Aerosol samples were collected during winter and summer season in Agra, India. The mass concentrations of TSP ranged from 206.1–380.5 μg/m3 with the average concentration of 306.1 μg/m3. The seasonal average concentrations of TSP were 273.4 ± 85.5 μg/m3 in summer and 338.6 ± 89.1 μg/m3 in winter. The high levels of mass concentration during winter may be attributed to different emission sources and meteorological conditions at this time of year. The morphology, size and elemental composition of individual aerosol particles were examined using a scanning electron microscope (SEM) coupled with an energy dispersive X-ray system (EDX). The particles analyzed in the study were mostly of large size, with equivalent diameters ranging from 2 to 70 μm. Based on the results of the elemental composition and morphology, 3,500 particles were classified into three groups: biogenic aerosol, geogenic and anthropogenic particles. Different groups of particles have varied morphologies. The soil related aerosols were dominant during the sampling period, showing that crustal materials are the primary contributor to airborne particles at this site. A distinct seasonal variation in the amount of carbonaceous particles was observed. The significant increase in mineral dust particles found during summer may be attributed to the contribution of dust storms, which is also supported by a trajectory cluster analysis.

The presence of organonitrate and organosulfate was found at Mahabaleshwar, a high altitude site, during the pre-monsoon season of 2016. A Time of Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) was used to measure the organic and inorganic components of non-refractory particulate matter (NR-PM1) aerosol. Positive Matrix Factorization (PMF) was performed on the (i) organics mass spectra of the aerosol (PMFOA), (ii) organics mass spectra merged with inorganics (PMFOA+IOA) and (iii) integrated mass spectra of organics with NO+ and NO2+ ions (PMFOA+NOx) to derive the chemical information on organonitrate and organosulfate. The results of PMFOA were used as a reference for validating the factors obtained through the PMFOA+IOA and PMFOA+NOx results. The analysis of PMFOA resolved four PMF factors: hydrocarbon-like OA (HOA); biomass burning OA (BBOA); oxygenated OA-1 (OOA-1) and OOA-2. The analysis of PMFOA+IOA identified two additional inorganic factors: sulfate organic aerosol (OA) and nitrate OA. Sulfate OA and nitrate OA contributed 36% and 6%, respectively, to the total aerosol mass. Although both originated as secondary organic aerosol, they displayed different diurnal profiles. The results of PMFOA+NOx were used for the quantification and apportionment of nitrate aerosol in two forms, organic nitrate and inorganic nitrate, which contributed 38% and 62%, respectively, to the total nitrate aerosol mass. The diurnal variation in organic nitrate highlights photochemical oxidation and nocturnal oxidation by the nitrate radical as the two major sources. This source apportionment study using a combined (organic and inorganic) dataset provides new source factors and improves our understanding about the sources and chemical nature of submicron aerosols in the atmosphere. However, uncertainties in the quantification of organosulfate remain a limitation.

PM2.5 samples were collected at traffic, rural and campus sites in Agra during Nov 2010 to Feb 2011 and characterized for carbonaceous aerosols. The average mass concentrations of PM2.5 were 308.3 ± 51.8 μg/m3, 91.2 ± 17.3 μg/m3 and 140.8 ± 22.3 μg/m3 at the traffic, rural and campus sites, respectively. The 24-h mass concentrations of PM2.5 were significantly higher than the limit of 60 μg/m3 prescribed in the National Ambient Air Quality Standards (Indian NAAQS) and 25 μg/m3 of those of the WHO (World Health Organization). The average concentrations of OC (organic carbon) and EC (elemental carbon) were 86.1 ± 5.2 and 19.4 ± 2.4 at the traffic site, 30.3 ± 12.9 and 4.0 ± 1.5 at the rural site and 44.5 ± 18.5 μg/m3 5.0 ± 1.4 μg/m3 at the campus one. The contributions of TCA (Total Carbonaceous Aerosol) at the traffic, campus and rural sites were found to be 52, 54 and 58% of PM2.5 mass, respectively. A significant correlation was observed between water soluble K+ and OC at the rural (R2 = 0.63) and campus (R2 = 0.53) sites compared to the traffic one (R2 = 0.35). This may be attributed to increased biomass burning emissions at the rural and campus sites. The concentrations of SOC (Secondary Organic Carbon) were estimated based on the minimum OC/EC ratio, and were found to be 15.3 ± 6.3, 8.2 ± 5.8 and 28.8 ± 15.8 μg/m3, accounting for 18, 24.7 and 60.7% of total OC at the traffic, rural and campus sites, respectively. The surface morphology of the particles was analyzed by scanning electron microscopy and energy- dispersive X-ray spectroscopy (SEM/EDX). The results indicated branched chain-like aggregates of carbon bearing spheres at the traffic and rural sites, while at the campus site carbon-rich and minerogenic (mineral dust) particles were the dominant ones.

This study presents a comprehensive set of 2 years of data (January 2009–December 2010) on the chemical composition of ambient aerosols collected at a university campus in Agra, which lies on the Indo-Gangetic Plain (IGP). The average concentration of total suspended particles (TSP) was 213.2 ± 91.4 μg/m3. The most abundant ions in TSP were Ca2+, NO3− and SO42−, which contributed about 3.2

Black carbon (BC) mass concentration observations were carried out using Aethalometer (AE-33) at an urban site Pune and at a high altitude forest site Mahabaleshwar during April 2018 to February 2019. The annual averaged BC mass concentration over Pune was observed to be ~2.8 times higher than Mahabaleshwar. Daily, seasonal and diurnal variations of BC over these two different environments were compared. The effect of meteorological parameters on the BC was also evaluated. Planetary boundary layer (PBL) plays a pivotal role in diluting the atmospheric pollutant BC during daytime at Pune, whereas, contribution of combustion sources mostly dominated over PBL dilution at Mahabaleshwar. Higher wind speed regime also tends to dilute the atmosphere whereas higher BC concentration was observed during RH condition depicting the significance of low dispersion under these conditions. The contribution of different sources namely biomass burning (BB) and fossil fuel (FF), wavelength dependent source apportionment study was also evaluated. Traffic emission contributed 72%–75% of the BC loading at Mahabaleshwar, whereas at Pune it was estimated to be 82%–94% during all the seasons indicating BB contributed more at Mahabaleshwar. Cluster analysis and concentration weighted trajectory (CWT) analysis were also performed to visualize the importance of regional transport for both the locations. The study confers the significance of regional transport in addition to local emissions over both the sites.

The effect of relative humidity and temperature on the submicron aerosol variability and its ageing process was studied over a high altitude site, Mahabaleshwar in south-west India. The mass composition of non-refractory particulate matter of 1 mu m (NR-PM1) size was obtained using Time of Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) along with the measurements on a few trace gases during winter (December 2017-February 2018) and summer season (20th March - 5th May 2018). Sulfate exhibited strong dependence on the relative humidity (RH) as its mass fraction increased with the increase in RH. The Sulfate oxidation ratio (SOR) calculated during summer season also showed an increasing trend with RH indicating the influence of aqueous phase oxidation on sulfate fraction. On the other hand, OOA showed remarkable enhancement in its mass fraction with the increase in temperature along with the corresponding increase in f(44) and tropospheric ozone. OOA, ozone and f(44) ratio increased 14-34%, 8-26% and 25-43% respectively with the increase in temperature from 18 to 30 degrees C. This is indicative of the dominance of photochemical ageing processes during high temperature conditions. The extent of photochemical ageing was found to be higher during summer season (mean temperature similar to 25.4 +/- 2.6 degrees C) as compared to winter season (mean temperature similar to 20.5 +/- 2.6 degrees C). The nitrate diurnal was majorly governed by gas to particle partitioning process during winter season, whereas the summertime nitrate diurnal was influenced primarily by its formation rate. The non parametric wind regression analysis revealed that the mass concentration during winter was majorly contributed by distant sources from north east direction while during summer the local sources were more dominant. (C) 2020 Elsevier Ltd. All rights reserved.

This study presents the characteristics of black carbon aerosol (BC) over a high-altitude site, Mahabaleshwar during the monsoon season. The mass concentration of BC exhibits a morning peak and a daytime build-up with a mean mass concentration of 303 ± 142 ng m−3. The simultaneous measurements of aerosol particle number concentration (PNC), cloud condensation nuclei concentration (CCN), and non-refractory particulate matter less than 1 μm size (NR-PM1) were also made by using a Wide-Range Aerosol Spectrometer (WRAS), CCN counter and Aerosol Chemical Speciation Monitor (ACSM) respectively. The source apportionment using wavelength-dependent light absorption model reveals the dominance by wood burning sources during morning hours and traffic sources during remaining hours of the day. The diurnal variation of PNC follows the variability of BC mass concentration. However, CCN concentrations were high during the morning hours coinciding with the increased fractional contribution of organics. The k-means clustering coupled with fuzzy algorithm highlights the effect of different sources on aerosol size distribution. On the basis of size distribution curve, the 3 clusters were attributed to wood burning (mean diameter range: 50–100 nm), traffic (30–50 nm), and background aerosols (65–95 nm). The combined analysis of k-means clustering, fractional contribution of organics, and kappa variation suggests that higher CCN concentration during morning is mainly attributed to probable emission of the water-soluble organic/inorganic compounds from wood burning.

This manuscript reports the seasonal variation of chemically speciated sub-micron aerosol particles (diameter < 1 mu m). An Aerosol Chemical Speciation Monitor (ACSM) was used to measure the mass concentration of non-refractory particulate matter (NR-PM1) at a high-altitude site in the Western Ghats, India from March 2016 to February 2017. The mass concentration of NR-PM1 averaged at 7.5 +/- 6.5 mu gm(-3), with major contributions from organics (59%) and sulfates (23%). Positive matrix factorization (PMF) was applied on the measured mass spectra of organic aerosol (OA) to derive the sources distinctive of each season (Summer, Monsoon, Post-Monsoon and Winter). The four OA factors (two primary OA and two oxygenated OA) resolved during summer, post-monsoon and winter season. However, only one oxygenated factor resolved during monsoon and contributed only 20% to the total OA. The factors associated with primary emissions dominated during the monsoon, whereas factors related to secondary formation dominated in other three seasons. During summer, an isoprene derived SOA - IEPOX-OA (isoprene-epoxydiol OA) contributed similar to 17% to the total OA. Cluster and concentration weighted trajectory (CWT) analyses were performed to identify the possible source regions of NR-PM1 mass concentration observed at the receptor site. The analysis identifies Central India as the potential source region of transported aerosol during post-monsoon and winter season. Our study suggests that contributions from both local sources and regional transport are important in governing mass concentration of PM1 over Mahabaleshwar.

Abstract. There is a lack of characterization of the aerosol population in Western India, how it is affected by meteorological parameters, and new particle formation and the influence on cloud condensation nuclei (CCN). For this reason, measurements of particle number size distribution, aerosol chemical composition, meteorology and cloud condensation nuclei number concentration were monitored at High Altitude Cloud Physics Laboratory (HACPL) in Mahabaleshwar mountain town in Western India between November 2016 and February 2017. Most air masses in this period originated from the Indian continent to the north-east of HACPL. New particle formation (NPF) events were observed on 47 days and mainly associated with these north-easterly air masses and high SO2 emissions and biomass burning activities, while weaker or non-NPF days were associated with westerly air masses and relatively higher influence of local air pollution. The growth of newly formed particles enhanced the mass concentration of secondary organic and inorganic species of aerosol particles. The mean growth rate, formation rate, condensation sink and coagulation loss for the 13 strongest events was found to be 2.58 ± 0.38 nm h−1, 2.82 ± 1.37 cm−3 s−1, 22.3 ± 2.87 * 10-3 s−1 and 1.62 ± 1.04 cm−3 s−1 respectively. A closer examination of 5 events showed that low relative humidity and solar radiation favoured new particle formation. These NPF events lead to a significant increase in CCN concentration (mean ~ 53 ± 36 %). The NanoMap method revealed that NPF took place up to several hundred kilometers upwind and to the north-east of HACPL.

The cloud condensation nuclei (CCN) closure study was performed to exemplify the effect of aerosol chemical composition on the CCN activity of aerosols at Mahabaleshwar, a high altitude background site in the Western Ghats, India. For this, collocated aerosol, CCN, Elemental Carbon (EC), Organic Carbon (OC), sub-micron aerosol chemical speciation for the period from 3rd June to 19th June 2015 was used. The chemical composition of non-refractory particulate matter (<1 mu m) as measured by Time of Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) was dominated by organics with average concentration of 3.81 +/- 1.6, 0.32 +/- 0.06, 0.15 +/- 0.02, 0.13 +/- 0.03 and 0.95 +/- 0.12 mu g m(-3) for organics, ammonium, chloride, nitrate and sulphate, respectively. The PM1 number concentration as obtained by Wide Range Aerosol Spectrometer (WRAS) varied from 750 to 6480 cm(-3). The average mass concentration of elemental carbon (EC) as measured by OC-EC analyzer was 1.16 +/- 0.4 mu g m(-3). The average CCN concentrations obtained from CCN counter (CCNC) at five super-saturations (SS's) was 118 +/- 58 cm(-3) (0.1% SS), 873 +/- 448 cm(-3) (0.31% SS), 1308 +/- 603 cm(-3) (0.52% SS), 1610 +/- 838 cm(-3) (0.73% SS) and 1826 +/- 985 cm(-3) (0.94% SS). The CCN concentrations were predicted using Kohler theory on the basis of measured aerosol particle number size distribution, size independent NR-PM1 chemical composition and calculated hygroscopicity. The CCN closure study was evaluated for 3 scenarios, B-I (all soluble inorganics), B-IO (all soluble organics and inorganics) and B-IOOA (all soluble inorganic and soluble oxygenated organic aerosol, OOA). OOA component was derived from the positive matrix factorization (PMF) analysis of organic aerosol mass spectra. Considering the bulk composition as internal mixture, CCN closure study was underestimated by 16-39% for B-I and overestimated by 47-62% for B-IO. The CCN closure result was appreciably improved for B-IOOA where the knowledge of OOA fraction was introduced and uncertainty reduced to within 8-10%. (C) 2017 Elsevier Ltd. All rights reserved.

A continuous measurement of organic carbon (OC) and elemental carbon (EC) in PM2.5 and TSP was carried out at a suburban site of North central region of India. PM2.5 and TSP samples were collected from May 2010 to April 2011 and were analyzed for OC and EC using thermal optical transmittance (TOT) protocol. The results showed that the annual average concentrations of PM2.5 and TSP were 79.7±40.5 and 247.5±128.3μg/m3, respectively. In PM2.5, OC and EC concentrations were 22.8±17.1 and 3.4±1.2μg/m3 while in TSP the concentrations were 42.1±22.6 and 6.1±3.2μg/m3 respectively. Both OC and EC exhibited a clear seasonal pattern with highest concentration observed in winter followed by summer and monsoon which may be due to the combined effect of changes in emission rates and different meteorology in various seasons. Diurnal variation indicated higher concentration during night in all seasons. TCA (Total carbonaceous aerosol) accounted for an averaged 50.3% of PM2.5 mass and 29.6% of TSP mass. The annual average OC/EC ratio was 6.6 which is similar ratio for biomass burning emissions. The SOC concentrations were found to be higher during winter season in both PM2.5 and TSP. To study the influence of natural singular events in aerosol composition, three types of episodic events have been identified. The SEM/EDX analysis revealed the dominance of carbonaceous particles during winter season which is also supported by back trajectory analysis which shows that the origin of these particles is mainly anthropogenic in nature.

Total suspended particulate (TSP) samples were collected during dust, haze, and two festival events (Holi and Diwali) from February 2009 to June 2010. Pollutant gases (NO2, SO2, and O3) along with the meteorological parameters were also measured during the four pollution events at Agra. The concentration of pollutant gases decreases during dust events (DEs), but the levels of the gases increase during other pollution events indicating the impact of anthropogenic emissions. The mass concentrations were about two times higher during pollution events than normal days (NDs). High TSP concentrations during Holi and Diwali events may be attributed to anthropogenic activities while increased combustion sources in addition to stagnant meteorological conditions contributed to high TSP mass during haze events. On the other hand, long-range transport of atmospheric particles plays a major role during DEs. In the dust samples, Ca2+, Cl−, NO3 −, and SO4 2− were the most abundant ions and Ca2+ alone accounted for 22 % of the total ionic mass, while during haze event, the concentrations of secondary aerosols species, viz., NO3 −, SO4 2−, and NH4 +, were 3.6, 3.3, and 5.1 times higher than the normal days. During Diwali, SO4 2− concentration (17.8 μg m−3) was highest followed by NO3 −, K+, and Cl− while the Holi samples were strongly enriched with Cl− and K+ which together made up 32.7 % of the total water-soluble ions. The ion balances indicate that the haze samples were acidic. On the other hand, Holi, Diwali, and DE samples were enriched with cations. The carbonaceous aerosol shows strong variation with the highest concentration during Holi followed by haze, Diwali, DEs, and NDs. However, the secondary organic carbon concentration follows the order haze > DEs > Diwali > Holi > NDs. The scanning electron microscope/EDX results indicate that KCl and carbon-rich particles were more dominant during Holi and haze events while DE samples were enriched with particles of crustal origin.

Ozone is currently the most important air pollutant that negatively affects growth and yield of agricultural crops in most parts of the world, and wheat is arguably the most important food crop in the Northern India. The higher ozone concentration in different regions is posing threat to food production. Measurement of surface ozone was made during the growing season (January-March 2011) of wheat crop at Agra. The daytime maximum was found to vary from 62-72 ppb and minima varied from 20-23 ppb. The effect of ozone on crop yield has been examined using exposure indices AOT40 and SUM06. The calculated AOT40 (2562 ppbh) and SUM06 (7470 ppbh) were found below the critical levels thereby indicating that wheat crop grown in Agra is safe from the threats of existing surface ozone levels.

Diesel fuel and diesel exhaust are known to be highly mutagenic partly because of the presence of polyaromatic hydrocarbons (PAHs) and their derivatives. The present study investigated the PAHs content in the diesel fuel fed to a diesel generator and also in the gas and particulate phase of generator emissions. Mutagenicity of the exhaust was also determined. Exhaust emissions were collected by a stack sampler: gas phase on XAD-2 resin while particulate phase on glass fibre thimble. PAHs were characterized by a gas chromatograph by using a flame ionization detector. The low molecular weight PAHs dominated in the fuel, whereas the high molecular weight PAHs dominated in the exhaust with a greater emission factor in the particulate phase. The results reveal the pyrosynthesis of high molecular weight PAHs during the combustion process. Emissions also increased with increase in load. Extract of exhaust emissions were positive in both Salmonella typhimurium tester strains TA 98 and TA 100 without metabolic activation, suggesting the presence of direct mutagens that can cause both frame-shift and base-pair mutation. The mutagenic response was greater for TA 100 than TA 98, suggesting greater activity for base-pair mutagenicity than frame-shift mutagenicity. Mutagenic activity increased with the increase in load. (C) 2012 American Society of Civil Engineers.

Fine airborne particulate matter and bound chemical compounds are potential mediators of adverse health effects. In this study, PM2.5 and PM10 were characterized for bound polycyclic aromatic hydrocarbons (PAHs) and the mutagenic potential of extracts was assessed. PM2.5 and PM10 samples were collected on glass fiber filters at Agra from July to December 2010 using a fine particulate sampler (Envirotech, APM 550). The content of PAH was analyzed by gas chromatography and the extract were tested for mutagenicity by the Ames test without using S-9. Individual PAH concentration varied from 13-172 ng m(-3) with concentration for Chrysene and a dominance of low molecular weight compounds. Both PM and PAH concentrations were higher in the winter and were negatively correlated with temperature and wind speed. Diagnostic ratio analysis indicated contributions from vehicular exhaust and emissions from combustion of domestic fuel like coal and wood. Mutagenicity assays indicated the presence of mutagens capable of causing base pair and frame shift mutagenicity; however, within the range of tested concentrations no significant toxic effects were detected.

Measurements of surface ozone (O 3 ), nitric oxide (NO), nitrogen dioxide (NO 2 ), oxides of nitrogen (NO x =NO+NO 2 ) and meteorological parameters have been made at Agra (North Central India, 27°10’N, 78°05’E) in post monsoon and winter season. The diurnal variation in O 3 concentration shows daytime in situ photochemical production with diurnal maximum in noon hours ranging from 51 to 54 ppb in post monsoon and from 76 to 82 ppb in winter, while minimum (16–24 ppb) during nighttime and early morning hours. Average 8-h O 3 concentration varied from 12.4 to 83.9 ppb. The relationship between meteorological parameters (solar radiation intensity, temperature, relative humidity, wind speed and wind direction) and surface O 3 variability was studied using principal component analysis (PCA), multiple linear regression (MLR) and correlation analysis (CA). PCA and MLR of daily mean O 3 concentrations on meteorological parameters explain up to 80 % of day to day ozone variability. Correlation with meteorology is strongly emphasized on days having strong solar radiation intensity and longer sunshine time.

The present study reports one year data of organic carbon (OC) and elemental carbon (EC) concentrations in total suspended particulates (TSP) at a suburban site. TSP concentrations varied from 80.0 to 396.2μgm−3 with an annual average of 216.3±80.7μgm−3. OC ranged from 2.5 to 91.0μgm−3 with an annual average of 25.4±19.8μgm−3 while EC ranged from 0.3 to 15.2μgm−3 with an annual average concentration of 3.3±3.0μgm−3. OC and EC contributed about 11.8% and 1.5% of TSP. Annual average of the OC/EC ratio was 8.7±6.5. Seasonally, OC and EC follow the trend: winter>post monsoon>summer>monsoon. High correlations were observed between OC and EC with correlation coefficient (r) ranging from 0.92 to 0.97 in the four seasons. OC concentrations in summer, winter and post monsoon were approximately three times higher than in monsoon. Total carbonaceous aerosols (TCA) accounted for 20.8±17.2% of TSP. In winter, percent contribution of TCA to TSP was high (33.2±24.4) as compared to other seasons. K+/EC and K+/OC ratios indicate biomass burning to be a source of carbonaceous aerosol at this site. Secondary organic carbon (SOC) fraction, estimated using the EC tracer method, was calculated to be 49.0 to 55.0% of OC at Dayalbagh. In winter, primary organic carbon (POC) concentration was almost twice the SOC concentration.

In the present study, the concentrations of three volatile organic compounds (VOCs), namely, acronym for benzene, toluene, and xylenes (BTX) were assessed because of their role in the tropospheric chemistry. Two representative sites, a roadside and a petrol pump, were chosen for sample collection. VOCs were collected using SKC-activated charcoal tubes and SKC personal sampler and characterized by gas chromatograph using flame ionization detector. Among BTX, benzene had the highest concentration. At the roadside, mean concentration of benzene, toluene, o-,m-xylene, and p-xylene were 14.7 ± 2.4 μ gm −3 , 8.1 ± 1.2 μ gm −3 , 2.1 ± 0.8 μ gm −3 , and 5.1 ± 1.2 μ gm −3 , respectively. At the petrol pump, the mean concentrations of benzene, toluene, o-,m-xylene and p-xylene were 19.5 ± 3.7 μ gm −3 , 12.9 ± 1.1 μ gm −3 , 3.6 ± 0.5 μ gm −3 and 11.1 ± 1.5 μ gm −3 , respectively, and were numerically higher by a fraction of 2. Monthly variation of BTX showed maximum concentration in winter. Inter-species ratios and inter-species correlation indicated traffic as the major source of BTX. Extracts of samples were positive in both Salmonella typhimurium tester strains TA98 and TA100 without metabolic activation suggesting the presence of direct mutagens in ambient air that can cause both frame-shift and base-pair mutation. The mutagenic response was greater for TA100 than TA98 suggesting greater activity for base-pair mutagenicity than frame-shift mutagenicity and was found to be statistically significant.

A systematic analysis of surface ozone and its precursor (NO and NO2) was carried out at Dayalbagh, a suburban site using continuous online O3 and NOx analyzers from November 2008 to October 2009. Diurnal patterns in ozone concentration show daytime maxima (50–60ppbv) around 1200–1400h due to in situ photochemical production and minimum (7–10ppbv) during night time. O3 followed inverse relationship with its precursor, NO2. Seasonal variations in ozone concentration show pronounced maxima in the summer and winter seasons and minima in monsoon and postmonsoon seasons. The high ozone episode days during peak summer were associated with meteorological parameters such as sunny and warm weather, and low relative humidity. The seasonal average concentration in summer ranged between 42 and 45ppbv, between 28 and 30ppbv in winters, and between 20 and 23ppbv in postmonsoon whereas, it is found to be 9–16ppbv in the monsoon season. The rate of formation as evaluated from 0800 to 1000h was observed to be maximum in the month of April (4.4ppbv/h) and minimum in the month of August (0.4ppbv/h). On the other hand, the rate of destruction of O3 from 1700 to 1900h was found to be maximum in February (−4.2ppbv/h) and minimum in the month of August (−0.3ppbv/h). On the basis of Environmental Protection Agency classification, 8-h ozone concentration remained good for 90% of days, moderate for 8.1% of the days, unhealthy for sensitive groups for 1.9% of the days during the study period.