Assessment, validation and intercomparison of operational models for predicting tritium migration from routine discharges of nuclear power plants: the case of Loire River

During last decades, a number of projects have been launched to validate models for predicting the behaviour of radioactive substances in the environment. The project of the "Aquatic" working group of the project EMRAS (Environmental Modelling for Radiation Safety) organised by the International Atomic Energy Agency (IAEA) was based on the validation and assessment of models for predicting the behaviour of radionuclides in the aquatic ecosystems. The present paper describes a blind test of models aimed at assessing the dispersion of tritium releases in the Loire River (France), on a large domain ( approximately 350km) and on a period of six months, by comparing the results obtained by operational-to-experimental values of tritium concentration at Angers, a city along the Loire River. The common conclusion is that the models used by the different participants namely 1D models and models based on a schematic hydraulic (box models) are reliable tools for tritium transport modelling. Nevertheless, the importance of proper and detailed hydrological data for the appropriate prediction of pollutant migration in water is demonstrated by the example provided during this study.     

Accelerating Adaptation of Natural Resource Management to Address Climate Change

Natural resource managers are seeking tools to help them address current and future effects of climate change. We present a model for collaborative planning aimed at identifying ways to adapt management actions to address the effects of climate change in landscapes that cross public and private jurisdictional boundaries. The Southwest Climate Change Initiative (SWCCI) piloted the Adaptation for Conservation Targets (ACT) planning approach at workshops in 4 southwestern U.S. landscapes. This planning approach successfully increased participants’ self‐reported capacity to address climate change by providing them with a better understanding of potential effects and guiding the identification of solutions. The workshops fostered cross‐jurisdictional and multidisciplinary dialogue on climate change through active participation of scientists and managers in assessing climate change effects, discussing the implications of those effects for determining management goals and activities, and cultivating opportunities for regional coordination on adaptation of management plans. Facilitated application of the ACT framework advanced group discussions beyond assessing effects to devising options to mitigate the effects of climate change on specific species, ecological functions, and ecosystems. Participants addressed uncertainty about future conditions by considering more than one climate‐change scenario. They outlined opportunities and identified next steps for implementing several actions, and local partnerships have begun implementing actions and conducting additional planning. Continued investment in adaptation of management plans and actions to address the effects of climate change in the southwestern United States and extension of the approaches used in this project to additional landscapes are needed if biological diversity and ecosystem services are to be maintained in a rapidly changing world. Acelerando la Adaptación del Manejo de Recursos Naturales para Atender el Cambio Climático     

Framework and Tools for Agricultural Landscape Assessment Relating to Water Quality Protection

While many scientific studies show the influence of agricultural landscape patterns on water cycle and water quality, only a few of these have proposed scientifically based and operational methods to improve water management. Territ’eau is a framework developed to adapt agricultural landscapes to water quality protection, using components such as farmers’ fields, seminatural areas, and human infrastructures, which can act as sources, sinks, or buffers on water quality. This framework allows us to delimit active areas contributing to water quality, defined by the following three characteristics: (i) the dominant hydrological processes and their flow pathways, (ii) the characteristics of each considered pollutant, and (iii) the main landscape features. These areas are delineated by analyzing the flow connectivity from the stream to the croplands, by assessing the buffer functions of seminatural areas according to their flow pathways. Hence, this framework allows us to identify functional seminatural areas in terms of water quality and assess their limits and functions; it helps in proposing different approaches for changing agricultural landscape, acting on agricultural practices or systems, and/or conserving or rebuilding seminatural areas in controversial landscapes. Finally, it allows us to objectivize the functions of the landscape components, for adapting these components to new environmental constraints.     

First evidence for a stereoselective incorporation of nonylphenol diastereomers in soil-derived organo-clay complexes

Environmental processes can affect the stereochemical properties of organic pollutants. In particular, biotic processes like microbial transformations or membrane penetration alter the ratios of enantiomers as well as diastereomers. These effects have been intensively used not only in environmental studies but also in medicine, toxicology, pharmacy, and agricultural sciences. However, in order to identify unambiguously biotic-initiated alteration of organic compounds, the knowledge on the stereoselective effect of all relevant processes is mandatory. Therefore, here we report the first evidence for a stereospecific formation of non-extractable residues of a xeniobiotic in a highly relevant soil subfraction, the organo-clay complexes. In this study, soils were spiked with labeled and unlabeled nonylphenol isomer, and incubation experiments were performed to study its long-term incorporation behavior into soil-derived organo-clay complexes under abiotic and biotic conditions. Besides the extractable particle-associated proportion especially the humic fractions comprising the bound residues have been analyzed by GC/MS. Our results from biotic experiments revealed alterations of the diastereomeric composition of the contaminant in the different soil humic subfractions. A depletion of the first eluting diastereomer as expressed by diastereomeric ratios around 0.6 has been observed for the extractable fraction, whereas the non-extractable proportion was enriched in the first diastereomer (diasteremoric ratio around 1.0). On the contrary, the diastereomeric ratios remained unaffected during the abiotic experiments (diasteremoric ratio around 0.8). These systematic observations give clear evidence that the process of microbial-assisted incorporation of nonylphenol into soil organo-clay complexes is a stereoselective process. To our knowledge, this is the first report on a stereoselective incorporation process of organic substances forming non-extractable residues. Consequently, the formation of non-extractable residues has to be considered in environmental studies dealing with stereoselective analysis of organic pollutants in soils to study their microbial transformation.     

Precipitation in Light Extinction Reconstruction

Abstract

The U.S. Environmental Protection Agency (EPA) published the Regional Haze Rule (RHR) in 1999.¹ The RHR default goal is to reduce haze linearly to natural background in 2064 from the baseline period of 2000–2004. The EPA default method^2,3 for estimating natural and baseline visibility uses the Interagency Monitoring of Protected Visual Environments (IMPROVE) formula. The IMPROVE formula predicts the light extinction coefficient from aerosol chemical concentrations measured by the IMPROVE network. The IMPROVE light scattering coefficient formula using data from 1994–2002 underestimated the measured light scattering coefficient by 700 Mm^?1, on average, on days with precipitation. Also, precipitation occurred as often on the clearest as haziest days. This led to estimating the light extinction coefficient of precipitation, averaged over all days, as the light scattering coefficient on days with precipitation (700 Mm^?1) multiplied by the percent of precipitation days in a year. This estimate added to the IMPROVE formula light extinction estimate gives a real world estimate of visibility for the 20% clearest, 20% haziest, and all days. For example, in 1993, the EPAs Report to Congress projected visibility in Class I areas would improve by 3 deciviews by 2010 across the haziest portions of the eastern United States because of the 1990 Clean Air Act Amendments. Omitted was the light extinction coefficient of precipitation. Adding in the estimated light extinction coefficient of precipitation, the estimated visibility improvement declines to <1 deci-view.     

The fear of being eaten reduces energy transfer in a simple food chain

Food chain length is an important property of ecosystems, but the mechanisms maintaining it remain elusive. Classical views suggest that energetic inefficiencies (the "energy-flow hypothesis") limit food chain length, but others have argued that better explanations reside in more complex scenarios that consider the stability of food webs or the combined effects of productivity and ecosystem size. We argue that abandonment of the energy-flow hypothesis is premature. For a simple tritrophic rocky intertidal food chain, we show that the efficiency of energy transfer is strongly influenced by predation risk and consumer density. Effects tied to predation risk were particularly strong, explaining 32% of the variation in growth efficiency (compared to 15% for density effects) and reducing it by 44-76%. Hence, the stress (fear of being eaten) that predators impose on prey may be instrumental in limiting energy transfer up the food chain and thus contribute to the shortening of food chains.     

Biodegradation of hydrocarbons vapors: Comparison of laboratory studies and field investigations in the vadose zone at the emplaced fuel source experiment, Airbase Vaerløse, Denmark

The natural attenuation of volatile organic compounds (VOCs) in the unsaturated zone can only be predicted when information about microbial biodegradation rates and kinetics are known. This study aimed at determining first-order rate coefficients for the aerobic biodegradation of 13 volatile petroleum hydrocarbons which were artificially emplaced as a liquid mixture during a field experiment in an unsaturated sandy soil. Apparent first-order biodegradation rate coefficients were estimated by comparing the spatial evolution of the resulting vapor plumes to an analytical reactive transport model. Two independent reactive numerical model approaches have been used to simulate the diffusive migration of VOC vapors and to estimate degradation rate coefficients. Supplementary laboratory column and microcosm experiments were performed with the sandy soil at room temperature under aerobic conditions. First-order kinetics adequately matched the lab column profiles for most of the compounds. Consistent compound-specific apparent first-order rate coefficients were obtained by the three models and the lab column experiment, except for benzene. Laboratory microcosm experiments lacked of sensitivity for slowly degrading compounds and underestimated degradation rates by up to a factor of 5. Addition of NH3 vapor was shown to increase the degradation rates for some VOCs in the laboratory microcosms. All field models suggested a significantly higher degradation rate for benzene than the rates measured in the lab, suggesting that the field microbial community was superior in developing benzene degrading activity.     

Anti-predatory vigilance and the limits to collective detection: visual and spatial separation between foragers

Collective detection concerns the idea that all members of a socially feeding group are alerted to an attack as long as at least one group member detects it. We found that collective detection in mixed flocks of emberizid sparrows is limited markedly by relatively small degrees of visual and spatial separation between foragers. These limits on collective detection appear to influence the degree to which flock members lower their vigilance with increasing group size (the group size effect). Specifically, the decrease in collective detection with increasing visual and spatial isolation between foragers is accompanied by a concomitant decrease in the strength of the vigilance group size effect. Explanations for the vigilance-related effects of such separation based upon a bird’s ability to monitor the vigilance behavior of flockmates can be ruled out for our experimental system. Our results also shed light on the issue of whether the vigilance group size effect is influenced more by collective detection or the simple dilution of risk with increasing group size. We argue that collective detection is not only an important determinant of the group size effect, but also that the phenomena of collective detection and risk dilution are interdependent. Received: 25 July 1995/Accepted after revision: 17 December 1995     

Some of the Nineteenth Century Origins of the Sustainability Concept

Interpreting and applying the concept of sustainable development is increasingly viewed as being the way to promulgate just and practicable economic, environmental and social policy. It is thus important that there be increased public and political awareness concerning the origins of economic theory, and its early relationship to sustainability concepts. While the term 'sustainable development' was popularised by the World Commission on Environment and Development report Our Common Future in 1987, it is generally recognised that notions of sustainability were promoted in `limits to growth' and 'green' discourses in the early 1970s (Meadows et al.: 1974, The Limits to Growth: A Report for the Club of Rome, Potomac Associates and Pan Books, London and Sydney). However, there is little acknowledgement of the way in which nineteenth century intellectuals, from a range of disciplines, conceptualised the importance of balancing economic, social and environmental sustainability in their quest for justice and the conservation of nature.There was a considerable exchange of ideas on `political economy' and nature across Europe, and later the Americas, from the middle of the eighteenth century. This discourse reached its intellectual peak in the nineteenth century. During that era there was a proliferation of literature that was aimed at improving the human condition and recognising humanity's dependence upon nature. In Europe and the USA the participants in the debate included Cantillon, Quesnay, Condorcet, Galiani, Von Hayek, Marx and George. Due to the breadth of this influential body of work, we focus here on the British Victorian thinkers such as Darwin, Malthus, Martineau and Mill. These thinkers influenced each other in developing their theories and ideas in science, politics, economics and philosophy, and were influenced in turn by an earlier generation of intellectuals, such as Adam Smith. For the Victorian thinkers, conserving nature while trying to improve the distribution of wealth was a not a paradox, but a moral duty, and for them Smith's `rational' pursuit of self-interest could only be followed if it did not interfere with 'the rules of justice'. We argue that the manner in which these thinkers conceptualised their theories and ideas represents the nineteenth century origins of sustainability concepts.