Asbestos Mobility and Remediation
The mobility of asbestos fibers in Earth’s surface or subsurface environment and groundwater has public health implications. The US EPA’s preferred remediation method to minimize asbestos exposure is to cap the contaminated soil, which minimizes or prevents asbestos exposure above ground in the air but does little to prevent the fiber mobility in the water below ground. This treatment method has been adopted based on the assumption that asbestos fibers should be retained within the first few “centimeters” in the soil (see the EPA report). However, recent field evidences, where asbestos fiber has been found far from the contaminated site, challenge this assumption and suggest that asbestos fibers may move through soil and water under certain conditions.
Despite advances in the knowledge of how colloids (mostly non-fibrous) move in the soil-water environment, the mobility of asbestos fibers in groundwater has not been studied, and the physical and geochemical triggers of asbestos fiber mobility in porous media remain elusive. The aim of this project is to improve the understanding of asbestos mobility and weathering in the environment so that the current remediation method can be improved.
In the first part of the project, I examine whether and how physical (e.g., dry-wet cycles, freeze-thaw cycles, flow perturbation or increases) and geochemical triggers (e.g., changes in pH, dissolved salt concentration or ionic strength, phosphate, and dissolved organic carbon) can affect the mobility of asbestos fibers (Chrysotile) in sand and soil columns (a simplified model system to simulate subsurface and groundwater flow).
In the second part of the project, I examine whether asbestos waste can be treated by plants and fungi, which typically release exudates to acquire trace elements including iron. Iron, a structural component of most asbestos, contributes to asbestos toxicity, partly because iron promotes generation of free radicals, which can damage DNA and cell membrane. This opens up new possibility for bioremediation of asbestos-contaminated soil.
- Prof. Jane Willenbring, University of Pennsylvania (postdoctoral advisor)
- Prof. Douglas Jerolmack, University of Pennsylvania
- Prof. Brenda Casper, University of Pennsylvania
Geochemical triggers of asbestos fiber mobility in groundwater
Our results show that the presence of dissolved organic carbon could enhance the transport of asbestos fibers, and changes in pH, ionic strength, and phosphate concentration have limited to no effect on the fiber mobility. These results challenge the current understanding of asbestos mobility in porous media and raise questions (or answers) on how to best design a remediation scheme that can minimize asbestos exposure not just above but below the ground. The manuscript summarizing results of the geochemical triggers of asbestos mobility is being written.
Iron dissolution kinetics from chrysotile: Effect of siderophores and organic acids
We examine the dissolution of iron from chrysotile, the most commonly used asbestos mineral, by microbial and fungal siderophores and organic acids present in rhizosphere. We document the changes in surface properties and morphology of asbestos fibers after iron dissolution. Our results show that the exudates have the potential to remove iron from asbestos even at high pH conditions, thereby rendering asbestos fiber less toxic. A manuscript summarizing these results is in preparation.