Surface modification of mineral dust particles by sulphuric acid processing: implications for ice nucleation abilities

P Reitz,F Stratmann,L Poulain,P J Demott,K Mildenberger,T Clauss,T F Mentel,R C Sullivan,H Wex,S Hartmann,D Niedermeier,C Spindler,M D Petters,J Schneider,B Sierau

doi:10.5194/acp-11-7839-2011

Abstract

Abstract. The ability of coated mineral dust particles to act as ice nuclei (IN) was investigated at LACIS (Leipzig Aerosol Cloud Interaction Simulator) during the FROST1- and FROST2-campaigns (Freezing of dust). Sulphuric acid was condensed on the particles which afterwards were optionally humidified, treated with ammonia vapour and/or heat. By means of aerosol mass spectrometry we found evidence that processing of mineral dust particles with sulphuric acid leads to surface modifications of the particles. These surface modifications are most likely responsible for the observed reduction of the IN activation of the particles. The observed particle mass spectra suggest that different treatments lead to different chemical reactions on the particle surface. Possible chemical reaction pathways and products are suggested and the implications on the IN efficiency of the treated dust particles are discussed.

Highlights

Aerosol particles have various direct and indirect effects on earth climate (Lohmann and Feichter, 2005)
We show evidence for reactions of the sulphuric acid with the particle surface and propose possible products for these reactions depending on the applied treatments
The detection limits have been calculated from the amplitude of the noise of the background signal similar as in Drewnick et al (2009) using an algorithm described in Reitz and Schneider (2011) to separate long scale background fluctuations from statistic noise

Summary

Introduction

Aerosol particles have various direct and indirect effects on earth climate (Lohmann and Feichter, 2005). In the atmosphere mineral dust is often internally mixed with organic and inorganic material due to particle ageing processes in the atmosphere (Wiacek and Peter, 2009; Sullivan et al, 2007; Sullivan and Prather, 2007; Hinz et al, 2005; Falkovich et al, 2001). Such additions may influence the efficiency of mineral dust to act as ice nuclei (Sullivan et al, 2010a,b; Niedermeier et al, 2010; Gallavardin et al, 2008; Mohler et al, 2005, 2008).

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