Spatiotemporal Variability of Wet Atmospheric Nitrogen Deposition to the Neuse River Estuary, North Carolina

Abstract

Excessive nitrogen (N) loading to N-sensitive waters such as the Neuse River estuary (North Carolina) has been shown to promote changes in microbial and algal community composition and function (harmful algal blooms), hypoxia and anoxia, and fish kills. Previous studies have estimated that wet atmospheric deposition of nitrogen (WAD-N), as deposition of dissolved inorganic nitrogen (DIN: NO3-, NH3/NH4+) and dissolved organic nitrogen, may contribute at least 15% of the total externally supplied or "new" N flux to the coastal waters of North Carolina. In a 3-yr study from June 1996 to June 1999, we calculated the weekly wet deposition of inorganic and organic N at eleven sites on a northwest-southeast transect in the watershed. The annual mean total (wet DIN + wet organics) WAD-N flux for the Neuse River watershed was calculated to be 956 mg N/m2/yr (15026 Mg N/yr). Seasonally, the spring (March-May) and summer (June-August) months contain the highest total weekly N deposition; this pattern appears to be driven by N concentration in precipitation. There is also spatial variability in WAD-N deposition; in general, the upper portion of the watershed receives the lowest annual deposition and the middle portion of the watershed receives the highest deposition. Based on a range of watershed N retention and in-stream riverine processing values, we estimate that this flux contributes approximately 24% of the total "new" N flux to the estuary.

Legacy Nutrient Dynamics at the Watershed Scale: Principles, Modeling, and Implications

“…Several tracer studies with isotopically labeled fertilizer N suggested that 40%-60% of the applied fertilizer N is incorporated into the soil organic matter, which result in the formation of organic N pool (Jenkinson et al, 2004;Sebilo et al, 2013). Some urban and suburban areas also retained 25%-95% of N inputs in residential soils (Groffman et al, 2004;Whitall and Paerl, 2001). Comparing soils in forest and agricultural land, agricultural soil total P concentrations can range from 2-to 10-fold greater than that in forest, implying a legacy of historical P fertilization (Nash and Hannah, 2011;Vitousek et al, 2009).…”

Molecular insights into a dinoflagellate bloom

“…Strong vertical stratification is especially common in summer when the mild, cross-channel, southwest winds prevail (Luettich et al, 2000). Over the past several decades, increasing agricultural and industrial activities along with coastal urbanization have accelerated nutrient inputs to the NRE (Paerl and Whitall, 1999;Whitall and Paerl, 2001). Combined with a long residence time and strong seasonal stratification, the NRE suffers from eutrophication (Paerl, 2006).…”

Impact of N-Saturated Upland Forests on Downstream N Pollution in the Tatara River Basin, Japan

“…Second, elevated N deposition rates increases the mineralization/nitrification in forested areas, leading to significant N leaching from those forested areas (Aber and others 1998). Finally, elevated N deposition rates can increase the exports of atmospherically derived N from urban/agricultural areas because atmospheric N deposition is also a source of N from urban/agricultural areas (Jaworski and others 1997; Whitall and Paerl 2001;Schaefer and others 2009).…”

“…Agricultural and urban activities are major non-point sources of N and P pollution to aquatic ecosystems (Novotny and Olem 1994;Sharpley and others 1994;Carpenter and others 1998). Atmospheric N deposition is an additional source of N (Jaworski and others 1997;Whitall and Paerl 2001;Schaefer and others 2009) which can be an important part of the systems nitrogen budget. Determining the relative importance of different non-point sources of N and P pollution is a suitable strategy for the efficient reduction of non-point sources of N and P pollution.…”