Wheeler, J.C.; Ilyinskaya, E.; Braban, C.F.; Oppenheimer, C.2012 The uptake of halogen (HF, HCl, HBr and HI) and nitric (HNO3) acids into acidic sulphate particles in quiescent volcanic plumes. Chemical Geology, 296-297. 19-25. 10.1016/j.chemgeo.2011.12.013 Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner.
P a g e | 1The uptake of halogen (HF, HCl, HBr and HI) and nitric (HNO 3 ) acids 1 into acidic sulphate particles in quiescent volcanic plumes 2 Published in Chemical Geology 8
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Abstract 9The uptake of halogen and nitric acids into acidic sulphate particles has important implications for 10 volcano monitoring and the environmental geochemistry of volcanic emissions. Using the Extended 11Aerosol Inorganics Model (E-AIM) for HCl, HBr and HNO 3 , combined with a simple three-parameter 12 model for HF and HI, we show that equilibrium partitioning of halogen and nitric acids into sulphate 13 particles is maximised at high relative humidity (RH), low temperature, low plume dilution (i.e., near-14 source) and high SO 4 2-/SO 2 . The addition of metal chlorides (i.e., NaCl) enhances acidic gas 15 partitioning at high RH, but diminishes acidic gas partitioning at low RH due to a decrease in the 16 water content of particles and the formation of Na sulphate salts. We predict that acidic gas 17 partitioning is quantitatively significant (>1%) only in cool humid conditions (e.g., >80% RH at 298 18 K), adding confidence to spectroscopic and/or electrochemical determinations of gas ratios (e.g., 19SO 2 /HCl, HCl/HF) for volcano monitoring. However, acidic gas partitioning remains environmentally 20 important over a wide range of conditions because of the significant variability in the amounts of 21 acidic gases in particle form (Cl Keywords: volcanic plume, equilibrium model, masaya, E-AIM 24 25 P a g e | 2
Introduction 26Active volcanoes are a major source of gases and particles to the atmosphere. A significant 27 contribution to global volcanic emissions comes from persistent degassing from volcanoes such as Mt 28 Etna (Sicily) and Masaya (Nicaragua). The activity at these volcanoes is characterised by the 29 sustained emission of volatile species (forming a quiescent volcanic plume) punctuated by sporadic 30 and typically minor eruptions. Volcanic gases are composed of > 90% H 2 O and CO 2 , and < 10% SO 2 , 31HCl and HF, with smaller and variable amounts of H 2 S, H 2 , CO, HBr and HI (Gerlach, 2004; Pyle and 32 Mather, 2009). A common feature of quiescent volcanic plumes is micron-sized sulphate particles, 33 with compositions between the acidic (e.g., H 2 SO 4 ) and metal-rich (primarily (Na,K) 2 SO 4 ) end-34 members (e.g., Mather et al., 2003;Martin et al., 2011) at a molar abundance of SO 4 2-/SO 2 ~ 0.01. 35The uptake of halogen acids (HF, HCl, HBr, HI) into sulphate particles has wide implications in 36 volcanology....
