A re-assessment of aerosols from Masaya volcano, Nicaragua

Martin, R. S. and Ilyinskaya, E. and Sawyer, G. M. and Tsanev, V. I. and Oppenheimer, C. (2011) A re-assessment of aerosols from Masaya volcano, Nicaragua. Atmospheric Environment, 45 (3). pp. 547-560. ISSN 1352-2310 DOI 10.1016/j.atmosenv.2010.10.049

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Abstract

Cascade impactors were used to sample volcanic aerosol from Masaya (Nicaragua) in 2007, 2009 and 2010. Differences were found in the size distributions of volcanic aerosol between these recent campaigns and with a campaign in 2001: (1) SO (sub)4(sub)(sup)2(sup)- showed modes in both the fine (<1 µm; with low Na+/K+) and coarse (> 1 µm; with high -Na+ -K+) fractions in all of the recent campaigns despite being unimodal in 2001 (<1 µm); (2) The modal diameters for SO(sub)4(sub)(sup)2(sup)- roughly doubled in 2009, compared to 2007 or 2010; (3) total Cl- was depleted in volcanic aerosol compared to background aerosol in all the more recent campaigns but was enriched in 2001. Other aspects of the volcanic aerosol appear to be persistent, such as a fine SO(sub)4(sub)(sup)2(sup)-H+ -Na+ -K+ mode, which was the most abundant mode in all Cl -F -Mg2+ -Ca2+ mode of lower abundance. Water uptake and speciation in the aerosol were investigated using the equilibrium model, ISORROPIA II. Results show that the coarse SO(sub)4(sub)(sup)2(sup)-rich mode deliquesces at lower relative humidity (40% RH) than the fine SO(sub)4(sub)(sup)2(sup)-rich mode (50% RH) due to increased Na+/K+ in the former. The aerosol was predicted to be dry at ambient relative humidity in 2009 and dominated by NaHSO 4 , KHSO 4 , CaSO 4 and MgSO 4 . In contrast, model results predict a liquid aerosol at ambient relative humidity in 2010. These results indicate that aerosol emissions from a volcano can vary in ionic composition and even more so in physical speciation (i.e., salts or solutions). These observations are set against a near-constant magmatic gas composition at Masaya, which highlights the significance of atmospheric and dynamic factors in the formation of volcanic aerosols.

Item Type: Article
Uncontrolled Keywords: 2010AREP; IA61,
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Journal or Publication Title: Atmospheric Environment
Volume: 45
Page Range: pp. 547-560
Identification Number: 10.1016/j.atmosenv.2010.10.049
Depositing User: Sarah Humbert
Date Deposited: 04 Nov 2010 11:25
Last Modified: 23 Jul 2013 10:00
URI: http://eprints.esc.cam.ac.uk/id/eprint/1954

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