Applying predictive models for ecological risk management during bio-remediation

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Propylthioiracil induced ANCA-associated vasculitis in a 14 year-old girl

Background: Antineutrophil cytoplasmic antibodies (ANCAs) are the serologic hallmark of ANCA-associated primary small-vessel vasculitides (AAVs), but these antibodies have also been described in other autoimmune diseases such as inflammatory bowel diseases. Furthermore, different drugs are linked to the induction of ANCA, including propylthiouracil (PTU). However progression into clinical overt vasculitis is less common. Case-diagnosis/treatment: We describe the case of a young girl with Graves' disease presenting with fatigue, fever, episcleritis and arthritis. The unexpected double myeloperoxidase/proteinase 3-ANCA positivity triggered a multidisciplinary diagnostic work-up and resulted in the diagnosis of a clinically overt PTU-induced AAV. After PTU-withdrawal and treatment with high-dose corticosteroids, a favorable clinical and biochemical evolution was obtained. Conclusions: The use of PTU in the management of hyperthyroidism is not considered first-line treatment in Europe and is even less commonly used in children. Nevertheless, pediatricians should be aware of the possibility of PTU-induced AAV, especially in the presence of multiple ANCA reactivities. Therefore, the use of this drug should be weighed carefully in children

Monitoring and modelling transport and emissions of volatile organic compounds during soil remediation

This dissertation deals with monitoring and modelling transport of gaseous pollutants in soils. The knowledge of the gas transport processes is important in soil remediation projects such as (bio)venting, and soil vapour extraction. An important aspect of these soil venting remediation techniques is the risk for VOC emissions to the atmosphere. Most of the models describe the gas flow for these remediation projects based on the convection-dispersion model. In this dissertation two rapid measurement devices were described to measure some of the parameters of the convection-dispersion equation. With the proposed devices, the effective air-filled porosity, the soil gas diffusion coefficient and soil gas dispersion coefficient can be measured automatically preventing the need to use approximate pedotransfer functions. In a next phase, a sensor device for in-situ, passive concentration measurements in the soil gas phase was developed. The prototype measured the O2 and CO2 concentration and an equivalent concentration of a broad range of volatile organic compounds (VOC) in the soil vapour phase. Mass balances of the volatile organic compound in a column test measured with the prototype have illustrated successfully the performance of the sensor in soil systems with a recovery that ranged from 90 to 101 % of the injected decane mass. The data generated by the devices was used to develop a predictive modelling system for the determination of the VOC emission towards the surface. The method assimilated sensor readouts in gas transport models to predict soil gas concentration profiles and emissions to the atmosphere during operation. During a column test, an increasing set of sensor gas concentration data became available for the continuous adaptive improvement of the model parameter estimates. The VOC concentrations near the soil surface and the associated VOC emission rates to the atmosphere were predicted with an accuracy ranging from 60 to 86 % depending on the number of sensors and their placing. The positioning of sensors near the contaminant source and near the soil surface was found to be optimal for fast and accurate prediction of VOC concentrations at the soil surface and in emissions. It was, therefore, concluded the predictive model could be used to control soil venting remediation techniques for optimisation with strict VOC emission control

Rapid automated measurement system for simultaneous determination of effective air-filled porosity and soil gas diffusivity

The effective air-filled porosity and the gas diffusion coefficient are important soil parameters determining the success of soil bioremediation projects such as (bio)venting and (bio)sparging methods in combination with soil vapor extraction. We have developed a new method to sequentially measure the effective air-filled porosity and the soil gas diffusion coefficient of a soil sample. During the purging of the sample, a fast and accurate measurement of the effective air-filled porosity can be obtained. The subsequent diffusion measurement does not require a zero-O(2) concentration in the soil sample. The procedure further allows the calculation of the soil gas diffusion coefficient before an equilibrium O(2) concentration has been reached. The results are obtained by combining the data of the inlet and outlet compartment in a single equation. A stable reading is reached when the results for the inlet and outlet compartment coincide with the results from the combined equation. The analysis time is reduced by 89 to 96% compared with methods that run until an equilibrium concentration has been reached. Moreover, combining data from inlet and outlet compartments increases the accuracy of the diffusivity measurement by a factor of two compared with previous methods