A review of radionuclides in tide-washed pastures on the Irish Sea coast in England and Wales and their transfer to food products

Close to the Sellafield Reprocessing Plant activity concentrations of many radionuclides including the long-lived 137Cs and actinides on tide-washed pastures bordering the Irish Sea are high compared with other terrestrial ecosystems in the United Kingdom. Despite the comparatively high deposition of radionuclides, contamination of agricultural products from tide-washed pastures is lower than would be predicted from studies in terrestrial ecosystems. This is because the main source of contamination in tide-washed pasture, radionuclides associated with sedimentary particles, has low availability for uptake by plant roots and in the gut of ruminants. Generalised Derived Limits (GDLs), published by the National Radiological Protection Board (NRPB) are estimates of environmental radioactivity concentrations which would potentially be radiologically significant. These provide a benchmark against which environmental measurements can be assessed. In the past, several comparisons of radioactivity concentrations in tide-washed pastures with GDLs have been made, but only some of these comparisons are valid since current approaches used to assess doses are not always strictly appropriate to these ecosystems. Directly applicable GDLs are needed, and are currently being developed by the NRPB.     

Modeling radium and radon transport through soil and vegetation

A one-dimensional flow and transport model was developed to describe the movement of two fluid phases, gas and water, within a porous medium and the transport of 226Ra and 222Rn within and between these two phases. Included in this model is the vegetative uptake of water and aqueous 226Ra and 222Rn that can be extracted from the soil via the transpiration stream. The mathematical model is formulated through a set of phase balance equations and a set of species balance equations. Mass exchange, sink terms and the dependence of physical properties upon phase composition couple the two sets of equations. Numerical solution of each set, with iteration between the sets, is carried out leading to a set-iterative compositional model. The Petrov-Galerkin finite element approach is used to allow for upstream weighting if required for a given simulation. Mass lumping improves solution convergence and stability behavior. The resulting numerical model was applied to four problems and was found to produce accurate, mass conservative solutions when compared to published experimental and numerical results and theoretical column experiments. Preliminary results suggest that the model can be used as an investigative tool to determine the feasibility of phytoremediating radium and radon-contaminated soil.     

Intermorph breeding and the potential for reproductive isolation in polymorphic mole salamanders (Ambystoma talpoideum)

The study of reproductive isolation as a prerequisite to sympatric speciation has been limited by the focus on species that have already experienced such isolation. However, a complete understanding of how such processes evolve depends on observing taxa before they complete the speciation process. We studied the potential for sexual isolation in the polyphenic mole salamander, Ambystoma talpoideum, using a series of laboratory and field experiments. This species consists of aquatic paedomorphic adults and terrestrial metamorphic adults which are exhibited by both sexes and which mate in the same aquatic habitat. Previous field studies on this species suggested that intermorph breeding would be less common during the winter months, because paedomorphic adults begin breeding in early autumn and thus may have less energy available for reproduction in the winter. Laboratory experiments conducted during the winter showed that the mating behavior of paedomorphic males occurred at a much lower frequency than that of metamorphic males. In contrast, field experiments that best mimicked natural conditions revealed symmetric intermorph breeding and included multiple paternity shared among males of each morph. This and other studies suggest that there is little evidence of sexual isolation among morphs based on behavioral interactions alone. However, the potential for partial isolation still occurs because of temporal and spatial differences in the frequencies of each morph in nature. Our results suggest that further studies on this system, and other similar polyphenisms, may provide valuable insight into the mechanisms that underlie the evolution of reproductive isolation.     

Parasitism in a social wasp: effect of gregarines on foraging behavior, colony productivity, and adult mortality

Behavior in eusocial insects likely reflects a long history of selection imposed by parasites and pathogens because the conditions of group living often favor the transmission of infection among nestmates. Yet, relatively few studies have quantified the effects of parasites on both the level of individual colony members and of colony success, making it difficult to assess the relative importance of different parasites to the behavioral ecology of their social insect hosts. Colonies of Polybia occidentalis, a Neotropical social wasp, are commonly infected by gregarines (Phylum Apicomplexa; Order Eugregarinida) during the wet season in Guanacaste, Costa Rica. To determine the effect of gregarine infection on individual workers in P. occidentalis, we measured foraging rates of marked wasps from colonies comprising both infected and uninfected individuals. To assess the effect of gregarines on colony success, we measured productivity and adult mortality rates in colonies with different levels of infection prevalence (proportion of adults infected). Foraging rates in marked individuals were negatively correlated with the intensity of gregarine infection. Infected colonies with high gregarine prevalence constructed nests with fewer brood cells per capita, produced less brood biomass per capita, and, surprisingly, experienced lower adult mortality rates than did uninfected or lightly infected colonies. These data strongly suggest that gregarine infection lowers foraging rates, thus reducing risk to foragers and, consequently, reducing adult mortality rates, while at the same time lowering per-capita input of materials and colony productivity. In infected colonies, queen populations were infected with a lower prevalence than were workers. Intra-colony infection prevalence decreased dramatically in the P. occidentalis population during the wet season.An erratum to this article can be found at     

Using pneumatic fracturing extraction to achieve regulatory compliance and enhance voc removal from low-permeability formations

The New Jersey Department of Environmental Protection and Energy (NJDEPE) has been developing cleanup regulations that focus on remediation, rather than extended delineation, and on integrating regulatory requirements with technological developments. To this end, the NJDEPE, under the regulatory aegis of the Environmental Cleanup and Responsibility Act (ECRA), is monitoring an innovative treatment technology pilot test at a TCE-contaminated ECRA site in Hillsborough, New Jersey. The purpose of the study is to determine the applicability of pneumatic fracturing extraction (PFE) as a source-removal technique for extracting volatile organic compounds (VOCs) trapped informations with low permeability. The technology being pilot tested is pneumatic fracturing extraction, a process for enhancing permeability to promote in-situ removal and treatment of VOCs. The patented process uses high-pressure air injected into an isolated subsurface zone at controlled rates and pressures. At a critical point, the geologic material ruptures, and fractures are created that radiate outward from the fracture location. At the pilot test site, formation air flow was increased from 400 percent to 700 percent. PFE is a key component of the overall remediation strategy at the Hillsborough site. Consistent with proposed NJDEPE regulations, a ground-water pump-and-treat system will be installed for plume migration control. Once the pump-and-treat system has been established and shown to be effective, a more aggressive source removal program will be implemented using PFE. This program will include construction of a vadose zone PFE system and evaluation of the use of pneumatic fracturing to remove saturated zone residual dense nonaqueous phase liquids (DNAPL). Preliminary calculations suggest that if source zone concentrations can be reduced to 10 ppm of TCE, then TCE groundwater concentrations may be reduced to background levels at the property boundary compliance points.     

Insights to false positive total cyanide measurements in wastewater plant effluents.

Many publicly owned treatment works in North America are exceeding permitted limits for total cyanide in their wastewater treatment effluents. A recently introduced rapid, segmented, flow-injection analysis procedure using UV digestion and amperometric detection of the membrane-separated cyanide was used to investigate the various scenarios by which elevated cyanide levels might be present in wastewater treatment plant effluent. A number of significant interferences can produce false positive bias during sample analysis with the traditional acid distillation technique, but are minimized or absent with the new analytical method. However, increased levels of cyanide were found in some chlorinated wastewaters compared to the levels before chlorination, suggesting a fast reaction mechanism associated with the disinfectant and some precursor in the wastewater. In particular, the contact of chlorine with nitrite in the presence of a carbon precursor appears to contribute to cyanide formation during wastewater treatment and sample handling. This paper explores the scenarios under which cyanide can form during wastewater treatment as well as those in which a false bias for total cyanide can be obtained during sample processing and provides guidance for appropriate sample handling, screening, and processing to ensure valid analytical results.     

Alternative mating behaviors of the queen polymorphic ant <Emphasis Type="Italic">Temnothorax longispinosus</Emphasis>

Mating behaviors of ants fall into two categories: female calling, in which a female alate releases pheromones that attract males, and male swarming, in which large male aggregations attract females. Female calling is common in species with queens that return to their natal nest to found colonies dependently after mating, while male swarming is common in species with queens that disperse to found independently. In some species that display both founding strategies, a queen-size polymorphism has evolved in which dependent-founding queens are smaller than independent-founding queens. Dependent founding is likely difficult if gynes (virgin queens) are mating in distant swarms. Therefore, a queen may adopt one or the other mating strategy based on its size and founding behavior. We investigated mating behaviors in the queen-polymorphic ant, Temnothorax longispinosus. Observations in laboratory mating arenas indicated that small gynes exhibited significantly lower flight activity than large gynes. Both forms mated in male swarms, and neither form exhibited female calling. The reduced flight activity of the small morph may facilitate returning to the natal nest after mating, provided the mating swarm is located nearby. Therefore, alternative colony-founding behaviors may be possible without the evolution of female-calling behavior; however, the reduced flight activity of small morphs may require that mating swarms are not distant from the natal nest.