Radium 228 in surface ocean waters is derived from sedimentary fluxes generated in estuaries, salt marshes, and fine-grained sediments of the inner shelf. Thus the 228Ra activity of shelf waters is a measure of their interaction with these sediments. Mixing of the 228Ra signal offshore follows known circulation patterns and examination of the 228Ra field as determined by the 228Ra/226Ra activity ratio (AR) reveals details of these patterns. During February, sinking of chilled shelf waters carries high AR water to depths of 80--130 m just below the shelf break. In April, upwelling from 500--700 m depth brings low AR water to the shelf break, where it replaces the high AR waters present 2 months earlier. During August, low AR waters at the shelf break could be traced to the surface, where they separated higher AR waters both inshore and offshore of the shelf break. Because of such short-term variability, one-dimensional steady state models which balance 228Ra decay with mixing do not provide a true measure of horizontal mixing rates. Fluxes necessary to support the 228Ra standing crop in the South Atlantic Bight are of the order of 2.5¿1014 dpm/yr. These are similar to estimates from the New York Bight but 25 times lower than the apparent flux from the Amazon system. ¿American Geophysical Union 1987