Highly time resolved chemical characterization of submicron organic aerosols at a polluted urban location

Kumar, B. Vinay; Chakraborty, Abhishek; Tripathi, S. N.; Bhattu, Deepika

doi:10.1039/c6em00392c

Cited by 26 publications

(19 citation statements)

References 63 publications

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“…The share of BC in PM fractions was found to be ∼ 13 % in PM 1 , 9 % in PM 2.5 and ∼ 4 % in PM 10 but the correlation coefficients of BC with three PM fractions were found to be 0.89 (PM 1 ), 0.88 (PM 2.5 ) and 0.69 (PM 10 ), indicating the commonality in the sources of these pollutants. The contribution of BC in PM 1 was found to be ∼ 12 % in Kanpur during February-March (Kumar et al, 2016a), similar to Lumbini. Regarding the share of BC in PM 10 , the share observed in Lumbini (∼ 4 %) was similar to that observed over Varanasi (∼ 340 km south of our site) in central IGP (5 %) (Tiwari et al, 2016) and Dibrugarh in eastern IGP (∼ 5 %) (Pathak et al, 2013).…”

Section: Meteorologymentioning

confidence: 66%

Pre-monsoon air quality over Lumbini, a world heritage site along the Himalayan foothills

et al. 2017

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Abstract. Lumbini, in southern Nepal, is a UNESCO world heritage site of universal value as the birthplace of Buddha. Poor air quality in Lumbini and surrounding regions is a great concern for public health as well as for preservation, protection and promotion of Buddhist heritage and culture. We present here results from measurements of ambient concentrations of key air pollutants (PM, BC, CO, O 3 ) in Lumbini, first of its kind for Lumbini, conducted during an intensive measurement period of 3 months (April-June 2013) in the pre-monsoon season. The measurements were carried out as a part of the international air pollution measurement campaign; SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley -Atmospheric Brown Clouds). The main objective of this work is to understand and document the level of air pollution, diurnal characteristics and influence of open burning on air quality in Lumbini. The hourly average concentrations during the entire measurement campaign ranged as follows: BC was 0.3-30.0 µg m −3 , PM 1 was 3.6-197.6 µg m −3 , PM 2.5 was 6.1-272.2 µg m −3 , PM 10 was 10.5-604.0 µg m −3 , O 3 was 1.0-118.1 ppbv and CO was 125.0-1430.0 ppbv. These levels are comparable to other very heavily polluted sites in South Asia. Higher fraction of coarsemode PM was found as compared to other nearby sites in the Indo-Gangetic Plain region. The BC / CO ratio obtained in Lumbini indicated considerable contributions of emissions from both residential and transportation sectors. The 24 h average PM 2.5 and PM 10 concentrations exceeded the WHO guideline very frequently (94 and 85 % of the sampled period, respectively), which implies significant health risks for the residents and visitors in the region. These air pollutants exhibited clear diurnal cycles with high values in the morning and evening. During the study period, the worst air pollution episodes were mainly due to agro-residue burning and regional forest fires combined with meteorological conditions conducive of pollution transport to Lumbini. Fossil fuel combustion also contributed significantly, accounting for more than half of the ambient BC concentration according to aerosol spectral light absorption coefficients obtained in Lumbini. WRF-STEM, a regional chemical transport model, was used to simulate the meteorology and the concentrations of pollutants to understand the pollutant transport pathways. The model estimated values were ∼ 1.5 to 5 times lower than the observed concentrations for CO and PM 10 , respectively. Model-simulated regionally tagged CO tracers showed that the majority of CO came from the upwind region of Ganges Valley. Model performance needs significant improvement Published by Copernicus Publications on behalf of the European Geosciences Union.

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Section: Meteorologymentioning

confidence: 66%

Pre-monsoon air quality over Lumbini, a world heritage site along the Himalayan foothills

et al. 2017

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“…Earlier studies (e.g. Kumar et al, 2016;Thamban et al, 2017;Chakraborty et al, 2018 emissions over a village in the IGP, Fleming et al, (2018) have characterized a wide range of particle phase compounds 10 produced by traditional cook stoves and pointed out various organic compounds originate from these sources. Viewed in this context, dominance of organics in the IGP outflow is not surprising.…”

Section: Non-refractive Pm10 Mass Concentrationsmentioning

confidence: 99%

Seasonal contrast in size distributions and mixing state of black carbon and its association with PM1.0 chemical composition from the eastern coast of India

Kompalli¹,

Satheesh²,

Moorthy³

et al. 2019

Preprint

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Over the Indian region, aerosol absorption is considered to have potential impact on regional climate, monsoon and hydrological cycle. Black carbon (BC) is the dominant absorbing aerosol, whose absorption potential is largely determined by its microphysical properties, including its concentration, size and mixing state with other aerosol components. The Indo-Gangetic Plains (IGP) is one of the regional aerosol hot spots with diverse sources, both natural and anthropogenic, but still 5 the information on the mixing state of the IGP aerosols, especially BC, is limited and a major source of uncertainty in understanding their climatic implications. In this context, we present the results from intensive measurements of refractory BC (rBC) carried out over Bhubaneswar, an urban site in the eastern coast of India, which experiences contrasting airmasses (the IGP outflow or coastal/marine airmasses) in different seasons. This study helps to elucidate the microphysical characteristics of BC over this region and delineates the IGP outflow from the other airmasses. The observations were carried 10 out as part of "South West Asian Aerosol Monsoon Interactions (SWAAMI)" collaborative field experiment during July 2016-May 2017, using a single particle soot photometer (SP2) that uses a laser-induced incandescence technique to measure the mass and mixing state of individual BC particles and an aerosol chemical speciation monitor (ACSM). Results highlighted the distinctiveness in aerosol microphysical properties in the IGP airmasses. BC mass concentration was highest during winter (~1935 ± 1578 ng m -3 ), when the prevailing air masses were mostly of IGP origin, followed by post-monsoon 15 (mean ~1338 ± 1396 ng m -3 ). Mass median diameter (MMD) of the BC mass size distributions were in the range 0.190-0.195 µm suggesting mixed sources of BC, and further, higher values (~1.3-1.8) of bulk relative coating thickness (RCT) (ratio of optical and core diameters) were seen indicating a large fraction of highly coated BC aerosols in the IGP outflow.During the pre-monsoon, when marine/coastal airmasses prevailed, BC mass concentration was lowest (~816 ± 835 ng m -3 ) and larger BC cores (MMD > 0.210 µm) were seen suggesting distinct source processes, while RCT was ~1.2-1.3, which 20 may translate into higher extent of absolute coating on BC cores which may have important regional climate implications.During the summer monsoon, BC size distributions were dominated by smaller cores (MMD ≤ 0.185 µm) with lowest coating, indicating fresher BC, likely from fossil fuel sources. A clear diurnal variation pattern of BC and RCT was noticed in all the seasons, and day time peak in RCT suggested enhanced coating on BC due to the condensable coating material originated from photochemistry. Examination of sub-micron aerosol chemical composition highlighted that the IGP outflow 25 is dominated by organics (47-49%) and marine/coastal airmasses contained greater amounts of sulphate (41-47%), while ammonium and nitrate were seen in minor amounts with sig...

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“…In Lumbini, the average (hourly) share of PM 1 in PM 2.5 , PM 1 in PM 10 and PM 2.5 in PM 10 was found to be ∼ 70, 34 and 47 %, respectively. Regarding other sites in IGP region, PM 2.5 / PM 10 ratios were reported to be 56 % in Kanpur (Snider et al, 2016), 60 % in Varanasi (Kumar et al, 2015), 57 % in Guwahiti (Tiwari et al, 2017), 90 % in Dribugarh (Pathak et al, 2013) and 62 % in Delhi , indicating local differences within IGP as well as suggesting that the influence of combustion sources at Lumbini is still lower compared to other locations in the Indian section of the IGP. A recent study (Putero et al, 2015) reported that the PM 1 / PM 10 during pre-monsoon of 2013 was found to be 0.39 in the Kathmandu Valley of Nepal.…”

Section: Meteorologymentioning

confidence: 96%

Compiled Response to the reviewers comments

Rupakheti¹

2017

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Lumbini, in southern Nepal, is a UNESCO world heritage site of universal value as the birthplace of Buddha. Poor air quality in Lumbini and surrounding regions is a great concern for public health as well as for preservation, protection and promotion of Buddhist heritage and culture. We present here results from measurements of ambient concentrations of key air pollutants (PM, BC, CO, O 3 ) in Lumbini, first of its kind for Lumbini, conducted during an intensive measurement period of 3 months (April-June 2013) in the pre-monsoon season. The measurements were carried out as a part of the international air pollution measurement campaign; SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley -Atmospheric Brown Clouds). The main objective of this work is to understand and document the level of air pollution, diurnal characteristics and influence of open burning on air quality in Lumbini. The hourly average concentrations during the entire measurement campaign ranged as follows: BC was 0.3-30.0 µg m −3 , PM 1 was 3.6-197.6 µg m −3 , PM 2.5 was 6.1-272.2 µg m −3 , PM 10 was 10.5-604.0 µg m −3 , O 3 was 1.0-118.1 ppbv and CO was 125.0-1430.0 ppbv. These levels are comparable to other very heavily polluted sites in South Asia. Higher fraction of coarsemode PM was found as compared to other nearby sites in the Indo-Gangetic Plain region. The BC / CO ratio obtained in Lumbini indicated considerable contributions of emissions from both residential and transportation sectors. The 24 h average PM 2.5 and PM 10 concentrations exceeded the WHO guideline very frequently (94 and 85 % of the sampled period, respectively), which implies significant health risks for the residents and visitors in the region. These air pollutants exhibited clear diurnal cycles with high values in the morning and evening. During the study period, the worst air pollution episodes were mainly due to agro-residue burning and regional forest fires combined with meteorological conditions conducive of pollution transport to Lumbini. Fossil fuel combustion also contributed significantly, accounting for more than half of the ambient BC concentration according to aerosol spectral light absorption coefficients obtained in Lumbini. WRF-STEM, a regional chemical transport model, was used to simulate the meteorology and the concentrations of pollutants to understand the pollutant transport pathways. The model estimated values were ∼ 1.5 to 5 times lower than the observed concentrations for CO and PM 10 , respectively. Model-simulated regionally tagged CO tracers showed that the majority of CO came from the upwind region of Ganges Valley. Model performance needs significant improvementPublished by Copernicus Publications on behalf of the European Geosciences Union. 11042 D. Rupakheti et al.: Pre-monsoon air quality over Lumbini in simulating aerosols in the region. Given the high air pollution level, there is a clear and urgent need for setting up a network of long-term air quality monitoring stations in the greater Lumbini region.

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Highly time resolved chemical characterization of submicron organic aerosols at a polluted urban location

Cited by 26 publications

References 63 publications

Pre-monsoon air quality over Lumbini, a world heritage site along the Himalayan foothills

Pre-monsoon air quality over Lumbini, a world heritage site along the Himalayan foothills

Seasonal contrast in size distributions and mixing state of black carbon and its association with PM1.0 chemical composition from the eastern coast of India

Compiled Response to the reviewers comments

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