Dissertation/Thesis Abstract

Resolving Spatial and Temporal Variability in Dissolved Organic Matter Characteristics within Combined Agricultural and Stormwater Conveyances
by Mihalevich, Bryce A., M.S., Utah State University, 2017, 143; 10602727
Abstract (Summary)

Dissolved organic matter (DOM) plays an important role in the cycling of nutrients within aquatic ecosystems; however, excess amounts can have detrimental effects on aquatic organisms. Stormwater runoff events in urban areas can contribute high concentrations of DOM to receiving waters, posing potential impairment to the aquatic ecosystems of urban streams and downstream water bodies. Characterizing compositional changes in DOM due to storm events is important for understanding potential downstream water quality effects and has been well studied in forested, agricultural, and urban landscapes. However, in situ sensors have not been widely applied to monitor stormwater contributions in urbanized areas, leaving the spatial and temporal characteristics within these systems poorly understood. Using laboratory measurements of dissolved organic carbon (DOC) concentration and excitation emission matrix spectroscopy (EEMS), fluorescent DOM (FDOM) sensors, and a mobile water quality sensing platform, this study investigated changes in DOM quantity and sources within the Northwest Field Canal (NWFC), an urban water conveyance located in Logan, Utah, USA that receives runoff during storm events. Under baseflow conditions, FDOM decreased and exhibited dampened diurnal variability as the summer irrigation season progressed, while FDOM values at the upstream and downstream monitoring sites were relatively similar. During storm events, FDOM concentrations were rapidly elevated to values orders of magnitude greater than in baseflow measurements, and DOC concentrations were more than 3 times greater at the downstream site than those at the upstream site due to high contributions of DOC being discharged from outfalls. Compositional changes in DOM indicated a shift during storm events from a more autochthonous, less degraded DOM in baseflow to more decomposed and terrestrially derived DOM in stormwater flows. These observations were consistent with results from custom, in situ fluorometers, which also revealed a seasonal transition to a more microbially derived composition in baseflow conditions as the summer season progressed. Deployment of a mobile sensing platform during stormflow conditions confirmed that contributions of DOM were associated with the locations of outfalls discharging runoff into the canal and revealed spatial changes in DOM composition and concentration along canal transects.

Indexing (document details)
Advisor: Horsburgh, Jeffery
Commitee: Baker, Michelle, Stevens, David
School: Utah State University
Department: Civil and Environmental
School Location: United States -- Utah
Source: MAI 56/05M(E), Masters Abstracts International
Subjects: Engineering, Civil engineering, Water Resource Management, Environmental engineering
Keywords: Dissolved organic matter, Fluorescence, In situ, Stormwater, Urban, Water quality
Publication Number: 10602727
ISBN: 9780355086621
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