Development of watershed-based modeling approach to pollution source identification

Identification of unknown pollution sources is essential to environmental protection and emergency response. A review of recent publications in source identification revealed that there are very limited numbers of research in modeling methods for rivers. What’s more, the majority of these attempts were to find the source strength and release time, while only a few of them discussed how to identify source locations. Comparisons of these works indicated that a combination of biological, mathematical and geographical method could effectively identify unknown source area(s), which was a more practical trial in a watershed. This thesis presents a watershed-based modeling approach to identification of critical source area. The new approach involves (1) identification of pollution source in rivers using a moment-based method and (2) identification of critical source area in a watershed using a hydrograph-based method and high-resolution radar rainfall data. In terms of the moment-based method, the first two moment equations are derived through the Laplace transform of the Variable Residence Time (VART) model. The first moment is used to determine the source location, while the second moment can be employed to estimate the total mass of released pollutant. The two moment equations are tested using conservative tracer injection data collected from 23 reaches of five rivers in Louisiana, USA, ranging from about 3km to 300 km. Results showed that the first moment equation is able to predict the pollution source location with a percent error of less than 18% in general. The predicted total mass has a larger percent error, but a correction could be added to reduce the error significantly. Additionally, the moment-based method can be applied to identify the source location of reactive pollutants, provided that the special and temporal concentrations are recorded in downstream stations. In terms of the hydrograph-based method, observed hydrographs corresponding to pollution events can be utilized to identify the critical source area in a watershed. The time of concentration could provide a unique fingerprint for each subbasin in the watershed. The observation of abnormally high bacterial levels along with high resolution radar rainfall data can be used to match the most possible storm events and thus the critical source area

13th International Bologna Conference on Magnetic Resonance in Porous Media - Bologna 2016 Conference Handbook and Book of Abstracts

This conference series, founded at the University of Bologna in 1990 and now at the 13th edition, is devoted to the progress in Magnetic Resonance in Porous Media and in our understanding of Porous Media themselves, and to stimulate the contact among people from various parts of Academia and Industry. Researchers in Physics, Chemistry, Engineering, Life Sciences, Mathematics, Computer Sciences, and in Industrial Applications will benefit from exchange of ideas, experiences, and new approaches. Topics will include innovative techniques to study structure, behavior of fluids, and their interactions in every kind of natural and artificial porous materials, including rocks, cements, biological tissues, foodstuffs, wood, particle packs, sediments, pharmaceuticals, zeolites, and bioconstructs. New data acquisition and processing techniques are also expected to be strong features

13th International Bologna Conference on Magnetic Resonance in Porous Media - Bologna 2016 Conference Handbook and Book of Abstracts

This conference series, founded at the University of Bologna in 1990 and now at the 13th edition, is devoted to the progress in Magnetic Resonance in Porous Media and in our understanding of Porous Media themselves, and to stimulate the contact among people from various parts of Academia and Industry. Researchers in Physics, Chemistry, Engineering, Life Sciences, Mathematics, Computer Sciences, and in Industrial Applications will benefit from exchange of ideas, experiences, and new approaches. Topics will include innovative techniques to study structure, behavior of fluids, and their interactions in every kind of natural and artificial porous materials, including rocks, cements, biological tissues, foodstuffs, wood, particle packs, sediments, pharmaceuticals, zeolites, and bioconstructs. New data acquisition and processing techniques are also expected to be strong features

Towards an understanding of mass transfer and hydrodynamics in packed bed reactors using Nuclear Magnetic Resonance

This thesis presents the implementation and development of nuclear magnetic resonance (NMR) techniques to study mass transfer and hydrodynamic phenomena that govern the performance of packed bed reactors. The aim of this work is to gain insight into factors that affect the process of fines deposition and mass transfer inside packed beds to ultimately enable optimisation of these processes. Although mass transfer correlations exist for pure components and mixtures, previous studies have failed to measure the mass transfer coefficient in situ without extensive pre-calibration. In this thesis, the T2-T2 method is used to measure in situ mass transfer coefficients for single components and mixtures without any prior calibration. For mixtures, the standard T2-T2 method was modified to achieve chemical selectivity. Both single component and mixture mass transfer coefficients were found to be in accordance with a semi-theoretical correlation. Moreover, depending on the Reynolds () and Schmidt () numbers characterising the systems, it was illustrated that traditional mass transfer correlations can under-predict mass transfer coefficients in excess of 96% due to incorrect assumptions. For accurate design or modelling of packed beds characterised by low and , this highlights the need for reconsidering the use of traditional mass transfer correlations. In addition, despite mass transfer correlations existing for mixtures, none address the non-ideal mixture effects upon the mass transfer coefficient. Although the chemically selective T2-T2 method was validated using ideal gas mixtures, some suggestions were offered for non-ideal mixtures that this pulse sequence can study in the future. Despite a plethora of existing studies on fines deposition, none have experimentally validated the pore-scale nature of deposits in realistic packed beds; neither have they considered how the mass transfer rate is affected by deposits. For the first time, through the combination of NMR velocimetry, compressed sensing, a pore analysis, and T2-T2 experiments, pore-scale phenomena were observed in a realistic bed, the guiding principles behind fines deposition were uncovered, and mass transfer coefficients between the bulk and pellet phase were measured. For two types of fines, the pore-scale fines deposition mechanism was identical. Both types of fines also experienced similar decreases in the mass transfer coefficient compared to the clean bed – for just under a five time increase in the pressure drop caused by more fines depositing, the mass transfer coefficient decreased by 40% and 47%, respectively. These results illustrate that standard correlations will over-predict the mass transfer coefficient if fines deposits are not accounted for. Monte Carlo simulations were also used to support the experimental findings, further illustrating that the mass transfer rate is affected by changes to the velocity, voidage, surface area and bed morphology that result from fines depositing. Furthermore, the properties of the fines appeared to only affect the number of molecules participating in mass transfer, and not the mass transfer rate itself. Lastly, comparison between the experiments with the two types of fines illustrated that verifying models by macroscopic experimental variables alone will not be a robust indicator of pore-scale fines deposition phenomena.Funded by Gates Cambridge Trus

Tracing back the source of contamination

From the time a contaminant is detected in an observation well, the question of where and when the contaminant was introduced in the aquifer needs an answer. Many techniques have been proposed to answer this question, but virtually all of them assume that the aquifer and its dynamics are perfectly known. This work discusses a new approach for the simultaneous identification of the contaminant source location and the spatial variability of hydraulic conductivity in an aquifer which has been validated on synthetic and laboratory experiments and which is in the process of being validated on a real aquifer

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described