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The discharge of nitrate‐contaminated groundwater from developed shoreline to marsh‐fringed estuary
Author(s) -
Portnoy J. W.,
Nowicki B. L.,
Roman C. T.,
Urish D. W.
Publication year - 1998
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/98wr02167
Subject(s) - estuary , groundwater , groundwater discharge , hydrology (agriculture) , environmental science , aquifer , marsh , nitrate , salt marsh , shore , salinity , surficial aquifer , groundwater flow , wetland , geology , oceanography , groundwater recharge , ecology , geotechnical engineering , biology
As residential development, on‐site wastewater disposal, and groundwater contamination increase in the coastal zone, assessment of nutrient removal by soil and sedimentary processes becomes increasingly important. Nitrogen removal efficiency depends largely on the specific flow paths taken by groundwater as it discharges into nitrogen‐limited estuarine waters. Shoreline salinity surveys, hydraulic studies, and thermal infrared imagery indicated that groundwater discharge into the Nauset Marsh estuary (Eastham, Massachusetts) occurred in high‐velocity seeps immediately seaward of the upland‐fringing salt marsh. Discharge was highly variable spatially and occurred through permeable, sandy sediments during low tide. Seepage chamber monitoring showed that dissolved inorganic nitrogen (principally nitrate) traversed nearly conservatively from the aquifer through shallow estuarine sediments to coastal waters at flux rates of 1–3 mmol m −2 h −1 . A significant relationship between pore water NO 3 ‐N concentrations and NO 3 ‐N flux rates may provide a rapid method of estimating nitrogen loading from groundwater to the water column.