Dataset: Measurements of Radium isotopes (Ra-224 and Ra-223) collected aboard the R/V Falkor cruise FK190211 in the Guaymas Basin of the Gulf of California from February to March 2019.

Water samples for radium isotope analysis were collected from both niskin bottles attached to the CTD rosette (‘C’ designator in data sheet) and from niskin bottles attached to the remotely operated vehicle (ROV).  Water samples were filtered through 47 mm GFF filters (unless otherwise noted), then passed slowly through 25 g (dry) acrylic fibers impregnated with MnO2 (Moore, 1976).  Fibers were then washed 10x with Ra-free freshwater to remove salts and dried to a mass between 35 and 57 g for optimal humidity levels (Sun and Torgersen, 1998).  Fibers were then immediately counted on a Radium Delayed Coincidence Counter (RaDeCC; Moore and Arnold, 1996) for total Ra-224 and Ra-223.  Roughly 3 weeks later, fibers were counted again for supported Ra-224.  Thus, excess (‘XS’) Ra-224 is the difference between total and supported Ra-224 measurements. 

Radium isotopes were analyzed with a Radium Delayed Coincidence Counter (Moore and Arnold, 1996).  This system was calibrated to standard MnO2 prepared from NIST-traceable solutions of Th-232 and Ac-227 (with daughters in equilibrium).