Solute Transport in Heterogeneous Aquifers and Implications for Risk Assessment

2017 Spring Cyberseminar Series

Presenter(s):
Felipe de Barros / University of Southern California

Talk Description:

Reliable quantification of the associated risks originating from toxic chemicals present in groundwater systems needs to take into consideration the ubiquitous heterogeneity of the hydrogeological properties (e.g., hydraulic conductivity). The spatial variability of the hydraulic conductivity leads to erratically shaped solute plumes which have a significant impact in augmenting mixing rates. The contrast between conductivity values and its spatial correlation structure not only controls the spreading rates of the plume but also the travel time between source and receptor, both which are critical in assessing the risk level.  However, capturing the patterns of heterogeneity of hydrogeological properties is not trivial since limited financial resources and high costs associated with data acquisition leads to incomplete characterization. As a consequence, solute transport predictions in subsurface environments as well as decision making metrics are subject to uncertainty. By adopting a probabilistic framework, we show through a series of examples, how the spatial geostatistical structure of the hydraulic conductivity field as well as engineering factors (i.e., the solute source dimension and pumping operations) affect and control the uncertainty of solute concentration and risk metrics used for assessing adverse human health effects.

Biography:

Dr. de Barros is an Assistant Professor at the University of Southern California. He received his B.Sc and M.Sc from the Federal University of Rio de Janeiro and Ph.D. from the University of California, Berkeley. His research interests are environmental fluid mechanics, stochastic hydrogeology, contaminant transport in heterogeneous porous media, site characterization and risk assessment,with emphasis on the scale issue, aquifer remediation and sustainability.

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).