Source characterization of volatile organic compounds measured by proton-transfer-reaction time-of-flight mass spectrometers in Delhi, India

Wang, Liwei; Slowik, Jay G.; Bhattu, Deepika; Rai, Pragati; Kumar, Varun; Vats, Pawan; Satish, Rangu; Baltensperger, Urs; Ganguly, Dilip; Rastogi, Neeraj; Sahu, L. K.; Tripathi, Sachchida Nand; Prévôt, A. S. H.

doi:10.5194/acp-20-9753-2020

Cited by 43 publications

(52 citation statements)

References 63 publications

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“…Figure 8 shows time series of monthly means of cityaverage IASI NH 3 in the four cities for 2008-2018. Mean IASI NH 3 is 15-20 times more in Delhi and Kanpur than in London and Birmingham due to larger emissions of NH 3 in the IGP, higher ambient temperatures promoting volatilisation of NH 3 , and greater sensitivity of IASI to NH 3 due to greater thermal contrast between the surface and the atmosphere over India (Van Damme et al, 2015;Dammers et al, 2016;T. Wang et al, 2020).…”

Section: Assessment Of Modis Aodmentioning

confidence: 99%

“…Seasonal enhancements come from intense agricultural fires along the Indo-Gangetic Plain (IGP) north of Delhi, frequent firework festivals, and dust storms originating from the Thar Desert and Arabian Peninsula (Ghosh et al, 2014;Parkhi et al, 2016;Yadav et al, 2017;Liu et al, 2018). Like the UK, the agricultural sector is not directly regulated, and intense agricultural activity in the IGP contributes to the largest global NH 3 hotspot (Warner et al, 2017;Van Damme et al, 2018;T. Wang et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Long-term trends in air quality in major cities in the UK and India: a view from space

et al. 2021

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Abstract. Air quality networks in cities can be costly and inconsistent and typically monitor a few pollutants. Space-based instruments provide global coverage spanning more than a decade to determine trends in air quality, augmenting surface networks. Here we target cities in the UK (London and Birmingham) and India (Delhi and Kanpur) and use observations of nitrogen dioxide (NO2) from the Ozone Monitoring Instrument (OMI), ammonia (NH3) from the Infrared Atmospheric Sounding Interferometer (IASI), formaldehyde (HCHO) from OMI as a proxy for non-methane volatile organic compounds (NMVOCs), and aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) for PM2.5. We assess the skill of these products at reproducing monthly variability in surface concentrations of air pollutants where available. We find temporal consistency between column and surface NO2 in cities in the UK and India (R = 0.5–0.7) and NH3 at two of three rural sites in the UK (R = 0.5–0.7) but not between AOD and surface PM2.5 (R < 0.4). MODIS AOD is consistent with AERONET at sites in the UK and India (R ≥ 0.8) and reproduces a significant decline in surface PM2.5 in London (2.7 % a−1) and Birmingham (3.7 % a−1) since 2009. We derive long-term trends in the four cities for 2005–2018 from OMI and MODIS and for 2008–2018 from IASI. Trends of all pollutants are positive in Delhi, suggesting no air quality improvements there, despite the roll-out of controls on industrial and transport sectors. Kanpur, identified by the WHO as the most polluted city in the world in 2018, experiences a significant and substantial (3.1 % a−1) increase in PM2.5. The decline of NO2, NH3, and PM2.5 in London and Birmingham is likely due in large part to emissions controls on vehicles. Trends are significant only for NO2 and PM2.5. Reactive NMVOCs decline in Birmingham, but the trend is not significant. There is a recent (2012–2018) steep (> 9 % a−1) increase in reactive NMVOCs in London. The cause for this rapid increase is uncertain but may reflect the increased contribution of oxygenated volatile organic compounds (VOCs) from household products, the food and beverage industry, and domestic wood burning, with implications for the formation of ozone in a VOC-limited city.

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Section: Assessment Of Modis Aodmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Long-term trends in air quality in major cities in the UK and India: a view from space

et al. 2021

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“…The marker peaks in Factor L5 are highly dominated by isoprene and its major oxidation products in the atmosphere, i.e., C 5 H 8 H + and C 4 H 6 OH + (Wennberg et al, 2018). Isoprene emissions strongly depend on light intensity (Monson and Fall, 1989;Kaser et al, 2013) and generally show high concentrations in the day.…”

Section: Factor L5: Isoprene and Its Oxidation Productsmentioning

confidence: 99%

“…Li et al: Atmospheric organic vapors in two European pine forests measured by a Vocus PTR-TOF ing the effects of atmospheric aerosols on climate change and air quality (Schell et al, 2001;Maria et al, 2004). Large amounts of VOCs with varying physicochemical properties are emitted from both biogenic and anthropogenic sources (Friedrich and Obermeier, 1999;Kesselmeier and Staudt, 1999), and their oxidation processes in the atmosphere can lead to the formation of thousands of structurally distinct products containing multiple functional groups (Hallquist et al, 2009;Wennberg et al, 2018). Due to the enormous challenge in characterizing these organic vapors at molecular level, knowledge of their sources or formation pathways has remained lacking.…”

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confidence: 99%

Atmospheric organic vapors in two European pine forests measured by a Vocus PTR-TOF: insights into monoterpene and sesquiterpene oxidation processes

Canagaratna

Riva

et al. 2021

Atmos. Chem. Phys.

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Abstract. Atmospheric organic vapors play essential roles in the formation of secondary organic aerosol. Source identification of these vapors is thus fundamental to understanding their emission sources and chemical evolution in the atmosphere and their further impact on air quality and climate change. In this study, a Vocus proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF) was deployed in two forested environments, the Landes forest in southern France and the boreal forest in southern Finland, to measure atmospheric organic vapors, including both volatile organic compounds (VOCs) and their oxidation products. For the first time, we performed binned positive matrix factorization (binPMF) analysis on the complex mass spectra acquired with the Vocus PTR-TOF and identified various emission sources as well as oxidation processes in the atmosphere. Based on separate analysis of low- and high-mass ranges, 15 PMF factors in the Landes forest and nine PMF factors in the Finnish boreal forest were resolved, showing a high similarity between the two sites. Particularly, terpenes and various terpene reaction products were separated into individual PMF factors with varying oxidation degrees, such as lightly oxidized compounds from both monoterpene and sesquiterpene oxidation, monoterpene-derived organic nitrates, and monoterpene more oxidized compounds. Factors representing monoterpenes dominated the biogenic VOCs in both forests, with lower contributions from the isoprene factors and sesquiterpene factors. Factors of the lightly oxidized products, more oxidized products, and organic nitrates of monoterpenes/sesquiterpenes accounted for 8 %–12 % of the measured gas-phase organic vapors in the two forests. Based on the interpretation of the results relating to oxidation processes, further insights were gained regarding monoterpene and sesquiterpene reactions. For example, a strong relative humidity (RH) dependence was found for the behavior of sesquiterpene lightly oxidized compounds. High concentrations of these compounds only occur at high RH; yet similar behavior was not observed for monoterpene oxidation products.

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“…There is also a mild correlation with chloride (Pearson's r = 0.62), which could be explained by the presence of polychlorinated dibenzodioxins (PCDDs). It is well known that diesel combustion is a source of PCDDs and therefore could be a form of organic chloride associated with NHOA (Laroo et al, 2012;Wang et al, 2012). However, NHOA could also be similar in volatility to ammonium chloride, which could also explain this.…”

Section: Elemental Analysismentioning

confidence: 99%

Seasonal analysis of submicron aerosol in Old Delhi using high-resolution aerosol mass spectrometry: chemical characterisation, source apportionment and new marker identification

et al. 2021

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Abstract. We present the first real-time composition of submicron particulate matter (PM1) in Old Delhi using high-resolution aerosol mass spectrometry (HR-AMS). Old Delhi is one of the most polluted locations in the world, and PM1 concentrations reached ∼ 750 µg m−3 during the most polluted period, the post-monsoon period, where PM1 increased by 188 % over the pre-monsoon period. Sulfate contributes the largest inorganic PM1 mass fraction during the pre-monsoon (24 %) and monsoon (24 %) periods, with nitrate contributing most during the post-monsoon period (8 %). The organics dominate the mass fraction (54 %–68 %) throughout the three periods, and, using positive matrix factorisation (PMF) to perform source apportionment analysis of organic mass, two burning-related factors were found to contribute the most (35 %) to the post-monsoon increase. The first PMF factor, semi-volatility biomass burning organic aerosol (SVBBOA), shows a high correlation with Earth observation fire counts in surrounding states, which links its origin to crop residue burning. The second is a solid fuel OA (SFOA) factor with links to local open burning due to its high composition of polyaromatic hydrocarbons (PAHs) and novel AMS-measured marker species for polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Two traffic factors were resolved: one hydrocarbon-like OA (HOA) factor and another nitrogen-rich HOA (NHOA) factor. The N compounds within NHOA were mainly nitrile species which have not previously been identified within AMS measurements. Their PAH composition suggests that NHOA is linked to diesel and HOA to compressed natural gas and petrol. These factors combined make the largest relative contribution to primary PM1 mass during the pre-monsoon and monsoon periods while contributing the second highest in the post-monsoon period. A cooking OA (COA) factor shows strong links to the secondary factor, semi-volatility oxygenated OA (SVOOA). Correlations with co-located volatile organic compound (VOC) measurements and AMS-measured organic nitrogen oxides (OrgNO) suggest SVOOA is formed from aged COA. It is also found that a significant increase in chloride concentrations (522 %) from pre-monsoon to post-monsoon correlates well with SVBBOA and SFOA, suggesting that crop residue burning and open waste burning are responsible. A reduction in traffic emissions would effectively reduce concentrations across most of the year. In order to reduce the post-monsoon peak, sources such as funeral pyres, solid waste burning and crop residue burning should be considered when developing new air quality policy.

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Source characterization of volatile organic compounds measured by proton-transfer-reaction time-of-flight mass spectrometers in Delhi, India

Cited by 43 publications

References 63 publications

Long-term trends in air quality in major cities in the UK and India: a view from space

Long-term trends in air quality in major cities in the UK and India: a view from space

Atmospheric organic vapors in two European pine forests measured by a Vocus PTR-TOF: insights into monoterpene and sesquiterpene oxidation processes

Seasonal analysis of submicron aerosol in Old Delhi using high-resolution aerosol mass spectrometry: chemical characterisation, source apportionment and new marker identification

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