Dataset: Radium isotope measurements from bottom waters in the South Atlantic Bight from 2015-2020 (SAB BMA project)

Methods & Sampling

Bottom water samples were obtained by lowering a submersible pump to near the seafloor and filling two 26-liter carboys. Subsamples for salinity were usually taken from each sample and measured with a YSI conductivity meter to confirm the CTD measurement. Radium samples were filtered through a column of Mn-fiber to quantitatively remove Ra [Moore, 1976]. The Mn-fiber was returned to the lab, where short-lived radium isotopes (223Ra, half-life = 11.4 days, and 224Ra, half-life = 3.66 days) were measured using a delayed-coincidence counting system [Moore and Arnold, 1996]. After the short-lived measurements were complete, Ra and Mn were stripped from the Mn-fiber and radium was coprecipitated with BaSO4 and transferred to a small tube. 226Ra and 228Ra were measured by gamma spectrometry after 222Rn had equilibrated with 226Ra [Moore et al., 1985]. The RaDeCC systems were calibrated for 224Ra with a NIST standard solution of 232Th adsorbed to Mn-fiber and for 223Ra by the technique of Moore and Cai [2013]. The gamma detector was calibrated with NIST standard solutions for 226Ra and 228Ra in a BaSO4 matrix [Moore, 1984].

Samples were taken from R/V Trinity, owned by a private charter company called Charleston SCUBA. This company is no longer in operation.