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Nitrogen Fate in Drainage Ditches of the Coastal Plain after Dredging
Author(s) -
Shigaki Francirose,
Schmidt John P.,
Kleinman Peter J. A.,
Sharpley Andrew N.,
Allen Arthur L.
Publication year - 2009
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2008.0268
Subject(s) - dredging , drainage , environmental science , coastal plain , hydrology (agriculture) , nitrogen , oceanography , geology , ecology , geotechnical engineering , biology , physics , quantum mechanics
Drainage ditches are a key conduit of nitrogen (N) from agricultural fields to surface water. The effect of ditch dredging, a common practice to improve drainage, on the fate of N in ditch effluent is not well understood. This study evaluated the effect of dredging on N transport in drainage ditches of the Delmarva Peninsula. Sediments from two ditches draining a single field were collected (0–5 cm) to represent conditions before and after dredging. Sediments were packed in 10‐m‐long recirculating flumes and subjected to a three‐phase experiment to assess the sediment's role as a sink or source of ammonium (NH 4 ) and nitrate (NO 3 ). Under conditions of low initial NH 4 –N and NO 3 –N concentrations in flume water, sediment from the undredged ditch released 113 times more NO 3 –N to water than did sediment from the dredged ditch. When flume water was spiked with NH 4 –N and NO 3 –N to simulate increases in N concentrations from drainage and runoff from adjacent fields, NO 3 –N in flume water increased during 48 h compared with the initial spiked concentration, while NH 4 –N decreased. These simultaneous changes were attributed to nitrification, with 23% more NO 3 –N observed in flume water with undredged ditch sediment compared with dredged ditch sediment. Replacing the N‐spiked water with deionized water resulted in two times more NO 3 –N released from the undredged ditch sediment than the dredged ditch sediment. These results suggest that ditch sediments could represent significant stores of N and that dredging could greatly affect the ditch sediment's ability to temporarily assimilate N input from field drainage.