1. Aims:
The main goal of the campaign was the specification of the various bromine compounds inside the plume of Masaya and the observation of their changed contribution during the aging of the plume.
In July 2016 we applied ground based alkaline trap and diffuse denuder systems and an UAV based halogen sampling and SO2/CO2 sensing system at Mt. Masaya in cooperation with INETER (Instituto Nicaragüense de Estudios Territoriales, Nicaragua).
UAV based sampling downwind at Mt. Masaya together with crater rim measurements of halogen species, SO2/CO2 ratios and SO2 fluxes can provide valuable insights into the fate of emitted halogen species by reaction with ambient air. They will hopefully show for the first time if our understanding of the evolution of halogen specification inside volcanic plumes is close to reality. Data analysis is currently taking place in the laboratory.
2. Measurements:
After two days of preparation in Managua, field measurement began on 14th July and lasted until 21st of July, 2016.
With the exception of the first day, when we mainly aimed to inter-compare all instruments due simultaneous measurements at the crater rim, each day two to three distances (plume ages) were sampled.
3. Preliminary results:
A very rough first look was done on the data in the evenings. The MAXDOAS spectra taken close to the NOVAC station Caracol resulted in a BrO/SO2 ratio of about 3 x 10-5. This ratio is still in the same range as the data taken during a measurement campaign in 2011.
Beside the DOAS – several flights were carried out with a drone – on the image below the SO2 mixing ratio is shown on the line of one flight. Parallel to the SO2 sensor – diffuse tubes were probed and will be elaborated in the laboratory at the University of Mainz.
SO2 mixing ratio tracked on a map. The plume was encountered first on a lower level and later due to less wind rising up. Blue indicates 0 ppm, green are medium values of SO2 and orange color indicate highest values, which are in the order of several ppm SO2.
On the Figure below a first rough evaluation of the MultiGAS data taken at the rim on 16th July 2016 are shown. CO2 is imaged in black and SO2 with red dots. The instrument used to collect the data is shown on the lower left panel. The same instrument was used during several drone flights carried out downwind in the valley.
On few days also traverses were done using the car. One example from a traverse taken with the instrumental set-up of INETER is shown in the Figure below. On various days traverses for SO2-flux determination have been carried out also by the OVSICORI team (Costa Rica).
4. Next steps:
Evaluation of data in the laboratory in Mainz, Germany. Summarizing results and sharing it with INETER. Interpretation of data. Evaluation of available NOVAC-data for BrO/SO2.