Biological and Chemical Activities in Confined Flows: The Role of Heterogeneity and Segregation

2017 Spring Cyberseminar Series

Presenter(s):
Pietro de Anna / University of Lausanne

Talk Description:

The fate of substances transported in porous subsurface environments is determined by a plethora of physical and bio-geo-chemical processes due to the presence of solids, fluids, gases and living organisms, which are in close interaction as a result of confinement. Heterogeneity in flow leads to segregation in reacting species and bacteria populations, which may transform the properties of the host medium itself. Current macro-scale approaches based on reaction-advection-dispersion dynamics and classical filtration theory are not able to quantify and predict field observations due to the complexity resulting from the coupling of micro-scale processes. The aim of my research is the investigation of non uniform flows through confined microstructures coupling with the activity of biotic and abiotic components of the subsurface. This is done with theoretical and numerical modeling, but mostly using experiments with microfluidics devices and time-lapse video-microscopy. My interdisciplinary research targets a framework for quantitative predictions of micro-scale processes that are relevant for the larger scale spreading of pathogens, chemical contamination and remediation in soils and aquifers or geothermal energy exploration.

Biography:

Pietro de Anna is a physicist, who is currently a tenure track assistant professor within the Applied and Environmental Geophysics Group at the Institute of Earth Sciences (ISTE) of the University of Lausanne (UNIL). He received his Master’s from the University of Florence (Italy) in Statistical Mechanics and a Ph. D in Geosciences from the University of Rennes 1 (Brittany, France). Pietro’s research focuses at the physics of small scale flow and mixing in near surface environments, with particular attention to their coupling with chemical and biological activities. He incorporates theoretical/numerical approaches to novel microfluidics experiments allowing the direct visualization and quantification of small scale processes in confined flows.

CUAHSI's Spring 2017 Cyberseminar Series on Heterogeneity, Complexity and Anomalous Transport in Hydrologic Systems

Real hydrologic systems are heterogeneous and hierarchical, leading to transport processes occurring over disparate and broad ranges of spatio-temporal scales. Many classical models of transport, while undoubtedly powerful and useful, are built on assumptions that simply fail to recognize these complexities.  As such they are incapable of predicting many features commonly observed in real systems. These behaviors are often called “anomalous”. They include processes with very large spatial jumps where solutes or particles quickly travel much larger distances than expected. Similarly trapping events can occur that hold back solutes and particles for much longer times than anticipated. Both the long jumps and trapping events are commonly characterized by power laws, rather than more conventional exponential and Gaussian distributions. Despite the name, anomalous transport is anything but that and is increasingly recognized as the norm across many disciplines in the hydrologic sciences, including flow and transport in highly heterogeneous aquifers as well as in flowing surface waters with hyporheic exchange. Additionally, such behaviors arise in related disciplines such as geomorphology in the fields of surficial processes and sediment transport. To overcome the limitations of classical modeling efforts, new classes of models have and continue to emerge, which successfully capture these so-called anomalous features. This cyberseminar series will focus on these efforts with expert speakers coming from the disciplines of subsurface and surface hydrology and geomorphology to outline these processes in accessible ways to the broader hydrology community.

The series was hosted by Diogo Bolster (Notre Dame University).