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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #163975


item Prior, Stephen - Steve
item Rogers Jr, Hugo
item Runion, George
item Torbert, Henry - Allen

Submitted to: Department Of Energy Annual Report
Publication Type: Other
Publication Acceptance Date: 4/9/2004
Publication Date: 4/9/2004
Citation: Wielopolski, L., Mitra, S., Hendrey, G., Orion, I., Prior, S.A., Rogers Jr, H.H., Runion, G.B., Torbert III, H.A. 2004. Non-destructive soil carbon analyzer (ND-SCA). Technical Report, Terrestrial Carbon Processes (TCP) program of the Office of Science, Biological and Environmental Research (BER), U.S. Department of Energy, Germantown, MD. 89 pp. Brookhaven National Laboratory Report 72200-2004.

Interpretive Summary: Management of soils in order to sequester carbon has been suggested as a means to mitigate the atmospheric buildup of anthropogenic CO2. Quantifying changes in soil carbon stocks will be essential to evaluating such schemes and documenting their performance. Current methods for quantifying carbon in soil by excavation and core sampling are invasive, slow, labor intensive and result in localized destruction of the system being studied. Some newly emerging technologies offer soil carbon analysis, such as Laser Induced Breakdown Spectroscopy and Near-Infrared Spectroscopy, are invasive and destructive. The INS approach permits quantification in a large volume of soil without disruption of the measurement site. The technique is very fast and can provide nearly instantaneous results that can reduce the cost, speed up the rate of analysis, and with the potential to cover large areas in a mobile scanning mode. These capabilities will provide a significant advance both for tracking carbon sequestration and as a tool for research in agronomy, forestry, soil ecology and biogeochemistry.

Technical Abstract: This report describes the feasibility, calibration, and safety considerations of a non-destructive, in-situ, quantitative, volumetric soil carbon analytical method based on inelastic neutron scattering (INS). The method is shown to be able to quantify values as low as 0.018 gC/cc, or about 1.2% carbon volume with the instrument configuration reported here. New instrumentation was developed for this purpose in response to a research solicitation from the U.S. Department of Energy (DOE LAB 00-09 Carbon Sequestration Research Program) supporting the Terrestrial Carbon Processes (TCP) program of the Office of Science, Biological and Environmental Research (BER). The solicitation called for the development and demonstration of novel techniques for quantitative measurement of changes in soil carbon. The report includes raw data and analyses of a set of proof-of-concept, double-blind studies to evaluate the INS approach in the first phase of the development of the instrument. Experience in prior work dealing with the quantification of carbon in humans, indicated that INS was a likely candidate for quantification of soil carbon. INS is based on the capture of a fast, 14 MeV, neutron by a carbon nucleus and subsequent prompt decay in about 10-15s of the excited carbon nucleus to the ground state by emitting a neutron and a 4.44 MeV gamma ray. Detection of the 4.4 MeV gamma rays using NaI detectors provides quantitative information on carbon concentration in the soil. A proof-of-principle of the INS method was demonstrated in our laboratory using a clinical facility to measure whole body carbon in human beings. A prototype of a field-deployable INS system was constructed, calibrated in terms of signal yield versus carbon concentration (gC/cc), and tested in double-blind studies against chemical analysis of core samples taken from three different field sites. Table 1 summarizes the agreement between carbon determination using INS and Chemical Analysis of the core samples. Preliminary results of basic simulations of the neutron transport in soil using Monte Carlo Neutron Photon (MCNP) code elucidated the details of the processes involved and assisted in system optimization. The proposed INS system is field deployable, measures directly the carbon compartment in soil, and allows multiple analyses of sub-plots at a particular location. A very important feature of this system, however, is that since it causes no physical disturbance to the plot examined, it also allows sequential field measurements in a static mode at the very same plot. Significant further developments in the proposed technology are possible. For example, if the INS system were mounted on a mobile carriage and used in a dynamic mode it could scan large areas in order to provide the true mean carbon concentration in the field as might be needed in forestry, agriculture, and for monitoring carbon sequestration claims for eligibility for carbon credits. Furthermore, the INS instrument could be modified to allow non-destructive determination of the soil carbon depth profile or its 3-Dimensional distribution. An alpha prototype of the INS system became operational in 2003. A path forward that identifies steps required to establish a beta testing site for final evaluation of the viability of INS for field measurements is presented. However, there is an urgent need to establish a soil laboratory to carry further developmental work. This report recommends continuation of the project in order to bring the INS approach to a fully operational state.