Predicting Neutron Attenuation from Bulk Density and Moisture for Soil Carbon Measurement

Fuente: arXiv
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Auteurs principaux: Larsen, William, Smykalov, Valerie, Castanha, Cristina, Brodie, Eoin, Unzueta, Mauricio Ayllon, Ludewigt, Bernhard, Persaud, Arun
Format: Preprint
Publié: 2026
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author Larsen, William
Smykalov, Valerie
Castanha, Cristina
Brodie, Eoin
Unzueta, Mauricio Ayllon
Ludewigt, Bernhard
Persaud, Arun
author_facet Larsen, William
Smykalov, Valerie
Castanha, Cristina
Brodie, Eoin
Unzueta, Mauricio Ayllon
Ludewigt, Bernhard
Persaud, Arun
contents Inelastic neutron scattering (INS) enables rapid, non-destructive in situ measurements of soil elemental composition over large soil volumes. Standard INS yields bulk elemental concentrations, but spatially resolved measurements require techniques such as Associated Particle Imaging (API), which pairs neutron detection with coincident alpha detection to reconstruct the location of the neutron interaction. One of the unique advantages of API is its capability to measure all major soil components simultaneously, allowing for the estimation of both bulk density and water content directly from the measured neutron-induced gamma-ray spectra. Accurate interpretation of bulk INS-API data depends on correcting for both gamma-ray and neutron attenuation in soil. Although gamma attenuation can be calculated from known mass attenuation coefficient data and density, neutron attenuation is more complex, depending on neutron energy, soil composition, bulk density, and hydrogen content from water and organic matter. We use Monte Carlo simulations of soils with varied compositions, bulk densities, and water contents to model neutron attenuation and develop a simple predictive model requiring only dry bulk density and volumetric water content. We validate this model experimentally using an INS-API system with controlled soil columns, finding agreement within 10 percent at 30 cm depth. This approach enables practical, field-ready correction of INS-API measurements for neutron attenuation, laying the groundwork for a self-consistent measurement framework that can address the elemental composition of soil carbon assessments.
format Preprint
id arxiv_https___arxiv_org_abs_2602_09032
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Predicting Neutron Attenuation from Bulk Density and Moisture for Soil Carbon Measurement
Larsen, William
Smykalov, Valerie
Castanha, Cristina
Brodie, Eoin
Unzueta, Mauricio Ayllon
Ludewigt, Bernhard
Persaud, Arun
Geophysics
Instrumentation and Detectors
Inelastic neutron scattering (INS) enables rapid, non-destructive in situ measurements of soil elemental composition over large soil volumes. Standard INS yields bulk elemental concentrations, but spatially resolved measurements require techniques such as Associated Particle Imaging (API), which pairs neutron detection with coincident alpha detection to reconstruct the location of the neutron interaction. One of the unique advantages of API is its capability to measure all major soil components simultaneously, allowing for the estimation of both bulk density and water content directly from the measured neutron-induced gamma-ray spectra. Accurate interpretation of bulk INS-API data depends on correcting for both gamma-ray and neutron attenuation in soil. Although gamma attenuation can be calculated from known mass attenuation coefficient data and density, neutron attenuation is more complex, depending on neutron energy, soil composition, bulk density, and hydrogen content from water and organic matter. We use Monte Carlo simulations of soils with varied compositions, bulk densities, and water contents to model neutron attenuation and develop a simple predictive model requiring only dry bulk density and volumetric water content. We validate this model experimentally using an INS-API system with controlled soil columns, finding agreement within 10 percent at 30 cm depth. This approach enables practical, field-ready correction of INS-API measurements for neutron attenuation, laying the groundwork for a self-consistent measurement framework that can address the elemental composition of soil carbon assessments.
title Predicting Neutron Attenuation from Bulk Density and Moisture for Soil Carbon Measurement
topic Geophysics
Instrumentation and Detectors
url https://arxiv.org/abs/2602.09032