Deposition fluxes of oxygenated volatile organic compounds (OVOCs) above FLONA Tapajós in central Amazon rainforest, Brazil.

Understanding of VOC deposition is highly uncertain due to a lack of direct flux measurements, but this loss process has been inferred to dominate the removal of VOC from the atmosphere. A recent study on ecosystem scale BVOC fluxes over Amazonian rainforest showed that some oxygenated volatile organic compounds (OVOCs), which are photochemically produced above the canopy, were depositing measurably into the forest. However, that study was limited to only a few compounds due to the technical difficulties. Very recently (June and July 2014), we deployed a PTR-TOF-MS (Proton Transfer Reaction - Time of Flight - Mass Spectrometer) to apply eddy covariance flux measurements of volatile organic compounds (VOC) above the FLONA Tapajós (Floresta Nacional do Tapajós) in the central Amazon rainforest in Brazil. The main goal of this study is to quantify emissions and depositions of a wide range of VOCs and their oxidation products formed above and below canopy. In this presentation, data analysis will be focused on some depositing OVOCs into the forest. From preliminary results for the first 3 days of eddy covariance flux measurement, m/z 31 (CH2OH+), m/z 45 (C2H4OH+), m/z 61 (C2H4O2H+), m/z 71 (C4H6OH+), and m/z 113 (C5H4O3H+) were observed as uniformly depositing compounds during the daytime.