Review and assessment of models used to predict the fate of radionuclides in lakes

A variety of models for predicting the behaviour of radionuclides in fresh water ecosystems have been developed and tested during recent decades within the framework of many international research projects. These models have been implemented in Computerised Decision Support Systems (CDSS) for assisting the appropriate management of fresh water bodies contaminated by radionuclides. The assessment of the state-of-the-art and the consolidation of these CDSSs has been envisaged, by the scientific community, as a primary necessity for the rationalisation of the sector. The classification of the approaches of the various models, the determination of their essential features, the identification of similarities and differences among them and the definition of their application domains are all essential for the harmonisation of the existing CDSSs and for the possible development and improvement of reference models that can be widely applied in different environmental conditions. The present paper summarises the results of the assessment and evaluation of models for predicting the behaviour of radionuclides in lacustrine ecosystems. Such models were developed and tested within major projects financed by the European Commission during its 4th Framework Programme (1994-1998). The work done during the recent decades by many modellers at an international level has produced some consolidated results that are widely accepted by most experts. Nevertheless, some new results have arisen from recent studies and certain model improvements are still necessary.     

Modelling Change in Ground Vegetation Response to Acid and Nitrogen Pollution, Climate Change and Forest Management at in Sweden 1500–2100 a.d.

The ForSAFE model, designed for modelling biogeochemical cycles (water, acidity, base cation, nitrogen and carbon) in terrestrial ecosystems, was modified with a vegetation response module (VEG), incorporating the effects of: nitrogen pollution, acidification, soil moisture, temperature, wind chill exposure, light and shading by trees, grazing by animals, competition between plants, above ground for light and below ground for water and nutrients. The model calculates the response of number ground vegetation plant groups. The integrated model was tested and validated at integrated level II forest monitoring sites across Sweden, four have been shown here, and used to assess the effect of acidification and nitrogen pollution in relation to factors such as climate change, forest management and changing grazing pressure. The response functions have been derived from single-factor experiments and integrated through the model structure for use on whole systems. The tests with the model suggest that the ground vegetation composition is reasonably well predicted, that much research remains before the model is fully tested and operational, and that the model may serve as a tool for assessing impacts of climate change, acid rain and forest management on plant biodiversity in forested areas.     

Mesoscale Air Pollution Transport in the Chicago Lake Breeze

A two-day field program in Chicago studied mesoscale pollution transport during typical lake breezes. Streamlines calculated from serial pibal data suggest that a nearly closed circulation cell traps pollutants emitted near a shore line. Optically tracked tetroons confirm the helical trajectory of air within the lake breeze regime. Pollutants released within the inflow layer move inland, rise in a narrow zone of updrafts (100 cm/sec) at the lake breeze front, advect lakeward in the return flow layer aloft, and then subside back down into the inflow layer. Pollution then fumigates back to the surface as the air returns inland a second time causing concentrations higher than would otherwise be expected. Spectral aerosol measurements (0.5-3.0 and 7.0-9.0 micrometer size ranges) made by an instrumented aircraft reveal a marked particle size sorting.     

Virtues and humanitarian ethics

This paper analyses the contribution of virtue ethics, the study of good character traits, to the humanitarian context. It argues that a virtue ethics perspective paints a realistic picture of the use of ethical standards in morally complex circumstances. Virtuous relief workers can employ standards in their thinking, but they are also committed to professional excellence that goes beyond any formal code. The concept of virtue ethics places a stress on moral development, which can be facilitated by role models that impart modest and feasible ideals. However, virtue ethics cannot provide simple guidelines on how to resolve difficult situations. It is possible that two virtuous persons can disagree on what should be done in a particular instance. In addition, a virtue ethics perspective emphasises the need for both individuals and organisations to discuss the actual purpose of relief work in order to pinpoint the virtues of a good relief professional.     

Is the first-trimester combined screening result associated with the phenotype of Down syndrome? A population-based cohort study

Objective

To investigate if the Down syndrome phenotype differs according to the result of first-trimester combined screening (FTS).

Method

We included all Down syndrome cases diagnosed by karyotype in pregnancy or after birth in Denmark during 2005–2018. We compared screen positive (odds ≥1:300) and screen negative (odds <1:300) cases as well as screen result subgroups with respect to anthropometrics, congenital malformations, childhood diseases, and hospitalization.

Results

Absolute measures of fetal and birth anthropometrics were comparable between groups. A prenatal malformation diagnosis was more prevalent among screen positive than screen negative cases. Analyses suggested that this could reflect a detection bias. Cases with a screen result of 1:2–1:10 had a higher probability of being diagnosed with a malformation prenatally and with severe congenital heart disease (CHD) postnatally compared with a result of 1:11–1:300. Screen positive cases more often had non-severe CHD but less often a non-heart malformation compared with screen negative cases, while proportions of severe CHD were similar in these groups. Data on hospitalizations showed inconsistent results.

Conclusion

The 1:300 screening threshold had limited or no value in predicting Down syndrome phenotype severity. In contrast, cases with a screen result between 1:2 and 1:10 may represent a more severe phenotype.     

A submodel for anaerobic mud-water exchange of phosphate

A submodel for anaerobic mud-water exchange of phosphate is obtained from experiments in the laboratory. Phosphorus in the sediment can be divided into exchangeable and non-exchangeable phosphorus. The exchangeable phosphorus is decomposed in accordance with a first-order reaction. The phosphorus moves, after the decomposition process, from the interstitial water to the water phase, in accordance with a diffusion expression. The yearly increase of the sediment was determined by means of the lead concentration as a function of the depth.     

Modeling habitat suitability for moose in coastal northern Sweden: empirical vs process-oriented approaches

Habitat models may provide viable tools for co-management of large ungulates and forest resources, yet their applicability has not been comprehensively evaluated in managed forest. We examined 2 inherently different approaches to model the relative winter habitat suitability for moose (Alces alces) in the coastal area of northern Sweden. An empirical approach based on GPS positions of 15 female moose was used to scrutinize the assumptions and functional mechanisms of a process-oriented, conceptual approach, based on published material on the species' preferences for habitat components related to food and cover. For both model approaches habitat was described using estimates of forest-stand characteristics based on satellite imagery. The empirical model also included variables relating to topographic properties of the landscape as well as distances to landscape features. The output from both models was a habitat suitability index (HSI) score, enabling the models to be compared with each other. The models showed different results, highlighting the need to include the spatially explicit distribution of environmental variables in future conceptual, process-oriented models.     

Determination of vapor pressures for chloroguaiacols,chloroveratroles, and nonylphenol by gas chromatography

Vapor pressures of six chlorinated phenols were measured by capillary gas chromatography using a 1.0-m BP-1 bonded phase column. GC-determined vapor pressures (P_GC) were correlated with known liquid-phase vapor pressures (P_L) by the equation: Log P_GC = 1.026 Log P_L — 0.132, r² = 0.975 (vapor pressures in pascals). This relationship was used to estimate P_L for chloroguaiacols, chloroveratroles, and 4-nonylphenol from their experimental P_GC.     

Dynamics of Turbulence in Low-Speed Oscillating Bottom-Boundary Layers of Stratified Basins

This paper focuses on the impact of an oscillating low-speed current on the structure and dynamics of the bottom-boundary layer (BBL) in a small stratified basin. A set of high-resolution current profile measurements in combination with temperature-microstructure measurements were collected during a complete cycle of the internal oscillation (`seiching') in the BBL of Lake Alpnach, Switzerland. It was found that even a relatively long seiching period of 24 hours significantly changed the form of the near-bottom current profiles as well as the dynamics of the turbulent dissipation rate compared to the steady-state law-of-the-wall. A logarithmic fit to the measured current profiles starting at a distance of 0.5 m above the sediment led to inconsistent estimates of both friction velocity and roughness length. Moreover, a phase lag between the current and the turbulent dissipation of 1.5 hours and a persistent maximum in the current profile at a height of 2.5 to 3 m above the sediment were observed. The experimental findings were compared to the results of a k- turbulence model and showed good agreement in general. Specifically, the inconsistent logarithmic fitting results and the observed phase lag were reproduced well by the model.