Nitrogen release from surface sand of a high energy beach along the southeastern coast of North Carolina,USA |
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Authors: | Jr" target="_blank">G Brooks AveryJr Robert J Kieber Kelly J Taylor |
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Institution: | (1) Department of Chemistry and Biochemistry, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403-5932, USA |
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Abstract: | This study examined changes in dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) in coastal seawater
after exposure to sand along a high energy beach face over an annual cycle between April 2004 and July 2005. Dissolved organic
nitrogen, NO3
−, and NH4
+ were released from sand to seawater in laboratory incubation experiments clearly demonstrating that they are a potential
source of N to underlying groundwater or coastal seawater. DON increases in seawater, after exposure to surface sands in laboratory
experiments, were positively correlated with in situ water column DON concentrations measured at the same time as sand collection.
Increase in NO3
− and NH4
+ were not correlated with their in situ concentrations. This suggests that DON released from beach sands is relatively more
recalcitrant while NO3
− and NH4
+ are utilized rapidly in the coastal ocean. The release of N was seasonal with carbon to nitrogen ratios indicating that
recent primary productivity was responsible for the largest fluxes in summer while more degraded humic material contributed
to lower fluxes in winter. Fluxes of total dissolved nitrogen (DON and DIN) from surface sand (2.1 × 10−4 mol m−2 h−1) were similar to that of groundwater and more than an order of magnitude larger than rain deposition indicating the potential
importance of surface sand derived nitrogen to the coastal zone with a corresponding impact on primary productivity. |
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Keywords: | Sandy beach Dissolved organic nitrogen Dissolved inorganic nitrogen Nitrate Ammonium |
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