Air-sea fluxes of methanol, acetone, acetaldehyde, isoprene and DMS from a Norwegian fjord following a phytoplankton bloom in a mesocosm experiment

[摘要] The ocean's influence on volatile organic compounds (VOCs) in the atmosphereis poorly understood. This work characterises the oceanic emission and/oruptake of methanol, acetone, acetaldehyde, isoprene and dimethyl sulphide(DMS) as a function of photosynthetically active radiation (PAR) and a suiteof biological parameters. The measurements were taken following aphytoplankton bloom, in May/June 2005 with a proton transfer reaction massspectrometer (PTR-MS), from mesocosm enclosures anchored in the Raunefjord,Southern Norway. The net flux of methanol was always into the ocean, and wasstronger at night. Isoprene and acetaldehyde were emitted from the ocean,correlating with light (r_{avcorr, isoprene}=0.49; r_{avcorr,acetaldehyde}=0.70) and phytoplankton abundance. DMS was also emitted tothe air but did not correlate significantly with light (r_{avcorr, dms}=0.01).Under conditions of high biological activity and a PAR of ~450 μmol photons m⁻² s⁻¹, acetone was emitted from the ocean,otherwise it was uptaken. The inter-VOC correlations were highest betweenthe day time emission fluxes of acetone and acetaldehyde (r_av=0.96),acetaldehyde and isoprene (r_av=0.88) and acetone and isoprene(r_av=0.85). The mean fluxes for methanol, acetone, acetaldehyde,isoprene and DMS were −0.26 ng m⁻² s⁻¹, 0.21 ng m⁻² s⁻¹,0.23 ng m⁻² s⁻¹, 0.12 ng m⁻² s⁻¹ and 0.3 ng m⁻² s⁻¹,respectively. This work shows that compound specific PARand biological dependency should be used for estimating the influence of theglobal ocean on atmospheric VOC budgets.

[学科分类] 大气科学