Size-Resolved Characterisation of Soluble Ions in the Particles in the Tropospheric Plume of Masaya Volcano, Nicaragua: Origins and Plume Processing |
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| Authors: | T A Mather A G Allen C Oppenheimer D M Pyle A J S McGonigle |
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| Institution: | (1) Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, U.K.;(2) Earth and Environmental Sciences, University of Birmingham, School of Geography, Edgbaston, Birmingham, B15 2TT, U.K;(3) Department of Geography, University of Cambridge, Downing Place, Cambridge, CB2 3EN, U.K |
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| Abstract: | We present the first application of a multi-stage impactor to study volcanic particle emissions to the troposphere from Masaya volcano, Nicaragua. Concentrations of soluble SO4
2–,Cl–, F–, NO3
–, K+, Na+,NH4
+, Ca2+ and Mg2+ were determined in 11 size bins from  0.07  m to >25.5 m. The near-source size distributions showed major modes at 0.5m (SO4
2–, H+,NH4
+); 0.2 m and 5.0 m (Cl–) and 2.0–5.0 m(F–). K+ and Na+ mirrored the SO4
2– size-resolvedconcentrations closely, suggesting that these were transported primarily asK2SO4 and Na2SO4 in acidic solution, while Mg2+ andCa2+ presented modes in both <1 m and >1 m particles. Changes in relative humidity were studied by comparing daytime (transparent plume) and night-time (condensed plume) results. Enhanced particle growth rates were observed in the night-time plume as well as preferential scavenging of soluble gases, such as HCl, by condensed water. Neutralisation of the acidic aerosol by background ammonia was observed at the crater rim and to a greater extent approximately 15 km downwind of the active crater. We report measurements of re-suspended near-source volcanic dust, which may form a component of the plume downwind. Elevated levels ofSO4
2–, Cl–, F–,H+, Na+, K+ and Mg2+ were observed around the 10 m particle diameter in this dust. The volcanic SO4
2– flux leaving the craterwas 0.07 kg s–1. |
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| Keywords: | aerosol diurnal impactor particles troposphere volcanic emissions |
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