Changes in the Flux of Nitrate during Storms in an Eastern Shore, Virginia Stream

Ren, Jennifer E. , Department of Environmental Sciences, University of Virginia
Mills, Aaron, AS-Environmental Sciences, University of Virginia
Herman, Janet, AS-Environmental Sciences, University of Virginia

During a storm event, transient changes in the hydraulic gradient can result in very different discharge rates, residence times of bank storage, and ultimately NO3- concentrations in the stream. During varying storm events, water samples were collected with an automatic storm sampler and hydraulic gradient fluctuations between the stream and stream bank were measured with pressure transducers. In the nine storms sampled, NO3- concentrations generally decreased during the passing of a flood wave. Furthermore, flood wave height and duration together controlled NO3- flux during the storm as there was a strong positive relationship between the change in NO3- flux when compared with base flow and the total storm discharge when compared with base flow. Small flood waves with small discharges resulted in a decrease in NO3- flux during the storm. Slower discharges created longer residence times for more NO3- removal. Large flood waves ultimately resulted in an increase in NO3- flux, although large flood waves with different flood durations had vastly different increases in NO3- flux. Short durations created high rainfall intensities which reduced head gradients, discharge and NO3- flux. Conversely, long durations created low rainfall intensities which increased head gradients, discharge and NO3- flux. These results provide better insight into NO3- transport into streams and will inform better models to help predict future watershed NO3- budgets.

BS (Bachelor of Science)
nitrate flux, Virginia’s Eastern Shore, storms
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