Determination of 228Ra, 226Ra and 224Ra in natural water via adsorption on MnO2-coated discs

A fast procedure based on sorption of Ra on MnO2 coated polyamide discs is presented for determination of radium isotopes (i.e. 228Ra, 226Ra, 224Ra) in aqueous samples. The sample discs can be used directly for low-level alpha-spectrometry without the need for further separation and preparation methods to produce planar sample sources. While the activity of alpha-emitting 224Ra and 226Ra can be determined during a first measurement, beta-emitting 228Ra is obtained via ingrowth of the progeny 228Th on the same sample disc after a standing time of about six months. Calculations are presented for optimizing the analytical accuracy as well as for predicting the sorption yield or chemical recovery of radium on the sample disc as a function of exposure time because the sorption uptake proceeds with first-order kinetics. The analyses can be carried out on small samples of 0.5-11 and, for long counting times of one week and use of high-purity silicon surface barrier detectors, a detection limit of 0.15 mBq l-1 is obtained for 226Ra. Since the half-life of 224Ra is only 3.7 d and since 228Th (as a measure for 228Ra) is built up only partially on the sample disc, a slightly higher detection limit of 0.24 mBq l-1 results for the latter isotopes. The procedure is therefore sufficiently sensitive to allow the investigation of Ra isotope relationships in aquifers at typical environmental levels.     

Multiphase extraction radius of influence: Evaluation of design and operational parameters

A common remedial technology for properties with subsurface soil and groundwater contamination is multiphase extraction (MPE). MPE involves the extraction of contaminated groundwater, free‐floating product, and contaminated soil vapor from the subsurface. A network of recovery wells conveys fluids to a vacuum pump and to the treatment system for the contaminated groundwater and soil vapor. This article describes a study of MPE operational data from nine similar remediation projects to determine the most important design parameters. Design equations from guidance manuals were used to estimate the expected radius of influence (ROI) based on measured field data. ROIs were calculated for the vapor flow rate through the subsurface and for the groundwater drawdown caused by the MPE remediation activities. The calculated ROIs were compared to the measured ROIs to corroborate the assumptions made in the calculations. Once it was established that the calculated and field‐measured ROIs were comparable, a sensitivity analysis determined ranges of different design and operational parameters that most affected the ROIs. © 2012 Wiley Periodicals, Inc.     

A multi-variate methodology for analyzing pre-existing lake water quality data

Environmental agencies are given the task of monitoring water quality in rivers, lakes, and other bodies of water, for the purpose of comparing the results with regulatory standards. Monitoring follows requirements set by regulations, and data are collected in a systematic way for the intended purpose. Monitoring enables agencies to determine whether water bodies are polluted. Much effort is spent per monitoring event, resulting in hundreds of data points typically used solely for comparison with regulatory standards and then stored for little further use. This paper devises a data analysis methodology that can make use of the pre-existing datasets to extract more useful information on water quality trends, without new sample collection and analysis. In this paper, measured lake water quality data are subjected to statistical analyses including Principal Component Analysis (PCA) to deduce changes in water quality spatially and temporally over several years. It was found that the lake as a whole changed temporally by season, rather than spatially. Storm events caused the greatest shifts in water quality, though the shifts were fairly consistent across sampling stations. This methodology can be applied to similar datasets, especially with the recent emphasis by the U.S. EPA on protection of lakes as water sources. Water quality managers using these techniques may be able to lower their monitoring costs by eliminating redundant water quality parameters found in this analysis.     

Intersexual dominance relationships and the influence of leverage on the outcome of conflicts in wild bonobos (Pan paniscus)

Dominance relationships between females and males are characteristic traits of species and are usually associated with sexual dimorphism. Exploring the social and contextual circumstances in which females win conflicts against males allows one to study the conditions triggering shifting power asymmetries between the sexes. This study investigates dominance relationships in bonobos (Pan paniscus), a species in which females are thought to display social dominance despite male-biased sexual dimorphism. To identify dominance relationships among females and males, we first explored how intrasexual dominance status affects the outcome of intersexual conflicts. Second, by incorporating social and behavioral information about the context of intersexual conflicts, we tested to which extent different components of power are relevant to the observed asymmetries in the relationships. Post-hoc analyses indicate a sex-independent dominance hierarchy with several females occupying the top ranks. Our results also reveal that two factors—female leverage and motivation to help offspring—had a significant influence on the outcome of intersexual conflicts. The results of our study do not indicate an overall reduction in male aggression against females but do show lower levels of male aggression in the mating context, and an absence of male aggression toward those females displaying visual signs of elevated fecundity. This indicates that both female sexuality and male mating strategies are involved in the shifting dominance relationships between the sexes.