Stakeholder involvement facilitates decision making for UK nuclear accident recovery

The importance of major stakeholders participating in the formulation of strategies for maintaining food safety and agricultural production following a nuclear accident has been successfully demonstrated by the UK 'Agriculture and Food Countermeasures Working Group' (AFCWG). The organisation, membership and terms of reference of the group are described. Details are given of the achievements of the AFCWG and its sub-groups, which include agreeing management options that would be included in a recovery handbook for decision-makers in the UK and tackling the disposal of large volumes of contaminated milk, potentially resulting from a nuclear accident.     

Impact of microbial activity on the hydraulic properties of fractured chalk

The impact of microbial activity on fractured chalk transmissivity was investigated on a laboratory scale. Long-term experiments were conducted on six fractured chalk cores (20 cm diameter, 23-44 cm long) containing a single natural fracture embedded in a porous matrix. Biodegradation experiments were conducted under various conditions, including several substrate and oxygen concentrations and flow rates. 2,4,6-Tribromophenol (TBP) was used as a model contaminant (substrate). TBP biodegradation efficiency depended mainly on the amount of oxygen. However, under constant oxygen concentration at the core inlet, elevating the flow rates increased the removal rate of TBP. Transmissivity reduction was clearly related to TBP removal rate, following an initial slow decline and a further sharp decrease with time. The fracture's transmissivity was reduced by as much as 97% relative to the initial value, with no leveling off of the clogging process. For the most extreme cases, reductions of 262 and 157 microm in the equivalent hydraulic apertures were recorded for fractures with initial apertures of 495 and 207 microm, respectively. The reductions in fracture transmissivity occurred primarily because of clogging by bacterial cells and extracellular polymeric substances (EPS) produced by the bacteria. Most of the biodegradation activity was concentrated near the fracture inlet, where the most suitable biodegradation conditions (nutrients and oxygen) prevailed, suggesting that the clogging had occurred in that vicinity. The clogging must have changed the structure of the fracture void, thereby reducing the active volume participating in flow and transport processes. This phenomenon caused accelerated transport of non-reactive tracers and doubled the fracture's dispersivity under constant flow rates.     

Brominated dioxin-like compounds: in vitro assessment in comparison to classical dioxin-like compounds and other polyaromatic compounds

Recently, several countries agreed to adopt the Stockholm convention on persistent organic pollutants (POPs). One future obligation will be to add other POPs as new evidence becomes available. In vitro cell-based bioassays offer a rapid, sensitive, and relatively inexpensive solution to screen possible POP candidates. In the present study, we investigated the aryl hydrocarbon (Ah)-receptor activity of several dioxin-like POPs by using the Micro-EROD (Ethoxy-Resorufin-O-Deethylase) and DR-CALUX (Dioxin-Responsive-Chemical Activated Luciferase gene eXpression) bioassays, which are two state-of-the-art methods. The Micro-EROD system used in our study utilizes a wild-type rat liver cell line (rat liver H4IIEC3/T cells), while the DR-CALUX bioassay consists of a genetically modified rat hepatoma H4IIE cell line that incorporates the firefly luciferase gene coupled to dioxin-responsive elements (DREs) as a reporter gene. In the case of the DR-CALUX bioassay, we used an exposure time of 24 h, whereas we used a 72-h exposure time in the Micro-EROD bioassay. The aim of this study was to compare conventional dioxin-like POPs (such as polychlorinated dibenzodioxins and -furans, PCDD/Fs and coplanar polychlorinated biphenyls, PCBs) with several other classes of possible candidates to be added to the current toxicity equivalent factor (TEF) model in the future. Therefore, this study compares in vitro CYP1A1 (Micro-EROD bioassay) and firefly luciferase induction (DR-CALUX bioassay) in several mixed polyhalogenated dibenzodioxins and -furans (PXDD/Fs; X=Br, Cl, or F), alkyl-substituted polyhalogenated dibenzodioxins and -furans (PMCDD/Fs; M=methyl), polyhalogenated biphenyls (PXBs, X=Br, Cl ), polybrominated diphenyl ethers (PBDEs), pentabromophenols (PBPs), and tetrabromobisphenol-A (TBBP-A). We also evaluate congener-specific relative potencies (REPs) and efficacies (% of TCDD(max)) and discuss the dose-response curves of these compounds, as well as the dioxin-like potency of several other Ah-receptor agonists, such as those of the polyaromatic hydrocarbons (PAHs) and polychlorinated naphthalenes (PCNs). The highest REP values were found for several PXDD/F congeners, followed by some coplanar PXBs, trichlorinated PCDD/Fs, PAHs, PBDE-126, 1-6-HxCN, and some brominated flame retardants (TBBP-A). These in vitro investigations indicate that further research is necessary to evaluate more Ah-receptor agonists for dioxin-like potency.     

Size-correlated division of labour and spatial distribution of workers in the driver ant,<Emphasis Type="Italic"> Dorylus molestus</Emphasis>

Driver ants ( Dorylus spp.) show a high degree of worker polymorphism. Previous reports suggest that large Dorylus workers are specialised for defensive tasks. In this study, we first quantitatively tested whether there is a size-correlated division of defensive labour among workers. Second, we determined whether the spatial distribution of workers outside the nest can be predicted based on such size-specific differences in task allocation. We show that the division of defensive behaviour among different-sized workers is not strict. However, there is a significant correlation between worker size and the tendency to carry out defensive tasks. First, workers of larger size were more likely than smaller workers to participate in colony defence. Second, larger workers were more frequent near the nest containing the reproducing individuals and the brood. Finally, large workers were more common in open sections of the trail than in covered sections, which are likely to be less exposed to predators.     

Analysis of the St. Petersburg Traffic Data using the OSPM Model

Since October 1998 two DOAS instruments were installed at the level of the first floor and at the top of a building located in St. Petersburg at Pestelya Street. The collected datacovers the time period of December 1998–March 2001, and include concentrations of benzene, toluene, NO and NO₂, ozone and SO₂. There is also an additional information about the traffic intensity and meteorological conditions. The results of the analysis of this data set, using the OSPM model, are presented here with the goal to understand the features of the air pollution dispersion in this street canyon and to analyse the information about the emission factors of the vehicles. In particular, the model results are used for the solution of the inverse problem of reconstructing the emission factors from measured concentrations. The results obtained indicate that most of the concentrations are well inside the Russian standards with the only exception of NO₂ (mean and 98-th percentile are equal to 57.8 and 119.2 g m^-3 for the street level). The same values for benzene are 18.5 and 62.6, respectively. Emission estimates show that there is a possibility that the NO_x and benzene basic emission factors recommended by the Russian national guidelines could result in overestimating the traffic emissions. These considerations are supplemented with the model sensitivity tests carried out in connection with the problem of predictability of NO₂ concentrations in the street canyon. Tests indicate that NO₂ concentrations are not very sensitive to NO_x emissions because of the usually low urban background ozone levels.     

Imaging of water flow in porous media by magnetic resonance imaging microscopy

Magnetic resonance imaging (MRI) was used to study the flow of water in a column 14 mm in diameter packed with glass heads. The sample was fully saturated and water was pumped through the column using a peristaltic pump, at flow rates of 125 and 250 mL h(-1). This corresponds to mean velocities of 0.5 and 1 mm s(-1), given a porosity of 0.46 m3 m(-3). Nuclear magnetic resonance (NMR) images of the proton density and velocities within a 2-mm slice were taken at a spatial resolution of 0.15 x 0.15 x 2 mm3. At a mean pore water velocity of 1 mm s(-1) we approximated hydrodynamic dispersion using NMR-measured velocity distributions in a 2-mm slice through the sample. Additionally, we conducted a step pulse tracer experiment with chloride through the same column and at identical initial and boundary conditions. We fitted the convection-dispersion equation to the breakthrough curve and compared the column scale dispersion of the tracer experiment with the respective NMR estimate derived at the slice scale.     

Zinc accumulation by the slime mold Fuligo septica (L.) Wiggers in the former Soviet Union and North Korea

Samples of the slime mold Fuligo septica (L.) Wiggers were collected from an ecologically diverse selection of sites across the former USSR and in North Korea to determine their Zn concentrations. Plasmodia were collected from trees, rocks, soils, the walls of buildings and a variety of other materials and structures from 1990 to 1996. The biomass collected ranged from 305 to 968 mg, whereas Zn concentrations in plasmodia of F. septica ranged from 8400 to 23,000 mg kg(-1) dry wt. (mean and standard error = 14,200 +/- 860 mg kg(-1) dry wt.). No clear trend as to which areas produced F. septica with the highest Zn concentrations was discernable. Nor was it possible to identify any particular substrate on which F. septica grew that produced noticeably high Zn concentrations. For example, forest litter on which F. septica was found had Zn concentrations of only 25 to 130 mg kg(-1) dry wt. Our data confirm the only other study showing hyperaccumulation of Zn in F. septica, which was carried out in Finland. This ability seems to be unique to this species, but how or why it does this, or why such high Zn concentrations are not toxic to F. septica, are questions requiring future research.