Abstract
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 chloro- and 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.
Highlights
Sources of organohalogens include emissions from plants, bacteria, sponges, fungi, insects, higher animals and humans [1]
Higher mixing ratios were observed for bromoacetone over chloroacetone
Haloacetones were measured in the complex transition interface of Australian salt lakes using a Teflon chamber
Summary
Sources of organohalogens include emissions from plants, bacteria, sponges, fungi, insects, higher animals and humans [1]. Abiotic formation of halogenated volatile organic compounds (VOX). Contributes significantly to the global VOX emissions; occurring in volcanoes, biomass burning, subsurface geothermal processes, soils, wetlands, oceans, the atmosphere and in and above salt lakes and saline soils [2,3,4,5,6]. Saline soils cover ~3.6 × 106 km of the terrestrial surface and are substantial sources of halogens to the troposphere [7]. Western Australia, it is necessary to study their emissions and atmospheric impact. A multitude of halogenated compounds were found (e.g., chlorofuran), that were abiotically formed in Australian salt lakes [8,9,10]. Lakes with pH 2.7 are located close to lakes with pH 7.1, five orders of magnitude difference in acidity, providing a real world laboratory for the investigation of different emission rates and mechanisms
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
