Using Nanotechnology to Characterize Flow Pathways in Hydrologic Systems
Over the past 10 years a new tracer concept that utilizes bio-molecular nanotechnology has been developed. Our DNA-labelled particle tracers, originally developed by Dr. Dan Luo and Dr. Todd Walter (Cornell University) (Sharma et al. 2012), are composed of FDA-approved Poly(D,L-lactide-co-glycolide) (PLGA) microspheres into which short strands of synthetic DNA (e.g. 100 base pairs) are incorporated. Using short, non-coding DNA strands ensures that the tracer does not have any genetic functionality and that placing it into the environment is safe. Because the DNA sequences (i.e. oligo or base-pairs) can be randomly combined the μtracer provides an enormous number of unique tracers (approximately 1.61 x 1060) with identical transport properties. The biodegradable PLGA microsphere of the tracer (used in human drug delivery and biomedicine) ensures that it will neither pollute the environment nor hinder future experiments with its persistence. By modifying the polymer characteristics of the PLGA microsphere the lifetime or degradation time of the tracer can be determined to accommodate different travel times of the tracer within hydrologic systems. Abundance of DNA-labelled particle tracers introduced to soil-water systems is determined from water samples collected in the field using real-time quantitative polymerase chain reaction (qPCR).
The goal of this project is to test the use and efficiency of our unique hydro-environmental tracers for the identification and characterization of hydrologic flow pathways in a variety of hydrologic systems with differing landscape settings and system complexities. This goal has the broader impact of providing invaluable information for the understanding of processes and system complexities of hydrologic systems needed to better constrain hydrological/ecological/biogeochemical models.
We have tested our DNA-labelled particles in a variety of increasingly complicated small-scale applications (e.g., 10 cm soil column) on relatively simple surfaces (e.g., 2D overland flow on an urban surface) (Sharma et al. 2012) to more complex field conditions (e.g. 3D flow in a glacier system) (Dahlke et al. 2015, McNew et al. 2017 in prep.) and in a 1m3 sloped lysimeter (miniLeo) at the Landscape Evolution Observatory at the Biosphere 2 in Arizona (Dahlke et al. 2017 in prep., Wang et al. 2017 in prep.). More recently we have tested four unique DNA-labelled tracers in a small hillslope equipped with a perched water collection system (PWCS) that is excavated to bedrock at the Sierra Foothill Research and Extension Center (SFREC) in Yuba County, northern California.
Presentations and Publications
Dahlke, H.E., Williamson, A.G., Georgakakos, C., Leung, S., Sharma, A.N., Lyon, S.W. and Walter, M.T., 2015. Using concurrent DNA tracer injections to infer glacial flow pathways. Hydrological Processes, 29(25), pp.5257-5274.
Dahlke, H.E., Wang, C., McNew, C., McLaughlin, S. and Lyon, S.W., 2016. Test of synthetic DNA tracers in a periodic hydrodynamic system for time-variable transit time distribution assessment. In AGU Fall Meeting Abstracts, H14D-05.
- McNew, C., Wang, C., Dahlke, H., Lyon, S. and Walter, T., 2017, April. Using DNA-labelled nano-and microparticles to track particle transport in the environment. In EGU General Assembly Conference Abstracts (Vol. 19, p. 10389).
Sharma, A.N., Luo, D. and Walter, M.T., 2012. Hydrological tracers using nanobiotechnology: proof of concept. Environmental science & technology, 46(16), pp.8928-8936.
Figure: SEM image of DNA-labelled particles containing synthetic DNA encapsulated into PLGA microspheres.