Malaguerra, Flavio

Forurening med organiske stoffer truer mange ferskvandsressourcer og dermed befolkningens sundhed. For at imødegå denne trussel er der behov for at udvikle modeller til at studere de væsentligste forureningsveje og til at beregne forureningsbelastningen. I mange lande benyttes grundvand til drikkevand, da en række processer under grundvandsdannelsen kan reducere forureningen og rense vandet ved at fjerne de organiske forureninger. Overfladevand forurenes derimod lettere og i det omfang der er kontakt mellem overfladevand og grundvand kan dette føre til grundvandsforurening. De mange faktorer, der påvirker de organiske forureninger i grundvand, kan være vanskelige at modellere og der er derfor behov for at identificere de væsentligste processer for at udvikle simplere modeller, der kan simulere, hvorledes forureningen opfører sig, men med den bedste balance mellem modellens kompleksitet og resultaternes pålidelighed. I dette PhD-arbejde er detaljerede modeller koblet med ’global sensitivity analysis’-teknikker for at identificere hovedprocesserne i nedbrydning af klorerede opløsningsmidler i undergrunden og i transport af pesticider fra overfladevand til nærliggende boringer i grundvandsmagasiner under lerlag. Ved at undersøge data over forureninger i drikkevandsboringer på Sjælland med statistiske teknikker blev der identificeret stor-skala forureningsprocesser Disse analyser viste at sværtnedbrydelige forureninger i overfladevand kan trænge ned til nærtliggende produktionsboringer – selv om de er dækket med lerlag. På denne måde ser det ud til, at vandstandsende lag ikke, som hidtil antaget, yder tilstrækkelig beskyttelse mod forurening med organiske stoffer. Etablering af sekventiel reduktiv deklorering er styret af fermentering af organiske stoffer og sulfatkoncentrationen i grundvandet, og simulering af nedbrydning af klorerede alifater er meget vanskeligt at beskrive med simple modeller. Statistiske analyser af forureningen af danske drikkevandsboringer viste, at koncentrationen af BAM, et pesticidnedbrydningsprodukt, navnlig er et problem i bymæssige områder og at på Sjælland er boringer tæt på overfladevand generelt mere følsomme over for pesticid forureningThe access to safe drinking water is essential for the well being of the population. The spread of micropollutant contamination jeopardise many freshwater reservoirs, and is a serious threat for human health, especially because of its long-term effects. To asses the threat of contamination, models are required to study the main contamination pathways, and to make predictions of pollution fluxes. Groundwater is used as drinking water in many countries because subsurface processes can mitigate pollution and purify the water by removing xenobiotic compounds. However, groundwater often interacts with surface water, which is more vulnerable to contamination, and can transfer pollution to groundwater. The fate of micropollutants in aquifers is influenced by many factors: sorption, degradation and dilution are processes that can interact together and create very complex systems, which are difficult to model. The identification of dominant processes is an essential step in the understanding of system behaviour, because it enables the development of simplified models that can approximate the fate of contaminants with the best trade-off between model complexity and reliability of results. In this thesis, global sensitivity analysis techniques are used to assess detailed models in order to identify the main processes involved in the degradation of chlorinated solvents in the subsurface, and in the transport of pesticides from surface water into nearby wells in confined aquifers. Statistical techniques are also employed to identify large-scale contamination processes by examining observations of contamination in drinking water wells in Zealand, Denmark. Results show that persistent compounds in surface water can leach into nearby pumping wells even if an impermeable clay layer overlies the well screen. Thus aquitards may not provide adequate protection against contamination by micropollutants in surface water, as generally thought. Results also show that the fermentation of organic compounds and the sulphate concentration in groundwater govern the success of sequential reductive dechlorination in aquifers, and that the simulation of chlorinated aliphatic hydrocarbon degradation cannot be approximated by simple models without losing the ability to simulate important system behaviour. The statistical analysis of contaminant concentrations in Danish drinking water wells demonstrates that drinking water well contamination by BAM, a pesticide metabolite, is mainly a problem in urban areas, and that in Zealand, wells close to surface water are generally more vulnerable to pesticide contamination

Online Research Database In Technology

Models and statistical analysis of organic micropollutants in groundwater-based drinking water resources

http://orbit.dtu.dk/ws/files/5661091/Flavio%20Malaguerra%20PhD%20thesis%20WWW-Version.pdf

Models and statistical analysis of organic micropollutants in groundwater-based drinking water resources

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Online Research Database In Technology