Radium and radon in Charlotte Harbor Estuary, Florida

Radium-226 and ²²²Rn activities are greater in the estuarine waters of northern Charlotte Harbor and the lower tidal Peace and Myakka Rivers, Florida, than in either the freshwater reaches of the rivers or waters of the lower estuary and the Gulf of Mexico. The activity of ²²⁶Ra in the tidal rivers increases with decreasing river inflow, with a maximum value of 548 dpm 1001⁻¹ measured in the tidal Myakka River. The source of the high activity of ²²⁶Ra and ²²²Rn is predominantly ground water inflow. Because of the large ground water input, the contribution of ²²⁶Ra from suspended and bottom sediments is a smaller fraction of the total ²²⁶Ra input than in many other estuaries. Although ground water ²²⁶Ra activity in the area varies widely, we estimate that artesian ground water inflow to the tidal rivers is similar in magnitude to the flow of the rivers above the tidal reach during the dry season.