PARENT SESSION
Oral Session #42: Decomposition.
Presiding: K. Gross
Tuesday, August 6. 1:00 PM to 4:45 PM. Apache Meeting Room, TCC.

An analytical method for the investigation of carbon decomposition in soils.

SONG, XIANZHI^*,1, FARWELL, SHERRY¹, BAKER, BRADLY¹, ¹ South Dakota School of Mines and Technology, Rapid City, SD.

ABSTRACT- A method based on sample pyrolysis with gas chromatography-atomic emission detection (SP/GC-AED) is being developed for the investigation of the decomposition of carbon-containing compounds in soils. It has been shown that nitrogen and carbon decomposition in soils are tightly coupled (Oades 1998; Knops 2000); therefore, the method focuses on nitrogen-containing compounds in soils as an indicator of carbon decomposition. This approach simplifies the soil matrix dramatically because there are far fewer nitrogen-containing compounds in soils than carbon-containing compounds. The method involves decomposing soil samples at high temperatures (e.g.,300, 400 and 500 degrees C), then pre-concentrating the effluent gas before injection to the GC-AED. Our results indicate that standard organic samples (humic and fulvic acids, lignin, and dry grass) have unique 'fingerprints' that can be obtained by observing the different volatile nitrogen-containing compounds evolved in the pyrolysis process. In addition, several of the nitrogen-containing compounds are common to both lignin, and humic and fulvic acids. This finding is consistent with the idea that lignin is a precursor to the more stable organic acid compounds. This method has the potential to be used for the quantitative determination of the relative amounts of different carbon pools (labile, intermediate, and stable) in soil samples.

KEY WORDS: Carbon, Decomposition, Analytical, Method