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Quantifying Whole-Reach Denitrification in Arizona Streams

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Elevated nitrate (NO3-) concentration in streams and rivers has contributed to environmental problems such as downstream eutrophication and loss of biodiversity. Sycamore Creek in Arizona is nitrogen limited, but previous studies have demonstrated high potential for denitrification, a microbial process

Elevated nitrate (NO3-) concentration in streams and rivers has contributed to environmental problems such as downstream eutrophication and loss of biodiversity. Sycamore Creek in Arizona is nitrogen limited, but previous studies have demonstrated high potential for denitrification, a microbial process in which biologically active NO3- is reduced to relatively inert dinitrogen (N2) gas. Oak Creek is similarly nitrogen limited, but NO3- concentration in reaches surrounded by agriculture can be double that of other reaches. We employed a denitrification enzyme assay (DEA) to compare potential denitrification rate between differing land uses in Oak Creek and measured whole system N2 flux using a membrane inlet mass spectrometer to compare differences in actual denitrification rates at Sycamore and Oak Creek. We anticipated that NO3- would be an important limiting factor for denitrifiers; consequentially, agricultural land use reaches within Oak Creek would have the highest potential denitrification rate. We expected in situ denitrification rate to be higher in Oak Creek than Sycamore Creek due to elevated NO3- concentration, higher discharge, and larger streambed surface area. DEA results are forthcoming, but analysis of potassium chloride (KCl) extraction data showed that there were no significant differences between sites in sediment extractable NO3- on either a dry mass or organic mass basis. Whole-reach denitrification rate was inconclusive in Oak Creek, and though a significant positive flux in N2 from upstream to downstream was measured in Sycamore Creek, the denitrification rate was not significantly different from 0 after accounting for reaeration, suggesting that denitrification does not account for a significant portion of the NO3- uptake in Sycamore Creek. Future work is needed to address the specific factors limiting denitrification in this system.

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2018-05

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The Effects of Nitrogen Fertilization of Wheatgrass on the South American Locust (Schistocerca cancellata)

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Locusts are a major crop pest in many parts of the world and different species are endemic to different countries. In Latin America, the South American Locust (Schistocerca cancellata) is the predominant species found mostly in Argentina, Chile, Bolivia, Paraguay,

Locusts are a major crop pest in many parts of the world and different species are endemic to different countries. In Latin America, the South American Locust (Schistocerca cancellata) is the predominant species found mostly in Argentina, Chile, Bolivia, Paraguay, and southern Brazil with Argentina being the most affected. Several control and management practices, including biological control, have been implemented in these countries in the past to control the locusts and reduce their impact on crop and vegetation, however, effective long-term control and management practices will require a detail understanding of how the predominant locust species in this region responds to resource variation. Research has shown that there is strong evidence that locusts, and many other organisms, will actively balance dietary macronutrients (protein, carbohydrates, and lipids) to optimize growth, survival, and/or reproduction. A study by Cease et. al, 2017, on the dietary preferences of the Mongolian locust (Oedaleus asiaticus) showed that it prefers diets that are high in carbohydrates over diets that are high in protein, in this case locusts self-selected a 1:2 ratio of protein:carbohydrate. This and many other studies provide vital insight into the nutritional and feeding preferences of these locust species but the effects that this difference in protein: carbohydrate preferences has on growth, egg production, flight potential, and survival has yet to be fully explored, hence, this study investigates the effects that nitrogen fertilization of wheatgrass will have on the growth, egg production, survival, and flight muscle mass of the South American locust in a controlled, laboratory environment.

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2018-05

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Aquatic Primary Productivity and Ecosystem Metabolism: Tres Rios Constructed Treatment Wetlands

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Freshwater ecosystems are increasingly threatened by anthropogenic eutrophication (Kolzau et al., 2014) and require mitigation efforts to prevent oxygen depletion and subsequent biodiversity loss. Tres Rios Constructed Treatment Wetland (CTW) relies on wetland ecosystem functioning to reduce nutrient concentrations in

Freshwater ecosystems are increasingly threatened by anthropogenic eutrophication (Kolzau et al., 2014) and require mitigation efforts to prevent oxygen depletion and subsequent biodiversity loss. Tres Rios Constructed Treatment Wetland (CTW) relies on wetland ecosystem functioning to reduce nutrient concentrations in order to meet regulatory guidelines. I investigated the impact of solar irradiance, temperature, and nutrient availability on aquatic net primary productivity, ecosystem respiration, and nutrient cycling using statistical analysis and quantitative modeling informed by field data generated by ASU’s Wetland Ecosystem Ecology Lab (WEEL) in partnership with the City of Phoenix Water Services Department. I found that the extent of daily solar insolation controls Aquatic Net Primary Productivity (ANPP) rates and the seasonal aquatic nutrient processing capacity of Tres Rios, resulting in the following approximate relationship: ANPP = 0.001344(W/m²) - 0.32634 (r² = 0.259; p = 0.005).

This formula was used to estimate the nutrient uptake performance of aquatic primary producers from sampling observations; ANPP accounted for 16.26 metric tons of system wide N uptake, while aquatic ER contributed 6.07 metric tons N of nighttime remineralization and 5.7 metric tons of N throughout the water column during the day. The estimated yearly net aquatic N flux is 4.49 metric tons uptake, compared to about 12 metric tons yearly N uptake by the vegetated marsh (Treese, 2019). However, not accounting for animal respiration results in an underestimation of system-wide N remineralization, and not accounting for soil processes results in an underestimation of N uptake.

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2020-05

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Analysis of Nitrogen Uptake in a Duckponics System

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Duckponics is an unconventional form of aquaponics that has recently been implemented by a small community in Washington State as an experiment in sustainable methods of food production. The community created the Duckponics system to test the possibility of using

Duckponics is an unconventional form of aquaponics that has recently been implemented by a small community in Washington State as an experiment in sustainable methods of food production. The community created the Duckponics system to test the possibility of using the waste of ducks present on the farm to fertilize crop plants. This research paper examines aspects of the nitrogen cycle within this system to determine the efficacy of nitrogen removal by plants and microbes. More specifically, the research examines (1) the microbial activity occurring in selected beds of the system, (2) the ability of hydroponic grow beds to retain inorganic nitrogen, and (3) how periodic flushing of the system affects nitrogen retention. Water data was collected in all system tanks using aquarium test strips, but water samples were collected for flow injection analysis in (1) one of the grow beds, (2) the duck pond, and (3) a control bed with no plants but filled with gravel and inoculated with the same bacteria from the grow bed. Samples were then analyzed for ammonia (NH4+-N) and combined nitrite and nitrate (NOx-N) concentrations. The results show that the treatment type (control, duck pond, or grow bed) was a significant (p<0.05) predictor of NH4+-N, NOx-N, and total inorganic nitrogen (TIN) in the porewater of the treatment beds. The grow bed was found to have 100% removal of TIN, whereas the control had 0% TIN removal (195% increase). Timing of the sample in relation to the flushing events was a moderately significant predictor of TIN, NH4+-N and NOx-N in the duck pond (p = 0.07 for TIN, p = 0.12 for NH4+-N, p = 0.11 for NOx-N), with an overall decrease in TIN after flood pulses. NH4+-N concentrations at the inlet and outlet were found to be significantly different in the grow bed (p=0.037), but not the control, and moderately significantly different (p<0.15) for NOx-N and TIN in the grow bed (p=0.072 for NOx-N, p=0.075 for TIN), but significant for the control (p=0.043). These findings show evidence of nitrification in the grow bed and control, plant presence significantly contributing to nitrogen removal in the grow bed, and some hydrologic flushing of NOx-N out of the duck pond during pump cycles.

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2016-05

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Community composition and nitrogen retention in an aridland wastewater treatment wetland

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City managers and policy makers are increasing looking to environmental systems to provide beneficial services for urban systems. Constructed wetland systems (CWS), highly managed and designed wetland ecosystems, are being utilized to remove pollution, particularly excess nitrogen (N), from treated

City managers and policy makers are increasing looking to environmental systems to provide beneficial services for urban systems. Constructed wetland systems (CWS), highly managed and designed wetland ecosystems, are being utilized to remove pollution, particularly excess nitrogen (N), from treated wastewater. Various wetland process remove N from effluent, such as denitrification, direct plant uptake, and soil accumulation. Emergent macrophytes provide direct uptake of N and improve conditions for microbially-mediated N processing. The role of different macrophytes species, however, is less understood and has primarily been examined in mesocosm and microcosm experiments and in mesic environments. I examined the effects of community composition on N removal and processing at the whole ecosystem scale in an aridland, constructed wetland (42 ha) through: 1) quantifying above- and belowground biomass and community composition from July 2011 \u2014 November 2012 using a non-destructive allometric technique, and; 2) quantifying macrophyte N content and direct macrophyte N uptake over the 2012 growing season. Average peak biomass in July 2011 & 2012 was 2,930 g dw/m2 and 2,340 g dw/m2, respectively. Typha spp. (Typha domingensis and Typha latifolia) comprised the majority (approximately 2/3) of live aboveground biomass throughout the sampling period. No statistically significant differences were observed in macrophyte N content among the six species present, with an overall average of 1.68% N in aboveground tissues and 1.29% N in belowground tissues. Per unit area of wetland, Typha spp. retained the most N (22 g/m2); total N retained by all species was 34 g/m2. System-wide direct plant N uptake was markedly lower than N input to the system and thus represented a small portion of system N processing. Soil accumulation of N also played a minor role, leaving denitrification as the likely process responsible for the majority of system N processing. Based on a literature review, macrophyte species composition likely influences denitrification through oxygen diffusion into soils and through the quality and quantity of carbon in leaf litter. While this study and the literature indicates Typha spp. may be the best species to promote wetland N processing, other considerations (e.g., bird habitat) and conditions (e.g., type of wastewater being treated) likely make mixed stands of macrophytes preferable in many applications. Additionally, this study demonstrated the importance of urban wetlands as scientific laboratories for scientists of all ages and as excellent stepping-off points for experiments of science-policy discourse.

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2013-05

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An Environmental and Economic Analysis of The Near Future of Lithium Ion Batteries

Description

Lithium ion batteries are quintessential components of modern life. They are used to power smart devices — phones, tablets, laptops, and are rapidly becoming major elements in the automotive industry. Demand projections for lithium are skyrocketing with production struggling to

Lithium ion batteries are quintessential components of modern life. They are used to power smart devices — phones, tablets, laptops, and are rapidly becoming major elements in the automotive industry. Demand projections for lithium are skyrocketing with production struggling to keep up pace. This drive is due mostly to the rapid adoption of electric vehicles; sales of electric vehicles in 2020 are more than double what they were only a year prior. With such staggering growth it is important to understand how lithium is sourced and what that means for the environment. Will production even be capable of meeting the demand as more industries make use of this valuable element? How will the environmental impact of lithium affect growth? This thesis attempts to answer these questions as the world looks to a decade of rapid growth for lithium ion batteries.

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2021-05

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Documenting enhanced nitrogen removal in an aridland Constructed Treatment Wetland

Description

The rise in urban populations is encouraging cities to pursue sustainable water treatment services implementing constructed treatment wetlands (CTW). This is especially important in arid climates where water resources are scarce; however, research regarding aridland CTWs is limited. The Tres

The rise in urban populations is encouraging cities to pursue sustainable water treatment services implementing constructed treatment wetlands (CTW). This is especially important in arid climates where water resources are scarce; however, research regarding aridland CTWs is limited. The Tres Rios CTW in Phoenix, Arizona, USA, presents the tradeoff between greater water loss and enhanced nitrogen (N) removal. Previous research has suggested that water loss due to transpiration is replaced by a phenomenon termed the Biological Tide. This trend has been documented since 2011 by combining transpiration values with a nitrogen budget. Calculations were made at both the marsh and whole-system scale. The purpose of this paper is to demonstrate how the Biological Tide enhances N uptake throughout the CTW. Results indicate that about half of the nitrogen taken up by the vegetated marsh is associated with new water entering the marsh via the Biological Tide with even higher values during warmer months. Furthermore, it is this phenomenon that enhances N uptake throughout the year, on average, by 25.9% for nitrite, 9.54% for nitrate, and 4.84% for ammonium at the whole-system scale and 95.5%, 147%, and 118% within the marsh. This paper demonstrates the Biological Tide’s significant impact on enhanced N removal in an aridland CTW.

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2019-05

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Lithium in EV Supply Chains: Charting a Path for Lithium Into the Future

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The project goal is aimed to research the most pressing issues facing the lithium supply chain today. It then is tasked with charting a path into the future through strategic recommendations that will help reduce risk, and make a greener, cleaner, and more ethical supply chain.

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2022-05