Concentration and patterns of PAHs along the salinity gradient of the Scheldt estuary

At MUMM a method was recently developed to determine Polycyclic Aromatic Hydrocarbons (PAHs) in surface waters, even with high particulate matter concentrations, as is the case for the Scheldt Estuary. The method is based on a solid phase extraction with Bakerbond Speedisk C18 cartridges (Baker Inc, Phillipsburg, NJ). After testing this method during a one-year international OSPAR pilot study, the same method was applied for water samples collected for the ENDIS-RISKS program during 2003. Total water concentrations varied between 10 ng/L and 1200 ng/L. Concentrations are tight linked to sources. Fluoranthene was found in the highest concentrations near Antwerp, while in Doel acenaphtylene seemed to be the most dominant compound. The patterns were generally dominated by the lower molecule weight PAHs. There is a clear gradient from Antwerp to the mouth of the estuary near Flushing. Concentrations and PAH patterns were further compared to previous results

Adsorption and desorption dynamics of citric acid anions in soil

The functional role of organic acid anions (e.g. citrate, oxalate, malonate, etc) in soil has been intensively investigated with special focus either on (i) microbial respiration and soil carbon dynamics, (ii) nutrient solubilization, or (iii) metal detoxification. Considering the potential impact of sorption processes on the functional significance of these effects, comparatively little is known about the adsorption and desorption dynamics of organic acid anions in soils. The aim of this study therefore was to experimentally characterize the adsorption and desorption dynamics of organic acid anions in different soils using citrate as a model carboxylate. Results showed that both adsorption and desorption processes were fast, reaching a steady state equilibrium solution concentration within approximately 1 hour. However, for a given total soil citrate concentration(ctot) the steady state value obtained was critically dependent on the starting conditions of the experiment (i.e. whether most of the citrate was initially present in solution (cl) or held on the solid phase (cs)). Specifically, desorption-led processes resulted in significantly lower equilibrium solution concentrations than adsorption led processes indicating time-dependent sorption hysteresis. As it is not possible to experimentally distinguish between different sorption pools in soil (i.e. fast, slow, irreversible adsorption/desorption), a new dynamic hysteresis model was developed that relies only on measured soil solution concentrations. The model satisfactorily explained experimental data and was able to predict dynamic adsorption and desorption behaviour. To demonstrate its use we applied the model to two relevant scenarios (exudation and microbial degradation), where the dynamic sorption behaviour of citrate occurs. Overall, this study highlights the complex nature of citrate sorption in soil and concludes that existing models need to incorporate both a temporal and sorption hysteresis component to realistically describe the role and fate of organic acids in soil processes

The use of integrative passive samplers as a source of contaminant mixtures in ecotoxicological laboratory experiments

The INRAM project aims to introduce a new application of passive sampling devices in ecological toxicity testing. Conventional (laboratory) ecotoxicity studies are mostly performed by exposing test organisms to various (high) concentrations of a single test compound. This clearly does not reflect in situ conditions: i.e. exposure to mixtures of low levels of various micro-pollutants. In order to expose organisms to environmentally realistic contaminant mixtures, this study explored a novel use of integrative passive samplers. Firstly, the dynamics of the contaminant release from the samplers was studied in the presence of organic material, i.e. algal cells. This study showed that the samplers released the compounds into the test medium as expected. Constant concentrations were achieved in the test medium, but the target concentrations (based on the amount of compound spiked on the samplers) were not reached. Additional experiments will be carried out in order to improve the dynamics of contaminant release. Secondly, samplers were used to collect micro-pollutants from three Belgian coastal harbours and were used ‘inversely’ as a contaminant mixture source in laboratory toxicity assays with Crassostrea gigas larvae. Significant differences in normal development of the oyster larvae were observed between the three harbours. Within each harbour a pollution gradient was apparent. These results show that the targeted application of passive samplers is feasible. As these passive samplers also allow to determine the aqueous concentrations of otherwise (nearly) undetectable trace compounds, they could be a powerful new tool in environmental toxicology

Mosque Design in the Netherlands

With the growth of the Muslim population in the Netherlands more and more mosques are being designed by Dutch architects. But while architects approach mosque design as a display of either traditional or modern values, for commissioners religion plays a crucial, if unspoken, role in the design. Through the design of their mosque commissioners aim to express their own vision of Islam and distinguish it from other visions

Action research and democracy

This contribution explores the relationship between research and learning democracy. Action research is seen as being compatible with the orientation of educational and social work research towards social justice and democracy. Nevertheless, the history of action research is characterized by a tension between democracy and social engineering. In the social-engineering approach, action research is conceptualized as a process of innovation aimed at a specific Bildungsideal. In a democratic approach action research is seen as research based on cooperation between research and practice. However, the notion of democratic action research as opposed to social engineering action research needs to be theorized. So called democratic action research involving the implementation by the researcher of democracy as a model and as a preset goal, reduces cooperation and participation into instruments to reach this goal, and becomes a type of social engineering in itself. We argue that the relationship between action research and democracy is in the acknowledgment of the political dimension of participation: ‘a democratic relationship in which both sides exercise power and shared control over decision-making as well as interpretation’. This implies an open research design and methodology able to understand democracy as a learning process and an ongoing experiment