Utility of radium isotopes for evaluating the input and transport of groundwater‐derived nitrogen to a Cape Cod estuary

• DOI: 10.4319/lo.2001.46.2.0465
• Publication Date: 2010-06-30T20:46:15Z
• Authors: Matthew A. Charette; Ken O. Buesseler; John E. Andrews
• Keywords: Submarine groundwater discharge; Radium; Groundwater discharge

Because of rapid increases in population, anthropogenic sources nitrogen have adversely impacted the water quality coastal ponds on Cape Cod. A major source "new" to these estuaries is groundwater, which intercepts septic tank fields its flow path coastline. Many attempts been made quantify this process; however, groundwater discharge often patchy nature and therefore difficult study by use traditional techniques such as seepage meters. In Waquoit Bay, MA, we tested an approach based radium, naturally enriched aquifer fluids has four isotopes with half-lives ranging from 4 d 1600 yr. Groundwater entering bay was low salinity contained several orders magnitude greater radium dissolved inorganic (DIN) relative ambient water. Using a mass-balance for calculated submarine flux ~37,000 m3 d−1, compared well recharge rates rainfall. From DIN content estimated that ~2100 mol N d−1 directly input estuary. However, small comparison literature values fluxes heavily populated subestuaries. Furthermore, our results suggest assimilated plant biomass during summer but may be exported embayment waters winter months.