Submarine groundwater discharge of nutrients and copper to an urban subestuary of Chesapeake Bay (Elizabeth River)
Limnol. Oceanogr., 49(2), 2004, 376-385 | DOI: 10.4319/lo.2004.49.2.0376
ABSTRACT: We investigated the role submarine groundwater discharge (SGD) plays in the delivery of nutrients and copper to the Elizabeth River (Virginia) estuary, a major subestuary of lower Chesapeake Bay. Using an approach based on radium isotopes, we concluded that two distinct sources of groundwater were equally impacting the estuary: a surface (marsh) aquifer and deep aquifer source each with a unique 228Ra/226Ra activity ratio. Considering each of these sources, we calculated an SGD flux of 1 x 106 m3 d-1 (±10%), which represented ~6% of the SGD flux for the entire Chesapeake Bay and ~5% of the James River, a major source of freshwater to lower Chesapeake Bay. SGD-derived dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) fluxes averaged 4.5 (±4.6) and 0.16 (±0.17) mmol m-2 d-1, respectively, and compared well with area-normalized fluxes to Chesapeake Bay. In contrast, SGD-derived Cu input of 730 (±390) kg yr-1 was a relatively small source of Cu (~3%) to the Elizabeth estuary given that surface water inputs, such as antifouling paints associated with naval operations, are a major component of the Cu budget for this system. These findings were in general agreement with prior studies of SGD for this region.