Report on volcanic plume measurements on volcanoes in Papua New Guinea
This report summarizes the findings of plume gas measurements conducted on volcanoes of Papua New Guinea (PNG) during September 2016, as part of the DECADE project. The total sulfur dioxide (SO2) and carbon dioxide (CO2) gas fluxes of Tavurvur, Bagana and Ulawun volcanoes were determined by combining ground- remote sensing and ground-/airborne direct sampling, depending on the particular conditions on each volcano. During the campaign Tavurvur was degassing passively, without forming a continuous plume, and it was accessible for direct sampling in the crater. Its SO2 emission was found to be 0.19 ± 0.05 kg/s from scanning-DOAS and a stationary wide-field-of-view (WFOV) DOAS monitor, and the fraction of CO2/SO2 molar ratios was 2.6, obtained with a compact multi-GAS instrument. Bagana, on the other hand, had permanent degassing, producing occasional explosions and ash emission. The plume was measured by ground-based scanning-DOAS and a compact multi-GAS instrument aboard a multi-rotor UAV, resulting in a SO2 flux of 13 ± 5 kg/s and a CO2/SO2 of 15. Ulawun presented continuous passive degassing, forming an elevated plume which flux and composition were measured by car-traverses with a mobile-DOAS, a stationary dual-beam scanning DOAS, and a multi-GAS/UAV sensor. The SO2 flux of Ulawun was 11 ± 2 kg/s and the CO2/SO2 equal to 4.8. A stationary WFOV-DOAS instrument was left with the Rabaul Volcano Observatory (RVO) for longer-term monitoring of the SO2 flux from Tavurvur.