites around the US to better understand the impacts of BMPs on the nitrogen (N) and phosphorus (P) concentrations in the waterbodies. Water quality data was obtained from 72 waterbodies across the United States using the National Water Quality Monitoring Council’s Water Quality Portal. This data was analyzed for trends using the Kaplan-Meier method, exceedance probability, and lag time analysis. Out of the seventy-two (72) watershed locations, twenty-two (22) did not have enough data for analysis. Of these fifty (50) remaining watersheds locations one hundred eighty-four (184) monitoring sites were analyzed. Only sixty-nine (69) of these monitoring sites were found to have enough data for analysis. Forty-eight (48) sites saw improvement in nutrient levels, where overall post-implementation exceedance probability for critical thresholds (defined as 1 mg/l for N and 0.1 mg/l for P) decreased. Twenty-one (21) sites did not see improvement, where post-implementation exceedance probabilities did not show any reduction; in some cases, it showed an increase. Even among the efficient sites, where improvement was found, significant variation was observed in changes in exceedance probability with time, with many sites not demonstrating an expected uniform decreasing trend. It was also found that 56 out of the 72 water bodies had some biological indicator present, these included dissolved oxygen concentrations, benthic macroinvertebrate populations, fish communities/aquatic life, bacteria, and index scores. However, data gaps were detrimental to conclusively assessing BMPs with biological indicators. It was determined that sparse biological indicators data were not indicative of BMP success. These observations highlight the importance of designing a monitoring strategy that can capture these unexpected trends and allow a better understanding of BMPs. Along with better monitoring strategies, consistent and frequent monitoring is needed. Therefore, the effectiveness of best management practices was inconclusive due to a lack of available data on many sites.
ContributorsBlair, Antonio (Author) / Baker, Kayla (Co-author) / Kumar, Saurav (Thesis director) / Weiss, Josh (Committee member) / Johnson, Abbey (Committee member) / Barrett, The Honors College (Contributor) / Civil, Environmental and Sustainable Eng Program (Contributor)
Created2024-05
Description
Cities can be sources of nitrate to downstream ecosystems resulting in eutrophication, harmful algal blooms, and hypoxia that can have negative impacts on economies and human health. One potential solution to this problem is to increase nitrate removal in cities by providing locations where denitrification¬— a microbial process in which nitrate is reduced to N2 gas permanently removing nitrate from systems— can occur. Accidental urban wetlands– wetlands that results from human activities, but are not designed or managed for any specific outcome¬– are one such feature in the urban landscape that could help mitigate nitrate pollution through denitrification.
The overarching question of this dissertation is: how do hydrology, soil conditions, and plant patches affect patterns of denitrification in accidental urban wetlands? To answer this question, I took a three-pronged approach using a combination of field and greenhouse studies. First, I examined drivers of broad patterns of denitrification in accidental urban wetlands. Second, I used a field study to test if plant traits influence denitrification indirectly by modifying soil resources. Finally, I examined how species richness and interactions between species influence nitrate retention and patterns of denitrification using both a field study and greenhouse experiment.
Hydroperiod of accidental urban wetlands mediated patterns of denitrification in response to monsoon floods and plant patches. Specifically, ephemeral wetlands had patterns of denitrification that were largely unexplained by monsoon floods or plant patches, which are common drivers of patterns of denitrification in non-urban wetlands. Several plant traits including belowground biomass, above- and belowground tissue chemistry and rooting depth influenced denitrification indirectly by changing soil organic matter or soil nitrate. However, several other plant traits also had significant direct relationships with denitrification, (i.e. not through the hypothesized indirect relationships through soil organic matter or soil nitrate). This means these plant traits were affecting another aspect of soil conditions not included in the analysis, highlighting the need to improve our understanding of how plant traits influence denitrification. Finally, increasing species richness did not increase nitrate retention or denitrification, but rather individual species had the greatest effects on nitrate retention and denitrification.
The overarching question of this dissertation is: how do hydrology, soil conditions, and plant patches affect patterns of denitrification in accidental urban wetlands? To answer this question, I took a three-pronged approach using a combination of field and greenhouse studies. First, I examined drivers of broad patterns of denitrification in accidental urban wetlands. Second, I used a field study to test if plant traits influence denitrification indirectly by modifying soil resources. Finally, I examined how species richness and interactions between species influence nitrate retention and patterns of denitrification using both a field study and greenhouse experiment.
Hydroperiod of accidental urban wetlands mediated patterns of denitrification in response to monsoon floods and plant patches. Specifically, ephemeral wetlands had patterns of denitrification that were largely unexplained by monsoon floods or plant patches, which are common drivers of patterns of denitrification in non-urban wetlands. Several plant traits including belowground biomass, above- and belowground tissue chemistry and rooting depth influenced denitrification indirectly by changing soil organic matter or soil nitrate. However, several other plant traits also had significant direct relationships with denitrification, (i.e. not through the hypothesized indirect relationships through soil organic matter or soil nitrate). This means these plant traits were affecting another aspect of soil conditions not included in the analysis, highlighting the need to improve our understanding of how plant traits influence denitrification. Finally, increasing species richness did not increase nitrate retention or denitrification, but rather individual species had the greatest effects on nitrate retention and denitrification.
ContributorsSuchy, Amanda Klara (Author) / Childers, Daniel L. (Thesis advisor) / Stromberg, Juliet C. (Thesis advisor) / Grimm, Nancy (Committee member) / Hall, Sharon (Committee member) / Sabo, John (Committee member) / Arizona State University (Publisher)
Created2016