Air–Water Partitioning of ²²²Rn and its Dependence on Water Temperature and Salinity

Abstract

Radon is useful as a tracer of certain geophysical processes in marine and aquatic environments. Recent applications include detection of groundwater discharges into surface waters and assessment of air/sea gas piston velocities. Much of the research performed in the past decade has relied on continuous measurements made in the field using a radon stripping unit connected to a radon-in-air detection system. This approach assumes that chemical equilibrium is attained between the water and gas phases and that the resulting air activity can be multiplied by a partition coefficient to obtain the corresponding radon-in-water activity. We report here the results of a series of laboratory experiments that describes the dependence of the partition coefficient upon both water temperature and salinity. Our results show that the temperature dependence for freshwater closely matches results that were previously available. The salinity effect, however, has largely been ignored and our results show that this can result in an overestimation of radon concentrations, especially in cooler, more saline waters. Related overestimates in typical situations range between 10 (warmer less saline waters) and 20% (cooler, more saline waters).

Dynamics of groundwater‐derived nitrate and nitrous oxide in a tidal estuary from radon mass balance modeling

“…The bottom water was pumped through the air-water exchanger at , 3 L min 21 . The 222 Rn concentrations were corrected for temperature and salinity (Schubert et al 2012). Individual grab-samples of the surface water were obtained approximately every hour and analyzed as above.…”

Atoll Groundwater Movement and Its Response to Climatic and Sea-Level Fluctuations

“…RAD7 radon detection systems were employed to measure Rn in air using a water/air exchanger. This setup allows for a near real-time calculation of the aqueous Rn concentration by measuring the air 222 Rn concentration and knowing the temperature-dependent 222 Rn partitioning coefficient [31,[36][37][38][39][40]. A peristaltic pump was used to produce a continuous stream of coastal surface water into the water/air exchanger, while air from the exchanger was continuously pumped into the RAD7 radon monitor.…”

Role of the Structural Factor in the Distribution of High-Radon Groundwater in the Southwestern Flank of the South Baikal Rift Basin

“…Данный вопрос требует отдельного целенаправленного исследования, так как мнения специалистов о характере подобной зависимости расходятся. Это позволяет на данном этапе работ в качестве основной причины выяв-ленной закономерности рассматривать изменение температуры воды, тем более что для некоторых регионов обратная связь между параметрами Q и T установлена достаточно определенно [Erdogan et al, 2013;Schubert et al, 2012]. Поскольку радиоак-тивный газ лучше растворяется в водах с более низкой температурой, повышение радиоактивно-сти наблюдается у побережья Байкала, где под влиянием озера происходит охлаждение подзем-ных вод.…”