TY - JOUR

T1 - Natural formation of chloro- and bromoacetone in salt lakes of Western Australia

AU - Sattler, Tobias

AU - Sörgel, Matthias

AU - Wittmer, Julian

AU - Bourtsoukidis, Efstratios

AU - Krause, Torsten

AU - Atlas, Elliot

AU - Benk, Simon

AU - Bleicher, Sergej

AU - Kamilli, Katharina

AU - Ofner, Johannes

AU - Kopetzky, Raimo

AU - Held, Andreas

AU - Palm, Wolf Ulrich

AU - Williams, Jonathan

AU - Zetzsch, Cornelius

AU - Schöler, Heinz Friedrich

N1 - Funding Information: This research was supported by the Bundesministerium für Bildung und Forschung (BMBF) within AFO 2000 and by the Deutsche Forschungsgemeinschaft (DFG) Research Unit 763.R. Kopetzky acknowledgesW. Ruck for supervising his diploma work at the University of Lüneburg, and M. Sörgel his supervisor O. Elsholz from the Hamburg University of Applied Sciences (HAW Hamburg) for supporting his work at the University of Lüneburg. Publisher Copyright: © 2019 by the authors.

PY - 2019/11/1

Y1 - 2019/11/1

N2 - Western Australia is a semi-/arid region known for saline lakes with a wide range of geochemical parameters (pH 2.5-7.1, Cl- 10-200 g L-1). This study reports on the haloacetones chloroand bromoacetone in air over 6 salt lake shorelines. Significant emissions of chloroacetone (up to 0.2 μmol m-2 h-1) and bromoacetone (up to 1. 5 μmol m-2 h-1) were detected, and a photochemical box model was employed to evaluate the contribution of their atmospheric formation from the olefinic hydrocarbons propene and methacrolein in the gas phase. The measured concentrations could not explain the photochemical halogenation reaction, indicating a strong hitherto unknown source of haloacetones. Aqueous-phase reactions of haloacetones, investigated in the laboratory using humic acid in concentrated salt solutions, were identified as alternative formation pathway by liquid-phase reactions, acid catalyzed enolization of ketones, and subsequent halogenation. In order to verify this mechanism, we made measurements of the Henry's law constants, rate constants for hydrolysis and nucleophilic exchange with chloride, UV-spectra and quantum yields for the photolysis of bromoacetone and 1,1-dibromoacetone in the aqueous phase. We suggest that heterogeneous processes induced by humic substances in the quasi-liquid layer of the salt crust, particle surfaces and the lake water are the predominating pathways for the formation of the observed haloacetones.

AB - Western Australia is a semi-/arid region known for saline lakes with a wide range of geochemical parameters (pH 2.5-7.1, Cl- 10-200 g L-1). This study reports on the haloacetones chloroand bromoacetone in air over 6 salt lake shorelines. Significant emissions of chloroacetone (up to 0.2 μmol m-2 h-1) and bromoacetone (up to 1. 5 μmol m-2 h-1) were detected, and a photochemical box model was employed to evaluate the contribution of their atmospheric formation from the olefinic hydrocarbons propene and methacrolein in the gas phase. The measured concentrations could not explain the photochemical halogenation reaction, indicating a strong hitherto unknown source of haloacetones. Aqueous-phase reactions of haloacetones, investigated in the laboratory using humic acid in concentrated salt solutions, were identified as alternative formation pathway by liquid-phase reactions, acid catalyzed enolization of ketones, and subsequent halogenation. In order to verify this mechanism, we made measurements of the Henry's law constants, rate constants for hydrolysis and nucleophilic exchange with chloride, UV-spectra and quantum yields for the photolysis of bromoacetone and 1,1-dibromoacetone in the aqueous phase. We suggest that heterogeneous processes induced by humic substances in the quasi-liquid layer of the salt crust, particle surfaces and the lake water are the predominating pathways for the formation of the observed haloacetones.

KW - Bromoacetone (1-bromopropan-2-one)

KW - Chloroacetone (1-chloropropan-2-one)

KW - Natural halogenation

KW - Salt lakes

KW - Chemistry

UR - http://www.scopus.com/inward/record.url?scp=85075667971&partnerID=8YFLogxK

U2 - 10.3390/atmos10110663

DO - 10.3390/atmos10110663

M3 - Journal articles

AN - SCOPUS:85075667971

VL - 10

JO - Atmosphere

JF - Atmosphere

SN - 2073-4433

IS - 11

M1 - 663

ER -