This project is a collaborative effort involving investigators from four institutions with complimentary expertise in measuring and interpreting biogenic volatile organic carbon (BVOC) compounds and associated reaction products. The project is envisioned as part of a longer-term research initiative designed to test the following hypothesis: "The impact of BVOC emissions on climate depends on the structures of the BVOC; while isoprene can impact ozone production, terpenes are more effective at nitrogen sequestration and aerosol production; the change to terpene-dominance in forests will lead to more carbon sequestration, other factors remaining the same." During year 1, the principal investigators (PIs) will construct and test in the laboratory an automated measurement system consisting of a sampling apparatus, a two-dimensional gas chromatograph (GCxGC), and a calibration system to quantify ambient mixing ratios of speciated BVOCs and reaction products hourly. The sampling apparatus will concentrate BVOCs and reaction products and transfer to a GC fitted with two secondary columns. One channel will feed a flame ionization detector (FID) to quantify BVOCs and the other an electron capture detector (ECD) to quantify oxidation products (including nitrates and hydroxynitrate). The general utility calibration source will include a temperature-controlled bath containing multiple compound-specific diffusion tubes and associated plumbing. During year 2, the PIs will deploy and continuously operate this novel semi-autonomous measurement system at the Program for Research on Oxidants: PHotochemistry, Emissions, & Transport (PROPHET) site at the University of Michigan Biological Station (UMBS) over a 4-week period during the growing season. The goal of the field deployment will be to test the instrument's performance in reliably quantifying a broad suite of heavy alkanes, alkenes, aromatics, isoprene, montoterpenes, sesquiterpenes, aldehydes and ketones, and alcohols, and organic nitrates in ambient air within and above the forest canopy.
The development of a semi-autonomous measurement system for BVOCs and reaction products will enhance observational resolution for investigations of interactions among forest dynamics, oxidation processes, aerosol production, nitrogen and carbon sequestration, and associated feedbacks on climate. Results from the project will also extend the PROPHET data archive, which has been a valuable community resource for broader investigations of forest-atmosphere interactions. Graduate and undergraduate students will participate directly in constructing and field testing the instrument. Results will be disseminated through articles in the scientific literature and also incorporated into an inquiry-based instructional webquest to help high school students understand biosphere-atmosphere research in the context of global climate change. This webquest would become part of a library of similar educational resources at UMBS.
This project was a collaborative effort between four individual laboratories. Together we have developed a scientific instrument that allows us to measure a large portion of the chemical profile of the lower atmosphere. This two-dimensional gas chromatography instrument separates volatile and semivolatile organic compounds so that they may be identified and quantified. We have developed and validated this approach in a series of field studies performed in northern Michigan, central Alabama (as part of the SOAS campaign), and southeastern Michigan. This instrument operates with minimal human intervention, and thus can be used to automatically monitor the chemical composition of the atmosphere over long periods of time. We have also written software that makes it much easier to analyze the large volumes of data produced by the technique. It is our intention to ultimately use this instrument to study the importance of naturally-produced compounds on the chemistry of the lower atmosphere. In the future, we hope to determine the chemical composition of the air at the PROPHET site in northern Michigan over a wide range of seasonal and meteorological conditions. The technologies that we have developed can also be used in a wide variety of studies outside of atmospheric science including biomedical analyses and the development of new fuels.
