loading page

Utilizing neutron scattering techniques to measure carbon-in-soil distribution
  • +8
  • Arun Persaud,
  • Bernhard Ludewigt,
  • Mauricio Ayllon Unzueta,
  • William Mixter,
  • Matthew Poska,
  • Zachary Croft,
  • Eoin Brodie,
  • Cristina Castanha,
  • Caitlin Hicks Pries,
  • Charles Gray,
  • Craig Brown
Arun Persaud
Lawrence Berkeley National Laboratory

Corresponding Author:apersaud@lbl.gov

Author Profile
Bernhard Ludewigt
Lawrence Berkeley National Laboratory
Author Profile
Mauricio Ayllon Unzueta
Lawrence Berkeley National Laboratory
Author Profile
William Mixter
Lawrence Berkeley National Laboratory
Author Profile
Matthew Poska
Lawrence Berkeley National Laboratory
Author Profile
Zachary Croft
Lawrence Berkeley National Laboratory
Author Profile
Eoin Brodie
Lawrence Berkeley National Laboratory
Author Profile
Cristina Castanha
Lawrence Berkeley National Laboratory
Author Profile
Caitlin Hicks Pries
Dartmouth College
Author Profile
Charles Gray
Adelphie Technology, Inc.
Author Profile
Craig Brown
Adelphi Technology, Inc.
Author Profile

Abstract

Carbon distribution in soil is intricately linked to soil health. However, repeatable measurements of carbon distribution typically require destructive sampling and laboratory analyses. Soil carbon distributions in both natural and managed landscapes significantly vary due to numerous factors related to topography, mineralogy, hydrology, land use history, and vegetation. In order to accurately inventory soil C distributions and dynamics over time, we are developing a new technique that relies on neutron inelastic scattering to measure elemental distribution. This approach can be used to image a volume of approximately 50 cm × 50 cm × 30 cm (depth) with a few centimeters resolution, for example the root zone of a plant. To achieve this, we use neutrons created in a deuterium-tritium fusion reaction. The products of this reaction are an alpha particle and a neutron. Due to momentum conservation, both particles are emitted in opposite directions in the center-of-mass frame. This allows us to measure the neutron direction by detecting the alpha particle with a position sensitive detector. The neutron can then induce an inelastic scattering reaction on a carbon nucleus present in the soil, and this event produces a gamma ray with a characteristic energy for the carbon isotope. Using a gamma detector, we measure these gamma rays, which allows us to perform time-of-flight analysis between arrival times of the alpha and gamma particles. Using the information from both measurements (alpha and gamma), we can reconstruct the spatial distribution of the carbon atoms and other elements in soil. We will report on the design, potential applications, and limitations of the instrument. We will also report on initial results from laboratory experiments and progress towards future field experiments. 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.