Investigating mechanisms for negative priming of soil organic carbon by pyrogenic carbon using NanoSIMS and LA-AMS
EMSL Project ID
47916
Abstract
Reduced turnover rate (often referred to as “negative priming”) of soil organic carbon (SOC) by pyrogenic black carbon (pyC) has the potential to have dramatic long-term effects on soil carbon stocks. However, the net impact of negative priming depends on which mechanisms are responsible for these effects, which is currently poorly characterized. We propose to test two mechanisms for negative priming of SOC by pyC: (1) direct adsorption of SOC on pyC, and (2) increased stabilization of SOC on soil minerals in the presence of pyC. These mechanisms have been proposed as possible explanations for the observed phenomenon of negative priming, but neither has been directly measured, tested, or observed. We will leverage samples from a soil incubation trial with 13C- and 15N-labelled pyC additions to test these two mechanisms, using nanoSIMS and laser ablation sampling with high spatial-resolution atomic mass spectrometry (LA-AMS). Combined, nanoSIMS and LA-AMS offer two of the most promising methods to understand how the physical and chemical makeup of soils give rise to stabilization of organic matter. We will use nanoSIMS to image the distribution in soil-pyC aggregates of (1) 13C and 12C to determine the location and stable isotope ratio of organic compounds and pyC; (2) 14N (as 12C14N) to provide a map of C:N ratio, which differs between pyC, npSOC, MB, and plant litter; and (3) Fe (as 56Fe16O), Al (as 27Al16O), 40Ca, and 28Si to map the correspondence of organic substances with soil minerals important in the formation of stable organo-mineral interactions in microaggregates. We will use LA-AMS to rapidly sample larger regions than possible using nanoSIMS, building on recent pioneering work at EMSL that used LA-AMS to map the spatial distribution of 12C and 13C in soil aggregates. In addition to providing data on C:N abundance and isotope ratios, LA-AMS will simultaneously provide spatially-resolved multi-elemental analysis of soil minerals and chemical classification of organic compounds present. The nanoSIMS and LA-AMS equipment and technical expertise at EMSL is not widely available elsewhere, and is ideally suited to answer our research questions. The proposed investigation would be a novel approach to understanding pyC-SOC interactions. Understanding these mechanisms is essential to predict the impact pyC-SOC priming has on the global C cycle and the net climate impact of intentional pyC production and management.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2013-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
DeCiucies S., T. Whitman, D. Woolf, A. Enders, and J.C. Lehmann. 2018. "Priming Mechanisms with Additions of Pyrogenic Organic Matter to Soil." Geochimica et Cosmochimica Acta 238. doi:10.1016/j.gca.2018.07.004
Whitman TL, Z Zhu, and JC Lehmann. 2014. "Carbon Mineralizability Determines Interactive Effects on Mineralization of Pyrogenic Organic Matter and Soil Organic Carbon." Environmental Science & Technology 48(23):13727-13734. doi:10.1021/es503331y