Disposition and metabolic profiling of [14C]-decabromodiphenyl ether in pregnant Wistar rats

Fully brominated diphenyl ether, decabromodiphenyl ether (DBDE), is one of the most widely used brominated flame retardants worldwide. Little data is available about the metabolic fate of DBDE in animal models and nothing at all about the extent of foetal exposure. In this work, pregnant Wistar rats were force-fed with 99.8% pure [14C]-DBDE over 96 h at a late stage of gestation (days 16 to 19). More than 19% of the administered dose was recovered in tissues and carcasses, demonstrating efficient absorption of DBDE despite its high molecular weight and low solubility. The highest concentrations of DBDE residues were found in endocrine glands (adrenals, ovaries) and in the liver, with lower values recorded for fat. In all tissue extracts, most of the radioactivity was associated with unchanged DBDE. The use of high-grade purity [14C]-DBDE allowed quantification of several metabolites present both in maternal tissues and in foetuses. These biotransformation products accounted for 9-27% of the extractable radioactivity in tissues and 14% of that in foetuses. Three nona-BDEs and one octa-BDE were identified by LC-APPI/MS. The unequivocal characterisation of a hydroxylated octa-BDE isolated from liver was confirmed by NMR. In rat, the main metabolic pathways of DBDE are debromination and oxidation. DBDE, and very likely most of its metabolites, are able to cross the placental barrier in rat. Metabolic profiles, obtained in vivo for the first time, demonstrated the presence of DBDE and major biotransformation products in endocrine glands as well as in foetuses. The biological activity of these metabolites still needs to be assessed in order to better understand the potential toxicity of DBDE.     

Modelling Replicated Weed Growth Data using Spatially-varying Growth Curves

Weed growth in agricultural fields constitutes a major deterrent to the growth of crops, often resulting in low productivity and huge losses for the farmers. Therefore, proper understanding of patterns in weed growth is vital to agricultural research. Recent advances in Geographical Information Systems (GIS) now allow geocoding of agricultural data, which enable more sophisticated spatial analysis. Our current application concerns the development of statistical models for conducting spatial analysis of growth patterns in weeds. Our data comes from an experiment conducted in Waseca, Minnesota, that recorded growth of the weed Setariaspp. We capture the spatial variation in Setaria spp. growth using spatially-varying growth curves. An added challenge is that these designs are spatially replicated, with each plot being a lattice of sub-plots. Therefore, spatial variation may exist at different resolutions – a macro level variation between the plots and micro level variation between the sub-plots nested within each plot. We develop a Bayesian hierarchical framework for this setting. Flexible classes of models result which are fitted using simulation-based methods.     

Diel variations in photoinduced oxidation of Hg0 in freshwater

Experiments have been conducted to determine diel variations in photoinduced Hg0 oxidation in lake water under natural Hg0(aq) concentrations. Pseudo-first-order rates of photooxidation (k') were calculated for water freshly collected in a Canadian Shield lake, Lake Croche (45 degrees 56' N, 74 degrees 00' W), at different periods of the day and subsequently incubated in the dark. Hg0 oxidation rates ranged from 0.02 to 0.07 h(-1), increasing from sunrise to noon and then decreasing throughout the remainder of the day. These changes paralleled those in sunlight intensity integrated over 1 h preceding water collection, and suggested that the water freshly collected in daylight was rich in photochemically produced Hg0 oxidants. It was also estimated that under intense solar radiation, even if oxidation rates reached a peak, reduction of Hg(II) was the prevalent redox process. Inversely, Hg0 oxidation overcame DGM production during the night or at periods of weaker light intensity. Overall, these findings explain the decreases in the DGM pool generally observed overnight. They also support previous reports that, during summer days, volatilization of Hg0 from water represent an important step in the Hg cycle in freshwater systems.     

Evaluation of the susceptibility of the cultured shrimp Litopenaeus vannamei to vibriosis when orally exposed to the insecticide methyl parathion

The causes of disease in cultured shrimp are difficult to ascertain but there is evidence that disease is correlated with environmental factors. Crustaceans are particularly sensitive to insecticides due to their close phylogenetic relationship with insects. The objective of this study was to investigate whether there was an increased susceptibility of the shrimp Litopenaeus vannamei to Vibrio parahaemolyticus, when exposed to methyl parathion. The outline of the study was the following: An LC50 96 h was determined to methyl parathion orally offered to juvenile shrimp. Further experiments were carried out in order to determine a concentration that affected the shrimp (verified by measuring the acethylcholinesterase activity) while producing minimal mortalities. This sublethal concentration was used in a susceptibility experiment where methyl parathion was offered to shrimp which were later injected with V. parahaemolyticus in a dose expected to kill less than 15%. Probit analysis estimated a 96 h median lethal concentration (LC50) of 1.56 microg g(-1). Mortality and AChE activity showed a concentration-response relationship in the exposure treatments. The median inhibitory concentration (IC50) determined was 0.029 microg g(-1). These results suggested that a concentration of 0.1 microg g(-1) was appropriate for the bacteria-pesticide interaction test as it was able to elicit 11.1% mortality after 10 days of exposure, while producing an AChE inhibition of 57.12%. Cumulative mortalities were significantly increased (P<0.01) in the treatment that combined exposure to methyl parathion and V. parahaemolyticus (35.19%) in comparison with methyl parathion or V. parahaemolyticus alone (9.26% and 7.41%, respectively).     

Allelopathic potential of Cistus ladanifer chemicals in response to variations of light and temperature

Summary. Earlier studies have demonstrated the allelopathic potential of the exudate of Cistus ladanifer leaves, and have identified the compounds responsible for the effect. It is here shown that the effect of each of these compounds and their interactions on germination and seedling development varies depending on the light and temperature parameters to which they are subjected. The allelochemicals show a fairly heterogeneous response when studied separately, there being no general pattern to the behaviour. When they act conjointly, however, their activity is enhanced by high temperatures, and the greatest phytotoxicity in inhibiting both germination and seedling development is attained with high temperatures and long photoperiods. These results suggest that the environmental factors temperature and photoperiod may alter the allelopathic effect of Cistus ladanifer. Received 5 December 2001; accepted 11 March 2002.     

The effect of wastewater treatment on antibiotic resistance in Escherichia coli and Enterococcus sp.

The effects of wastewater treatment on the proportion of Escherichia coli and Enterococcus sp. resistant to specific antibiotics were investigated at two facilities in Davis County, Utah, one of which received hospital waste. Samples were taken from the influent, effluent before disinfection, and secondary anaerobic sludge digester effluent. There was very little difference in antibiotic resistance among E. coli in the inflow waters of the plants but the plant receiving hospital waste had a significantly higher proportion of antibiotic resistant Enterococcus. The effect of wastewater treatment on antibiotic resistance was more pronounced on enterococci than E. coli. Although some increases in antibiotic resistance were observed, the general trend seemed to be a decrease in resistance, especially in the proportion of multidrug resistant Enterococcus sp.     

Distributed process modeling for regional assessment of coastal vulnerability to sea-level rise

Sea-level rise involves increases in the coastal processes of inundation and erosion which are affected by a complex interplay of physical environmental parameters at the coast. Many assessments of coastal vulnerability to sea-level rise have been detailed and localised in extent. There is a need for regional assessment techniques which identify areas vulnerable to sea-level rise. Four physical environmental parameters – elevation, exposure, aspect and slope, are modeled on a regional scale for the Northern Spencer Gulf (NSG) study area using commonly available low-resolution elevation data of 10 m contour interval and GIS-based spatial modeling techniques. For comparison, the same parameters are modeled on a fine-scale for the False Bay area within the NSG using high-resolution elevation data. Physical environmental parameters on the two scales are statistically compared to coastal vulnerability classes as identified by Harvey et al. [1] using the Spearman rank-correlation test and stepwise linear regression. Coastal vulnerability is strongly correlated with elevation and exposure at both scales and this relationship is only slightly stronger for the high resolution False Bay data. The results of this study suggest that regional scale distributed coastal process modeling may be suitable as a first cut in assessing coastal vulnerability to sea-level rise in tide-dominated, sedimentary coastal regions. Distributed coastal process modeling provides a suitable basis for the assessment of coastal vulnerability to sea-level rise of sufficient accuracy for on-ground management and priority-setting on a regional scale.     

Valorization of EVA waste from footwear industry as natural aggregates substitutes in mortar: the effect of granulometry

Journal of Material Cycles and Waste Management - The increased consumption of polymers and the consequent generation of waste requires the development of efficient recycling strategies. In this...     

Performance of mortars with PET

Journal of Material Cycles and Waste Management - The massive amount of plastic production inevitably leads to huge levels of pollution and, consequently, is threatening the environment and...     

Learning and local government in coastal South Australia: towards a community of practice framework for adapting to global change

Social learning can be a vital tool in assisting communities to adapt to change. Local governments can be a conduit between the communities they serve and the policy that they are trying to implement. Social learning in this context can be an iterative, often organic process. Based on a case study of coastal planning in South Australia, Australia, this paper presents the results of a qualitative mixed-method approach that documents the aspects of social learning within coastal management and evaluates the various lessons learned by local governments in South Australia. The role of social learning and adaptive governance is discussed. The paper concludes that by deliberatively incorporating the notion of communities of practice into learning frameworks, local governments can more effectively manage their coastal zones in response to global change.