Atmospheric Chemistry Program Seminar
Ecosystem-atmosphere fluxes of volatile organic compounds: Which ones matter? by Dylan Millet, University of Minnesota
"Volatile organic compounds (VOCs) play several key roles in the atmosphere: their oxidation leads to the formation of health- and climate-relevant pollutants; they affect the nitrogen cycle by interacting with atmospheric NOx; and they modulate the atmosphere’s oxidizing capacity and therefore the lifetimes of greenhouse gases and other pollutants. Terrestrial ecosystems are simultaneously the largest source and a major sink of atmospheric VOCs; however, our understanding of these fluxes and their atmospheric impacts is challenged by a number of outstanding uncertainties, including complex emission sources, bidirectional exchange with the land surface, and chemical interactions with anthropogenic pollutants. In this talk I will present results from my group’s research applying observations to better characterize these ecosystem-atmosphere interactions and their effects on atmospheric chemistry. Discussion will focus on two specific themes. I will first present results focusing specifically on formic acid, which is a major source of atmospheric acidity and an integrated marker of hydrocarbon oxidation, but which has large missing sources. I will then discuss new measurements from my group using high-resolution time-of-flight mass spectrometry to directly measure forest-atmosphere fluxes of VOCs simultaneously across the entire mass spectrum, and explore these results with the aim of better understanding i) how well our models capture this 2-way land-atmosphere carbon exchange, and ii) to what degree the fluxes for the large number of ions outside of the traditionally-measured subset matter for tropospheric composition."