Distribution and partitioning of depleted uranium (DU) in soils at weapons test ranges - investigations combining the BCR extraction scheme and isotopic analysis

Depleted uranium (DU) has become a soil contaminant of considerable concern in many combat zones and weapons-testing sites around the world, including locations in Europe, the Middle East and the USA, arising from its dispersion via the application of DU-bearing munitions. Once DU is released into the environment its mobility and bioavailability will, like that of other contaminants, largely depend on the type of associations it forms in soil and on the nature of the soil components to which it binds. In this study we used the BCR sequential extraction scheme to determine the partitioning of DU amongst soil fractions of texturally varying soils from locations affected by weapons-testing activities. Isotopic analyses (MC-ICP-MS and alpha-spectrometry) were performed to verify the presence of DU in whole soils and soil fractions and to determine any preferential partitioning of the contaminant. Results identified soil organic matter as being consistently the most important component in terms of DU retention, accounting for 30-100% of DU observed in the soils examined. However, at greater distances from known contamination points, DU was also found to be largely associated with the exchangeable fraction, suggesting that DU can be mobilised and transported by surface and near-surface water and does remain in an exchangeable (and thus potentially bioavailable) form in soils.     

Model and input uncertainty in multi-media fate modeling: benzo[a]pyrene concentrations in Europe

This paper evaluates the contribution of (i) uncertainty in substance properties, (ii) lack of spatial variability, (iii) intermodel differences and (iv) neglecting sorption to black carbon (BC) to the uncertainty of Benzo[a]pyrene (BaP) concentrations in European air, soil and fresh water predicted by the multi-media fate model Simplebox. Uncertainty in substance properties was quantified using probabilistic modeling. The influence of spatial variability was quantified by estimating variation in predicted concentrations with three spatially explicit fate models (Impact 2002, EVn BETR and BETR Global). Intermodel differences were quantified by comparing concentration estimates of Simplebox, Impact 2002, EVn BETR and the European part of BETR Global. Finally, predictions of a BC-inclusive version of Simplebox were compared with predictions of a BC-exclusive version. For air concentrations of BaP, the lack of spatial variability in emissions was most influential. For freshwater concentrations of BaP, intermodel differences and lack of spatial variability in dimensions of fresh water bodies were the dominant sources of uncertainty. For soil, all sources of uncertainty were of comparable magnitude. Our results indicate that uncertainty in Simplebox can be as large as three orders of magnitude for BaP concentrations in the environment and would be substantially underestimated by focusing on one source of uncertainty only.     

Contributions of Private Landowners to the Conservation of the Gopher Tortoise (<Emphasis Type="Italic">Gopherus polyphemus</Emphasis>)

Private landowners play a pivotal role in determining whether or not rare species persist in regions where privately owned land is extensive. The range of the gopher tortoise (Gopherus polyphemus) is confined to the Southeastern U.S., a region predominantly under private ownership, and thus the status of this species is largely dependent upon land management decisions made by private landowners. We sent an anonymous mail survey to 2,584 individuals to examine factors affecting gopher tortoise occurrence on private lands in Mississippi (adjusted response rate of 23%). Few respondents (19%) reported currently having tortoises on their property, although many had them in the past (30%). Tortoises were persisting primarily on larger properties with longleaf pine that were not managed chiefly for timber production. In general, respondents were largely unaware of habitat requirements of tortoises or effects of various land management practices on them, and few reported using management techniques that benefit tortoises, such as prescribed burning. Most respondents (57%) knew of wildlife incentive programs, but were hesitant to enroll because they did not want to commit to managing their property in a particular manner (34%). We suggest actions that could improve the likelihood of tortoise persistence in this region, as well as changes that could be made to incentive programs to increase landowner participation. These suggestions should be relevant to the conservation of other rare species on private lands in other regions.     

The Capacity to Detect Change Stream Fish Communities Characteristics at the Site-Level in the Lake Ontario Basin

We investigate natural inter-annual variability of fish community measures within streams of the Lake Ontario basin. Given this variability, we examined coefficients of variation (CV) among the community measures and three scenarios pertaining to the capacity of biologists to detect changes in the fish community at the stream site level. Results indicate that Ontario's stream fish communities are highly variable in time. Young-of-the-year rainbow trout growth was the least variable whereas biomass density scored the highest CV of 0.50 among streams (range 0.22-0.99). Given the CVs and relatively equal sample sizes, our measures of the fish community can be ranked from least to most powerful: biomass, density, richness, diversity, and growth of young-of-the-year rainbow trout. Only large changes in measures can typically be detected. For instance, it would take 4-6 years of monitoring before and after a pulse perturbation to detect a 50 % change in species richness or diversity. We suggest that monitoring abundance is unlikely to result in the detection of small impacts within a short period of time and that large effects can be masked by low statistical power. This evidence voices the need for more research into better sampling methods, experimental designs, and choice of indicators to support monitoring programs for flowing waters.     

Laboratory Investigation of a New Trommel Model

Abstract

Rotary screens, or trommels, are an important unit operation in material and fuel processing. A computer model has been developed based upon fundamental mechanics. The coefficients and variables employed in the model thus have real physical meaning; adjusting them based upon laboratory data allows the model user to draw conclusions about the behavior of the trommel that can be applied to design and operational changes. The laboratory testing program was specifically designed to test the model described in this paper.

The model proved able to track the laboratory data. Important phenomena that were validated or revealed included the significance of particle layering, changes in bed sliding with rotational velocity, and the pre-eminence of residence time.     

Echoes from the Past: A Healthy Baltic Sea Requires More Effort

Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal increased sea surface temperatures and expanded seafloor anoxia (in deep basins) during earlier natural warm climate phases, such as the Medieval Climate Anomaly. Under future IPCC scenarios of global warming, there is likely no improvement of bottom water conditions in the Baltic Sea. Thus, the measures already designed to produce a healthier Baltic Sea are insufficient in the long term. The interactions between climate change and anthropogenic impacts on the Baltic Sea should be considered in management, implementation of policy strategies in the Baltic Sea environmental issues, and adaptation to future climate change.     

Fate of atrazine in switchgrass–soil column system

Atrazine, a broad-leaf herbicide, has been used widely to control weeds in corn and other crops for several decades and its extensive used has led to widespread contamination of soils and water bodies. Phytoremediation with switchgrass and other native prairie grasses is one strategy that has been suggested to lessen the impact of atrazine in the environment. The goal of this study is to characterize: (1) the uptake of atrazine into above-ground switchgrass biomass; and (2) the degradation and transformation of atrazine over time. A fate study was performed using mature switchgrass columns treated with an artificially-created agricultural runoff containing 16 ppm atrazine. Soil samples and above-ground biomass samples were taken from each column and analyzed for the presence of atrazine and its chlorinated metabolites. Levels of atrazine in both soil and plant material were detectable through the first 2 weeks of the experiment but were below the limit of detection by Day 21. Levels of deethylatrazine (DEA) and didealkylatrazine (DDA) were detected in soil and plant tissue intermittently over the course of the study, deisopropylatrazine (DIA) was not detected at any time point. A radiolabel study using [¹⁴C]atrazine was undertaken to observe uptake and degradation of atrazine with more sensitivity. Switchgrass columns were treated with a 4 ppm atrazine solution, and above-ground biomass samples were collected and analyzed using HPLC and liquid scintillation counting. Atrazine, DEA, and DIA were detected as soon as 1 d following treatment. Two other metabolites, DDA and cyanuric acid, were detected at later time points, while hydroxyatrazine was not detected at all. The percentage of atrazine was observed to decrease over the course of the study while the percentages of the metabolites increased. Switchgrass plants appeared to exhibit a threshold in regard to the amount of atrazine taken up by the plants; levels of atrazine in leaf material peaked between Days 3 and 4 in both studies.     

Effect of modified montmorillonites on the biodegradation and adsorption of biomarkers such as hopanes, steranes and diasteranes

The effect of modified montmorillonites on the biodegradation and adsorption of selected steranes, diasteranes and hopanes was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The unmodified montmorillonite was treated with didecyldimethylammonium bromide, hydrochloric acid and the relevant metallic chloride to produce organomontmorillonite, acid activated montmorillonite and homoionic montmorillonite respectively which were used in this study. The study indicated that organomontmorillonite, acid activated montmorillonite and potassium montmorillonite did not support the biodegradation of the selected steranes, diasteranes and hopanes as alteration of the biomarkers via biodegradation varied from a paltry 2–6 %. The adsorption of the selected biomarkers on acid activated montmorillonite and organomontmorillonite was also poor. However, adsorption of the biomarkers on potassium montmorillonite was relatively high. Sodium montmorillonite and unmodified montmorillonite appear to stimulate the biodegradation of the selected biomarkers moderately (30–35 %) with adsorption occurring at low level. Calcium montmorillonite and ferric montmorillonite effected significant biodegradation (51–60 %) of the selected biomarkers.     

Dietary exposure to technical hexabromocyclododecane (HBCD) alters courtship, incubation and parental behaviors in American kestrels (Falco sparverius)

Hexabromocyclododecane (HBCD) is a high production volume brominated flame retardant that has been detected in the environment and wildlife at increasing concentrations. This study was designed to determine potential effects of dietary exposure to environmentally relevant levels of HBCD on behavior during reproduction in captive American kestrels. Twenty kestrel pairs were exposed to 0.51 μg technical HBCD g⁻¹ kestrel d⁻¹ from 4 weeks prior to pairing until chicks hatched (∼75 d). Ten pairs of controls received the safflower oil vehicle only and were used for comparison. During the courtship period the chitter-calls were reduced in both sexes (p = 0.038) and females performed fewer bonding displays (p = 0.053). Both sexes showed a propensity to be less active than controls during courtship. The reduction in male courtship behavior was correlated with reduced courtship behaviors of females (p ? 0.008) as well as reduced egg mass (p = 0.019). During incubation, nest temperatures of treatment pairs were lower at mid-incubation (p = 0.038). HBCD-exposed males performed fewer key parental behaviors when rearing nestlings, including entering the nest-box, pair-bonding displays and food-retrievals. HBCD-exposed females appeared to compensate for the reduced parental behavior of their mates by performing these same behaviors more frequently than controls (p = 0.004, p = 0.027, p = 0.025, respectively). This study demonstrates that HBCD affects breeding behavior in American kestrels throughout the reproductive season and behavioral alterations were linked to reproductive changes (egg size). This is the first study to report HBCD effects on reproductive behavior in any animal model.     

Spring-harvested game birds in the Western James Bay region of Northern Ontario, Canada: the amount of organochlorines in matched samples of breast muscle, skin, and abdominal fat

We examined matched-tissue samples (the right pectoral muscle plus the associated skin and fat was considered a breast portion) of 81 spring-harvested waterfowl and 19 summer-harvested godwits (Limosa spp.) to assess the potential of these water birds contributing to the body burden of PCBs and DDT noted in First Nation people of the western James Bay region, northern Ontario, Canada. In general, the dabbling ducks (mallard duck, Anas platyrhynchos; and northern pintail, A. acuta) had significantly lower percent lipid (gravimetrically determined) values in skin tissue, fat tissue, and breast muscle compared to the goose species (Canada goose, Branta canadensis; lesser snow goose, Chen caerulescens); godwits had percent lipid values not significantly different than ducks and geese. Also, the percent lipid values in skin for all species of birds examined approached those found in fat tissue. Organochlorine data were expressed as the amount (microg) of each contaminant per breast portion to show contaminant consumption in terms of typical and easily recognizable dietary portions; direct comparisons were made to acceptable daily intake (ADI) or tolerable daily intake (TDI) values as recommended by Health Canada. Significant differences in the amount of organochlorines between bird species for skin, fat tissue, and breast muscle samples were found. In general, breast portions from snow geese contained the least amount of organochlorines, followed by godwits (except for mirex) and then Canada geese; the dabbling ducks had the greatest amount of organochlorines on a breast portion basis. However, on average, no 60 kg person would exceed the calculated organochlorine ADI/TDI values consuming one breast portion (i.e., breast + associated skin and fat), but the maximum value of SigmaPCBs for skin tissue alone in male mallards (47 microg) was more than twice the ADI/TDI (18 microg/day); while, that in fat tissue alone (17 microg) approached the ADI/TDI. Thus, the consumption of dabbling ducks by children is an issue that should be explored further, if tissue other than breast muscle is eaten. Lastly, the consumption of waterfowl was a source of PCBs for people of Fort Albany and Kashechewan, but not DDT, as this organochlorine was infrequently detected.