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Title: Structural investigation of bio-char by analytical pyrolysis (Py-GC-MS). Relationships with environmental stability and the occurrence of polyaromatic hydrocarbons (PAHs)

item TORRI, CRISTIAN - University Of Bologna
item ROMBOLA, ALESSANDRO - University Of Bologna
item CONTI, ROBERTO - University Of Bologna
item FABBRI, DANIELE - University Of Bologna
item Spokas, Kurt

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2011
Publication Date: 5/24/2011
Citation: Torri, C., Rombola, A., Conti, R., Fabbri, D., Spokas, K.A. 2011. Structural investigation of bio-char by analytical pyrolysis (Py-GC-MS). Relationships with environmental stability and the occurrence of polyaromatic hydrocarbons (PAHs)[abstract]. UK Biochar Conference 2011. On-line.

Interpretive Summary:

Technical Abstract: The structural assemblage of biochar is connected to the nature of feedstock and the conditions of production and has important implications to its fate in the environment. However, the relationships between the molecular characteristics of biochar and its agro/environmental behavior have not been fully understood yet. Pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC-MS) is a well-known technique to gather information on the structure of complex organic materials at a molecular level. The aim of this study was that to evaluate possible correspondences between the structural data of biochar gathered by Py-GC-MS and microbial respiration rates as well as the content of noxious contaminants such as polycyclic aromatic hydrocarbons (PAHs). A set of biochars produced from pyrolysis of different biomass feedstock (hardwood, softwood, shell nuts, wastes, etc.) and produced under different pyrolysis conditions (400 °C – 800 °C) were analysed by Py-GC-MS at 900 °C. The yields of pyrolysis products were evaluated by internal calibration with o-isoeugenol. PAHs were determined after solvent extraction and SIM-GC-MS analysis, with quantification through an internal standard method using spiked deuterated PAHs. Total yields of pyrolysis products covered a wide interval (230-16000 µg gC-1) and were positively correlated with volatile matter (VM). The proportion of products associated to the charred fraction (e.g., benzene derivatives, PAHs) ranged from 32 to 99%. The remaining fraction was associated to partially preserved “uncharred” biomass (e.g., anhydrosugars, furans, methoxyphenols) and its molecular composition reflected the nature of the starting material. In particular, relatively high levels of protein fragments (e.g., pyrrole, indole) were evolved from biochars characterized by high nitrogen content. The short term CO2 suppression/stimulation of biochar amended soils presented large differences without marked correlations with bulk analyses. With regard to Py-GC-MS, in general, biochars characterized by large yields of pyrolysis products from holocellulose exhibited a positive priming effect on mineralization rates in incubated soils. PAHs were detected in all the examined biochar samples and correlations with chemical/microbial characteristics are currently under investigation. Py-GC-MS resulted a rapid and reliable method to complement VM data with a molecular picture of the less thermal recalcitrant component of biochar probably associated to its lability in soil.