Submarine groundwater discharge of nutrients and copper to an urban subestuary of Chesapeake bay (Elizabeth River)

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 Ra-228/Ra-226 activity ratio. Considering each of these sources, we calculated an SGD flux of 1 x 10(6) m(3) d(-1) (+/-10%), which represented similar to6% of the SGD flux for the entire Chesapeake Bay and similar to5% 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 (similar to3%) 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.