HR: 17:25h
AN: A34C-06    [Abstracts]
TI: The Influence of Sodium Methanesulfonate on Hygroscopic and Reactive Properties of NaCl Particles
AU: * Liu, Y
EM: yong.liu@pnl.gov
AF: W.R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, United States
AU: Desyaterik, Y
EM: yuri.desyaterik@pnl.gov
AF: W.R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, United States
AU: Zhu, Z
EM: zihua.zhu@pnl.gov
AF: W.R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, United States
AU: Minofar, B
EM: babak.minofar@marge.uochb.cas.cz
AF: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, CZ-16610, Czech Republic
AU: Jungwirth, P
EM: pavel.jungwirth@uochb.cas.cz
AF: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, CZ-16610, Czech Republic
AU: Wang, H
EM: haiw@usc.edu
AF: Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA 90089, United States
AU: Laskin, A
EM: Alexander.Laskin@pnl.gov
AF: W.R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, United States
AB: The most important precursor for sulfate aerosol over the oceans is gaseous dimethyl sulfide (DMS), which is produced by phytoplankton and subsequently emitted to the atmosphere where it is oxidized yielding variety of products. In the past, much attention has been given to the physico-chemical properties of the mixed sea salt/sulfate particles that can be formed as a result of DMS-to-SO₂-to-H₂SO₄ reaction sequence. For many years, effective conversion of DMS to particulate sulfate was assumed to be the dominant reaction pathway for DMS in the marine boundary layer. However, recent modeling studies and field observations indicate that under certain conditions DMS does not predominantly convert to sulfate, but rather ends up in sea salt particles as methanesulfonic sodium salt (CH₃SO₃Na), which previously have been considered only of minor importance. In contrast to the NaCl and Na₂SO₄ salts, CH₃SO₃Na is a surfactant and presence of this specie in sea salt particles can lower the surface tension, impact molecular processes at the air/water interface, thus affecting heterogeneous reactivity of sea salt aerosol as well as CCN activity. The presented work is focused on combined experimental and modeling studies aimed at characterizing the hygroscopic properties and chemical reactivity of mixed NaCl/CH₃SO₃Na particles. Heterogeneous reaction kinetics of gaseous nitric acid with particles were investigated with a novel Particle-on-Substrate Stagnation Flow Reactor approach under conditions, including particle size, relative humidity and reaction time, directly relevant to the atmospheric chemistry of sea salt particles. The reaction kinetics was followed by observing chloride depletion in the particles by computer-controlled scanning electron microscopy with energy- dispersive X-ray analysis (CCSEM/EDX). We also investigated the influence of CH3SO3Na on hygroscopic property of NaCl particles by Micro-FTIR. In addition, scanning electron microscopy (SEM) mapping, time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging and depth profiling, and Molecular Dynamic (MD) simulation were performed to provide a better understanding of layered structures of deliquesced and dry NaCl/CH₃SO₃Na particles and assess their effects on chemical reactivity and hygroscopicity. Experimental results show that presence of CH₃SO₃Na has little influence on hygroscopic properties of NaCl particles. However, it could alter reactive uptake of HNO₃ onto NaCl to varying degrees, depending on the RH and amount of CH₃SO₃Na present in particles.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting