We present a new method to determine 226Ra in aqueous environmental samples, based on the rate of ingrowth of 222Rn from 226Ra, using the radium delayed coincidence counter (RaDeCC). We use the same instrument setup that is used for the determination of 223Ra and 224Ra. In contrast to methods published earlier, the approach does not require a modification of the counting equipment, counting separately for 226Ra, or waiting for radioactive equilibrium.
Acrylic fibers impregnated with MnO2 (Mn-fiber) have become a valuable tool for concentrating dissolved radium for oceanographic applications. With four naturally-occurring radium isotopes (223Ra, 224Ra, 226Ra, and 228Ra) of vastly different half-lives (3.6 days to 1600 years), radium can be a powerful tool for tracing terrestrial water discharges into the ocean and studying coastal mixing processes.
Four radium isotopes, decay products of the 238U–232Th–235U series radionuclides, occur in nature: 224Ra (t1/2=3.66 days), 223Ra (t1/2=11.4 days), 228Ra (t1/2=5.75 years), and 226Ra (t1/2=1600 years). Beginning with the GEOSECS program of the late 1960s – early 1970s, these radium isotopes have been widely applied to the study of a variety of oceanographic processes (Moore, 1972; Trier et al., 1972).