Soil carbon measurements using inelastic neutron scattering

Soil carbon sequestration is a whole new area of energy related research that provides a fundamentally new approach for dealing with climate change resulting from the substantial increase in CO₂ concentration in the atmosphere. Carbon sequestration in soil is recognized to play a major role in allowing fossil fuels to remain a vital component of the national energy mix. At present soil carbon is measured by taking core samples and involves extensive laboratory work. We propose a novel nondestructive in situ method for carbon analysis using the Inelastic Neutron Scattering (INS) (n,n\´γ) reaction. The feasibility of detecting carbon in soil was demonstrated using a clinical in vivo body composition facility, located in the Medical Department at BNL. A D-T generator, operated at 55 kV, irradiated 12"×12"×14" aluminum boxes filled with 70 lb. Clean sand and mixtures of sand with 2%, 5% and 10% carbon powder by weight. The spectra were acquired for 1 hr and subsequently the carbon peaks were analyzed using the trapezoidal method for peak extraction. The results demonstrate that the proposed method is suitable for carbon analysis in soil, and it should allow sequential sampling of soil carbon within a soil volume of about 0.5 m³ with an error of about 1% or less. It is expected that, with final optimization, changes of about 1% in the soil carbon content would be observable with sufficient confidence levels