Salt marsh submarine groundwater discharge as traced by radium isotopes Academic Article uri icon

abstract

  • Submarine groundwater discharge (SGD) generally occurs through permeable sediments where the hydraulic head of an aquifer is above sea level, and often includes a recirculated seawater component. In order to determine SGD to the Great Sippewissett Marsh, West Falmouth, MA, we measured the activities of four radium isotopes ( super(226)Ra, super(228)Ra, super(223)Ra, super(224)Ra) at the marsh inlet in July 1999 and 2001 and compared our data with Ra activities measured at the same location in 1983 and 1985. A radium-based approach for estimating SGD to the marsh yielded a summer average of 3900 m super(3) day super(-1). This flux was in good agreement with independent estimates from the literature, which ranged from 600 to 23,000 m super(3) day super(-1). Radium activities of the long-lived isotopes ( super(226)Ra, super(228)Ra) were on average more than two times higher in 1999 than during the three other time periods. These results suggest that drought conditions leading to enhanced seawater-sediment interactions may be an important mechanism in delivering certain dissolved substances to coastal waters.

publication date

  • December 2003