• Copper in the terrestrial environment: Verification of a laboratory-derived terrestrial biotic ligand model to predict earthworm mortality with toxicity observed in field soils

      Koster, Marijke; Groot, Arthur de; Vijver, Martina G; Peijnenburg, Willie J G M (Elsevier, 2006-02-21)
      This study was set up for validation of a regression model to predict mortality in the terrestrial earthworm Aporrectodea caliginosa following exposure to copper. This model was derived from a terrestrial biotic ligand model and incorporates the protective effects of H+ and Na+ on copper toxicity. Three soil sets were used for the experiments, all of which had a different copper contamination history over more than 20 years and were considered to be aged field soils. The soils were characterized by analysis of various copper pools in the solid phase and in the pore water, analysis of physical and chemical soil properties and by regression analysis. Measured and calculated copper activities (expressed as pCu) correlated reasonably well. Measured copper activities correlated with the total copper concentration in the pore water and the pH. The organic matter in the solid phase had no influence on the pCu in these soil sets. Earthworms were exposed to the soils for 28 days, after which survival was scored. Observed earthworm mortality after 28-days exposure was plotted as a function of the log-transformed difference between predicted (log10 transformed) LC50-values and measured values of pCu for validation of the regression model. The results obtained were in agreement with the assumption that mortality is to be observed in those soils where the predicted LC50 exceeds the measured pCu. However, a structural underestimation of toxicity was apparent, which is most likely due to mixture effects related to the presence of additional substances in field soils. Nevertheless, the trend of the results in the validation tests demonstrates that the newly developed toxicity model is a useful tool in predicting lethality of copper contamination to earthworms in field soils.
    • Probabilistic inversion for chicken processing lines

      Cooke, Roger M; Nauta, Maarten; Havelaar, Arie H; Fels, Ine van der (Elsevier, 2006-01-25)
      We discuss an application of probabilistic inversion techniques to a model of campylobacter transmission in chicken processing lines. Such techniques are indicated when we wish to quantify a model which is new and perhaps unfamiliar to the expert community. In this case there are no measurements for estimating model parameters, and experts are typically unable to give a considered judgment. In such cases, experts are asked to quantify their uncertainty regarding variables which can be predicted by the model. The experts’ distributions (after combination) are then pulled back onto the parameter space of the model, a process termed “probabilistic inversion”. This study illustrates two such techniques, iterative proportional fitting (IPF) and PARmeter fitting for uncertain models (PARFUM). In addition, we illustrate how expert judgement on predicted observable quantities in combination with probabilistic inversion may be used for model validation and/or model criticism.
    • Safety distances for hydrogen filling stations

      Matthijsen, A J C M; Kooi, E S (Elsevier, 2006-06-30)
      In the context of spatial planning the Dutch Ministry of Housing, Spatial Planning and the Environment asked the Centre for External Safety of the National Institute for Public Health and the Environment (RIVM) to advice on safe distances pertaining to hydrogen filling stations. The RIVM made use of failure modeling and parameters for calculating the distance in detail. An imaginary hydrogen filling station for cars is used in the determination of ‘external safety’ or third party distances for the installations and the pipe work for three different sizes of hydrogen filling stations. For several failure scenarios ‘effect’ distances are calculated for car filling at 350 and 700 bar. Safe distances of filling stations from locations where people live and work appear to be similar for compressed hydrogen, gasoline/petrol and compressed natural gas. Safe distances for LPG are greater. A filling unit for hydrogen can be placed at gasoline/petrol-filling stations without increasing safety distances