Long-range volcanic ash transport and fallout during the 2008 eruption of Chaitén volcano, Chile

• Autores: Durant, Adam J.; Villarosa, Gustavo; Rose, William I.; Delmelle, Pierre; Prata, Alfred J.; Viramonte, Jose German
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Aggregation; Chaitén; Fallout; Ocean Fertilisation; Satellite Remote Sensing; Volcanic Ash
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

The May 2008 eruption of Chaitén volcano, Chile, provided a rare opportunity to measure the long-range transport of volcanic emissions and characteristics of a widely-dispersed terrestrial ash deposit. Airborne ash mass, quantified using thermal infrared satellite remote sensing, ranged between 0.2 and 0.4. Tg during the period 3-7 May 2008. A high level of spatiotemporal correspondence was observed between cloud trajectories and changes in surface reflectivity, which was inferred to indicate ash deposition. The evolution of the deposit was mapped for the first time using satellite-based observations of surface reflectivity.The distal (>80. km) ash deposit was poorly sorted and fine grained, and mean particle size varied very little beyond a distance >300. km. There were three particle size subpopulations in fallout at distances >300. km which mirror those identified in fallout from the 18 May 1980 eruption of Mount St. Helens, known to have a high propensity for aggregation. Discrete temporal sampling and characterisation of fallout demonstrated contributions from specific eruptive phases. Samples collected at the time of deposition were compared to bulk samples collected months after deposition and provided some evidence for winnowing.Experimentally-derived ash leachates had near-neutral pH values and charge balance which indicates minimal quantities of adsorbed acids. X-ray Photoelectron Spectroscopy (XPS) analyses revealed surface enrichments in Ca, Na and Fe and the presence of coatings of mixed Ca-, Na- and Fe-rich salts on ash particles prior to deposition. Low S:Cl ratios in leachates indicate that the eruption had a low S content, and high Cl:F ratios imply gas-ash interaction within a Cl-rich environment. We estimate that ash fallout had potential to scavenge ~42% of total S released into the atmosphere prior to deposition. XPS analyses also revealed ash particle surfaces were strongly enriched in Fe (in contrast to the results from bulk leachate analyses), which suggests that Chaitén ash fallout over oceans had potential to influence productivity in high-nutrient, low-chlorophyl regions of the oceans. Therefore ash particle surface geochemical analysis should be applied to quantify Fe-modulated biologically-forced CO 2 draw-down potential of volcanic ash fallout over oceans.
Fil: Durant, Adam J.. Norwegian Institute for Air Research; Noruega. Michigan Technological University; Estados Unidos. University of Cambridge; Estados Unidos
Fil: Villarosa, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina
Fil: Rose, William I.. Michigan Technological University; Estados Unidos
Fil: Delmelle, Pierre. University of York; Reino Unido
Fil: Prata, Alfred J.. Norwegian Institute for Air Research; Noruega
Fil: Viramonte, Jose German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; Argentina