Collaborative Research: Dissolved pyrogenic organic matter dynamics in the environment

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Pyrogenic organic matter, or black carbon (BC), is derived from the incomplete combustion of biomass and fossil fuels. It is now recognized that this type of organic matter has a great impact on soil chemistry, transport of pollutants, climate and global carbon cycling. Further, its impacts will likely grow due to increased climate change-related wildfires and intentional addition of BC (as biochar) to soils to enhance soil fertility and carbon sequestration. However, while knowledge of the properties of natural and anthropogenic particulate BC has increased in recent years, there has been relatively little study of the properties and cycling of the organic matter that can leach from BC; pyrogenic dissolved organic matter (py-DOM). Although release of py-DOM into the environment may have unrecognized carbon cycling and environmental impacts, py-DOM has been quantified in only a few systems using methods that have not been comprehensively evaluated. This research will examine the fundamental chemical properties and mechanisms associated with py-DOM production and fate and the chemical markers used to quantify it. In addition, in order to broaden general awareness of the importance of fire on climate and the carbon cycle, the investigators will develop an interactive exhibit at a local hands-on science museum that will include touch screen graphics, narrated videos by each of the principal investigators illustrating the scientific process and the research results. To establish the chemical properties and mechanisms associated with py-DOM production and fate and the chemical markers used to quantify it, the project will: 1) produce py-DOM from a logical series of BC solids, both freshly produced and "aged" via microbial and photic treatments, 2) chemically characterize these BC parent solids and their aqueous dissolved products using FTIR, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and 1- and 2-dimensional NMR, 3) examine py-DOM loss and transformation after microbial and photodegradation treatments, and 4) quantify the yields of putative pyrogenic molecular markers; levoglucosan, benzenepolycarboxylic acids (BPCA) and oxygenated polycyclic aromatic hydrocarbons (O-PAH), from fresh and "aged" BC solids and leachates. Using the same methods and experiments, the leachates and leachate alteration products of potentially interfering non-pyrogenic terrestrial organic materials, some of which the investigators have recently shown to contain "BC-like" compounds will also be examined. This work will test whether py-DOM chemistry can be linked to its parent BC type and "aging" processes, the extent to which py-DOM and its molecular markers undergo major losses and chemical transformation through microbial and photo-oxidation, and whether currently used molecular markers for py-DOM accurately represent actual pyrogenic OM contributions to environmental samples.