An Evaluation of Nitrogen Concentrations in the Neuse River Basin

Abstract

Norton, April. Master of Environmental Assessment. An Evaluation of Nitrogen Concentrations in the Neuse River Basin Excessive nutrient loading has been a water quality concern in the Neuse River Basin since before the 1990’s. Efforts to minimize water quality impairment were accelerated in the mid-1990’s, resulting in the implementation of the Neuse River nitrogen (N) reduction strategy, mandated by the Environmental Management Commission (EMC). The reduction strategy requires a 30% N reduction in the average annual load to the Neuse River Estuary from point and nonpoint sources, for the period 1991 – 1995. This study evaluates the mean annual load of N in the Neuse River and tributaries of the Neuse River, comparing the 1991 – 1995 study period to the 2007 – 2015 study period. The data used in this study was provided by the North Carolina Division of Water Resources, Basin Planning Section. Twenty-three sites were evaluated in this study. For consistency, monitoring sites for which data were not available for all study years (1991 – 1995 and 2007 – 2015) were excluded from the analysis. Site specific calculations of means and standard errors of the means were conducted using Microsoft EXCEL. Two overall analyses were conducted; one showing the trends over time across all monitoring sites and a second showing the N concentrations at individual monitoring sites across all years in each study period. This study shows that nitrate-nitrite (NOx) concentrations decreased, ammonia (NH3) concentrations remained relatively constant, and total Kjeldahl N (TKN) increased. However, total nitrogen (TN) concentrations decreased approximately 15 % in the Neuse River during the 2007 – 2015 study period and TN in tributaries of the Neuse River decreased 42%. While the mandatory 30% N reduction has not been met at the Fort Barnwell monitoring site (considered the mouth of the river and used as the baseline), there has been a 23% decrease which shows that significant progress has been made.