Publication Date

2016

Document Type

Thesis

Committee Members

Silvia Newell, Ph.D. (Advisor); Mark McCarthy, Ph.D. (Committee Member); Chad Hammerschmidt, Ph.D. (Committee Member)

Degree Name

Master of Science (MS)

Abstract

The Lower Great Miami River (LGMR) has recently experienced algal blooms due to excess nitrogen (N) and phosphorus (P). Some Ohio water treatment plants were ordered to reduce the amount of P that they release into the river, but N also can stimulate eutrophication and algal blooms, either alone or in combination with P. In this study, LGMR sediment N transformations and effects of river impoundments on N cycling were compared with external N loads during different flow conditions to determine the extent to which N is removed or recycled within the system. Sediment nutrient fluxes, sediment N sinks and sources (denitrification/anammox and N fixation, respectively), and potential dissimilatory nitrate reduction to ammonium (DNRA) were evaluated. Results suggest that LGMR sediments were a net N sink, with high rates of denitrification during spring and summer. In contrast, LGMR sediments were a source of NH4+ and o-PO43-, which may support algal blooms. LGMR sediments removed between 8 and 33% of N loads via denitrification/anammox, but can also return nutrients to the water column, where they might fuel additional production and eutrophication. River impoundments had inconsistent effects on N cycling along the LGMR during the study period. While LGMR sediments can remove a large percentage of N load, at least 67% of N is exported, lending support to the need for watershed control of N to protect downstream systems.

Page Count

80

Department or Program

Department of Earth and Environmental Sciences

Year Degree Awarded

2016

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