Small Molecules to Particles - Do Interfaces Promote New Particle Formation over Remote Oceans?
Oceans are the largest reservoir of organic carbon on Earth. However, marine sources of volatile organic compounds (VOC) are insignificant (<1%) compared to terrestrial environments. The net marine organic carbon source to the atmosphere is dominated by DMS, primary organic aerosol, and questions related to sources of oxygenated VOC (OVOC). Field observations of water soluble OVOC have been puzzling researchers for ~30 years, and challenge our understanding of air-sea exchange. Understanding trace gas emissions that can modify particles are relevant because: 1) changes in global cloud albedo are sensitive to assumptions about biogenic (pre-industrial) emissions; 2) nucleation in the free troposphere contributes a significant fraction of the CCN in the remote boundary layer, but 3) nanoparticle growth is deemed limited to DMS oxidation products. Marine OVOC also 4) modify oxidative capacity, including bromine from sea-spray, which affects the lifetime of tropospheric ozone (O3) and methane (CH4). This talk presents laboratory experiments of direct photolysis of fatty acids at interfaces, and assesses the relevance of such interfacial chemistry to help explain missing sources of marine OVOC and to grow nanoparticles. The latitude, longitude and altitude distributions of ultrafine, Aitken mode, and Accumulation mode sized particles are presented, and the atmospheric implications of marine OVOC for nanoparticle growth are discussed.