Elucidating real-world vehicle emission factors from mobile measurements over a large metropolitan region: a focus on isocyanic acid, hydrogen cyanide, and black carbon
<p>A mobile laboratory equipped with state-of-the-art gaseous and particulate instrumentation was deployed across the Greater Toronto Area (GTA) during two seasons. A high-resolution time-of-flight chemical ionization mass spectrometer (HR-TOF-CIMS) measured isocyanic acid (HNCO) and hydrogen...
Main Authors: | , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-11-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/18/16979/2018/acp-18-16979-2018.pdf |
Summary: | <p>A mobile laboratory equipped with state-of-the-art gaseous and particulate
instrumentation was deployed across the Greater Toronto Area (GTA) during two
seasons. A high-resolution time-of-flight chemical ionization mass spectrometer (HR-TOF-CIMS)
measured isocyanic acid (HNCO) and hydrogen cyanide (HCN), and a
high-sensitivity laser-induced incandescence (HS-LII) instrument measured
black carbon (BC). Results indicate that on-road vehicles are a clear source
of HNCO and HCN and that their impact is more pronounced in the winter, when
influences from biomass burning (BB) and secondary photochemistry are weakest.
Plume-based and time-based algorithms were developed to calculate
fleet-average vehicle emission factors (EFs); the algorithms were found to
yield comparable results, depending on the pollutant identity. With respect
to literature EFs for benzene, toluene, C2 benzene (sum of <i>m-</i>, <i>p-</i>, and <i>o</i>-xylenes and
ethylbenzene), nitrogen oxides, particle number concentration (PN), and black
carbon, the calculated EFs were characteristic of a relatively clean vehicle
fleet dominated by light-duty vehicles (LDV). Our fleet-average EF for BC (median:
25 mg kg<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mi mathvariant="normal">fuel</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="15pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="1a8c532b1720d0ea4f5d9751953cb03e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-16979-2018-ie00001.svg" width="15pt" height="17pt" src="acp-18-16979-2018-ie00001.png"/></svg:svg></span></span>; interquartile range, IQR:
10–76 mg kg<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mi mathvariant="normal">fuel</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="15pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="48fd5fdeb4645549a8bae777d7aa0128"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-16979-2018-ie00002.svg" width="15pt" height="17pt" src="acp-18-16979-2018-ie00002.png"/></svg:svg></span></span>) suggests that overall vehicular
emissions of BC have decreased over time. However, the distribution of EFs
indicates that a small proportion of high-emitters continue to contribute
disproportionately to total BC emissions. We report the first fleet-average
EF for HNCO (median: 2.3 mg kg<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mi mathvariant="normal">fuel</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="15pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="e08f0bbebdfe31f89c0e2f6e51d785d1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-16979-2018-ie00003.svg" width="15pt" height="17pt" src="acp-18-16979-2018-ie00003.png"/></svg:svg></span></span>, IQR:
1.4–4.2 mg kg<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mi mathvariant="normal">fuel</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="15pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="fccb73420823b2a60e142c38952459d4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-16979-2018-ie00004.svg" width="15pt" height="17pt" src="acp-18-16979-2018-ie00004.png"/></svg:svg></span></span>) and HCN (median:
0.52 mg kg<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mi mathvariant="normal">fuel</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="15pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="85c4438be8656632e84fdb276e716b80"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-16979-2018-ie00005.svg" width="15pt" height="17pt" src="acp-18-16979-2018-ie00005.png"/></svg:svg></span></span>, IQR:
0.32–0.88 mg kg<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mi mathvariant="normal">fuel</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="15pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="6d432e3c7b89e1482addd742dfbd47fe"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-16979-2018-ie00006.svg" width="15pt" height="17pt" src="acp-18-16979-2018-ie00006.png"/></svg:svg></span></span>). The distribution of the estimated
EFs provides insight into the real-world variability of HNCO and HCN
emissions and constrains the wide range of literature EFs obtained from
prior dynamometer studies. The impact of vehicle emissions on urban HNCO
levels can be expected to be further enhanced if secondary HNCO formation
from vehicle exhaust is considered.</p> |
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ISSN: | 1680-7316 1680-7324 |