Collaborative Research: Forest-Atmosphere Volatile Organic Compound (VOC) Exchange for a Coniferous Ecosystem - Closing the Flux Budget

This project is focused on the two-way exchange of biogenic volatile organic compounds (BVOCs) between coniferous forests and the atmosphere. Recent observations include ecosystem-atmosphere fluxes for many hundreds of organic species, vastly more than are included in current chemical transport models. The impacts of these 'missing' organic species is unknown, resulting in models that are fundamentally limited in their ability to simulate forest-atmosphere volatile organic carbon exchange. This research will better define the ecosystem-atmosphere fluxes that take place in coniferous forests, enabling models to better predict the carbon exchange that is taking place. Carbon is an essential element for all life, so understanding how it moves helps us to understand biological processes and factors that influence them.

This research will address the following scientific questions: (1) What is the reactive carbon flux budget across the mass spectrum for a coniferous forest? What is the importance of these two-way fluxes for atmospheric OH reactivity? Is there a significant role for previously unidentified or unmodeled compounds? (2) How do the emissions and deposition of individual organic molecules, classes of BVOCs (by O:C ratio, OH rate constant, degree of unsaturation, etc.), and the overall reactive ensemble, vary temporally and as a function of environmental drivers? To what extent do current models capture these dependencies? (3) How do individual ecosystem components (e.g., overstory, understory, soils), in-canopy chemistry, and deposition combine to drive the overall net forest-atmosphere flux budget? Can we close the ecosystem-level BVOC flux budget by reconciling these different terms? And (4) What are the broader implications of this full suite of BVOC fluxes for atmospheric composition, near-surface ozone, and HOx chemistry? The research plan combines two high-resolution TOF-CIMS to measure canopy-level BVOC fluxes across the entire mass range over a coniferous forest to assess the importance of those fluxes for OH reactivity.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.