Modeling the transport and fate of oil-particle aggregates after an oil spill in inland waterways

This dissertation was motivated by a study of the July 2010 Kalamazoo River oil spill. The spill occurred due to a pipeline rupture, releasing approximately 1.1 million US gallons of diluted bitumen into Talmadge Creek, which is a tributary of the Kalamazoo River, located in the state of Michigan, United States. It was even more unfortunate that a 50-year flood event occurred in the Kalamazoo River at the same time, which significantly transported and spread the released heavy crude oil. It is considered the largest inland oil spill and one of the costliest (1.2 billion US dollars as of 2014 for cleanup) spills in U.S. history. After tremendous cleanup efforts of floating oil and oil contaminated soil on river banks and floodplain areas within one year following the spill, substantial residual deposits from the oil spill were found remaining in the waterway system, mostly due to the formation of oil-particle aggregates (OPAs). OPAs are a mixture of oil droplets and solid particles (e.g. suspended sediment) under turbulent flow conditions. Their density can be heavier than water and they sink onto river bed, especially in the areas where flow velocity is low. The recovery of OPAs lasted for more than three years after the spill. There are many unknowns about OPAs, such as how oil droplets and particles interact, where they deposit, when they can be entrained into water and transported, what are their impacts on aquatic life. Thus the understanding of the fate and transport of OPAs is very important for recovery efforts and future management. It is believed that this study is not only useful for the Kalamazoo River oil spill, but also a good reference for other potential oil spills in freshwater environments. Subjected to increasing demand of crude oil transport, the ageing pipelines all over the country are running the risks of rupture at a higher possibility, especially for those located around inland waterways where there's a closer interaction between water environment and people. Therefore, oil spills in inland waterways should attract more attention and researches. Moreover, the lessons, tools, and knowledge we learned from oil spills in freshwater environment could be helpful for studying the oil residue in marine environments. Also, the tools developed in this study have the potential to be applied to contaminated sediment in general, including those polluted by other contaminates such as hazardous industrial chemicals. Numerical models were developed for this study, with the help of laboratory experiments and field surveys for model calibration and validation. A particle tracking algorithm for OPAs was developed and coupled with a 3D hydrodynamic for Morrow Lake, where the effects of wind and dam operation cannot be neglected. The three-dimensional Eulerian/Lagrangian model was used to locate where OPAs would deposit in Morrow Lake and when OPAs could be resuspended under different scenarios. Selected sediment traps in the Kalamazoo River were studied with 2D shallow water models to understand where and when OPAs deposit. A new parallelized 2D hydrodynamic, sediment transport, and bed morphology model was also developed. The new model was parallelized with the domain decomposition method using MPI. A k-epsilon turbulence model was also implemented into the model. Any OPAs flowing downstream of Morrow Lake have the potential to reach Lake Michigan

Spatiotemporal correlation analysis of hydraulic fracturing and stroke in the United States

Hydraulic fracturing or fracking has led to a rapid growth of oil and gas production in the United States, but the impact of fracking on public health is an important but underresearched topic. We designed a methodology to study spatiotemporal correlations between the risk of fracking and stroke mortality. An annualized loss expectancy (ALE) model is applied to quantify the risk of fracking. The geographically and temporally weighted regression (GTWR) model is used to analyze spatiotemporal correlations of stroke mortality, fracking ALE, and nine other socioeconomic- and health-related factors. The analysis shows that fracking ALE is moderately correlated with stroke mortality at ages over 65 in most states of fracking, in addition to cardiovascular disease and drug overdose being positively correlated with stroke mortality. Furthermore, the correlations between fracking ALE and stroke mortality in men appear to be higher than in women near the Marcellus Shale, including Ohio, Pennsylvania, West Virginia, and Virginia, while stroke mortality among women is concentrated in the Great Plains, including Montana, Wyoming, New Mexico, and Oklahoma. Lastly, within two kilometers of the fracking mining activity, the level of benzene in the air was found to be significantly correlated with the fracking activity in Colorado

Simulation of suspended sediment and contaminant transport in shallow water using two-dimensional depth-averaged model with unstructured meshes

With growing global populations and human activities, the problems of sediment transport and environmental hydraulics have been becoming more and more important and valued. Computational fluid dynamics is a very useful and powerful tool in those studies. In 2008, Dr. Liu developed a two-dimensional model HydroSed which solves for 2D shallow water equations and sediment bedload transport equation at Hydrosystems Laboratory, UIUC. In this thesis, the author further modifi es and improves the HydroSedv1.0 model so that the model is able to deal with the transport of contaminant. In addition, the transport of suspended sediment is added and it is coupled with bed evolution. The 2D advection-di usion equation with source/sink terms is solved by finite volume method using Godunov scheme explicitly on unstructured meshes. Roe's approach is used to solve Riemann problem because the analytical solver is much computationally slower. Slope-limiter approaches are applied in order to get higher accuracy. Several pure advection tests are simulated to evaluate the performance of the model and the effect of diff erent slope-limiter approaches. Furthermore, a dye-tracer study in the Chicago River is simulated for verifying the model in a real-world project. The numerical results show satisfactory matches with the field measurement data. A widely used three-dimensional model EFDC is also used for comparison. Both pure advection tests and dye-tracer study demonstrate that the performance of the model is satisfactory. The model is applied to study the potential impacts of planned hydraulic structures in the Canar River, Ecuador. The effects to both water flow during flood and sediment transport are studied. Due to the lack of eld data in terms of water surface elevation, flow discharges and velocities in this river, the HydroSed model can help to a large extent to understand the problem and work together with a 1D model and other techniques for optimized designs

Mechanisms governing the eyewall replacement cycle in numerical simulations of tropical cyclones

Eyewall replacement cycle (ERC) is frequently observed during the evolution of intensifying Tropical Cyclones (TCs). Although intensely studied in recent years, the underlying mechanisms of ERC are still poorly understood, and the forecast of ERC remains a great challenge. To advance our understanding of ERC and provide insights in improvement of numerical forecast of ERC, a series of numerical simulations is performed to investigate ERCs in TC-like vortices on a f-plane. The simulated ERCs possess key features similar to those observed in real TCs including the formation of a secondary tangential wind maximum associated with the outer eyewall. The Sawyer-Eliassen equation and tangential momentum budget analyses are performed to diagnose the mechanisms underlying the secondary eyewall formation (SEF) and ERC. Our diagnoses reveal crucial roles of outer rainband heating in governing the formation and development of the secondary tangential wind maximum and demonstrate that the outer rainband convection must reach a critical strength relative to the eyewall before SEF and the subsequent ERC can occur. A positive feedback among low-level convection, acceleration of tangential winds in the boundary layer, and surface evaporation that leads to the development of ERC and a mechanism for the demise of inner eyewall that involves interaction between the transverse circulations induced by eyewall and outer rainband convection are proposed. The tangential momentum budget indicates that the net tendency of tangential wind is a small residual resultant from a large cancellation between tendencies induced by the resolved and sub-grid scale (SGS) processes. The large SGS contribution to the tangential wind budget explains different characteristics of ERC shown in previous numerical studies and poses a great challenge for a timely correct forecast of ERC. The sensitivity experiments show that ERCs are strongly subjected to model physics, vortex radial structure and background wind. The impact of model physics on ERC can be well understood with the interaction among eyewall/outer rainband heating, radilal inflow in the boundary layer, surface layer turbulent processes, and shallow convection in the moat. However, further investigations are needed to fully understand the exhibited sensitivities of ERC to vortex radial structure and background wind

Enhanced inference of ecological networks by parameterizing ensembles of population dynamics models constrained with prior knowledge

Abstract Background Accurate network models of species interaction could be used to predict population dynamics and be applied to manage real world ecosystems. Most relevant models are nonlinear, however, and data available from real world ecosystems are too noisy and sparsely sampled for common inference approaches. Here we improved the inference of generalized Lotka–Volterra (gLV) ecological networks by using a new optimization algorithm to constrain parameter signs with prior knowledge and a perturbation-based ensemble method. Results We applied the new inference to long-term species abundance data from the freshwater fish community in the Illinois River, United States. We constructed an ensemble of 668 gLV models that explained 79% of the data on average. The models indicated (at a 70% level of confidence) a strong positive interaction from emerald shiner (Notropis atherinoides) to channel catfish (Ictalurus punctatus), which we could validate using data from a nearby observation site, and predicted that the relative abundances of most fish species will continue to fluctuate temporally and concordantly in the near future. The network shows that the invasive silver carp (Hypophthalmichthys molitrix) has much stronger impacts on native predators than on prey, supporting the notion that the invader perturbs the native food chain by replacing the diets of predators. Conclusions Ensemble approaches constrained by prior knowledge can improve inference and produce networks from noisy and sparsely sampled time series data to fill knowledge gaps on real world ecosystems. Such network models could aid efforts to conserve ecosystems such as the Illinois River, which is threatened by the invasion of the silver carp

Multiple‐scale simulations of stratocumulus clouds

This study introduces a flexible multiple nested modeling framework developed from the Weather Research and Forecasting (WRF) model for boundary layer cloud research. It features a nested large‐eddy simulation in a hindcasting mode that allows a direct comparison between simulations and observations. Using this approach, we simulated two stratocumulus cases observed at the southern Great Plains observing site. The simulation‐observation comparisons demonstrate that the multiple nested WRF well reproduces the cloud properties and vertical velocity fields detected by cloud radar and other remote sensing instruments. The simulations show that (1) the cloud fields can be strongly modulated by mesoscale organizations; (2) the vertical velocity variance and skewness in the boundary layer have well‐defined diurnal variations and are strongly dependent on external forcings, but the in‐cloud turbulent statistics appears to be more controlled by the internal turbulent processes; (3) the organized structures of stratocumulus are only slightly skewed, which is consistent with the cloud radar observations that the updraft fraction is close to 50%; and (4) the vertical distribution of cloud water and the associated high‐order moments of continental stratocumulus can be substantially different from its marine counterpart due to different ambient thermodynamic structures. This study suggests that the multiple‐scale WRF modeling system provides a great numerical framework that can be used to address various issues regarding the parameterization of boundary layer clouds

Data_Sheet_1_E-DBCM: A dynamically coupled upland and in-stream water quality model for watershed water quality simulation.ZIP

A dynamic bidirectional coupled modeling framework for water environment simulation (E-DBCM), including an upland watershed model (UWSM) and a two-dimensional (2D) downstream waterbody model (DWBM), is proposed. The UWSM is implemented to describe the rainfall-runoff and determine the pollutant load to downstream waterbodies, whereas the DWBM is used to simulate the pollutant transport and flood processes on downstream waterbodies. The UWSM and DWBM are spatially connected through a moving boundary, which can ensure the mass and momentum conservation. The proposed E-DBCM is verified using three case studies and the results indicate that the E-DBCM has satisfactory numerical accuracy, which can effectively reproduce the pollutant transport process and achieve satisfactory results. The water environment in Yanqi River Basin is assessed based on the proposed model. The simulated results are consistent with the measured data, indicating that the E-DBCM is reliable and the prediction accuracy can meet the requirements of engineering practices. Water is seriously polluted in this watershed, especially during peak tourist season when many pollutants are produced. Various measures should be taken to protect the water environment in this basin.</p

Impact of combined sewer overflow on urban river hydrodynamic modelling: a case study of the Chicago waterway

<p>Combined sewer overflow (CSO) can be a critical inflow source for urban rivers during storm events. This paper presents a case study of the Chicago waterway. A three-dimensional (3D) river hydrodynamic model was developed and integrated with an urban rainfall-runoff model using the Open Modelling Interface (OpenMI). Both the effects of CSO discharge on river and river water levels on CSO outlets were considered by the integrated model. A historical storm, which was similar to a 100-year return period rain event, was simulated and compared with field measurements. This study highlights the necessity of quantifying CSO for hydraulic modelling of urban rivers under extreme storm event conditions, and shows that an integrated hydrologic and hydraulic approach can be used to address this challenge. The 3D river hydrodynamic model can deal with the complex hydrodynamics at river confluences and provide better hydrodynamic results for water quality modelling in the future.</p