Air pollution pertaining to particulate matter (PM) is a major issue in most of the metropolitan cities across the world. Inhalation exposure to organic species like polycyclic aromatic hydrocarbons (PAHs), derivatives of PAHs (oxygenated and nitrated PAHs), and phthalic acid esters (PAEs) bound to PM is of major concern owing to its carcinogenic, mutagenic, and endocrine disrupting nature. In this study for the first time, we report a total of 22 aromatic organic species which include PAHs, derivatives of PAHs, and PAEs using an optimized high-performance liquid chromatography coupled to the tandem mass spectrometer (HPLC–MS/MS) method. Further, this optimized method was used to carry out the measurements of the 22 targeted organic constituents bound to the ambient fine particulate matter (PM2.5) collected in Bengaluru, a metropolitan city in India as a part of a pilot study during the pre-summer season. Among the reported compounds, benzo[b]fluoranthene (3.82 ng m−3), 9-nitroanthracene (10.47 ng m−3), and diethyl phthalate (5.38 ng m−3) are the most abundant PAHs, the derivatives of PAHs, and PAEs, respectively. Determined diagnostic ratios of PAHs have shown that the sampling site is majorly influenced by traffic emissions. Benzo[a]pyrene, a Group 1 carcinogen has occasionally exceeded the limits set by National Ambient Air Quality Standards (NAAQs), India during the sampling period. Further, a preliminary study was performed using a yeast model of amyotrophic lateral sclerosis (ALS) expressing transactive response DNA binding protein 43 (TDP43) and we demonstrated that commonly reported organics such as PAHs and PAEs bound to PM2.5 have induced significantly elevated aggregation in wild type TDP43. Preliminary results of this study indicate that there is a need for further detailed health risk assessment due to inhalation exposure of organic constituents bound to the ambient PM in Bengaluru.

In recent times, microplastics (MPs) pollution has become a growing concern across the globe. MPs are easily transferred and ubiquitously found in ambient air. These MPs in the air can act as carriers for several toxic pollutants and exposure to MPs could lead to pulmonary diseases in humans. Polyethylene terephthalate (PET) is one of the most abundant airborne MPs in the ambient environements and nylon 66 is one of the most abundant MPs found in microenvironments. However, there are no studies reported for the quantification of airborne PET and nylon 66 microplastics present in inhalable fraction of ambient fine particulate matter. This study describes the methods optimized for the quantification of PET microplastics and nylon 66 microplastics bound to aiborne PM2.5 using LC-MS/MS. Teflon and Quartz fiber filters were tested for extraction efficiency in measuring the mass concentrations of airborne PET MPs and nylon 66 MPs. Teflon filters have shown good recovery (80 % – 120 %) compared to Quartz filters. Using the optimized methods, a pilot study was carried out at Delhi, the National Capital of India and Mohali, a suburban city in Northwest Indo-Gangetic Plain (NWIGP) for the determination of mass concentrations of PET MPs present in airborne inhalable fraction of ambient PM2.5 and a pilot study was carried out to measure the mass concentrations of nylon 66 microplastics present in the inhalable fraction of particulate matter collected in a shopping complex. Observed maximum mass concentrations of PET MPs in airborne PM2.5 at Delhi and Mohali are 135.2 ng m-3 and 158.0 ng m-3, respectively. The observed mass concentrations of nylon 66 MPs in the microenvironment in this study are in the range of 0.30 ng m-3 to 4.37 ng m-3.

Microplastics (MPs) in the air are one of the major concerns due to their possible health risks. In addition, airborne microplastics act as a carrier for several toxic air pollutants and cause carcinogenic, mutagenic and teratogenic effects. Nylon 66 is one of the most abundant MPs in the microenvironments. In this study, we report an optimized method for the quantification of nylon 66 MPs present in the fine particulate matter (PM2.5) using high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). The optimized method exhibited excellent linearity, recovery rates, intraday and interday precision and sensitivity. The optimized method was deployed to carry out a pilot study to measure the mass concentrations of nylon 66 microplastics present in the inhalable fraction of particulate matter collected in a shopping complex. The observed mass concentrations of nylon 66 MPs in this study are in the range from 0.30 ng m-3 to 4.37 ng m-3. This study demonstrates the presence of inhalable fraction of nylon 66 MPs in the indoor environment and their mass concentrations were determined using HPLC-MS/MS.

This study investigates the PM2.5 bound metals using yearlong measurements at a regionally representative suburban site in the Northwest Indo-Gangetic Plain (NWIGP). The order of the measured annual average concentrations of PM2.5 bound metals is Fe > Zn > Ba > Sn > Pb > Cd > Ni > Mn > Cr > Li. Lithium bound to airborne PM2.5 has been reported for the first time in NWIGP. Ni (72.4 ng m-3) and Cd (36.9 ng m-3) have exceeded the acceptable limits set by NAAQS, India. Estimated the hazard quotient (HQ > 1) of Mn and hazard index (HI > 1) of measured metals exceeded the threshold limits indicating the potential non-carcinogenic health risk due to inhalation exposure of PM2.5 bound trace metals. Further, excessive lifetime cancer risk due to inhalation exposure to Cd, Ni and Cr was estimated and found to exceed the threshold limit set by the USEPA for adults and children.

Microplastics (MPs) have recently become a growing environmental pollution concern. MPs are easily transferred and ubiquitously found in ambient air. MPs in the air can act as carriers for several toxic pollutants, and exposure to MPs can lead to pulmonary diseases in humans. Polyethylene terephthalate (PET) is one of the most abundant MPs used in the manufacturing of various fibres and plastics. In this study, we present a method for the determination of mass concentrations of PET MPs in the airborne inhalable fraction of fine particulate matter (PM2.5) using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Teflon and quartz fiber filters were tested for extraction efficiency in measuring the mass concentrations of airborne PET MPs. Teflon filters showed good recovery (80-120%) compared to quartz fiber filters. Using this method, a pilot study was carried out in Delhi, the national capital of India, and Mohali, a suburban city in the northwest Indo-Gangetic Plain (NWIGP), for the determination of mass concentrations of PET MPs present in airborne PM2.5. The observed maximum mass concentrations of PET MPs in airborne PM2.5 in Delhi and Mohali are 135.20 ng m-3 and 157.98 ng m-3, respectively. Ubiquitous airborne microplasctics are present in the inhalable fraction of ambient particulate matter. They may induce lesions in the respiratory system dependent on individual susceptibility and particle properties.

<p><strong> </strong></p> <p>Phthalic acid esters (PAEs) and polycyclic aromatic hydrocarbons (PAHs) are classified as priority pollutants by United States Environment Protection Agency (USEPA). Some of the PAEs and PAHs are considered as human carcinogens by International Agency for Research on Cancer (IARC). In the present study, an ultra-high performance liquid chromatography coupled to triple quadruple mass spectrometry (LC-MS QQQ) method was developed and validated for the simultaneous determination of PAEs and PAHs bound to ambient particulate matter. After the method validation, it was deployed for the quantification of PAEs and PAHs bound to PM<sub>2.5</sub> collected at a sub urban site in the Northwest Indo-Gangetic Plain. The targeted PAEs in this study are dimethyl phthalate (DMP), diethyl phthalate (DEP), benzyl butyl phthalate (BBP), di butyl phthalate (DBP), bis (2-ethyl hexyl) phthalate (DEHP), bis (2-ethylhexyl) adipate (DEHA), di-n-octyl phthalate (DNOP) and PAHs are benzo[a]anthracene (B[a]A), benzo[b]fluorenthene (B[b]F), benzo[k]fluorenthene (B[k]F), benzo[a]pyrene (B[a]P), dibenzo[ah]anthracene (D[ah]A), benzo[ghi]perylene (B[ghi]P), and indeno[1,2,3-cd]pyrene (IND). The measured concentrations of PAEs and PAHs are seasonally varied and the higher concentrations of PAEs were observed in summer and PAHs in winter. DEHP (17.94 ng m<sup>-3</sup>) and B[b]F (36.13 ng m<sup>-3</sup>) are the most abundant PAE and PAH measured at the sampling site. The concentrations of B[a]P (4.66 ng m<sup>-3</sup>; Group 1 carcinogen) exceeded the threshold limits (1 ng m<sup>-3</sup>) set by the National Ambient Air Quality Standards of India (NAAQS). Further, the incremental lifetime cancer risk due to inhalation exposure to DEHP and B[a]P were estimated for adults (0.3678 × 10<sup>-6</sup> and 1.40 × 10<sup>-5</sup> respectively) and children (0.8792 × 10<sup>-6</sup> and 3.272 × 10<sup>-5</sup> respectively). Also, the cancer risk associated with the inhalation exposure to B[a]P has exceeded the limits (1 ×10<sup>-3</sup>) set by USEPA at the measurement site.</p>

Presence of heavy metal ionic contaminants in water is a matter of global concern, owing to their disastrous impact on human health and environment. Cerium intercalated, ceria decorated titanate nanotubes (CCTNT) was developed for efficient adsorption of toxic heavy metal ions: Pb(II),Hg(II),As(V),As(III) and Cr(VI) from water. The phase and structure of the material was confirmed using XRD, FTIR and Raman analysis. The TEM images established the morphology. The chemical properties of the surface were confirmed using the EDS and XPS analysis. The surface area was measured using the BET method. The adsorptive properties of CCTNT were evaluated in the batch mode. It was observed that CCTNT, with wide pH window for adsorption of heavy metal ions, is applicable for both groundwater and wastewater remediation. In addition, it exhibited ultrafast adsorption of all five contaminants using a low adsorbent dosage. The Langmuir adsorption capacities of the adsorbent were calculated to be 66.76, 97.18, 189.59, 199.80, 288.23 mg/g respectively for the removal of Cr(VI),Pb(II),As(V), Hg(II) and As(III) from water. CCTNT is further suitable for highly efficient and simultaneous removal of all five heavy metal ions water. These attractive properties make CCTNT a superior material for adsorption of heavy metal ions from water.

Airborne particulate matter (PM) is a serious health threat when it is bound to hazardous pollutants like phthalic acid esters (PAEs) (endocrine disruptors) and polycyclic aromatic hydrocarbons (PAHs). In this study, an optimized method was developed and validated for the simultaneous screening and quantification of PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), bis (2-ethyl hexyl) phthalate (DEHP), bis(2-ethylhexyl) adipate (DEHA), di-n-octyl phthalate (DNOP)) and PAHs (benzo[a] anthracene (B[a]A), benzo[b]fluorenthene (B[b]F), benzo[k]fluorenthene (B[k]F), benzo[a]pyrene (B[a]P), dibenzo[ah]anthracene (D[ah]A), benzo[ghi]perylene (B[ghi]P), and indeno[1,2,3-cd]pyrene (IND)) bound to ambient PM2.5 using liquid chromatography coupled to electrospray ionization tandem mass spectrometer (LC-ESI-MS/MS). The developed method exhibited excellent linearity (r(2) > 0.99), precision error less than 10%, good recovery percentages (90%-120%, except for DMP asymptotic to 65%). After the validation, this method was deployed to investigate the seasonal variation and source identification of targeted compounds bound to ambient PM2.5 at a measurement site in the North West Indo-Gangetic Plain (NWIGP). In this study, the most abundant PAE and PAH are DEHP (17.94 ng m(- 3)) and B[b]F (36.13 ng m(-3)), respectively. Measured concentrations of B[a]P, Group 1 carcinogen (4.66 ng m(-3)) had exceeded the National Ambient Air Quality Standards, India (1 ng m(-3)). Diagnostic ratios (DRs) revealed that fossil fuel/diesel combustions are the major emission sources of PAHs in summer and monsoon while biomass/coal combustions in winter season at the sampling site. Further, incre-mental lifetime cancer risk (ILCR) for adults and children due to exposure to PM2.5 bound DEHP (adults: 0.3678 x 10(6) and children: 0.8792 x10(6)) and B[a]Peq (adults: 1.40 x10(5) and children: 3.272 x10(5)) were estimated. Estimated ILCR values for B[a]Peq exceeded the threshold value (1 x10(6)) set by USEPA. Findings in this study reveal that the health risk due to exposure to PAEs and PAHs bound to PM(2.5 )should be of concern.

Smoke influence in urban areas is relatively easy to detect at high concentrations, but more challenging to detect at low concentrations. For this reason, we have evaluated an approach using thermal desorption gas chromatography mass spectrometry (TD-GC-MS) to detect volatile organic compounds (VOCs) in particular oxygenated VOCs in urban areas. The goal of this work is to develop a method that can reliably quantify smoke tracers in an urban environment at relatively low cost and complexity. We present here the development and validation of a double-bedded thermal desorption tube with an auto sampler to collect continuous samples of VOCs. To evaluate the method performance, we have tested stability during storage, interferences (e.g., water and O3), and reproducibility for six VOCs, namely, acetonitrile, acetone, pentane, iso-pentane, benzene, and toluene. The results demonstrate that these can be quantified reproducibly with an error ≤ 20% between the collection and analysis with a storage time of up to 21 days. For acetone, similar results were obtained until day 14. Calibration experiments performed over a dynamic range of 10–150 ng loaded over thermal desorption tubes at different relative humidity showed excellent linearity (r2 ≥ 0.91). At this time, we are utilizing this method during the summer 2019 FIREX-AQ intensive experiment at the Boise ground site in Idaho. These results will be presented along with the quality control data.

Forest fire smoke influence in urban areas is relatively easy to detect at high concentrations but more challenging to detect at low concentrations. In this study, we present a simplified method that can reliably quantify smoke tracers in an urban environment at relatively low cost and complexity. For this purpose, we used dual-bed thermal desorption tubes with an auto-sampler to collect continuous samples of volatile organic compounds (VOCs). We present the validation and evaluation of this approach using thermal desorption gas chromatography mass spectrometry (TD-GC-MS) to detect VOCs at ppt to ppb concentrations. To evaluate the method, we tested stability during storage, interferences (e.g., water and O3), and reproducibility for reactive and short-lived VOCs such as acetonitrile (a specific chemical tracer for biomass burning), acetone, n-pentane, isopentane, benzene, toluene, furan, acrolein, 2-butanone, 2,3-butanedione, methacrolein, 2,5- dimethylfuran, and furfural. The results demonstrate that these VOCs can be quantified reproducibly with a total uncertainty of ≤30% between the collection and analysis, and with storage times of up to 15 days. Calibration experiments performed over a dynamic range of 10–150 ng loaded on to each thermal desorption tube at different relative humidity showed excellent linearity (r2 ≥ 0.90). We utilized this method during the summer 2019 National Oceanic and Atmospheric Administration (NOAA) Fire Influence on Regional to Global Environments Experiment–Air Quality (FIREX-AQ) intensive experiment at the Boise ground site. The results of this field study demonstrate the method’s applicability for ambient VOC speciation to identify forest fire smoke in urban areas.

Accurate emission inventories serve as critical inputs for air quality and climate models but are poorly constrained over India. We present a new municipal open waste burning emission inventory from India (OWBEII), at a resolution of 0.1° × 0.1°. Out of the 216 (201-232) Tg y-1 of waste produced in the year 2015, 68 (45-105) Tg y-1 was burned in the open. To determine emissions from waste burning, emission factors of 59 non-methane volatile organic compounds (NMVOCs), CH4, CO2, CO, and NO x were measured from garbage fires in rural and urban sites in India. The NMVOC emissions from open waste burning of 1.4-2 Tg y-1 increase India's total anthropogenic NMVOC budget by 8-12%, while BC emissions (40-110 Ggy-1) increase the total anthropogenic BC emissions by 8-12%. Open waste burning in India emits 3-7 Tg y-1 of CO and 58-130 Tg y-1 of CO2. Emissions increase the total anthropogenic CO and CO2 in the MIX-Asia inventory by 4-11% and 2-6%, respectively. Open waste burning may affect atmospheric OH reactivity and ozone formation rates downwind of urban centers through the emission of other highly reactive compounds such as acetaldehyde (20-320 Gg y-1), propene (50-170 Gg y-1), and ethene (50-190 Gg y-1) and is s source of carcinogenic benzene (30-280 Gg y-1).

We report the first ambient measurements of thirteen VOCs for investigations of emissions and air quality during fog and non-fog wintertime conditions at a tower site (28.57° N, 77.11° E, 220 m amsl) in the megacity of Delhi. Measurements of acetonitrile (biomass burning (BB) tracer), isoprene (biogenic emission tracer in daytime), toluene (a traffic exhaust tracer) and benzene (emitted from BB and traffic), together with soluble and reactive oxygenated VOCs such as methanol, acetone and acetaldehyde were performed during the winters of 2015-16 and 2016-17, using proton transfer reaction mass spectrometry. Remarkably, ambient VOC composition changes during fog were not governed by solubility. Acetaldehyde, toluene, sum of C8-aromatics (e.g. xylenes), sum of C9-aromatics (e.g. trimethyl benzenes) decreased by ≥30% (>95% confidence interval), whereas acetonitrile and benzene showed significant increases by 20% (>70% confidence interval), even after accounting for boundary layer dilution. During fog, the lower temperatures appeared to induce an emissions feedback from enhanced open BB within Delhi for warming, releasing both gaseous and aerosol pollutants with consequences for fog chemistry, sustenance and intensity. The potential feedback is important to consider for improving current emission parametrizations in models used for predicting air quality and fog in such atmospheric environments.

Carbon nanotubes (CNTs) are effective supports for nanometals and together they represent hybrids that combine the unique properties of both. A microwave-induced reaction was used to deposit nanopalladium on carboxylated and octadecylamine functionalized multiwall CNTs, which were used to carry out C–C coupling reactions in dimethylformamide (DMF) and toluene. These hybrids showed excellent catalytic activity with yield as high as 99.8%, while its enhancement with respect to commercially available Pd/C catalyst reached as high as 109%, and the reaction times were significantly lower. The polarity of the functionalized form was found to be a significant factor with the polar carboxylated CNT showing better activity in DMF while the relatively nonpolar octadecyl amine was better in toluene. The results suggest the possibility of tailor making functionalized CNTs when used as catalyst supports.

We studied the impact of the odd-even traffic rule (implemented in Delhi during 1-15 January 2016) on primary traffic emissions using measurements of 13 volatile organic compounds, carbon monoxide, carbon dioxide and methane at a strategic arterial road in Delhi (28.57 degrees N, 77.11 degrees E, 220 m amsl). Whole air samples (n = 27) were collected during the odd-even rule active (OA) and inactive (OI) days, and analysed at the IISER Mohali Atmospheric Chemistry Facility. The average mass concentration ranking and toluene/cbenzene ratio were characteristic of primary traffic emissions in both OA and OI samples, with the largest fraction comprising aromatic compounds (55-70% of total). Statistical tests showed likely increase (p <= 0.16; OA > OI) in median concentration of 13 out of 16 measured gases during morning and afternoon periods (sampling hours: 07 : 00-08 : 00 and 13 : 30-14 : 30 IST), whereas no significant difference was observed for evening samples (sampling hour: 19 : 00-20 : 00 IST). This suggests that many four-wheeler users chose to commute earlier, to beat the 8 : 00 AM-8 : 00 PM restrictions, and/or there was an increase in the number of exempted public transport vehicles. Thus, the odd-even rule did not result in anticipated traffic emission reductions in January 2016, likely due to the changed temporal and fleet emission behaviour triggered in response to the regulation.

Biomass fires impact global atmospheric chemistry. The reactive compounds emitted and formed due to biomass fires drive ozone and organic aerosol formation, affecting both air quality and climate. Direct hydroxyl (OH) Reactivity measurements quantify total gaseous reactive pollutant loadings and comparison with measured compounds yields the fraction of unmeasured compounds. Here, we quantified the magnitude and composition of total OH reactivity in the north-west Indo-Gangetic Plain. More than 120% increase occurred in total OH reactivity (28 s−1 to 64 s−1) and from no missing OH reactivity in the normal summertime air, the missing OH reactivity fraction increased to ~40 % in the post-harvest summertime period influenced by large scale biomass fires highlighting presence of unmeasured compounds. Increased missing OH reactivity between the two summertime periods was associated with increased concentrations of compounds with strong photochemical source such as acetaldehyde, acetone, hydroxyacetone, nitromethane, amides, isocyanic acid and primary emissions of acetonitrile and aromatic compounds. Currently even the most detailed state-of-the art atmospheric chemistry models exclude formamide, acetamide, nitromethane and isocyanic acid and their highly reactive precursor alkylamines (e.g. methylamine, ethylamine, dimethylamine, trimethylamine). For improved understanding of atmospheric chemistry-air quality-climate feedbacks in biomass-fire impacted atmospheric environments, future studies should include these compounds.

The objectives of the Winter Fog Experiment (WIFEX) over the Indo-Gangetic Plains of India are to develop better now-casting and forecasting of winter fog on various time-and spatial scales. Maximum fog occurrence over northwest India is about 48 days (visibility <1000 m) per year, and it occurs mostly during the December-February time-period. The physical and chemical characteristics of fog, meteorological factors responsible for its genesis, sustenance, intensity and dissipation are poorly understood. Improved understanding on the above aspects is required to develop reliable forecasting models and observational techniques for accurate prediction of the fog events. Extensive sets of comprehensive ground-based instrumentation were deployed at the Indira Gandhi International Airport, New Delhi. Major in situ sensors were deployed to measure surface micrometeorological conditions, radiation balance, turbulence, thermodynamical structure of the surface layer, fog droplet and aerosol microphysics, aerosol optical properties, and aerosol and fog water chemistry to describe the complete environmental conditions under which fog develops. In addition, Weather Forecasting Model coupled with chemistry is planned for fog prediction at a spatial resolution of 2 km. The present study provides an introductory overview of the winter fog field campaign with its unique instrumentation.

Ambient volatile organic compounds play a key role in atmospheric chemistry and air pollution studies due to their chemical reactivity and in several instances high toxicity. Quantification of ambient whole air samples which contain reactive and short-lived VOCs such as acetaldehyde, isoprene, dimethylsulphide and trimethyl-benzenes at ppt-ppb concentrations is analytically challenging and generally accomplished using online proton transfer reaction mass spectrometry. Deployment of online instrumentation is still not feasible in several regions of the world due to practical constraints (power, safety issues). Consequently there is paucity of VOC data in vast regions of the world. We present here, the validation and application of a novel method for ambient VOC speciation and emission factor studies using low cost (< 100 USD) whole air glass flask samplers and offline proton transfer reaction mass spectrometry that can help reduce the paucity of VOC datasets. Experiments to assess the stability during storage of thirteen VOCs, many of which are very reactive, showed that acetaldehyde, acetonitrile, acetone, dimethylsulphide, methyl vinyl and methyl ethyl ketones, benzene, xylenes, trimethyl-benzenes and monoterpenes can be quantified reproducibly within the respective precision error (e.g. 40% at 100ppt alpha-pinene and 3% at 13 ppb acetaldehyde) between collection and storage (at > 95% confidence), for samples analyzed within 10 days of collection. For toluene and isoprene, similar results were obtained until day 9 and 1, respectively and at confidence > 70%, over the 10 day period. A storage artefact was observed for methanol resulting in higher analytical uncertainty of upto 40%. We applied the method for measuring toluene/benzene emission ratios and aromatic VOCs in traffic plumes, and determining VOC emission factors (gVOC/kg fuel) from an agricultural wheat straw fire in India. The results of this study demonstrate that use of the low cost glass flask samplers described herein can significantly improve acquisition of spatially and temporally resolved datasets for atmospheric chemistry and air quality studies at sites where online deployment of instruments remains unfeasible.

Angstrom exponent measurements of equivalent black carbon (BCeq) have recently been introduced as a novel tool to apportion the contribution of biomass burning sources to the BCeq mass. The BCeq is the mass of ideal BC with defined optical properties that, upon deposition on the aethalometer filter tape, would cause equal optical attenuation of light to the actual PM2.5 aerosol deposited. The BCeq mass hence is identical to the mass of the total light-absorbing carbon deposited on the filter tape. Here, we use simultaneously collected data from a seven-wavelength aethalometer and a high-sensitivity proton-transfer reaction mass spectrometer installed at a suburban site in Mohali (Punjab), India, to identify a number of biomass combustion plumes. The identified types of biomass combustion include paddy- and wheat-residue burning, leaf litter, and garbage burning. Traffic plumes were selected for comparison. We find that the combustion efficiency, rather than the fuel used, determines αabs, and consequently, the αabs can be ∼1 for flaming biomass combustion and >1 for older vehicles that operate with poorly optimized engines. Thus, the absorption angstrom exponent is not representative of the fuel used and, therefore, cannot be used as a generic tracer to constrain source contributions.

In the north west Indo-Gangetic Plain (N.W.IGP), large scale post-harvest paddy residue fires occur every year during the months of October–November. This anthropogenic perturbation causes contamination of the atmospheric environment with adverse impacts on regional air quality posing health risks for the population exposed to high concentrations of carcinogens such as benzene and toxic VOCs such as isocyanic acid. These gases and carbon monoxide are known to be emitted from biomass fires along with acetonitrile. Yet no long-term in-situ measurements quantifying the impact of this activity have been carried out in the N.W. IGP. Using high quality continuous online in-situ measurements of these gases at a strategic downwind site over a three year period from 2012 to 2014, we demonstrate the strong impact of this anthropogenic emission activity on ambient concentrations of these gases. In contrast to the pre-paddy harvest period, excellent correlation of benzenoids, isocyanic acid and CO with acetonitrile (a biomass burning chemical tracer); (r≥0.82) and distinct VOC/acetonitrile emission ratios were observed for the post-paddy harvest period which was also characterized by high ambient concentrations of these species. The average concentrations of acetonitrile (1.62±0.18ppb), benzene (2.51±0.28ppb), toluene (3.72±0.41ppb), C8-aromatics (2.88±0.30ppb), C9-aromatics (1.55±0.19ppb) and CO (552±113ppb) in the post-paddy harvest periods were about 1.5 times higher than the annual average concentrations. For isocyanic acid, a compound with both primary and secondary sources, the concentration in the post-paddy harvest period was 0.97±0.17ppb. The annual average concentrations of benzene, a class A carcinogen, exceeded the annual exposure limit of 1.6ppb at NTP mandated by the National Ambient Air Quality Standard of India (NAAQS). We show that mitigating the post-harvest paddy residue fires can lower the annual average concentration of benzene and ensure compliance with the NAAQS. Calculations of excessive lifetime cancer risk due to benzene amount to 25 and 10 per million inhabitants for children and adults, respectively, exceeding the USEPA threshold of 1 per million inhabitants. Annual exposure to isocyanic acid was close to 1ppb, the concentration considered to be sufficient to enhance risks for cardiovascular diseases and cataracts. This study makes a case for urgent mitigation of post-harvest paddy residue fires as the unknown synergistic effect of multi-pollutant exposure due to emissions from this anthropogenic source may be posing grave health risks to the population of the N.W. IGP.

Many sites in the densely populated Indo-Gangetic Plain (IGP) frequently exceed the national ambient air quality standard (NAAQS) of 100 μg m−3 for 24 h average PM10 and 60 μg m−3 for 24 h average PM2.5 mass loadings, exposing residents to hazardous levels of particulate matter (PM) throughout the year. We quantify the contribution of long-range transport to elevated PM levels and the number of exceedance events through a back-trajectory climatology analysis of air masses arriving at the IISER Mohali Atmospheric Chemistry facility (30.667° N, 76.729° E; 310 m a.m.s.l.) for the period August 2011–June 2013. Air masses arriving at the receptor site were classified into six clusters, which represent synoptic-scale air-mass transport patterns. Long-range transport from the west leads to significant enhancements in the average fine- and coarse-mode PM mass loadings during all seasons. The contribution of long-range transport from the west and south-west (source regions: Arabia, Thar Desert, Middle East and Afghanistan) to coarse-mode PM varied between 9 and 57 % of the total PM10–2.5 mass. Local pollution episodes (wind speed < 1 m s−1) contributed to enhanced PM2.5 mass loadings during both the winter and summer seasons and to enhanced coarse-mode PM only during the winter season. South-easterly air masses (source region: eastern IGP) were associated with significantly lower fine- and coarse-mode PM mass loadings during all seasons. The fraction of days in each season during which the PM mass loadings exceeded the national ambient air quality standard was controlled by long-range transport to a much lesser degree. For the local cluster, which represents regional air masses (source region: NW-IGP), the fraction of days during which the national ambient air quality standard (NAAQS) of 60 μg m−3 for 24 h average PM2.5 was exceeded varied between 36 % of the days associated with this synoptic-scale transport during the monsoon, and 95 % during post-monsoon and winter seasons; the fraction of days during which the NAAQS of 100 μg m−3 for the 24 h average PM10 was exceeded, varied between 48 % during the monsoon and 98 % during the post-monsoon season. Long-range transport was responsible for both, bringing air masses with a significantly lower fraction of exceedance days from the eastern IGP and air masses with a moderate increase in the fraction of exceedance days from the west (source regions: Arabia, Thar Desert, Middle East and Afghanistan). In order to bring PM mass loadings into compliance with the NAAQS and to reduce the number of exceedance days, mitigation of regional combustion sources in the NW-IGP needs to be given highest priority.