Isotopic constraints on the role of hypohalous acids in sulfate aerosol formation in the remote marine boundary layer
Sulfate is an important component of global atmospheric aerosol, and has partially compensated for greenhouse gas-induced warming during the industrial period. The magnitude of direct and indirect radiative forcing of aerosols since preindustrial times is a large uncertainty in climate models, w...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/11433/2016/acp-16-11433-2016.pdf |
| Summary: | Sulfate is an important component of global atmospheric aerosol, and has
partially compensated for greenhouse gas-induced warming during the
industrial period. The magnitude of direct and indirect radiative forcing of
aerosols since preindustrial times is a large uncertainty in climate models,
which has been attributed largely to uncertainties in the preindustrial
environment. Here, we report observations of the oxygen isotopic composition
(Δ<sup>17</sup>O) of sulfate aerosol collected in the remote marine boundary
layer (MBL) in spring and summer in order to evaluate sulfate production
mechanisms in pristine-like environments. Model-aided analysis of the
observations suggests that 33–50 % of sulfate in the MBL is formed via
oxidation by hypohalous acids (HOX = HOBr + HOCl), a production
mechanism typically excluded in large-scale models due to uncertainties in
the reaction rates, which are due mainly to uncertainties in reactive halogen
concentrations. Based on the estimated fraction of sulfate formed via HOX
oxidation, we further estimate that daily-averaged HOX mixing ratios on the
order of 0.01–0.1 parts per trillion (ppt = pmol/mol) in the remote MBL
during spring and summer are sufficient to explain the observations. |
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| ISSN: | 1680-7316 1680-7324 |