Comparison of solubility databases used for HLW performance assessment

Elemental solubility limits are employed in many performance assessment studies of the disposal of high-level radioactive waste. A comparison of solubility databases used in a number of recent assessments from Canada, Finland, Japan, Sweden, Switzerland and the U.S.A. is presented. Despite similarities in the chemical conditions under which such solubilities are defined, there are very large ranges in the values selected for most elements (several orders of magnitude). In some cases, differences in solubilities can be attributed to differences in the thermodynamic databases used but, due to generally incomplete documentation, both of such databases and the criteria for data selection, detailed analysis of the reason for such discrepancies is precluded. A key factor, however, is the fairly subjective choice of the solid phase considered to be “solubility-limiting”. Procedures are recommended which would increase the transparency of solubility database compilation in future analyses.     

Investigation of evaporation and biodegradation of fuel spills in Antarctica. I. A chemical approach using GC-FID

Little effort has been devoted to differentiating between hydrocarbon losses through evaporation and biodegradation in treatability studies of fuel-contaminated Antarctic soils. When natural attenuation is being considered as a treatment option, it is important to be able to identify the mechanism of hydrocarbon loss and demonstrate that rates of degradation are sufficient to prevent off-site migration. Similarly, where complex thermally enhanced bioremediation schemes involve nutrient addition, water management, air stripping and active heating, it is important to appreciate the relative roles of these mechanisms for cost minimisation. Following the loss of hydrocarbons by documenting changes in total petroleum hydrocarbons offers little insight into the relative contribution of evaporation and biodegradation. We present a methodology here that allows identification and quantification of evaporative losses of diesel range organics at a range of temperatures using successively less volatile compounds as fractionation markers. We also present data that supports the general utility of so-called biodegradation indices for tracking biodegradation progress. We are also able to show that at 4 degrees C indigenous Antarctic soil bacteria degrade Special Antarctic Blend fuel components in the following order: naphthalene and methyl-napthalenes, light n-alkanes, then progressively heavier n-alkanes; whereas isoprenoids and the unresolved complex mixture are relatively recalcitrant.     

Potential application of synchronous fluorescence spectroscopy to determine benzo[a]pyrene in soil extracts

Benzo[a]pyrene (BaP) is a significant environmental pollutant and rapid, accurate methods to quantify this compound in soil for both research and environmental investigation purposes are required. In this work, solvent extracts from five contrasting soils spiked with four different polycyclic aromatic hydrocarbons (PAHs) were rapidly analysed by using a synchronous fluorescence spectroscopy (SFS) method. The SFS method was validated using HPLC with ultraviolet detection. A good correlation for the quantification of BaP in soil extracts by the two methods was observed. The detection limit of the SFS method was 1.6 x 10(-9) g/ml in CTAB micellar medium (7.8 mmol/l). The work demonstrates that SFS has potential as a sensitive, accurate, rapid, simple and economic methodology and an efficient alternative to HPLC for fast confirmation and quantification of BaP in complex soil extracts.     

A global evaluation of metabolic theory as an explanation for terrestrial species richness gradients

We compiled 46 broadscale data sets of species richness for a wide range of terrestrial plant, invertebrate, and ectothermic vertebrate groups in all parts of the world to test the ability of metabolic theory to account for observed diversity gradients. The theory makes two related predictions: (1) In-transformed richness is linearly associated with a linear, inverse transformation of annual temperature, and (2) the slope of the relationship is near -0.65. Of the 46 data sets, 14 had no significant relationship; of the remaining 32, nine were linear, meeting prediction 1. Model I (ordinary least squares, OLS) and model II (reduced major axis, RMA) regressions then tested the linear slopes against prediction 2. In the 23 data sets having nonlinear relationships between richness and temperature, split-line regression divided the data into linear components, and regressions were done on each component to test prediction 2 for subsets of the data. Of the 46 data sets analyzed in their entirety using OLS regression, one was consistent with metabolic theory (meeting both predictions), and one was possibly consistent. Using RMA regression, no data sets were consistent. Of 67 analyses of prediction 2 using OLS regression on all linear data sets and subsets, two were consistent with the prediction, and four were possibly consistent. Using RMA regression, one was consistent (albeit weakly), and four were possibly consistent. We also found that the relationship between richness and temperature is both taxonomically and geographically conditional, and there is no evidence for a universal response of diversity to temperature. Meta-analyses confirmed significant heterogeneity in slopes among data sets, and the combined slopes across studies were significantly lower than the range of slopes predicted by metabolic theory based on both OLS and RMA regressions. We conclude that metabolic theory, as currently formulated, is a poor predictor of observed diversity gradients in most terrestrial systems.     

Test of a behavior-based individual-based model: response of shorebird mortality to habitat loss.

In behavior-based individual-based models (IBMs), demographic functions are emergent properties of the model and are not built into the model structure itself, as is the case with the more widely used demography-based IBMs. Our behavior-based IBM represents the physiology and behavioral decision making of individual animals and, from that, predicts how many survive the winter nonbreeding season, an important component of fitness. This paper provides the first test of such a model by predicting the change in winter mortality of a charadriid shorebird following removal of intertidal feeding habitat, the main effect of which was to increase bird density. After adjusting one calibration parameter to the level required to replicate the observed mortality rate before habitat loss, the model predicted that mortality would increase by 3.65%, which compares well with the observed increase of 3.17%. The implication that mortality was density-dependent was confirmed by predicting mortality over a range of bird densities. Further simulations showed that the density dependence was due to an increase in both interference and depletion competition as bird density increased. Other simulations suggested that an additional area of mudflat, equivalent to only 10% of the area that had been lost, would be needed by way of mitigation to return mortality to its original level. Being situated at a high shore level with the flow of water in and out impeded by inlet pipes, the mitigating mudflat would be accessible to birds when all mudflats in the estuary were covered at high tide, thus providing the birds with extra feeding time and not just a small replacement mudflat. Apart from providing the first, and confidence-raising, test of a behavior-based IBM, the results suggest (1) that the chosen calibration procedure was effective; (2) that where no new fieldwork is required, and despite being parameter rich, a behavior-based IBM can be parameterized quickly (few weeks), and thus cheaply, because so many of the parameter values can be obtained from the literature and are embedded in the model; and (3) that behavior-based IBMs can be used to explore system behavior (e.g., the role of depletion competition and interference competition in density-dependent mortality).     

Global Supply of Biomass for Energy and Carbon Sequestration from Afforestation/Reforestation Activities

In this paper we provide an analytical framework to estimate the joint production of biomass and carbon sequestration from afforestation and reforestation activities. The analysis is based on geographical explicit information on a half-degree resolution. For each grid-cell the model estimates forest growth using a global vegetation model and chooses forest management rules. Land prices, cost of forest production and harvesting are determined as a function of grid specific site productivity, population density and estimates of economic wealth. The sensitivity of the results due to scenario storylines is assessed using different population and economic growth assumptions, which are consistent with B1 and A2 of the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC-SRES) marker scenarios. Considerable differences in the economic supply schedules are found. However, technical potentials seem to converge given constancy in other underlying assumptions of the model.     

Cost-effective mitigation strategies to reduce bycatch threats to cetaceans identified using return-on-investment analysis

Globally, fisheries bycatch threatens the survival of many whale and dolphin species. Strategies for reducing bycatch can be expensive. Management is inclined to prioritize investment in actions that are inexpensive, but these may not be the most effective. We used an economic tool, return-on-investment, to identify cost-effective measures to reduce cetacean bycatch in the trawl, net, and line fisheries of Australia. We examined 3 management actions: spatial closures, acoustic deterrents, and gear modifications. We compared an approach for which the primary goal was to reduce the cost of bycatch reduction to fisheries with an approach that aims solely to protect whale and dolphin species. Based on cost-effectiveness and at a fine spatial resolution, we identified the management strategies across Australia that most effectively abated dolphin and whale bycatch. Although trawl-net modifications were the cheapest strategy overall, there were many locations where spatial closures were the most cost-effective solution, despite their high costs to fisheries, due to their effectiveness in reducing all fisheries interactions. Our method can be used to delineate strategies to reduce bycatch threats to mobile marine species across diverse fisheries at relevant spatial scales to improve conservation outcomes.     

Generation lengths of the world's birds and their implications for extinction risk

Birds have been comprehensively assessed on the International Union for Conservation of Nature (IUCN) Red List more times than any other taxonomic group. However, to date, generation lengths have not been systematically estimated to scale population trends when undertaking assessments, as required by the criteria of the IUCN Red List. We compiled information from major databases of published life-history and trait data for all birds and imputed missing life-history data as a function of species traits with generalized linear mixed models. Generation lengths were derived for all species, based on our modeled values of age at first breeding, maximum longevity, and annual adult survival. The resulting generation lengths varied from 1.42 to 27.87 years (median 2.99). Most species (61%) had generation lengths <3.33 years, meaning that the period of 3 generations—over which population declines are assessed under criterion A—was <10 years, which is the value used for IUCN Red List assessments of species with short generation times. For these species, our trait-informed estimates of generation length suggested that 10 years is a robust precautionary value for threat assessment. In other cases, however, for whole families, genera, or individual species, generation length had a substantial impact on their estimated extinction risk, resulting in higher extinction risk in long-lived species than in short-lived species. Although our approach effectively addressed data gaps, generation lengths for some species may have been underestimated due to a paucity of life-history data. Overall, our results will strengthen future extinction-risk assessments and augment key databases of avian life-history and trait data.     

Thermogenic hydrocarbons in seawater of the Gippsland Shelf,southeast Australia

An offshore survey measured the concentration of thermogenic hydrocarbons (THCs) in samples extracted from seawater at 718 locations along 22 traverse lines across the Gippsland Shelf, southeast Australia, and recorded compounds typical of subsurface crude oil and natural gas (petroleum) accumulations. Background concentrations of 8 ppm, with isolated peak levels of 20 to 52 ppm, were detected in samples extracted from seawater at depths of 30 to 50 m over distances of 10 km. Two sources have been suggested — seepage of THCs from subsurface accumulations of petroleum, or THCs in waste-water discharged by several offshore petroleum production facilities which are present on the shelf. A waste-water source is favoured because of the transitory nature of the concentrations, and changes in composition consistent with plume drift away from the point(s) of discharge. Overall, however, the concentration of THCs in waters of the Gippsland Shelf compare favourably with levels in waters affected by urban runoff. The concentration of THCs in other coastal waters from urban and onshore sources is low, equivalent to the background concentration in the major oceans of the world.     

Functional traits and the growth-mortality trade-off in tropical trees

A trade-off between growth and mortality rates characterizes tree species in closed canopy forests. This trade-off is maintained by inherent differences among species and spatial variation in light availability caused by canopy-opening disturbances. We evaluated conditions under which the trade-off is expressed and relationships with four key functional traits for 103 tree species from Barro Colorado Island, Panama. The trade-off is strongest for saplings for growth rates of the fastest growing individuals and mortality rates of the slowest growing individuals (r2 = 0.69), intermediate for saplings for average growth rates and overall mortality rates (r2 = 0.46), and much weaker for large trees (r2 < or = 0.10). This parallels likely levels of spatial variation in light availability, which is greatest for fast- vs. slow-growing saplings and least for large trees with foliage in the forest canopy. Inherent attributes of species contributing to the trade-off include abilities to disperse, acquire resources, grow rapidly, and tolerate shade and other stresses. There is growing interest in the possibility that functional traits might provide insight into such ecological differences and a growing consensus that seed mass (SM), leaf mass per area (LMA), wood density (WD), and maximum height (H(max)) are key traits among forest trees. Seed mass, LMA, WD, and H(max) are predicted to be small for light-demanding species with rapid growth and mortality and large for shade-tolerant species with slow growth and mortality. Six of these trait-demographic rate predictions were realized for saplings; however, with the exception of WD, the relationships were weak (r2 < 0.1 for three and r2 < 0.2 for five of the six remaining relationships). The four traits together explained 43-44% of interspecific variation in species positions on the growth-mortality trade-off; however, WD alone accounted for > 80% of the explained variation and, after WD was included, LMA and H(max) made insignificant contributions. Virtually the full range of values of SM, LMA, and H(max) occurred at all positions on the growth-mortality trade-off. Although WD provides a promising start, a successful trait-based ecology of tropical forest trees will require consideration of additional traits.