Ah Receptor Agonists in UV-exposed Toluene Solutions of Decabromodiphenyl Ether (decaBDE) and in Soils Contaminated with Polybrominated Diphenyl Ethers (PBDEs) (9 pp)

Goal, Scope and Background The use of polybrominated diphenyl ethers (PBDEs) as flame retardants increases the risk for emissions of other brominated compounds, such as polybrominated dibenzodioxins (PBDDs) and dibenzofurans (PBDFs). The large homology in structure of PBDD/Fs and mechanism of toxic action, i.e. the capacity to activate the Ah receptor (AhR) pathway, compared to their well-studied chlorinated analogues, justifies a raised concern to study the environmental levels and fate of these compounds. Decabromodiphenyl ether (decaBDE) is the most widely used PBDE today. Studies on photolytic debromination of decaBDE in organic solvents have shown debromination of decaBDE, as well as formation of PBDFs. However, little is known about the transformation mechanisms and there are only scarce data on photoproducts and PBDE transformation in environmentally relevant matrices. In this study, mechanism-specific dioxin bioassays were used to study photolytic formation of AhR agonists in toluene solutions of decaBDE. In addition, the influence of irradiation time and UV-light wavelength on the formation was studied. PBDE congener patterns and presence of PBDD/Fs were analysed. Further, AhR agonists were analysed in agricultural soils contaminated with PBDEs. Soils were also exposed to UV-light to study changes in AhR agonist levels. Methods Toluene solutions of decaBDE were irradiated using three different spectra of UV-light, simulating UV-A (320-400 nm), UV-AB (280-400 nm), and UV-ABC (250-400 nm). Additionally, decaBDE solutions were exposed to narrow wavelength intervals (10 nm bandwidth) with the central wavelengths 280, 290, 300, 310, 320, 330, 340, 350, 360 nm. AhR agonists in decaBDE solutions were analysed with two different bioassays, the chick embryo liver-cell assay for dioxins (Celcad) and the dioxin responsive, chemically activated luciferase expression assay (DR-Calux). Also, the decaBDE solutions were analysed with LRGC-LRMS to obtain PBDE congener patterns for breakdown of decaBDE, and with HRGC-HRMS, for presence of PBDD/Fs. Four soils were exposed to UV-AB light, under both dry and moist conditions. Levels of AhR agonists in soil extract fractions, before and after UV-exposure, were analysed with the DR-Calux. Results and Discussion Significant levels of photoproducts able to activate the AhR pathway, up to 31 ng bio-TEQ/ml, were formed in UV-exposed decaBDE solutions. The transformation yield of decaBDE into AhR agonists was estimated to be at the 0.1%-level, on a molar basis. The net formation was highly dependent on wavelength, with the sample irradiated at 330 nm showing the highest level of dioxin-like activity. No activity was detected in controls. PBDE analysis confirmed decaBDE degradation and a clear time-dependent pattern for debromination of PBDE congeners. AhR agonist effect in the recalcitrant fractions of the soils corresponded to the levels of chemically derived TEQs, based only on chlorinated dioxin-like compounds in an earlier study. It was concluded that no significant levels of other AhR agonists, e.g. PBDFs, were accumulated in the soil. UV-light caused changes in AhR-mediated activity in the more polar and less persistent fractions of the soils, but it is not known which compounds are responsible for this. Recommendations and Perspective . The laboratory experiments in this study show that high levels of AhR agonists can be formed as photoproducts of decaBDE and it is important to elucidate if and under which conditions this might occur in nature. However, soil analysis indicates that photoproducts of PBDE do not contribute to the accumulated levels of persistent dioxin-like compounds in agricultural soil. Still, more data is needed to fully estimate the environmental importance of PBDE photolysis and occurrence of its photoproducts in other environmental compartments. Analysis with dioxin bioassays enabled us to gather information about photoproducts formed from decaBDE even though the exact identities of these compounds were not known. Conclusion Bioassays are valuable for studying environmental transformation processes like this, where chemical analysis and subsequent toxicological evaluation requires available standard compounds and information on toxicological potency. The use of bioassays allows a rapid evaluation of toxicological relevance.     

Water localisation and reclamation: steps towards low impact urban design and development

Numerous drivers are providing stimulus for increased water cycle localisation within urban neighbourhoods. This paper uses predominantly Australasian case studies to highlight trends, successes and challenges in the transition to neighbourhood centred water-based services using 'Low Impact' and 'Water Sensitive' design and development techniques. Major steps towards urban sustainability are demonstrated, for example, up to 70% reduction in the demand for potable water (Aurora, Melbourne), removal of contaminated stormwater and sewage effluent discharge to natural waterways vulnerable to nutrient or toxin accumulation, and up to 55% of the area of the greenfield site planted in indigenous species (Regis Park, New Zealand). Reduced demand for potable water would enable continued undiluted use of 'pure' water sources from limited bush catchments (Waitakere Ranges, New Zealand), and less dependence on rivers stressed by low flows. Reductions and dispersion of sewage effluent discharges protects receiving waters, such as Port Phillip Bay, Melbourne, from eutrophication. Reduced stormwater discharge favours retention of the natural hydrological regime of rivers and minimises bioaccumulation of toxins in aquatic ecosystems.     

Phosphorus leaching from cow manure patches on soil columns

The loss of P in overland flow or leachate from manure patches can impair surface water quality. We studied leaching of P from 10-cm-high lysimeters filled with intact grassland soil or with acid-washed sand. A manure patch was created on two grassland and two sand-filled lysimeters, and an additional two grass lysimeters served as blanks. Lysimeters were leached in the laboratory during 234 d with a diluted salt solution, and column effluent was passed through a 0.45-microm filter, analyzed for pH, dissolved reactive P (DRP), and total dissolved P (TDP). At the end of the experiment lysimeter soil was sampled and analyzed for pH, available P, and oxalate-extractable P, Fe, and Al. The concentration of TDP in the effluent from the sand column increased to 25 mg L-1 during the first weeks and remained above 10 mg L-1 during the rest of the percolation. In effluent from grass + patch lysimeters TDP gradually increased to 4 mg L-1. Both in the manure and in the effluent of the sand lysimeter P was found mainly in the form of DRP, but in the effluent from the grass lysimeters was found mainly as dissolved unreactive P (DUP=TDP-DRP). Earthworm activity was responsible for decomposition of the manure patch on the grass lysimeters. Manure patches and their remains were found to be a long-term source of high concentrations of P in leachates. Spreading of patches after a grazing period could reduce their possible negative impacts on the environment.     

Assessing the efficiency gains of improved spatial targeting of policy interventions; the example of an agri-environmental scheme

GIS-based spatial targeting is increasingly recognised as a potentially useful tool to design more efficient policy interventions. The use of this tool has also been advocated in the context of incentive-based agri-environmental schemes, but there has been little work to date to estimate the level of efficiency gains which it may help to achieve. This paper investigates the requirements to arrive at such estimates, using a Scottish farm woodland scheme as a case study. This agri-environmental scheme aims to provide visual amenity and biodiversity. Maps of these two benefits are used to develop improved spatial targeting scenarios that deliver significant efficiency gains in comparison to the existing scheme design. The paper discusses the nature of the spatial distribution of the relevant benefits at the landscape scale and the data requirements for the realistic estimation of efficiency gains. It concludes that although much work needs to be done, the methods available today could and should play a much greater role in improving the landscape-scale design of existing land use schemes focused on the delivery of non-market benefits.     

Steam demand reduction of water–gas shift reaction in IGCC power plants with pre-combustion CO2 capture

This paper presents the results of system assessments that were conducted to compare conventional and advanced water–gas shift reactor sections. The latter are specifically tailored for Integrated Gasification Combined Cycles (IGCC) power plants with pre-combustion CO₂ capture. The advanced shift reactor section comprises four staged reactors with distributed feeds of synthesis gas and quench water in between the reactors. Conventional shift reactor sections consist of two sequential reactors with intermediate cooling, where the entire synthesis gas stream passes both reactors.The advanced shift reactor section reduces the steam requirement of the water–gas shift reaction up to 70% in comparison with conventional configurations, at carbon dioxide capture ratios of approximately 85%. This reduction allows for lower electric efficiency penalties, thus higher net electric outputs for IGCC power plants with CO₂ capture. For each case, the CO₂ capture ratio was optimised for the lowest specific lost work per amount of captured CO₂. Both the number of reactors and the total catalyst volume are higher for the advanced shift reactor sections, resulting in increased capital expenses. In case of four staged reactors, the additional expenses are expected to be outperformed by the increased revenues associated with the higher net electric output.     

Understanding the use of science in decision-making on cockle fisheries and gas mining in the Dutch Wadden Sea: Putting the science–policy interface in a wider perspective

The use of science to inform and underpin decision-making on natural resources is not self-evident as stakeholders often use science in a selective and strategic way. Scientific analyses of science utilisation often focus on how the science–policy interface is organised and from this perspective provide recommendations to scientists about how they can increase their contribution to decision-making. Yet in this paper we argue that a wider perspective on the science–policy interface, in particular by analysing the roles and interactions of actors other than those directly involved, provides both additional explanations and new points of application for strategies aimed at enhancing science utilisation. We illustrate our claim by means of an analysis of decision-making on cockle fisheries and gas mining in the Dutch Wadden Sea between the 1990s and 2004. For many years, scientific studies addressing the ecological effects of these activities were not used to meaningfully contribute to decision-making. In 2004 this situation changed radically. Explanations include the role of intermediaries between scientists, stakeholders and decision-makers and new legislation. Scientists could enhance the chances of knowledge utilisation both by creating a more open science–policy interface and by reframing the policy problems at issue.     

Carbon speciation in municipal solid waste incinerator (MSWI) bottom ash in relation to facilitated metal leaching

The release of inorganic and organic contaminants from municipal solid waste incinerator (MSWI) bottom ash is controlled to a large extent by the release of dissolved organic carbon (DOC), and in particular by the reactive humic (HA) and fulvic acids (FA) subfractions of DOC. The properties of organic matter contributing to the release of DOC, HA and FA are, therefore, important for environmental risk assessment. In this study we have quantitatively measured the carbon speciation, and its relation with the leaching of Cu, in three fresh and carbonated MSWI bottom ash samples. Results show that up to only 25% of loss on ignition (LOI) consists of organic carbon (OC), while about 17% of OC in the three samples consists of HA and FA. Up to 50% of DOC in MSWI bottom ash leachates was identified as fulvic acid (FA). This value is substantially higher than previously estimated for these MSWI bottom ash samples and is consistent with the higher recovery of the new method that was applied. The results of this study imply that methods focusing on specific carbon fractions are more appropriate for assessment of environmentally relevant organic carbon species than the measurement of LOI.