Date of Completion

8-23-2016

Embargo Period

8-23-2016

Advisors

John Clausen, Timothy Vadas

Field of Study

Natural Resources

Degree

Master of Science

Open Access

Open Access

Abstract

Nitrogen (N) is a critical element for aquatic ecosystem function that can degrade water quality and cause eutrophication if in excess of natural levels. Anthropogenic nonpoint sources contribute more than 90% of total N added to major watersheds in the U.S, in excess of natural levels, and they are increasing with land development. Storms mobilize N from anthropogenic sources and generate periods of high N export to aquatic ecosystems. In this thesis, I explore how a gradient of watershed development affects the volume-weighted load, composition, and timing of N exported from first-order streams in New England during storms. I find that volume-weighted loads of total N and total organic N increase with increasing watershed development, and that volume- weighted loads of ammonium and nitrate during storms increase with watershed impervious cover. I also find that, for all levels of watershed development, total organic N composes more than 60% of total N exported during storms. Finally, I find that, for all levels of watershed development, N export increases with increasing stream discharge volume during storms. There are significant seasonal differences in the relationships between watershed development and N export, perhaps affected by factors such as watershed septic system prevalence, snowmelt contributions, and summer drought. These factors should be taken into account when estimating parameters of N export across watersheds of varying degrees of development.

Major Advisor

Ashley M Helton

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