1. Department of Biological and Environmental Engineering
Eliminating 'Nonpoint:' Using nanotechnology to identify pollution sources in the landscape
(NSF award # )
Todd Walter and Dan Luo
Cornell University
Department of Biological and Environmental Engineering

2. The tracers are composed of synthetic DNA encapsulated in PLA microspheres
The DNA is used to identify and quantify the tracers using PCR and qPCR, respectively.
The size, surface properties, density, and degradation rate of the microsphere can be controlled during fabrication.
Percentage (%)
Basic Tracer Concept.
Verification of fairly tight size distribution using dynamic light scattering
Microsphere diameter (mm)

3. A New Tracer Concept:
Because we use DNA to label or tag our tracers, we can make nearly limitless uniquely distinguishable tracers with identical transport properties
The next five slides (including this one) illustrate how the tracers would be used. I think they are self explanatory.
MAIN POINT: we can make lots of tracers that have the same transport characteristics but still distinguishable from each other.
The different colors are meant to represent tracers with different base-pair sequences in their DNA

4. The tracers can be placed at different places in the landscape.
A New Tracer Concept:
Applying the tracers to the field
The tracers can be placed at different places in the landscape.
For example, we are interested in parts of a watershed that may be sources of nonpoint source pollution

5. A New Tracer Concept:
Collecting water samples down stream
Water samples are collected at the watershed outlet

6. A New Tracer Concept:
qPCR used to identify and quantify tracers
Samples are analyzed on qPCR to determine which traces were in the water sample and their abundance

7. A New Tracer Concept:
The qPCR results are used to interpret flowpaths in the landscape. In the context of nonpoint source pollution, the results tell us the locations of likely pollutant sources that are reaching the stream
The results are used to interpret the hydrologic connections between the landscape and the stream

8. SOME SUMMARY POINTS DNA as a “tag” without genetic functionality
Millions of identical tracers of the same size
e.g. for 100 bases, number of potential tracers in principle = 4100 = 1.6 x 1060
Synthetic DNA: Can use new tracers each time
Biodegradable: Polylactic acid degrades over several months; additives can be included to control the degradation rate
Detection by the highly sensitive Polymerase Chain Reaction (PCR)
Some random summary points of the properties of our tracers that make them notable.
DNA image from Wikepedia