The Biogenic Volatile Organic Compound Environment of a Tropical Rain Forest in Central Amazonia (Invited Presentation)

Tropical rainforests emit and consume large amounts of biogenic volatile organic compounds (BVOCs). BVOCs alter the oxidative state of the troposphere and serve as precursors to the secondary organic aerosols which aggregate and activate to form cloud condensation nuclei and influence precipitation processes, and thus play a large but poorly understood role in the global climate system. BVOC production and consumption within the forest canopy are determined by light, temperature, biological processes, deposition, and atmospheric transport, all of which exhibit complex diurnal and vertical dynamics. Here, we use proton transfer reaction mass spectroscopy (PTR-MS) and gas chromatography-mass spectroscopy (GC-MS) to characterize the vertical variability of BVOCs across the diurnal cycle within a tropical rain forest canopy in central Amazonia. Isoprene and methanol dominate BVOC mixing ratios with nontrivial contributions from terpenes, acetaldehyde, and acetone. Fluxes are estimated using a constrained source optimization approach informed by a vertical array of ten sonic anemometers, which reveal both canopy and forest floor sources of many BVOCs. Intermittently large concentrations of certain compounds like isoprene may be attributable to the biological diversity of the canopy and are important to consider when interpreting the atmospheric impacts of BVOCs in tropical rain forest canopies.