Discrimination in Degradability of Soil Pyrogenic Organic Matter Follows a Return-On-Energy-Investment Principle

Journal Article · Tue Aug 16 00:00:00 EDT 2016 · Environmental Science and Technology

DOI:https://doi.org/10.1021/acs.est.6b01010· OSTI ID:1298387

Harvey, Omar R.; Myers-Pigg, Allison N.; Kuo, Li-Jung; Singh, Bhupinder Pal; Kuehn, Kevin A.; Louchouarn, Patrick

A fundamental understanding of biodegradability is central to elucidating the role(s) of pyrogenic organic matter (PyOM) in biogeochemical cycles. Since microbial community and ecosystem dynamics are driven by net energy flows, then a quantitative assessment of energy value versus energy requirement for oxidation of PyOM should yield important insights into their biodegradability. We used bomb calorimetry, step-wise isothermal thermogravimetric analysis (isoTGA) and 5-year in-situ bidegradation data, to develop energy-biodegradability relationships for a suite of plant- and manure-derived PyOM (n = 10). The net energy value (ΔE) for PyOM was between 4.0 and 175 kJ mol-1; with manure-derived PyOM having the highest ΔE. Thermal-oxidation activation energy (Ea) requirements ranged from 51 to 125 kJ mol-1, with wood-derived PyOM having the highest Ea requirements. We propose a return-on-investment (ROI) parameter (ΔE/Ea) for differentiating short-to-medium term biodegradability of PyOM and deciphering if biodegradation will most likely proceed via co-metabolism (ROI < 1) or direct metabolism (ROI ≥ 1). The ROI-biodegradability relationship was sigmoidal with higher biodegradability associated with PyOM of higher ROI; indicating that microbes exhibit a higher preference for “high investment value” PyOM.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1298387
• Report Number(s): PNNL-SA-119275
• Journal Information: Environmental Science and Technology, Vol. 50, Issue 16; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English