An analysis of volcanic SO2 and ash emissions from Copahue volcano

Abstract

During 2016, Copahue volcano (Neuquén, Argentina) made several eruptions and emitted ash and gases. This paper presents an analysis of the volcanic plume using dispersion models, remote sensor data, and analysis of sedimentary ash collected at the Caviahue Health Center from early October to 21st December 2016. Water-soluble elements contained in volcanic ash leachates were quantified. We have carried out a qualitative comparison of HYSPLIT dispersion simulations with SO2 and aerosol data obtained from OMI and OMPS sensor on board of AURA and SUOMI NPP satellites, as well as between modeled concentrations and sampled surface sediments. Good agreement was observed between gas dispersion plumes from HYSPLIT and total column SO2 values, as well as between volcanic ash plumes and satellite aerosol indices.

The average SO2 emission rate in the analyzed events was 985.7 ± 492.9 t/d and the average emission rate of ash 2.6 103 kt/d (2.9 104 kg/s). In situ observations of ash deposition rates peaked at 0.23 g/h on 30th November. The average measured deposition rate from 1st October to 21st December was 0.12 g/h, consistent with modeled values. The geochemical analysis of ash leachate showed major content of sodium (Na), calcium (Ca) and magnesium (Mg) with 207.8 mg/kg, 209.5 mg/kg, and 195.3 mg/kg, respectively. Concentrations sulfate, chlorides, and fluoride anions were 990.7 mg/kg, 352.34 mg/kg, and 129.15 mg/kg, respectively. The SO2/HCl molar ratio was 1.05. In addition, traces of As, Cr, Hg, Mo, Pb, and Se were detected in concentrations ranging from 0.2 mg/kg to 6.0 mg/kg