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Repeatable, non-destructive, spatially resolved measurements of carbon-in-soil
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  • Mauricio Ayllon Unzueta,
  • Tanay Tak,
  • Andrew Rosenstrom,
  • Eoin Brodie,
  • Craig Brown,
  • Cristina Castanha,
  • Charles Gary,
  • Caitlin Hicks Pries,
  • William Larsen,
  • Bernhard Ludewigt,
  • Arun Persaud
Mauricio Ayllon Unzueta
Lawrence Berkeley National Laboratory
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Tanay Tak
Lawrence Berkeley National Laboratory
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Andrew Rosenstrom
Lawrence Berkeley National Laboratory
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Eoin Brodie
Lawrence Berkeley National Laboratory
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Craig Brown
Adelphi Technology Inc.
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Cristina Castanha
Lawrence Berkeley National Laboratory
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Charles Gary
Adelphi Technology Inc.
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Caitlin Hicks Pries
Dartmouth College Life Sciences Center, room 349 78
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William Larsen
Rice University
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Bernhard Ludewigt
Lawrence Berkeley National Laboratory
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Arun Persaud
Lawrence Berkeley National Laboratory

Corresponding Author:[email protected]

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Abstract

Carbon sequestration in soils represents an important opportunity to reduce the amount of greenhouse gases in the atmosphere and thereby offsetting the effects of climate change. To monitor carbon sequestration accurate measurements of soil carbon are needed that can be repeated over several growing cycles. Furthermore, soil carbon is an important indicator of soil health; accurately measuring carbon distribution is therefore important for informing land use management practices. We are developing a new instrument that images a volume of approximately 50 cm × 50 cm × 30 cm (depth) with a few centimeters resolution by applying neutron scattering techniques. Contrary to current coring methods, this approach is non-destructive, samples a large area, and allows real-time analysis of the soil carbon density. In this technique a neutron and an alpha particle are created in a deuterium-tritium fusion reaction. Due to momentum conservation the two particles move in opposite directions. Creating the particles in a small point source allows us to calculate the direction in which the neutron is moving by tracking the associated alpha particle using a position sensitive detector. The neutron can then enter the soil and inelastically scatter off atoms in the soil, creating an isotope-specific gamma ray in the process. Measuring the energy of the gamma ray allows identification of the isotope. Measuring the time-of-flight between the alpha detection and the gamma detection together with the direction of travel of the neutron allows the calculation of the 3D position of the scattering center. Using this Associate Particle Imaging (API) technique 3D density plots of carbon, oxygen, silicon, and aluminum can be obtained. In this poster we present first results from applying API to pre-mixed and standard soil samples in a laboratory setting (field tests are planned in the future). We will compare measured data to neutron-transport simulations and discuss our data analysis algorithm to reconstruct the carbon density in the soil from API data. We will further discuss achievable resolution and time requirement for measurements in the field. The information, data, or work presented herein was funded by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Contract No. DE-AC02-05CH11231.