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

Sarkar, Chinmoy; Sinha, Vinayak; Kumar, Vinod; Rupakheti, Maheswar; Panday, Arnico K.; Mahata, Khadak; Rupakheti, Dipesh; Kathayat, Bhogendra; Lawrence, M. G.

doi:10.5194/acp-16-3979-2016

Cited by 112 publications

(188 citation statements)

References 104 publications

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“…This could be due to the overnight/early morning accumulation of CO emissions, due to poor ventilation In addition to CO, observations of VOCs made at Bode (Sarkar et al, 2016) also showed similar diurnal variations with two peaks and having their levels up to about 15 ppbv. Similar to CO, many…”

Section: Variations In Co and Hydrocarbons At Bodementioning

confidence: 83%

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Variations in surface ozone and carbon monoxide in the Kathmandu Valley and surrounding broader regions during SusKat-ABC field campaign: Role of local and regional sources

Bhardwaj¹,

Naja²,

Rupakheti³

et al. 2017

Preprint

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Abstract. Air pollutants emitted from rapid urbanization and associated human activities in the Kathmandu Valley of Nepal over the past two decades are causing serious air quality and health concerns. These concerns led to a multinational field campaign SusKat-ABC (Sustainable atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) that measured different trace gases, aerosols and meteorological parameters in the Kathmandu Valley and surrounding regions during December 2012 to June 2013 to understand the factors influencing air quality of the Kathmandu Valley. This study provides information about the regional distribution of ozone and some precursor gases using simultaneous in situ measurements from a SusKat-ABC supersite at Bode, Nepal and two Indian sites: a high-altitude site Nainital located in the central Himalayan region and a low altitude site Pantnagar located in the Indo-Gangetic Plain (IGP). The diurnal variations at Bode showed a daytime buildup in O3 while CO shows morning and evening peaks. Similar variations (with lower levels) were also observed at Pantnagar but not at Nainital. Several events of hourly ozone levels exceeding 80 ppbv were also observed at Bode. The CO levels showed a decrease from their peak level of above 2000&#8201;ppbv in January to about 680&#8201;ppbv in June at Bode. The hourly mean ozone and CO levels showed a strong negative correlation during winter (r2&#8201;=&#8201;0.82 in January and r2&#8201;=&#8201;0.71 in February), but this negative correlation gradually becomes weaker, with the lowest value in May (r2&#8201;=&#8201;0.12). The background O3 and CO mixing ratios at Bode were estimated to be about 14&#8201;ppbv and 325&#8201;ppbv respectively. The rate of change of ozone at Bode showed a more rapid increase (~&#8201;17&#8201;ppbv/hour) during morning than the decrease in the evening (5&#8211;6&#8201;ppbv/hour), suggesting a semi urban kind of environment at Bode. The slower evening time ozone decrease rates and lower CO levels during spring suggests an important contribution of regional transport than the contribution of local sources to the springtime ozone enhancement in the Kathmandu Valley. The winter time higher ozone levels at Bode are largely due to local sources with relatively less contributions from regional sources. We show that regional pollution resulting from agricultural crop residue burning in north-western IGP led to large (~&#8201;2-fold) increase in O3 and CO levels simultaneously at all three sites, i.e., Bode, Pantnagar and Nainital during first week of May 2013. Biomass burning induced increase in ozone and related gases was also confirmed by a global model and balloon borne observations over Nainital. A comparison of surface ozone variations and composition of light non-methane hydrocarbons among different sites indicated the differences in emission sources of the Kathmandu Valley and the IGP. These results highlight the contribution of regional sources to air pollution in the Kathmandu Valley versus the local sources in the Valley.

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Section: Variations In Co and Hydrocarbons At Bodementioning

confidence: 83%

“…However, that study lacked the collocated measurements of O3 precursors. Sarkar et al, (2016) presented the measurements of non-methane volatile organic compounds (NMVOCs) at one-second resolution using Proton Transfer Reaction-Time of FlightAtmos. Chem.…”

Section: Introductionmentioning

confidence: 99%

Variations in surface ozone and carbon monoxide in the Kathmandu Valley and surrounding broader regions during SusKat-ABC field campaign: Role of local and regional sources

Bhardwaj¹,

Naja²,

Rupakheti³

et al. 2017

Preprint

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“…The comparison of the March-May period with other months showed an increase in coarse-mode particles with a modal radius of 3 to 6 µm due to the presence of soil dust particles, as mentioned above. Enhanced fine-mode aerosols with a modal radius of 0.1-0.3 µm in the pre-monsoon period can be explained by more emissions of accumulation-mode particles from brick kilns (Sarkar et al, 2016), motor vehicles, diesel generator sets, and forest fires and the frequent occurrence of new particle formation and subsequent growth events (Venzac et al, 2008). The aerosol volume size distribution in the monsoon and post-monsoon periods indicated a minimal content of coarse particles.…”

Section: Methodsmentioning

confidence: 99%

“…Particulate air pollution in the Kathmandu Valley has reached severe levels that is mainly due to uncontrolled emissions from motor vehicles (e.g., super-emitters such as diesel trucks), brick kilns, fugitive soil dust, and biomass and garbage burning (Panday and Prinn, 2009;Kim et al, 2015;Sarkar et al, 2016). Electrical power shortages in the Kathmandu Valley, especially during dry cold months, have led to not only increased low-grade coal and biomass/biofuel burnings but also the use of mostly small diesel generators between 2011 and 2016 (Chen et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Wintertime aerosol optical and radiative properties in the Kathmandu Valley during the SusKat-ABC field campaign

et al. 2017

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Abstract. Particulate air pollution in the Kathmandu Valley has reached severe levels that are mainly due to uncontrolled emissions and the location of the urban area in a bowl-shaped basin with associated local wind circulations. The AERONET measurements from December 2012 to August 2014 revealed a mean aerosol optical depth (AOD) of approximately 0.30 at 675 nm during winter, which is similar to that of the post-monsoon but half of that of the pre-monsoon AOD (0.63). The distinct seasonal variations are closely related to regional-scale monsoon circulations over South Asia and emissions in the Kathmandu Valley. During the SusKat-ABC campaign (December 2012-February 2013, a noticeable increase in both aerosol scattering (σ s ; 313 → 577 Mm −1 at 550 nm) and absorption (σ a ; 98 → 145 Mm −1 at 520 nm) coefficients occurred before and after 4 January 2013. This can be attributed to the increase in wood-burned fires due to a temperature drop and the start of firing at nearby brick kilns. The σ s value in the Kathmandu Valley was a factor of 0.5 lower than that in polluted cities in India. The σ a value in the Kathmandu Valley was approximately 2 times higher than that at severely polluted urban sites in India. The aerosol mass scattering efficiency of 2.6 m 2 g −1 from PM 10 measurements in the Kathmandu Valley is similar to that reported in urban areas. However, the aerosol mass absorption efficiency was determined to be 11 m 2 g −1 from PM 10 measurements, which is higher than that reported in the literature for pure soot particles (7.5 ± 1.2 m 2 g −1 ). This might be due to the fact that most of the carbonaceous aerosols in the Kathmandu Valley were thought to be mostly externally mixed with other aerosols under dry conditions due to a short travel time from their sources. The σ s and σ a values and the equivalent black carbon (EBC) mass concentration reached up to 757 Mm −1 , 224 Mm −1 , and 29 µg m −3 at 08:00 LST (local standard time), respectively but decreased dramatically during the daytime (09:00-18:00 LST), to one-quarter of the morning average (06:00-09:00 LST) due to the development of valley winds and an atmospheric bounder layer. The σ s and σ a values and the EBC concentration remained almost constant during the night at the levels of 410 Mm −1 , 130 Mm −1 , and 17 µg m −3 , respectively. The average aerosol direct radiative forcings over the intensive measurement period were estimated to be −6.9 ± 1.4 W m −2 (top of the atmosphere) and −20.8 ± 4.6 W m −2 (surface). Therefore, the high atPublished by Copernicus Publications on behalf of the European Geosciences Union. 12618 C. Cho et al.: Wintertime aerosol optical and radiative properties in the Kathmandu Valley mospheric forcing (i.e., 13.9 ± 3.6 W m −2 ) and forcing efficiency (74.8 ± 24.2 W m −2 τ −1 ) can be attributed to the high portion of light-absorbing aerosols in the Kathmandu Valley, as indicated by the high black carbon (or elemental carbon) to sulphate ratio (1.5 ± 1.1).

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“…Another reason for choosing BTEX as our target VOC group is that humidity effects in breath samples can be ignored when measuring BTEX by PTR-TOF-MS, as previous studies have shown little humidity dependence on their sensitivity [91][92][93].…”

Section: Methodsmentioning

confidence: 99%

Real-time monitoring of respiratory absorption factors of volatile organic compounds in ambient air by proton transfer reaction time-of-flight mass spectrometry

Huang

Yan

Zhang

et al. 2016

Journal of Hazardous Materials

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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

Cited by 112 publications

References 104 publications

Variations in surface ozone and carbon monoxide in the Kathmandu Valley and surrounding broader regions during SusKat-ABC field campaign: Role of local and regional sources

Variations in surface ozone and carbon monoxide in the Kathmandu Valley and surrounding broader regions during SusKat-ABC field campaign: Role of local and regional sources

Wintertime aerosol optical and radiative properties in the Kathmandu Valley during the SusKat-ABC field campaign

Real-time monitoring of respiratory absorption factors of volatile organic compounds in ambient air by proton transfer reaction time-of-flight mass spectrometry

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