Characteristics of VOC Composition at Urban and Suburban Sites of New Delhi, India in Winter

Sahu, L. K.; Wang, Liwei; Vats, Pawan; Soni, Meghna; Kumar, Purushottam; Satish, Rangu; Bhattu, Deepika; Sahu, Ravi; Patel, Khageshwar Singh; Rai, Pragati; Kumar, Varun; Rastogi, Neeraj; Ojha, Narendra; Tiwari, Shashi; Ganguly, Dilip; Slowik, Jay G.; Prévôt, Andrê S. H.; Tripathi, Sachchida Nand

doi:10.1029/2021jd035342

Cited by 29 publications

(6 citation statements)

References 162 publications

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“…2k). Simulated isoprene is in agreement with diurnal observations in Delhi (Tripathi et al, 2022) and in accordance with observed mean level in Leicester (Sommariva et al, 2021). The nitrate radical (NO 3 ), which is a nighttime oxidant, is formed through reaction between NO 2 and O 3 (G36).…”

Section: Box Model Setupsupporting

confidence: 85%

Comprehensive multiphase chlorine chemistry in the box model CAABA/MECCA: Implications to atmospheric oxidative capacity

Soni

Sander

Sahu

et al. 2023

Preprint

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Abstract. Tropospheric chlorine chemistry can strongly impact the atmospheric oxidation capacity and composition, especially in urban environments. To account for these reactions, the gas- and aqueous-phase Cl chemistry of the community atmospheric chemistry box model CAABA/MECCA has been extended. In particular, an explicit mechanism for ClNO2 formation following N2O5 uptake to aerosols has been developed. The updated model has been applied to two urban environments with different concentrations of NOx (NO and NO2): New Delhi (India) and Leicester (United Kingdom). The model shows a sharp build-up of Cl at sunrise through Cl2 photolysis in both environments. Besides Cl2 photolysis, ClO+NO reaction, and photolysis of ClNO2 and ClONO are prominent sources of Cl in Leicester. High-NOx conditions in Delhi tend to suppress the night-time build-up of N2O5 due to titration of O3 and thus lead to lower ClNO2, in contrast to Leicester. Major loss of ClNO2 is through its uptake on chloride, producing Cl2 , which consequently leads to the formation of Cl through photolysis. The reactivities of Cl and OH are much higher in Delhi, however, the Cl/OH ratio is up to ≈7 times greater in Leicester. The contribution of Cl to the atmospheric oxidation capacity is significant and even exceeds (by ≈2.9 times) that of OH during the morning hours in Leicester. Sensitivity simulations suggest that the additional consumption of VOCs due to active gas and aqueous-phase chlorine chemistry enhances OH, HO2, RO2 near the sunrise. The simulation results of the updated model have important implications for future studies on atmospheric chemistry and urban air quality.

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Section: Box Model Setupsupporting

confidence: 85%

Comprehensive multiphase chlorine chemistry in the box model CAABA/MECCA: Implications to atmospheric oxidative capacity

Soni

Sander

Sahu

et al. 2023

Preprint

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“…VOC/NO x ratio was 1.8 in contrast to a ratio of 0.4 for traffic emissions. Greater reductions of VOCs suppress the increase in O 3 in Delhi, which is a VOC-limited environment [88][89][90]. However, the O 3 formation regime may vary for different sites within Delhi depending on VOCs/NO x [28,91].…”

Section: Challenges and Mitigation Pathways For Co-controlling Pm 25 ...mentioning

confidence: 99%

Mechanisms and Pathways for Coordinated Control of Fine Particulate Matter and Ozone

et al. 2022

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Purpose of Review Fine particulate matter (PM 2.5 ) and ground-level ozone (O 3 ) pose a significant risk to human health. The World Health Organization (WHO) has recently revised healthy thresholds for both pollutants. The formation and evolution of PM 2.5 and O 3 are however governed by complex physical and multiphase chemical processes, and therefore, it is extremely challenging to mitigate both pollutants simultaneously. Here, we review mechanisms and discuss the science-informed pathways for effective and simultaneous mitigation of PM 2.5 and O 3 . Recent Findings Global warming has led to a general increase in biogenic emissions, which can enhance the formation of O 3 and secondary organic aerosols. Reductions in anthropogenic emissions during the COVID-19 lockdown reduced PM 2.5 ; however, O 3 was enhanced in several polluted regions. This was attributed to more intense sunlight due to low aerosol loading and non-linear response of O 3 to NO x . Such contrasting physical and chemical interactions hinder the formulation of a clear roadmap for clean air over such regions. Summary Atmospheric chemistry including the role of biogenic emissions, aerosol-radiation interactions, boundary layer, and regional-scale transport are the key aspects that need to be carefully considered in the formulation of mitigation pathways. Therefore, a thorough understanding of the chemical effects of the emission reductions, changes in photolytic rates and boundary layer due to perturbation of solar radiation, and the effect of meteorological/seasonal changes are needed on a regional basis. Statistical emulators and machine learning approaches can aid the cumbersome process of multi-sector multi-species source attribution.

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“…The PTR-TOF-MS is widely used for measuring NMVOCs with high mass resolution and sensitivity. A detailed description of the instrument can be found in other studies (Graus et al, 2010;Jordan et al, 2009;Tripathi et al, 2022;Tripathi and Sahu, 2020), while a brief description is given here. The PTR-TOF-MS is based on the chemical ionisation method, facilitated by proton-transfer reactions with hydronium (H3O + ) ions as the primary reactant ion, which causes much less fragmentation of organic molecules in the sampled air.…”

Section: 2mentioning

confidence: 99%

“…The calibration of the instrument was performed at the starting, middle and end of the campaign using a certified standard gas mixture (L5388, Ionicon Analytik GmbH Innsbruck, with a stated accuracy better than 8%) containing ~1.0 ppmv of VOCs. A 145 detailed description of the similar set-up and unit is given in the previous studies (Jain et al, 2022;Tripathi et al, 2022). The exact mass-identified chemical formula and family of species of the observed NMVOCs (173 in number) is given in supplementary Table S1.…”

Section: 2mentioning

confidence: 99%

“…The sources of these OVOCs could be direct emissions from biogenic and anthropogenic activities and from the secondary/ photochemical processes also. Diurnal variations of secondary formation, anthropogenic emission level, weather, and PBL heights can be 275 explained by OVOCs/benzene ratios (Sahu et al, 2017(Sahu et al, , 2016Tripathi et al, 2022) to some extent. The diurnal patterns of acetaldehyde/benzene, acetone/benzene, and acetic acid/benzene ratios are plotted to check the influence of biogenic and secondary sources (see Figure 3 (a-c)).…”

Section: 𝐶 𝑆𝑂𝐴 (𝑗) = 𝑌 𝑆𝑂𝐴(𝑗) × 𝑉𝑂𝐶 𝑗mentioning

confidence: 99%

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Real-time measurements of NMVOCs in the central IGB, Lucknow, India: Source characterization and their role in O₃ and SOA formation

Jain

Tripathi

Gupta

et al. 2022

Preprint

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Abstract. Lucknow is the capital of India’s largest state, Uttar Pradesh, one of South Asia’s most polluted urban cities. Tropospheric photochemistry relies on non-methane volatile organic compounds (NMVOCs), which are ozone and secondary organic aerosol precursors. Using the proton-transfer reaction time of flight mass spectrometer (PTR-ToF-MS) at an urban background site in Lucknow, the chemical characterisation of NMVOCs was performed in real-time from Dec-2020–May 2021. The campaign mean concentrations of the NMVOCs were 125.5 ±37.5 ppbv. The average concentrations of NMVOCs are relatively high during winter. An advanced multi-linear engine (ME-2) model was used to perform the NMVOCs source apportionment using positive matrix factorisation (PMF). It resolves the five main sources contributing to these organic compounds in the atmosphere. They include traffic, two solid fuel combustion factors, secondary volatile organic compounds and volatile chemical products. Biomass burning contributes most to the NMVOCs and SOA formation, while interestingly, traffic sources most influence ozone formation. Significant differences in the composition of the two solid fuel combustion indicate the influence of local emissions and transport of regional pollution to the city. The high temperature during summer leads to more volatilisation of oxygenated VOCs.

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Characteristics of VOC Composition at Urban and Suburban Sites of New Delhi, India in Winter

Cited by 29 publications

References 162 publications

Comprehensive multiphase chlorine chemistry in the box model CAABA/MECCA: Implications to atmospheric oxidative capacity

Comprehensive multiphase chlorine chemistry in the box model CAABA/MECCA: Implications to atmospheric oxidative capacity

Mechanisms and Pathways for Coordinated Control of Fine Particulate Matter and Ozone

Real-time measurements of NMVOCs in the central IGB, Lucknow, India: Source characterization and their role in O₃ and SOA formation

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Characteristics of VOC Composition at Urban and Suburban Sites of New Delhi, India in Winter

Cited by 29 publications

References 162 publications

Comprehensive multiphase chlorine chemistry in the box model CAABA/MECCA: Implications to atmospheric oxidative capacity

Comprehensive multiphase chlorine chemistry in the box model CAABA/MECCA: Implications to atmospheric oxidative capacity

Mechanisms and Pathways for Coordinated Control of Fine Particulate Matter and Ozone

Real-time measurements of NMVOCs in the central IGB, Lucknow, India: Source characterization and their role in O3 and SOA formation

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Real-time measurements of NMVOCs in the central IGB, Lucknow, India: Source characterization and their role in O₃ and SOA formation