Measurement techniques for identifying and quantifying hydroxymethanesulfonate (HMS) in an aqueous matrix and particulate matter using aerosol mass spectrometry and ion chromatography
<p>Oxidation of sulfur dioxide (<span class="inline-formula">SO<sub>2</sub></span>) in the gas phase and in cloud and fog water leads to the formation of sulfate that contributes to ambient particulate matter (PM). For severe haze events with low-light conditi...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-10-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/12/5303/2019/amt-12-5303-2019.pdf |
| Summary: | <p>Oxidation of sulfur dioxide
(<span class="inline-formula">SO<sub>2</sub></span>) in the gas phase and in cloud and fog
water leads to the formation of sulfate that contributes to ambient
particulate matter (PM). For severe haze events with low-light conditions,
current models underestimate the levels of sulfate formation that occur
exclusively via the oxidation of sulfur dioxide. We show here that
measurement techniques commonly used in the field to analyze PM composition
can fail to efficiently separate sulfur-containing species, resulting in
the possible misidentification of compounds. Hydroxymethanesulfonate (HMS), a
sulfur(IV) species that can be present in fog and cloud water, has been
largely neglected in both chemical models and field measurements of PM
composition. As HMS is formed without oxidation, it represents a pathway for
<span class="inline-formula">SO<sub>2</sub></span> to contribute to PM under low-light
conditions. In this work, we evaluate two techniques for the specific
quantification of HMS and sulfate in PM, ion chromatography (IC) and aerosol
mass spectrometry (AMS). In cases in which the dominant sulfur-containing
species are ammonium sulfate or HMS, differences in AMS fragmentation
patterns can be used to identify HMS. However, the AMS quantification of HMS
in complex ambient mixtures containing multiple inorganic and organic sulfur
species is challenging due to the lack of unique organic fragments and
the variability of fractional contributions of
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi>x</mi></msub><msubsup><mi mathvariant="normal">SO</mi><mi>y</mi><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="37pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="c08a8c3ba91d4a484d53e2adf49480f2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-12-5303-2019-ie00001.svg" width="37pt" height="16pt" src="amt-12-5303-2019-ie00001.png"/></svg:svg></span></span> ions
as a function of the matrix. We describe an improved IC method that provides
efficient separation of sulfate and HMS and thus allows for the identification and
quantification of both. The results of this work provide a technical
description of the efficiency and limitations of these techniques as well as
a method that enables further studies of the contribution of S(IV)
versus S(VI) species to PM under low-light atmospheric conditions.</p> |
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| ISSN: | 1867-1381 1867-8548 |