Sources of non-methane hydrocarbons in surface air in Delhi, India

Rapid economic growth and development have exacerbated air quality problems across India, driven by many poorly understood pollution sources and understanding their relative importance remains critical to characterising the key drivers of air pollution. A comprehensive suite of measurements of 90 non-methane hydrocarbons (NMHCs) (C2–C14), including 12 speciated monoterpenes and higher molecular weight monoaromatics, were made at an urban site in Old Delhi during the pre-monsoon (28-May to 05-Jun 2018) and post-monsoon (11 to 27-Oct 2018) seasons using dual-channel gas chromatography (DC-GC-FID) and two-dimensional gas chromatography (GC×GC-FID). Significantly higher mixing ratios of NMHCs were measured during the post-monsoon campaign, with a mean night-time enhancement of around 6. Like with NOx and CO, strong diurnal profiles were observed for all NMHCs, except isoprene, with very high NMHC mixing ratios between 35–1485 ppbv. The sum of mixing ratios of benzene, toluene, ethylbenzene and xylenes (BTEX) routinely exceeded 100 ppbv at night during the post-monsoon period, with a maximum measured mixing ratio of monoaromatic species of 370 ppbv. The mixing ratio of highly reactive monoterpenes peaked at around 6 ppbv in the post-monsoon campaign and correlated strongly with anthropogenic NMHCs, suggesting a strong non-biogenic source in Delhi. A detailed source apportionment study was conducted which included regression analysis to CO, acetylene and other NMHCs, hierarchical cluster analysis, EPA UNMIX 6.0, principal component analysis/absolute principal component scores (PCA/APCS) and comparison with NMHC ratios (benzene/toluene and i-/n-pentane) in ambient samples to liquid and solid fuels. These analyses suggested the primary source of anthropogenic NMHCs in Delhi was from traffic emissions (petrol and diesel), with average mixing ratio contributions from Unmix and PCA/APCS models of 38% from petrol, 14% from diesel and 32% from liquified petroleum gas (LPG) with a smaller contribution (16%) from solid fuel combustion. Detailed consideration of the underlying meteorology during the campaigns showed that the extreme night-time mixing ratios of NMHCs during the post-monsoon campaign were the result of emissions into a very shallow and stagnant boundary layer. The results of this study suggest that despite widespread open burning in India, traffic-related petrol and diesel emissions remain the key drivers of gas-phase urban air pollution in Delhi

A comparison of PM2.5-bound polycyclic aromatic hydrocarbons in summer Beijing (China) and Delhi (India)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in air, soil, and water and are known to have harmful effects on human health and the environment. The diurnal and nocturnal variations of 17 PAHs in ambient particle-bound PAHs were measured in urban Beijing (China) and Delhi (India) during the summer season using gas-chromatography–quadrupole time-of-flight mass spectrometry (GC-Q-TOF-MS). The mean concentration of particles less than 2.5 µm (PM2.5) observed in Delhi was 3.6 times higher than in Beijing during the measurement period in both the daytime and night-time. In Beijing, the mean concentration of the sum of the 17 PAHs (P17 PAHs) was 8.2 ± 5.1 ng m−3 in daytime, with the highest contribution from indeno[1,2,3-cd]pyrene (12 %), while at nighttime the total PAHs was 7.2 ± 2.0 ng m−3, with the largest contribution from benzo[b]fluoranthene (14 %). In Delhi, the mean P17 PAHs was 13.6 ± 5.9 ng m−3 in daytime and 22.7 ± 9.4 ng m−3 at night-time, with the largest contribution from indeno[1,2,3-cd]pyrene in both the day (17 %) and night (20 %). Elevated mean concentrations of total PAHs in Delhi observed at night were attributed to emissions from vehicles and biomass burning and to meteorological conditions leading to their accumulation from a stable and low atmospheric boundary layer. Local emission sources were typically identified as the major contributors to total measured PAHs in both cities. Major emission sources were characterized based on the contribution from each class of PAHs, with the four-, five- and six-ring PAHs accounting ∼ 95 % of the total PM2.5-bound PAHs mass in both locations. The high contribution of five-ring PAHs to total PAH concentration in summer Beijing and Delhi suggests a high contribution from petroleum combustion. In Delhi, a high contribution from six-ring PAHs was observed at night, suggesting a potential emission source from the combustion of fuel and oil in power generators, widely used in Delhi. The lifetime excess lung cancer risk (LECR) was calculated for Beijing and Delhi, with the highest estimated risk attributed to Delhi (LECR = 155 per million people), which is 2.2 times higher than the Beijing risk assessment value (LECR = 70 per million people). Finally, we have assessed the emission control policies in each city and identified those major sectors that could be subject to mitigation measures

Emissions of non-methane volatile organic compounds from combustion of domestic fuels in Delhi, India

Twenty-nine different fuel types used in residential dwellings in northern India were collected from across Delhi (76 samples in total). Emission factors of a wide range of non-methane volatile organic compounds (NMVOCs) (192 compounds in total) were measured during controlled burning experiments using dualchannel gas chromatography with flame ionisation detection (DC-GC-FID), two-dimensional gas chromatography (GC×GC-FID), proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and solid-phase extraction two-dimensional gas chromatography with time-offlight mass spectrometry (SPE-GC×GC-ToF-MS). On average, 94% speciation of total measured NMVOC emissions was achieved across all fuel types. The largest contributors to emissions from most fuel types were small non-aromatic oxygenated species, phenolics and furanics. The emission factors (in g kg-1) for total gas-phase NMVOCs were fuelwood (18.7, 4.3-96.7), cow dung cake (62.0, 35.3-83.0), crop residue (37.9, 8.9-73.8), charcoal (5.4, 2.4-7.9), sawdust (72.4, 28.6-115.5), municipal solid waste (87.3, 56.6- 119.1) and liquefied petroleum gas (5.7, 1.9-9.8). The emission factors measured in this study allow for better characterisation, evaluation and understanding of the air quality impacts of residential solid-fuel combustion in India

Emissions of intermediate-volatility and semi-volatile organic compounds from domestic fuels used in Delhi, India

Biomass burning emits significant quantities of intermediate-volatility and semi-volatile organic compounds (I/SVOCs) in a complex mixture, probably containing many thousands of chemical species. These components are significantly more toxic and have poorly understood chemistry compared to volatile organic compounds routinely quantified in ambient air; however, analysis of I/SVOCs presents a difficult analytical challenge. The gases and particles emitted during the test combustion of a range of domestic solid fuels collected from across Delhi were sampled and analysed. Organic aerosol was collected onto Teflon (PTFE) filters, and residual low-volatility gases were adsorbed to the surface of solid-phase extraction (SPE) discs. A new method relying on accelerated solvent extraction (ASE) coupled to comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-ToF-MS) was developed. This highly sensitive and powerful analytical technique enabled over 3000 peaks from I/SVOC species with unique mass spectra to be detected. A total of 15 %-100% of gas-phase emissions and 7 %-100% of particle-phase emissions were characterised. The method was analysed for suitability to make quantitative measurements of I/SVOCs using SPE discs. Analysis of SPE discs indicated phenolic and furanic compounds were important for gas-phase I/SVOC emissions and levoglucosan to the aerosol phase. Gas- and particle-phase emission factors for 21 polycyclic aromatic hydrocarbons (PAHs) were derived, including 16 compounds listed by the US EPA as priority pollutants. Gas-phase emissions were dominated by smaller PAHs. The new emission factors were measured (mg kg-1) for PAHs from combustion of cow dung cake (615), municipal solid waste (1022), crop residue (747), sawdust (1236), fuelwood (247), charcoal (151) and liquefied petroleum gas (56). The results of this study indicate that cow dung cake and municipal solid waste burning are likely to be significant PAH sources, and further study is required to quantify their impact alongside emissions from fuelwood burning

Characterization of particulate-bound polycyclic aromatic hydrocarbons and trace metals composition of urban air in Delhi, India

The concentrations of sixteen polycyclic aromatic hydrocarbons (PAHs) and trace metals adsorbed to 2.5 mm) respirable particulate matter (PM 10 mm) and the fine fraction of particulate matter (PM were determined at a site in Delhi (India) during the winter and summer periods in 2007e2008. The annual mean concentrations for PM10 and PM2.5 were 138.5 Æ 40.4 mg mÀ3 and 50.6 Æ 20.4 mg mÀ3,respectively, with higher concentrations during winter than summer period. Concentrations of PM10 and PM2.5 have been found that were higher than the prescribed limits of the WHO and the NAAQS given by CPCB, India. The trace metals detected in the PM10 and PM2.5 were Al, Ca, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn and their concentrations were similar to those observed in heavily polluted urban areas from local traffic and other anthropogenic emissions. Total PAH concentrations for PM10 and PM2.5 were much higher in winter (81.5 and 96 ng mÀ3, respectively) compared to summer (33.1 and 45.8 ng mÀ3, respectively) with high molecular weight homologues (4e6 ring PAHs), which account for 80e95.8% of total PAHs. In general, the PM2.5 PAH concentrations were higher than PM10 particles. The results of diagnostic ratio and enrichment factor analyses showed that vehicular and anthropogenic emissions related to combustion, industrial processes as well as natural sources associated with the transport of dust from the roadside area were the main pollutant sources for PAHs and trace metals

Emissions of Polycyclic Aromatic Hydrocarbons in the Atmosphere: An Indian Perspective

Organic compounds form a major fraction of airborne particles in the atmosphere and hence it is important to measure and identify them, especially the proportion of Polycyclic (Polynuclear) Aromatic Hydrocarbons (PAHs). The control and abatement of PAHs contamination requires the knowledge of the nature, source, and extent of pollution and hence existing literature on Indian studies was reviewed to gather information on the sources and emission rates of PAHs. Based on the results of the present study along with the data available from literature for particular PAHs in the ambient atmosphere, the vehicular and residential sector was identified as a major source of PAHs emission in many major Indian cities including Ahmedabad, Agra, Delhi, Kanpur, Lucknow, Mumbai, and Nagpur. Emissions of total PAHs range from 23–190 ng/m3, 369–1067 ng/m3, 20.8–100.8 ng/m3, and 12.7–206.4 μg/m3 from gasoline, diesel, petroleum refinery, and biomass, respectively, although it is recognized that this will vary from location to location. Additionally, the regulation and control of PAHs emission, and air quality standards for PAHs were also examined. Based on the toxicity assessment, the study highlights the need to include not only benzo[a]pyrene but also other probable human carcinogenic PAHs while developing a new air quality index for India

Levels, Sources, and Toxic Potential of Polycyclic Aromatic Hydrocarbons in Urban Soil of Delhi, India

This study was done to determine the concentration of PAHs in urban soil of Delhi (India). Surface top soil (up to 10 cm depth) samples were collected from four different sampling sites including industrial, roadside, residential, and agricultural areas of Delhi and 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were evaluated. Total PAH concentrations at industrial, roadside, residential, and agricultural sites were 11.46 +/- 8.39, 6.96 +/- 4.82, 2.12 +/- 1.12, and 1.55 +/- 1.07 mg/kg (dry weight), respectively, with 3-7 times greater concentrations in industrial and roadside soils than that in residential and agricultural soils. The PAH pattern was dominated by 4- and 5-ring PAHs (contributing > 50% to the total PAHs) at industrial and roadside sites with greater concentration of fluoranthene, chrysene, benzo[b] fluoranthene, benzo[k] fluoranthene, benzo[a] anthracene, benzo[ghi] perylene, and pyrene, whereas, residential and agricultural sites showed a predominance of low molecular weight 2- and 3-ring PAHs (fluoranthene, acenaphthene, naphthalene, chrysene, and anthracene). Isomeric pair ratios suggested biomass combustion and fossil fuel emissions as the main sources of PAHs. The toxic equivalency factors (TEFs) showed that carcinogenic potency (benzo[a] pyrene-equivalent concentration (B[a]P-eq) of PAH load in industrial and roadside soils was similar to 10 and similar to 6 times greater than the agricultural soil

Characterization of Gaseous and Particulate Polycyclic Aromatic Hydrocarbons in Ambient Air of Delhi, India

Three seasonal sampling campaigns were undertaken at an urban site of Delhi for collection of PAHs in particulate and gas phase. Sampling was done by using modified Respirable Dust (PM <= 10 mu m) sampler attached with polyurethane foam (PUF) plugs and compared with conventional Respirable Dust (PM <= 10 mu m) sampler. Total 16 EPA PAH (gaseous + particulate) were determined by Gas Chromatograph-Mass Spectrophotometer (GC-MS). The 3-ring PAH constitutes approximately 90% of the gaseous PAHs with phenanthrene, fluoranthene, acenapthylene, and acenaphthene being the most abundant gaseous PAHs. PAHs with 4- to 6- rings accounted for 92%, 87% and 78% in samples collected during winter, summer and monsoon season respectively. Gaseous PAHs, particulate PAHs and total PAHs were higher during winter as compared to summer and monsoon seasons. The contribution of particulate PAHs were 1.4, 2.1, and 2.5 times higher in winter, summer and monsoon, respectively than of gaseous PAHs. Indeno[123-cd]pyrene, benzo[ghi]perylene, dibenzo[ah]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene and chrysene were found to be the most abundant PAH compounds in the particulate PAHs during all the seasons. The result from application of diagnostic ratio suggests that the higher particulate PAHs emissions were predominantly associated with vehicular emissions along with emissions from biomass burning during winter season

Seasonal variations and source profile of n-alkanes in particulate matter (PM10) at a heavy traffic site, Delhi

Delhi is one of the most polluted cities in the world. The generation of aerosols in the lower atmosphere of the city is mainly due to a large amount of natural dust advection and sizable anthropogenic activities. The compositions of organic compounds in aerosols are highly variable in this region and need to be investigated thoroughly. Twenty-four-hour sampling to assess concentrations of n-alkanes (ng/m(3)) in PM10 was carried out during January 2015 to June 2015 at Indira Gandhi Delhi Technical University for Women (IGDTUW) Campus, Delhi, India. The total average concentration of n-alkanes, 243.7 +/- 5.5 ng/m(3), along with the diagnostic tools has been calculated. The values of CPI1, CPI2, and CPI3 for the whole range of n-alkanes series, petrogenic n-alkanes, and biogenic n-alkanes were 1.00, 1.02, and 1.04, respectively, and C-max were at C-25 and C-27. Diagnostic indices and curves indicated that the dominant inputs of n-alkanes are from petrogenic emissions, with lower contribution from biogenic emissions. Significant seasonal variations were observed in average concentrations of n-alkanes, which is comparatively higher in winter (187.4 +/- 4.3 ng/m(3)) than during the summer season (56.3 +/- 1.1 ng/m(3))

Characterization and source apportionment of organic compounds in PM10 using PCA and PMF at a traffic hotspot of Delhi

An attempt has been made to develop a cement paint composites containing MWCNT, fly ash & ferrite encapsulated glass fibers for absorbing electromagnetic interference (EMI) pollution. The ferrite particles were encapsulated onto glass fibers by in situ polymerization method. However fly ash has been added in controlled amount to the composite in order to perform a dual function, first as dielectric filler and second to reduce solid waste generated from the thermal power plants. These composites have been used to evaluate shielding effectiveness in X b and (8.2-12.4 GHz). The results have shown that this composite can provide an effective absorption dominated shielding effectiveness of 66 dB in X band (8.2-12.4 GHz) with the incorporation of 12 wt% loading of MWCNT along with fly ash and ferrite encapsulated glass fibers in the cement paint matrix. Moreover, the cement paint composites were also tested for surface morphology, hardness, electrical conductivity and structural analysis using TEM, shore hardness test, electrical conductivity and XRD technique, respectively