Co-precipitation of radium in high ionic strength systems: 2. Kinetic and ionic strength effects

High concentrations of naturally occurring radium pose environmental and health concerns in natural and industrial systems. The adsorption of Ra²⁺ in saline water is limited compared to its adsorption in fresh water, but the process of co-precipitation may be effective in decreasing its concentration. However, despite its importance, Ra co-precipitation has rarely been studied in high ionic strength environments such as those in evaporitic systems.The fate of Ra in the reject brine of a desalination plant was studied via evaporation batch experiments at ionic strengths (I) ranging from 0.7 to 7.0 mol kg⁻¹. Precipitation sequences revealed that Ra co-precipitated with barite, even though the latter was a trace mineral compared to the precipitated gypsum. The concentration-based effective partition coefficient, , for the co-precipitation reaction was 1.04 ± 0.01. This value of is significantly lower than the value for relatively diluted solutions (1.8 ± 0.1). This low value of is mainly the result of a kinetic effect but is also slightly affected by the ionic strength.Both effects are quantitatively examined in the present paper. It is suggested that a kinetic effect influences the nucleation of (Ra,Ba)SO₄, reducing the value of the partition coefficient. This kinetic effect is caused by the favorable nucleation of a more soluble phase (i.e., a phase with a higher BaSO₄ fraction). An additional decrease in the partition coefficient results from the ionic strength effect. Considering the activity of Ra²⁺ and Ba²⁺ in the solution (rather than their concentration) makes it possible to determine the activity-based partition coefficient (), which accounts for the ionic strength effect. was calculated empirically from the experiments and theoretically via a kinetic model. The two derived values are consistent with one another and indicate the combined effect of ionic strength and precipitation kinetics.Finally, the common assumption that γ_Ra²⁺/γ_Ba²⁺=1 was re-examined using a numerical model to predict the experimental results. As the ionic strength increases, this assumption becomes less appropriate for predicting the change in as calculated in the experiments. Understanding the co-precipitation of Ra in such systems is crucial for risk assessments in which both Ra concentration and ionic strength are relatively high.     

Solar interaction regions,geomagnetic indices and the troposphere

Using key dates associated with solar interaction regions (SIR), a superposed epoch analysis is performed on the zonal and meridional kinetic energy density and square of the vorticity (enstrophy) of the main motion at 500 mb height. No relationships are found between SIR and these atmospheric dynamical parameters irrespective of the polarity (North or South) of the enhanced interplanetary magnetic fields (IMF) within the SIR, or with latitude and season. This investigation and other available results suggest that the short term solar variations do not influence large volumes of the troposphere but only localized regions.The average atmospheric kinetic energy density during active solar conditions is higher than during quiet solar condition, with no significant differences in enstrophy. This confirms an earlier result.It is also shown that SIR with enhanced southward directed IMF correspond to higher level of geomagnetic index (A_p > 10, K_p > 3) than randomly selected days.     

Crystal spectrometer studies of the Sun employing a rotation modulation collimator

The use of rotating modulation collimators in high resolution solar X-ray spectroscopy is discussed with reference to the recent flight of a sounding rocket payload. This rocket carried an experiment which combined a modulation collimator and a Bragg crystal spectrometer to make moderately high resolution spectral and spatial measurements simultaneously. The response of the instrument to extended sources is described. It is shown that the technique is particularly suited to long term observations of active region emission, but that useful measurements can be made even during a short rocket flight.Our observations were made in 1972 October 26 between 0432 UT and 0436 UT. During the flight a scan of the solar X-ray spectrum was made which covered the wavelength range 1.45–1.71 nm. A small flare commenced at about 0432 UT in McMath calcium plage region 12094; the emission from this provided the major contribution to the observed spectrum. X-ray emission from a group of active regions in the SW and the small McMath region 12090 has also been detected.Spectral and spatial observations have been combined to investigate the conditions in both active region and flare plasmas.