High super(2) super(2) super(6)Ra and super(2) super(2) super(8)Ra activities in Nueces Bay, Texas indicate large submarine saline discharges

We have investigated submarine groundwater discharge to Nueces Bay (Texas) using naturally occurring Ra isotopes. Dissolved Ra activities in Nueces Bay are among the highest observed in coastal estuaries; as great as 2600 dpm m super(-) super(3) for super(2) super(2) super(8)Ra and 1000 dpm m super(-) super(3) for super(2) super(2) super(6)Ra. Using a combination of salt and Ra mass balances, we demonstrate that river discharge and bay bottom sediments cannot supply the Ra needed to balance tidal export. In the case of super(2) super(2) super(6)Ra there is an additional source of 218x10 super(6)+ /-105% dpm day super(-) super(1) which is 9 times the maximum supply from bay bottom sediments and 50 times the Ra supplied by the Nueces River. A groundwater flux of 310,000 m super(3) day super(-) super(1) is required to supply the needed super(2) super(2) super(6)Ra, based on the measured maximum Ra activity of local groundwater. Though as little as 10% of this flux may be advecting terrestrial groundwater this would still represent 160% of the Nueces River discharge. This makes it unlikely that groundwater discharge alone is supplying all of the additional super(2) super(2) super(6)Ra. Oil-field brine could potentially account for the remainder. Leakage of 6290 m super(3) day super(-) super(1) of oil-field brine from the submerged petroleum wells and pipelines within the bay could supply all of the needed super(2) super(2) super(6)Ra. Such large fluxes of brackish groundwater and oil-field brine could significantly affect bay nitrogen budgets, salinities, and dissolved oxygen concentrations and should be considered when determining the freshwater inflow requirements for Nueces Bay and similar estuaries.