Date of Award


Degree Type


Degree Name

Master of Science in Oceanography



First Advisor

S. B. Moran


Submarine ground water discharge (SGWD) represents a significant, yet diffuse and largely neglected source of fresh water and dissolved constituents to the coastal environment. Quantification of this term therefore proves important with respect to coastal hydrological and geochemical mass balances. In order to better constrain SGWD to southern Rhode Island's coastal waters, the naturally-occurring radionuclide 226Ra was used as a tracer of ground water input.

Activities of 226Ra were determined in river water, salt ponds, coastal ocean and ground water in southern Rhode Island during the summer of 1997 (June-August). Coastal lagoons and shelf waters were analyzed to quantify excess radium inventories, signifying an input of ground water. Using these results, a radium box model was constructed from which the ground water flux to the salt ponds and/or shelf waters was calculated. For shelf waters off southern Rhode Island, ground water results appear unrealistic compared to river input to the region and watershed recharge estimates, implying that sources of 226Ra in the ground water reservoirs of southern Rhode Island may not have been accounted for in this study. For the salt ponds, estimates of ground water flux are in most cases one order of magnitude less than inputs of river/stream water, with ground water inputs corresponding to ~ 1 to 42 x 105 L d-1. Using these calculated ground water flows to the salt ponds, total inorganic N fluxes of ~ 0.3 to 15 kg N d-1were determined based on local measurements of ground water nutrient concentration for Rhode Island's salt pond region.



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