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Potential of combined neutron and X‐ray imaging to quantify local carbon contents in soil

DOI: 10.1111/ejss.13178 DOI Help

Authors: J. Koestel (Swedish University of Agricultural Sciences; Agroscope Reckenholz-Tanikon) , J. Fukumasu (Swedish University of Agricultural Sciences) , M. Larsbo (Swedish University of Agricultural Sciences) , A. M. Herrmann (Swedish University of Agricultural Sciences) , P. Ariyathilaka (Scitech Precision Limited) , O. V. Magdysyuk (Diamond Light Source) , G. Burca (ISIS Pulsed Neutron and Muon Source; University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: European Journal Of Soil Science

State: Published (Approved)
Published: September 2021
Diamond Proposal Number(s): 22974

Open Access Open Access

Abstract: In this study, we investigated the potential and limitations of using joint X-ray and time-of-flight (TOF) neutron imaging for mapping the 3-dimensional organic carbon distribution in soil. This approach is viable because neutron and X-ray beams have complementary attenuation properties. Soil minerals consist to a large part of silicon and aluminium, elements that are relatively translucent to neutrons but attenuate X-rays. In contrast, attenuation of neutrons is strong for hydrogen, which is abundant in soil organic matter (SOM), while hydrogen barely attenuates X-rays. In theory, TOF neutron imaging does further more allow the imaging of Bragg edges, which correspond to d-spacings in minerals. This could help to distinguish between SOM and clay minerals, the mineral group in soil that is most strongly associated with hydrogen atoms. We collected TOF neutron imaging data at the IMAT beamline at the ISIS facility and synchrotron imaging data at the I12 beamline at the Diamond Light source, both located within the Rutherford Appleton Laboratory, Harwell, UK. The white beam (the full energy spectrum) neutron image clearly showed variations in neutron attenuation within soil aggregates at approximately constant X-ray attenuations. This indicates a constant bulk density with varying organic matter and/or clay content. Unfortunately, the combination of TOF neutron and X-ray imaging was not suited to allow for a distinction between SOM and clay minerals at the voxel scale. While such a distinction is possible in theory, it is prevented by technical limitations. One of the main reasons is that the neutron frequencies available at modern neutron sources are too large to capture the main d-spacings of clay minerals. As a result, inference to voxel scale SOM concentrations is presently not feasible. Future improved neutron sources and advanced detector designs will eventually overcome the here encountered technical problems. On the positive side, combined X-ray and TOF neutron imaging demonstrated abilities to identify quartz grains and to distinguish between plastics and plant seeds.

Subject Areas: Earth Science, Technique Development

Instruments: I12-JEEP: Joint Engineering, Environmental and Processing

Other Facilities: IMAT at ISIS

Added On: 27/09/2021 13:25


Discipline Tags:

Earth Sciences & Environment Technique Development - Earth Sciences & Environment Agriculture & Fisheries

Technical Tags:

Imaging Tomography