Distributions of C2–C5 NMHCs and related trace gases at a tropical urban site in India

Sahu, L. K.; Lal, Shyam

doi:10.1016/j.atmosenv.2005.10.021

Cited by 89 publications

(53 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…seasons are also examined in several other pollutants over Ahmedabad as discussed in previous studies (Sahu and Lal, 2006;Mallik et al, 2016). Maximum concentrations of CO 2 and CO are observed to be 424.8 ± 17 and 0.83 ± 0.53 ppm respectively during November.…”

Section: Seasonal Variations Of Co 2 and Comentioning

confidence: 99%

Temporal variations of atmospheric CO<sub>2</sub> and CO at Ahmedabad in western India

et al. 2016

View full text Add to dashboard Cite

Abstract. About 70 % of the anthropogenic carbon dioxide (CO 2 ) is emitted from the megacities and urban areas of the world. In order to draw effective emission mitigation policies for combating future climate change as well as independently validating the emission inventories for constraining their large range of uncertainties, especially over major metropolitan areas of developing countries, there is an urgent need for greenhouse gas measurements over representative urban regions. India is a fast developing country, where fossil fuel emissions have increased dramatically in the last three decades and are predicted to continue to grow further by at least 6 % per year through to 2025. The CO 2 measurements over urban regions in India are lacking. To overcome this limitation, simultaneous measurements of CO 2 and carbon monoxide (CO) have been made at Ahmedabad, a major urban site in western India, using a state-of-the-art laser-based cavity ring down spectroscopy technique from November 2013 to May 2015. These measurements enable us to understand the diurnal and seasonal variations in atmospheric CO 2 with respect to its sources (both anthropogenic and biospheric) and biospheric sinks. The observed annual average concentrations of CO 2 and CO are 413.0 ± 13.7 and 0.50 ± 0.37 ppm respectively. Both CO 2 and CO show strong seasonality with lower concentrations (400.3 ± 6.8 and 0.19 ± 0.13 ppm) during the south-west monsoon and higher concentrations (419.6 ± 22.8 and 0.72 ± 0.68 ppm) during the autumn (SON) season. Strong diurnal variations are also observed for both the species. The common factors for the diurnal cycles of CO 2 and CO are vertical mixing and rush hour traffic, while the influence of biospheric fluxes is also seen in the CO 2 diurnal cycle. Using CO and CO 2 covariation, we differentiate the anthropogenic and biospheric components of CO 2 and found significant contributions of biospheric respiration and anthropogenic emissions in the late night (00:00-05:00 h, IST) and evening rush hours (18:00-22:00 h) respectively. We compute total yearly emissions of CO to be 69.2 ± 0.07 Gg for the study region using the observed CO : CO 2 correlation slope and bottom-up CO 2 emission inventory. This calculated emission of CO is 52 % larger than the estimated emission of CO by the emissions database for global atmospheric research (EDGAR) inventory. The observations of CO 2 have been compared with an atmospheric chemistry-transport model (ACTM), which incorporates various components of CO 2 fluxes. ACTM is able to capture the basic variabilities, but both diurnal and seasonal amplitudes are largely underestimated compared to the observations. We attribute this underestimation by the model to uncertainties in terrestrial biosphere fluxes and coarse model resolution. The fossil fuel signal from the model shows fairly good correlation with observed CO 2 variations, which supports the overall dominance of fossil fuel emissions over the biospheric fluxes in this urban region.

show abstract

Section: Seasonal Variations Of Co 2 and Comentioning

confidence: 99%

Temporal variations of atmospheric CO<sub>2</sub> and CO at Ahmedabad in western India

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Concentration ratios between CO and ethane, propane, ethyne and benzene determined from CARIBIC samples were compared to source emission ratios for biomass burning (tropical forests) and biofuel burning (Andreae and Merlet, 2001), and to concentration ratios from urban samples collected in Ahmedabad, India in 2002 (Sahu and Lal, 2006a) (Table 3). Biomass and biofuel burning emissions are presumed to be from suburban and rural areas and are expected to have little influence in urban areas.…”

Section: Nmhc-co Relationships and Source Identificationmentioning

confidence: 99%

“…In fact, there is a lack of measurements of trace gases in this region during all seasons. Ground-based measurements are limited to a handful of studies, focusing on either large urban areas in India (Lal et al, 2009;Sahu and Lal, 2006a) or rural/background measurements (Lal et al, 2000(Lal et al, , 2006Sahu and Lal, 2006b). The largest study of chemical composition in this region was INDOEX (Indian Ocean Experiment), which took place during February and March of 1999 ).…”

Section: Introductionmentioning

confidence: 99%

Characterization of non-methane hydrocarbons in Asian summer monsoon outflow observed by the CARIBIC aircraft

et al. 2011

View full text Add to dashboard Cite

Abstract. Between April and December 2008 the CARIBIC commercial aircraft conducted monthly measurement flights between Frankfurt, Germany and Chennai, India. These flights covered the period of the Asian summer monsoon (June-September), during which enhancements in a number of atmospheric species were observed in the upper troposphere over southwestern Asia. In addition to in situ measurements of trace gases and aerosols, whole air samples were collected during the flights, and these were subsequently analyzed for a suite of trace gases that included a number of C 2 -C 8 non-methane hydrocarbons. Non-methane hydrocarbons are relatively short-lived compounds and the large enhancements in their mixing ratios in the upper troposphere over southwestern Asia during the monsoon, sometimes more than double their spring and fall means, provides qualitative evidence for the influence of convectively uplifted boundary layer air. The particularly large enhancements of the combustion tracers benzene and ethyne, along with the similarity of their ratios with carbon monoxide and emission ratios from the burning of household biofuels, indicate a strong influence of biofuel burning to NMHC emissions in this region. Conversely, the ratios of ethane and propane to carbon monoxide, along with the ratio between i-butane and n-butane, indicate a significant source of these compounds from the use of fossil fuels, and comparison to previous campaigns suggests that this source could be increasing. Photochemical aging patterns of NMHCs showed that the CARIBIC samples were collected in two distinctly different regions of the monsoon circulation: a southern region where air masses had been recently influenced by low level contact and a northern region, where air parcels had Correspondence to: A. K. Baker (angela.baker@mpic.de) spent substantial time in transit in the upper troposphere before being probed. Estimates of age using ratios of individual NMHCs have ranges of 3-6 days in the south and 9-12 days in the north.

show abstract

“…Thus, it could be associated with such agricultural activities in this region. Similarly, the annual average CH 4 at Bode during 2013-2014 was found comparable to an urban site in Ahmedabad (1.880 ± 0.4 ppm, i.e., RSD: 21.3 %) in India for 2002 (Sahu and Lal, 2006) and 14 % higher than in Shadnagar (1.92 ± 0.07 ppm, i.e., RSD: 3.6 %), a semi-urban site in Telangana state (∼ 70 km north from Hyderabad) during 2014 (Sreenivas et al, 2016). Likewise, the difference between annual mean mixing ratios at Bode (419.3 ± 6.0 ppm, 1.4 % RSD) vs. Mauna Loa (396.8 ± 2.0 ppm, 0.5 % RSD) and Bode vs. Waliguan (397.7 ± 3.6 ppm, 0.9 % variability; Dlugokencky et al, 2016b) was statistically significant (p<0.05).…”

Section: Resultsmentioning

confidence: 91%

Seasonal and diurnal variations in methane and carbon dioxide in the Kathmandu Valley in the foothills of the central Himalayas

Mahata

Panday

Rupakheti³

et al. 2017

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. The SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) international air pollution measurement campaign was carried out from December 2012 to June 2013 in the Kathmandu Valley and surrounding regions in Nepal. The Kathmandu Valley is a bowl-shaped basin with a severe air pollution problem. This paper reports measurements of two major greenhouse gases (GHGs), methane (CH 4 ) and carbon dioxide (CO 2 ), along with the pollutant CO, that began during the campaign and were extended for 1 year at the SusKat-ABC supersite in Bode, a semi-urban location in the Kathmandu Valley. Simultaneous measurements were also made during 2015 in Bode and a nearby rural site (Chanban) ∼ 25 km (aerial distance) to the southwest of Bode on the other side of a tall ridge. The ambient mixing ratios of methane (CH 4 ), carbon dioxide (CO 2 ), water vapor, and carbon monoxide (CO) were measured with a cavity ring-down spectrometer (G2401; Picarro, USA) along with meteorological parameters for 1 year (March 2013-March 2014. These measurements are the first of their kind in the central Himalayan foothills. At Bode, the annual average mixing ratios of CO 2 and CH 4 were 419.3 (±6.0) ppm and 2.192 (±0.066) ppm, respectively. These values are higher than the levels observed at background sites such as Mauna Loa, USA (CO 2 : 396.8 ± 2.0 ppm, CH 4 : 1.831 ± 0.110 ppm) and Waliguan, China (CO 2 : 397.7 ± 3.6 ppm, CH 4 : 1.879 ± 0.009 ppm) during the same period and at other urban and semi-urban sites in the region, such as Ahmedabad and Shadnagar (India). They varied slightly across the seasons at Bode, with seasonal average CH 4 mixing ratios of 2.157 (±0.230) ppm in the pre-monsoon season, 2.199 (±0.241) ppm in the monsoon, 2.210 (±0.200) ppm in the post-monsoon, and 2.214 (±0.209) ppm in the winter season. The average CO 2 mixing ratios were 426.2 (±25.5) ppm in the pre-monsoon, 413.5 (±24.2) ppm in the monsoon, 417.3 (±23.1) ppm in the postmonsoon, and 421.9 (±20.3) ppm in the winter season. The maximum seasonal mean mixing ratio of CH 4 in winter was only 0.057 ppm or 2.6 % higher than the seasonal minimum during the pre-monsoon period, while CO 2 was 12.8 ppm or 3.1 % higher during the pre-monsoon period (seasonal maximum) than during the monsoon (seasonal minimum). On the other hand, the CO mixing ratio at Bode was 191 % higher during the winter than during the monsoon season. The enhancement in CO 2 mixing ratios during the pre-monsoon season is associated with additional CO 2 emissions from forest fires and agro-residue burning in northern South Asia in addition to local emissions in the Kathmandu Valley. Published CO/CO 2 ratios of different emission sources in Nepal and India were compared with the observed CO/CO 2 ratios in this study. This comparison suggested that the major sources in the Kathmandu Valley were residential cooking and vehicle exhaust in all seasons except winter. In winter, brick kiln emissions were a major source. Simultaneous measurements in Bode and Chanban (15 July-3 O...

show abstract

Distributions of C2–C5 NMHCs and related trace gases at a tropical urban site in India

Cited by 89 publications

References 30 publications

Temporal variations of atmospheric CO<sub>2</sub> and CO at Ahmedabad in western India

Temporal variations of atmospheric CO<sub>2</sub> and CO at Ahmedabad in western India

Characterization of non-methane hydrocarbons in Asian summer monsoon outflow observed by the CARIBIC aircraft

Seasonal and diurnal variations in methane and carbon dioxide in the Kathmandu Valley in the foothills of the central Himalayas

Contact Info

Product

Resources

About

Distributions of C2–C5 NMHCs and related trace gases at a tropical urban site in India

Cited by 89 publications

References 30 publications

Temporal variations of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; and CO at Ahmedabad in western India

Temporal variations of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; and CO at Ahmedabad in western India

Characterization of non-methane hydrocarbons in Asian summer monsoon outflow observed by the CARIBIC aircraft

Seasonal and diurnal variations in methane and carbon dioxide in the Kathmandu Valley in the foothills of the central Himalayas

Contact Info

Product

Resources

About

Temporal variations of atmospheric CO<sub>2</sub> and CO at Ahmedabad in western India

Temporal variations of atmospheric CO<sub>2</sub> and CO at Ahmedabad in western India