Sources of non-methane hydrocarbons in surface air in Delhi, India

Stewart, Gareth J.; Nelson, Beth S.; Drysdale, Will S.; Acton, W. Joe F.; Vaughan, Adam; Hopkins, James R.; Dunmore, Rachel E.; Hewitt, C. Nicholas; Nemitz, Eiko; Mullinger, Neil; Langford, B.; Shivani, .; Reyes-Villegas, Ernesto; Gadi, Ranu; Rickard, Andrew R.; Lee, James; Hamilton, Jacqueline F.

doi:10.1039/d0fd00087f

Cited by 27 publications

(27 citation statements)

References 61 publications

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“…The diel profile of NO, and to a lesser extent CO, have a U-shaped profile, with much higher concentrations observed at night compared to the day (Figure 3). This profile results from a shallow and stagnant nocturnal boundary layer, described in more detail in Stewart et al, 2021a. Average daytime concentrations (06:00 -18:00, roughly in-line with sunrise and sunset times)…”

Section: Observed Nox Co and O3mentioning

confidence: 69%

“…GC instrumentation included a dual-channel gas chromatography flame ionisation detector, (DC)-GC-FID, measuring C2-C8 hydrocarbons and some o-VOCs and a two-dimensional GC flame ionisation detector (GC × GC-FID) to Laboratory, UK) respectively, containing a variety of VOCs and o-VOCs. The linearity of the detector response to higher mixing ratios was tested on both instruments prior to the campaigns, as described by Stewart et al, 2021a.…”

Section: Voc and O-voc Measurementsmentioning

confidence: 99%

“…This was connected to a polar BPX50 column (SGE Analytical 2 m x 0.25 μm x 0.25 mm) held at 23 psi via a modulator held at 180 °C (5 s modulation, Analytical Flow Products MDVG-HT). The oven was held for 2 mins at 35 °C, then ramped up to 130 °C at a rate of 2.5 °C min -1 and held for 1 min before a final ramp to 180 °C at 10 °C min -1 where it was held for 8 mins (Dunmore et al, 2015;Stewart et al, 2021a).…”

Section: Voc and O-voc Measurementsmentioning

confidence: 99%

“…Top down and bottom-up approaches have shown gasphase organic air pollution to be predominantly from petrol (gasoline) and diesel fuel sources. In two 2018 studies at two different urban sites in Delhi, Stewart et al, 2021a and showed that 52 % and 57 % of the measured mixing ratio were from combined petrol and diesel sources. Smaller contributions to the overall VOC burden were found from solid fuel combustion, 16 % (Stewart et al, 2021a) and 27 % .…”

Section: Introductionmentioning

confidence: 99%

“…In two 2018 studies at two different urban sites in Delhi, Stewart et al, 2021a and showed that 52 % and 57 % of the measured mixing ratio were from combined petrol and diesel sources. Smaller contributions to the overall VOC burden were found from solid fuel combustion, 16 % (Stewart et al, 2021a) and 27 % . These data were in line with Guttikunda and Calori, 2013, who produced an inventory which showed that petrol and diesel sources were responsible for 65% by mass of hydrocarbons in Delhi.…”

Section: Introductionmentioning

confidence: 99%

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In situ Ozone Production is highly sensitive to Volatile Organic Compounds in the Indian Megacity of Delhi

Nelson

Stewart

Drysdale

et al. 2021

Preprint

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Abstract. The Indian megacity of Delhi suffers from some of the poorest air quality in the world. While ambient NO2 and particulate matter (PM) concentrations have received considerable attention in the city, high ground level ozone (O3) concentrations are an often overlooked component of pollution. O3 can lead to significant ecosystem damage, agricultural crop losses, and adversely affect human health. During October 2018, concentrations of speciated non-methane hydrocarbons volatile organic compounds (C2 – C13), oxygenated volatile organic compounds (o-VOCs), NO, NO2, HONO, CO, SO2, O3, and photolysis rates, were continuously measured at an urban site in Old Delhi. These observations were used to constrain a detailed chemical box model utilising the Master Chemical Mechanism v3.3.1. VOCs and NOx (NO + NO2) were varied in the model to test their impact on local O3 production rates, P(O3), which revealed a VOC-limited chemical regime. When only NOx concentrations were reduced, a significant increase in P(O3) was observed, thus VOC co-reduction approaches must also be considered in pollution abatement strategies. Of the VOCs examined in this work, mean morning P(O3) rates were most sensitive to monoaromatic compounds, followed by monoterpenes and alkenes, where halving their concentrations in the model led to a 15.6 %, 13.1 % and 12.9 % reduction in P(O3), respectively. P(O3) was not sensitive to direct changes in aerosol surface area but was very sensitive to changes in photolysis rates, which may be influenced by future changes in PM concentrations. VOC and NOx concentrations were divided into emission source sectors, as described by the EDGAR v5.0 Global Air Pollutant Emissions and EDGAR v4.3.2_VOC_spec inventories, allowing for the impact of individual emission sources on P(O3) to be investigated. Reducing road transport emissions only, a common strategy in air pollution abatement strategies worldwide, was found to increase P(O3), even when the source was removed in its entirety. Effective reduction in P(O3) was achieved by reducing road transport along with emissions from combustion for manufacturing and process emissions. Modelled P(O3) reduced by ~20 ppb h−1 when these combined sources were halved. This study highlights the importance of reducing VOCs in parallel with NOx and PM in future pollution abatement strategies in Delhi.

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Section: Observed Nox Co and O3mentioning

confidence: 69%

Section: Voc and O-voc Measurementsmentioning

confidence: 99%

Section: Voc and O-voc Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%