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United States Department of Agriculture

Agricultural Research Service

Research Project: ASSESSING CLIMATE, SOIL AND LANDSCAPE PROCESSES AFFECTING AGRICULTURAL ECOSYSTEMS Title: Mid-intrared Diffuse Reflectance Spectroscopic (DRIFTS) Examination of Charred Pine Wood, Bark Cellulose and Lignin: Implications for the Quantitative Determination of Charcoal in Soils

Authors
item Reeves Iii, James
item McCarty, Gregory
item Rutherford, David - USGS
item Wershaw, Robert - USGS

Submitted to: Journal of Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 28, 2007
Publication Date: February 28, 2008
Citation: Reeves III, J.B., Mccarty, G.W., Rutherford, D.W., Wershaw, R.L. 2008. Mid-infrared Diffuse Reflectance Spectroscopic (DRIFTS) Examination of Charred Pine Wood, Bark Cellulose and Lignin: Implications for the Quantitative Determination of Charcoal in Soils. Journal of Applied Spectroscopy. 62:182-189.

Interpretive Summary: Due to the impact of carbon emissions on global warming, there is intense interest in determining if carbon can be sequestered in soils. However, to make such determinations it is necessary to be able to determine the amount and types of carbon already present and those that accumulate over time. Fires in terrestrial ecosystems produce large amounts of charcoal which is persistent in the environment and represents a substantial pool of sequestered carbon in soil. However, there is presently no accepted method for determining charred materials or charcoal in soils. Mid-infrared spectroscopy uses light beyond the range or human site to determine the composition of materials such as soils. The objective of this research was to investigate the effect of charring on mid-infrared spectra of materials likely to be present in forest fires in order to determine the feasibility of determining charcoal or charred C in soils. Four materials (cellulose, lignin, pine bark and pine wood) and char from these materials created by charring for various durations (1 to 168 h) and at various temperatures (200 to 450 C) were studied. Mid-infrared spectra were taken of 56 different charred materials and examined for their ability to determine charring in the form of acidity. Results showed spectral changes that varied widely with the material, temperature and duration of charring. Despite the while range of spectral changes seen with the differing materials and length/temperature of charring results showed that mid-infrared spectroscopy could easily determine four measures of acidity in the charred materials. This work supports the conclusion that with further efforts mid-infrared spectroscopy will be able to accurately determine the concentrations of charred materials in soils.

Technical Abstract: Fires in terrestrial ecosystems produce large amounts of charcoal which is persistent in the environment and represents a substantial pool of sequestered carbon in soil. The objective of this research was to investigate the effect of charring on mid-infrared spectra of materials likely to be present in forest fires in order to determine the feasibility of determining charred C in soils. Four materials (cellulose, lignin, pine bark and pine wood) and char from these materials created by charring for various durations (1 to 168 h) and at various temperatures (200 to 450 C) were studied. Mid-infrared spectra and measures of acidity (total acids, carboxylic acids, lactones and phenols as determined by titration) were available for 56 different samples (Not all samples charred at all temperatures/durations). Results showed spectral changes that varied with the material, temperature and duration of charring. Despite the while range of spectral changes seen with the differing materials and length/temperature of charring partial least squares calibrations for total acids, carboxylic acids, lactones and phenols were successfully created (R2 and RMSD of 0.970 and 0.380; 0.933 and 0.227; 0.976 and 0.118 and 0.982 and 0.101, respectively) indicating that there is a sufficient commonality in the changes to develop calibrations without the need for unique calibrations for each specific material or condition of char formation.

Last Modified: 10/25/2014
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