• Application of molecular spectroscopy tools to the analysis of natural organic matter for insight to composition, structure, origin, and reactivity.
• Biogeochemical fate and cycling of organic combustion byproducts in terrestrial and marine environments
• The application of isotope geochemistry to probe the dynamics of the carbon and nitrogen pools
• The roles and mechanisms of chemical and physical sorption in the fate and transport of anthropogenic contaminants

Soil Carbon Oxidation State Project

The oxidation state of carbon in soil organic matter can serve as indicator of ecosystem-level changes. Oxidation state measurements are a first step in determining ecosystem oxidative ratio (moles O₂ released/CO₂ fixed), another parameter necessary to detect the fate of anthropogenic CO₂ emissions within the Earth system. However, we currently lack well-constrained techniques to measure this property. The oxidation state of mineral-free organic matter can be measured easily via combustion elemental analysis, but the large quantities of oxygen in soil minerals preclude the application of this technique to whole soils. Solid-state ¹³C nuclear magnetic resonance (NMR) offers an alternative to the problem of determining organic oxygen because NMR can determine organic matter composition in the presence of (non iron-bearing) minerals. We are currently developing NMR methods for measuring how soil carbon oxidation state is altered by changes in land-use [link to poster]. The long term ecological research site at Kellogg Biological Station (http://lter.kbs.msu.edu/) offers a soil archive where changes can be studied across a wide land-use gradient on decadal time-scale.

Publications

P. Trompowsky, V. Benites, A. Pimenta, B. Madari, W. Hockaday, P. Hatcher, Characterization of humic-like substances obtained by chemical oxidation of eucalyptus charcoal, Organic Geochemistry, 36, 1480-1489, 2005. pdf

W. Hockaday, S. Kim, A. Grannas, P. Hatcher, Direct molecular-level evidence for the degradation of black carbon in soils from ultrahigh resolution mass spectral analysis of dissolved organic matter from a fire impacted forest soil, Organic Geochemistry, 37, 501-510, 2006. pdf

A. Grannas, W. Hockaday, P. Hatcher, L. Thompson, E. Mosley-Thompson, New revelations on the nature of organic matter in ice cores, Journal of Geophysical Research-Atmospheres, 111, D04304, 2006. pdf

W. Hockaday, A. Grannas, S. Kim, P. Hatcher, The transformation and mobility of charcoal black carbon in a fire-impacted watershed, Geochimica et. Cosmochimica Acta., accepted and under revision.

W. Hockaday and P. Hatcher, Pyrene sorption by environmental charcoal. 1. The influence of natural organic matter, Environmental Science and Technology, submitted.

W. Hockaday and P. Hatcher, Pyrene sorption by environmental charcoal. 2. Predicting uptake in fire-impacted soils, Environmental Science and Technology, submitted.