Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley
The Kathmandu Valley in Nepal suffers from severe wintertime air pollution. Volatile organic compounds (VOCs) are key constituents of air pollution, though their specific role in the valley is poorly understood due to insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the Kathm...
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| Language: | English |
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Copernicus Publications
2016-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/3979/2016/acp-16-3979-2016.pdf |
| _version_ | 1818517708202835968 |
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| author | C. Sarkar V. Sinha V. Kumar M. Rupakheti M. Rupakheti A. Panday K. S. Mahata D. Rupakheti B. Kathayat M. G. Lawrence |
| author_facet | C. Sarkar V. Sinha V. Kumar M. Rupakheti M. Rupakheti A. Panday K. S. Mahata D. Rupakheti B. Kathayat M. G. Lawrence |
| author_sort | C. Sarkar |
| collection | DOAJ |
| description | The Kathmandu Valley in Nepal suffers from severe wintertime air pollution.
Volatile organic compounds (VOCs) are key constituents of air pollution,
though their specific role in the valley is poorly understood due to
insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the
Kathmandu Valley–Atmospheric Brown Clouds) field campaign conducted in Nepal
in the winter of 2012–2013, a comprehensive study was carried out to
characterise the chemical composition of ambient Kathmandu air, including the
determination of speciated VOCs, by deploying a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) – the first such deployment in South
Asia. In the study, 71 ion peaks (for which measured ambient concentrations exceeded the
2<i>σ</i> detection limit) were detected in the PTR-TOF-MS mass scan
data, highlighting the chemical complexity of ambient air in the valley. Of
the 71 species, 37 were found to have campaign average concentrations greater
than 200 ppt and were identified based on their spectral
characteristics, ambient diel profiles and correlation with specific emission
tracers as a result of the high mass resolution (<i>m</i> ∕ Δ<i>m</i> > 4200) and temporal resolution (1 min) of the PTR-TOF-MS. The
concentration ranking in the average VOC mixing ratios during our wintertime
deployment was acetaldehyde (8.8 ppb) > methanol (7.4 ppb)
> acetone + propanal (4.2 ppb) > benzene (2.7 ppb) >
toluene (1.5 ppb) > isoprene (1.1 ppb) > acetonitrile
(1.1 ppb) > C8-aromatics ( ∼ 1 ppb) > furan
( ∼ 0.5 ppb) > C9-aromatics (0.4 ppb). Distinct diel
profiles were observed for the nominal isobaric compounds isoprene
(<i>m</i> ∕ <i>z</i> = 69.070) and furan (<i>m</i> ∕ <i>z</i> = 69.033).
Comparison with wintertime measurements from several locations elsewhere in
the world showed mixing ratios of acetaldehyde ( ∼ 9 ppb),
acetonitrile ( ∼ 1 ppb) and isoprene ( ∼ 1 ppb) to
be among the highest reported to date. Two "new" ambient compounds,
namely formamide (<i>m</i> ∕ <i>z</i> = 46.029) and acetamide
(<i>m</i> ∕ <i>z</i> = 60.051), which can photochemically produce isocyanic
acid in the atmosphere, are reported in this study along with nitromethane (a
tracer for diesel exhaust), which has only recently been detected in ambient
studies. Two distinct periods were selected during the campaign for detailed
analysis: the first was associated with high wintertime emissions of biogenic
isoprene and the second with elevated levels of ambient acetonitrile,
benzene and isocyanic acid from biomass burning activities. Emissions from
biomass burning and biomass co-fired brick kilns were found to be the
dominant sources for compounds such as propyne, propene, benzene and
propanenitrile, which correlated strongly with acetonitrile (<i>r</i><sup>2</sup> > 0.7), a
chemical tracer for biomass burning. The calculated total VOC OH reactivity
was dominated by acetaldehyde (24.0 %), isoprene (20.2 %)
and propene (18.7 %), while oxygenated VOCs and isoprene
collectively contributed to more than 68 % of the total ozone
production potential. Based on known secondary organic aerosol (SOA) yields and measured ambient concentrations in the Kathmandu Valley, the relative SOA production potential of VOCs were benzene > naphthalene > toluene > xylenes > monoterpenes > trimethylbenzenes > styrene > isoprene.
The first ambient measurements from any site in South Asia of compounds with
significant health effects such as isocyanic acid, formamide, acetamide,
naphthalene and nitromethane have been reported in this study. Our results
suggest that mitigation of intense wintertime biomass burning activities, in
particular point sources such biomass co-fired brick kilns, would be
important to reduce the emission and formation of toxic VOCs (such as benzene
and isocyanic acid) in the Kathmandu Valley. |
| first_indexed | 2024-12-11T00:59:57Z |
| format | Article |
| id | doaj.art-4d1cfa55012644659ab4c029f482bb6a |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-11T00:59:57Z |
| publishDate | 2016-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-4d1cfa55012644659ab4c029f482bb6a2022-12-22T01:26:22ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242016-03-01163979400310.5194/acp-16-3979-2016Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu ValleyC. Sarkar0V. Sinha1V. Kumar2M. Rupakheti3M. Rupakheti4A. Panday5K. S. Mahata6D. Rupakheti7B. Kathayat8M. G. Lawrence9Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S. A. S. Nagar, Manauli PO, Punjab, 140306, IndiaDepartment of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S. A. S. Nagar, Manauli PO, Punjab, 140306, IndiaDepartment of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S. A. S. Nagar, Manauli PO, Punjab, 140306, IndiaInstitute for Advanced Sustainability Studies (IASS), Berliner Str. 130, 14467 Potsdam, GermanyHimalayan Sustainability Institute (HIMSI), Kathmandu, NepalInternational Centre for Integrated Mountain Development (ICIMOD), Khumaltar, Lalitpur, NepalInstitute for Advanced Sustainability Studies (IASS), Berliner Str. 130, 14467 Potsdam, GermanyKey Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, ChinaHimalayan Sustainability Institute (HIMSI), Kathmandu, NepalInstitute for Advanced Sustainability Studies (IASS), Berliner Str. 130, 14467 Potsdam, GermanyThe Kathmandu Valley in Nepal suffers from severe wintertime air pollution. Volatile organic compounds (VOCs) are key constituents of air pollution, though their specific role in the valley is poorly understood due to insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley–Atmospheric Brown Clouds) field campaign conducted in Nepal in the winter of 2012–2013, a comprehensive study was carried out to characterise the chemical composition of ambient Kathmandu air, including the determination of speciated VOCs, by deploying a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) – the first such deployment in South Asia. In the study, 71 ion peaks (for which measured ambient concentrations exceeded the 2<i>σ</i> detection limit) were detected in the PTR-TOF-MS mass scan data, highlighting the chemical complexity of ambient air in the valley. Of the 71 species, 37 were found to have campaign average concentrations greater than 200 ppt and were identified based on their spectral characteristics, ambient diel profiles and correlation with specific emission tracers as a result of the high mass resolution (<i>m</i> ∕ Δ<i>m</i> > 4200) and temporal resolution (1 min) of the PTR-TOF-MS. The concentration ranking in the average VOC mixing ratios during our wintertime deployment was acetaldehyde (8.8 ppb) > methanol (7.4 ppb) > acetone + propanal (4.2 ppb) > benzene (2.7 ppb) > toluene (1.5 ppb) > isoprene (1.1 ppb) > acetonitrile (1.1 ppb) > C8-aromatics ( ∼ 1 ppb) > furan ( ∼ 0.5 ppb) > C9-aromatics (0.4 ppb). Distinct diel profiles were observed for the nominal isobaric compounds isoprene (<i>m</i> ∕ <i>z</i> = 69.070) and furan (<i>m</i> ∕ <i>z</i> = 69.033). Comparison with wintertime measurements from several locations elsewhere in the world showed mixing ratios of acetaldehyde ( ∼ 9 ppb), acetonitrile ( ∼ 1 ppb) and isoprene ( ∼ 1 ppb) to be among the highest reported to date. Two "new" ambient compounds, namely formamide (<i>m</i> ∕ <i>z</i> = 46.029) and acetamide (<i>m</i> ∕ <i>z</i> = 60.051), which can photochemically produce isocyanic acid in the atmosphere, are reported in this study along with nitromethane (a tracer for diesel exhaust), which has only recently been detected in ambient studies. Two distinct periods were selected during the campaign for detailed analysis: the first was associated with high wintertime emissions of biogenic isoprene and the second with elevated levels of ambient acetonitrile, benzene and isocyanic acid from biomass burning activities. Emissions from biomass burning and biomass co-fired brick kilns were found to be the dominant sources for compounds such as propyne, propene, benzene and propanenitrile, which correlated strongly with acetonitrile (<i>r</i><sup>2</sup> > 0.7), a chemical tracer for biomass burning. The calculated total VOC OH reactivity was dominated by acetaldehyde (24.0 %), isoprene (20.2 %) and propene (18.7 %), while oxygenated VOCs and isoprene collectively contributed to more than 68 % of the total ozone production potential. Based on known secondary organic aerosol (SOA) yields and measured ambient concentrations in the Kathmandu Valley, the relative SOA production potential of VOCs were benzene > naphthalene > toluene > xylenes > monoterpenes > trimethylbenzenes > styrene > isoprene. The first ambient measurements from any site in South Asia of compounds with significant health effects such as isocyanic acid, formamide, acetamide, naphthalene and nitromethane have been reported in this study. Our results suggest that mitigation of intense wintertime biomass burning activities, in particular point sources such biomass co-fired brick kilns, would be important to reduce the emission and formation of toxic VOCs (such as benzene and isocyanic acid) in the Kathmandu Valley.https://www.atmos-chem-phys.net/16/3979/2016/acp-16-3979-2016.pdf |
| spellingShingle | C. Sarkar V. Sinha V. Kumar M. Rupakheti M. Rupakheti A. Panday K. S. Mahata D. Rupakheti B. Kathayat M. G. Lawrence Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley Atmospheric Chemistry and Physics |
| title | Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley |
| title_full | Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley |
| title_fullStr | Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley |
| title_full_unstemmed | Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley |
| title_short | Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley |
| title_sort | overview of voc emissions and chemistry from ptr tof ms measurements during the suskat abc campaign high acetaldehyde isoprene and isocyanic acid in wintertime air of the kathmandu valley |
| url | https://www.atmos-chem-phys.net/16/3979/2016/acp-16-3979-2016.pdf |
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