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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #415674

Research Project: Sustaining Productivity and Ecosystem Services of Agricultural and Horticultural Systems in the Southeastern United States

Location: Soil Dynamics Research

Title: Advancements in field measurement of soil composition: Introducing the tagged neutron technique mobile system

item Yakubova, Galina
item Kavetskiy, Aleksandr
item Prior, Stephen - Steve
item Torbert, Henry - Allen

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/31/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: We will present the development and implementation of a mobile system designed for in-situ field measurement of soil composition utilizing the tagged neutron technique (TNT). The system is comprised of a portable neutron generator API-120 equipped with a built-in alpha detector, a diameter 7.62×25.4 cm LaBr(Ce) gamma detector with a thermostabilizing module, a 4-channel digital pulse processor running on a Linux operating system (Pixie-Net) for data acquisition, radiation shielding, GPS, autonomous power system, and an operational laptop. This equipment, particularly the Pixie-Net pulse processor, enables the measurement of gamma rays’ spectra using the tagged neutron technique. These gamma spectra are generated solely by inelastic neutron scattering in soil or other samples, excluding contributions from external sources or other processes. Deconvolution of these spectra into their component parts facilitates the determination of the content of the studied object. The TNT gamma spectra of reference components (SiO2, Al2O3, Fe2O3, CaO, H2O, and carbon, C) are essential for the deconvolution procedure. Reference samples of oxides and C were sized (approximate diameter 100×50 cm) to ensure that the intensity of the tagged neutron technique (TNT) gamma spectra reached a steady state and did not increase with further sample size. To define this, Monte Carlo simulations of neutron-stimulated gamma spectra (using the MCNP6.2 code) were employed. Experimental TNT gamma spectra of reference oxides and C were measured in a box with the aforementioned dimensions using the TNT Mobile system and utilized in the deconvolution procedure. This procedure accounts for neutron and gamma-ray attenuation during their propagation in samples and soil. The deconvolution algorithm was rigorously tested against both Monte-Carlo simulations and experimental gamma spectra, demonstrating good agreement between defined and actual sample component content. In this poster presentation, we will delve into the detailed design of the TNT Mobile system, present results of samples measurements (including time-of-flight and energy spectra), discuss the deconvolution procedure using both Monte-Carlo simulated and experimental spectra, and compare field results of soil composition measurements with those obtained by various other methods including chemical analysis, dry combustion method, weight method, moisture determination by time domain reflectometry, and nuclear methods.