Short-Term Variability of Atmospheric DMS and Its Oxidation Products at Amsterdam Island during Summer Time

Abstract

A one-month experiment was performed at Amsterdam Island in January 1998, to investigate the factors controlling the short-term variations of atmospheric dimethylsulfide (DMS) and its oxidation products in the mid-latitudes remote marine atmosphere. High mixing ratios of DMS, sulfur dioxide (SO2) and dimethylsulfoxide (DMSO) have been observed during this experiment, with mean concentrations of 395 parts per trillion by volume (pptv) (standard deviation, σ = 285, n = 500), 114 pptv (σ = 125, n = 12) and 3 pptv (σ = 1.2, n = 167), respectively. Wind speed and direction were identified as the major factors controlling atmospheric DMS levels. Changes in air temperature/air masses origin were found to strongly influence the dimethylsulfoxide (DMSO)/DMS and SO2/DMS molar ratios, in line with recent laboratory data. Methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO4 2−) mean concentrations in aerosols during this experiment were 12.2± 6.5 pptv (1σ, n=47) and 59 ± 33 pptv (1σ, n=47), respectively. Evidence of vertical entrainment was reported following frontal passages, with injection of moisture-poor, ozone-rich air. High MSA/ nss-SO4 2− molar ratios (mean 0.44) were calculated during these events. Finally following frontal passages, few spots in condensation nuclei (CN) concentration were also observed.