Submarine groundwater discharge from the South Australian Limestone Coast region estimated using radium and salinity

Hydrochemical and geological controls on dissolved radium and radon in northwestern Algeria hydrothermal groundwaters

This study presents the results of the first investigation on natural occurrence of radium and radon in Algerian thermal water systems. Activity concentrations of Rn and Ra isotopes were measured in sixteen hydrothermal springs of northwestern Algeria. Samples displayed high activities, especially for ²²²Rn, ²²⁴Ra and ²²⁶Ra (up to 377 × 10³ Bq/m³, 730 Bq/m³ and 4470 Bq/m³, respectively). Approximately, 50% of the investigated springs displayed activities of combined long-lived Ra (²²⁶Ra + ²²⁸Ra) in excess of the maximum contaminant level (MCL) of the WHO and EPA for drinking water. Factors controlling the distribution of radionuclides in the aquifer system are investigated. The observed correlation between Ra isotope and TDS suggests that adsorption/desorption is not the dominant process controlling the distribution of Ra in waters. Our results indicate that the excess SO₄^2- limits the concentration of dissolved Ba²⁺ and thereby, the elevated Ra activities in these hydrothermal systems are not simply limited by co-precipitation with BaSO₄ (barite). The data shows that Ra activities are likely dominated by the recoil process of parent isotopes in the aquifer solids. The minimal abundance of clay minerals and oxides in the aquifer, in addition to thermal activities in northwestern Algeria, significantly enhances the mobilization of Ra into waters.

Error-control and processes optimization of (223/224)Ra measurement using Delayed Coincidence Counter (RaDeCC)

RaDeCC has proved to be a precise and standard way to measure (224)Ra and (223)Ra in water samples and successfully made radium a tracer of several environmental processes. In this paper, the relative errors of (224)Ra and (223)Ra measurement in water samples via a Radium Delayed Coincidence Count system are analyzed through performing coincidence correction calculations and error propagation. The calculated relative errors range of 2.6% ∼ 10.6% for (224)Ra and 9.6% ∼ 14.2% for (223)Ra. For different radium activities, effects of decay days and counting time on final radium relative errors are evaluated and the results show that these relative errors can decrease by adjusting the two measurement factors. Finally, to minimize propagated errors in Radium activity, a set of optimized RaDeCC measurement parameters are proposed.