Neutralization of acidic sulfates with ammonia in volcanic origin aerosol particles

Abstract

Volcanic pollutants emitted during the Grimsvötn volcano eruption in Iceland on 21 May 2011 were unexpectedly captured from 24 until 29 May 2011 at the Institute of Physics, Vilnius. Measurements were performed using an Aerodyne quadrupole aerosol mass spectrometer. This paper aims to address the question whether the extent of neutralization is dependent on the aerosol particle size in submicron range particles (PM1). Data from two episodes of volcanic pollutants in advected air masses were chosen for examination. The first episode lasted from 0700 to 1400 UTC 25 May and the second episode lasted from 0400 until 1100 UTC 26 May. It was observed that the extent of acidic sulfate particle neutralization with atmospheric ammonia depends on the aerosol particle size. The extent of neutralization decreased when the particle aerodynamic diameter increased. Particles with an aerodynamic diameter of few tenths of nanometres tended to be fully neutralized and those with a consecutively increasing diameter of up to 1 µm were only partially neutralized. The assessment of ambient ammonia flux onto the adjacent aerosol particle surface was performed. It was shown that the flux of ammonia can vary approximately from 30 to 74 µg m^–2 h^–1