Investigation of the levels, composition and reactivity of OVOCs in the marine boundary layer of Bermuda

Oxidation of volatile organic compounds (VOC) in the atmosphere leads to the formation of secondary oxidized VOC (OVOC) which can form new aerosol particles and/or increase the size of existing ones through condensation. Aerosol particles are the most uncertain parameters affecting Earth's radiation balance. However, OVOC sources and reactivity in the marine boundary layer (MBL) are still poorly understood. We present the first measurements of VOCs levels and distribution in the MBL in Bermuda. The field measurements include HONO, NO_x (NO+NO₂), nitric acid, ozone and particulate nitrate (pNO₃), in addition to VOCs and meteorological parameters. The measurements took place in spring and late summer of 2019 at the Tudor Hill Marine Atmospheric Observatory of Bermuda. VOCs were collected every three hours on adsorption tubes and were analyzed using thermal desorption and GC/MS, following the TO-17 EPA method. Initial results indicate that the measurements were impacted by two different air mases, east/northeast (from Hamilton), carrying local biogenic and anthropogenic emission, and westerly winds, carrying marine air masses. OVOCs were especially abundant in marine air masses. Previous studies show that OVOCs from marine source are formed through heterogeneous oxidation processes at the interface between ocean and the atmosphere. Origin, levels and composition and possible formation mechanism for OVOCs will be investigated. Measured VOCs and the other species will be constrained to a box model to investigate the atmospheric oxidizing capacity and HONO formation in the MBL in Bermuda. Implications on the global MBL, radiation balance and climate will be also investigated using the CESM model.