We are grateful for funding from: National Science Foundation, American Chemical Society, Social Science Research Council, University of California, AXA Research Fund, Marie Curie Actions, Graduate Women in Science, The Royal Society of Edinburgh.
Anomalous transport in porous media
Early or delayed arrival of solutes, which leads to poor mixing and long residence times, is a phenomenon known as ”anomalous transport”. Typical upscaling transport models attribute anomalous transport behavior to structures such as fractures. Nevertheless, anomalous transport has been observed even in highly homogeneous porous media, thus highlighting the multiscale complexity of transport mechanisms and our insufficient understanding of it. This work aims to establish formal relationships between structural features of the pore-space and the observed intensity of anomalous transport.
Soil architecture effects on colloid filtration
Landfill and agricultural soils are expected to receive large loads of colloids and engineered nanoparticles (ENPs) through land application of wastewater sludge. This puts soil and water quality at risk. The aims of this study are i) to assess the efficiency of interfaces within pores in immobilizing colloids and ENPs for various typical moisture contents and chemistry conditions, and ii) determine how flow-induced aggregation contributes to immobilization of particles along the pore network.
Enhanced transport of colloids by dissolved organic matter
Transport of colloid contaminants is enhanced in soils amended with manure, but the mechanisms are not well understood. Results of this work indicate that organic matter from manure creates a hairy structure on the colloid surface, the so-called "corona". The hair length, density and electrostatic charge of this structure greatly alters the short-range forces that provide particles with stability. When the hairy layer is dense and uniform, the colloids are typically highly mobile. When the hairy layer is sparse the colloids become entangled and deposited.
Groundwater contamination teaching web-tool
Our team's educational goal is to raise awareness and broaden overall understanding of the processes that lead to groundwater contamination for the general public. To do so, we created openly available interactive visualization tools to teach interested users about hydrologic concepts that control contaminant spreading. These tools overturn traditional teaching approaches with student-centered learning activities in which pupils first interact with visual data and gain a conceptual sense of the problem at hand, and then work on comprehending the math behind the problem.
Drying drop dynamics
Evaporation deposition is a common phenomenon observed daily in coffee-stains, yet it is central to the microfabrication industry. This work provides a framework for controlling the shape and attachment strength of deposition stains with solutes. Specifically, we show that the addition of nonionic surfactant can be tuned to control (i) the surface tension of the drop, (ii) dynamics of the contact line during evaporation, (iii) colloid-substrate friction, (iv) morphology of deposited stains, and (v) attachment strength of stains.
Publications: Morales et al., 2013
Reverse engineering of biochar
Biochar is a growingly popular biomass carbonization tool with wide-ranging agronomic and environmental gains. However, the benefits of adding biochar to a soil greatly depend on how it is produced, and the links between biochar properties and its production parameters are not well understood. To address this issue, this study built a meta-data library from which links between biochar properties and production parameters were statistically ascertained. Based on these relationships, the Biochar Engineering web-tool was constructed to help producers determine the optimal parameters needed to generate biochar that is tailored to mitigate specific soil deficiencies.