Atmospheric chemistry and cancer risk assessment of Polycyclic Aromatic Hydrocarbons (PAHs) and Nitro-PAHs over a semi-arid site in the Indo-Gangetic plain.

Polycyclic Aromatic Hydrocarbons (PAHs) and Nitro-PAHs were collected over a year at a traffic dominated site in Agra, to determine the dominant partitioning mechanism. During the entire sampling period, total PAHs and Nitro-PAHs were 3465 ± 3802 and 26.1 ± 25.9 ng m-3 respectively. The gas-particle partitioning behavior of PAHs was studied by applying the Pankow model, Absorption model, and Dual model. Amongst all the partitioning models, the Dual model fits well and indicates that the partitioning of PAHs at the traffic site in Agra depends on both the physical adsorption of PAHs on the Total Suspended Particulate (TSP) surface and absorption of PAHs into the organic layer present on the TSP surface. Pankow model indicates that PAHs are emitted from the source close to the sampling point and due to this PAHs do not get enough time to get partitioned in between both the phases. Incremental lifetime Cancer Risk (ILCR) shows that adults and children are more prone to cancer risk in comparison to infants for both PAHs and Nitro-PAHs. Cancer risk by inhalation was minimum in comparison to both ingestion and dermal exposure. Nitro-PAHs in the particulate phase were high enough to exceed the minimum permissible limit (10-6) of causing cancer by ingestion and dermal exposure.

Mutagenic and Cancer Risk Estimation of Particulate Bound Polycyclic Aromatic Hydrocarbons from the Emission of Different Biomass Fuels.

Smoke samples from combustion of different biomass fuels were analyzed for the particulate bound Polycyclic Aromatic Hydrocarbons (PAHs) due to their carcinogenic and mutagenic nature. Out of 16 priority PAHs, 11 PAHs were detected in the emission of fuels, while the remaining 5 PAHs (chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-cd]pyrene, and benzo[g,h,i]perylene) were below the detection limit. The highest emission factor for the sum of all the PAHs was found for coal (353.08 mg kg-1), charcoal (27.28 mg kg-1), and the various wood types. Emission rates of total PAHs ranged from 0.37 to 5.15 mg h-1 with the highest value for bituminous coal (5.15 mg h-1) and lowest for Polyalthia longifolia (0.37 mg h-1). A cancer risk assessment was done for infants, children, and adults using the incremental lifetime cancer risk (ILCR) model via ingestion, inhalation, and dermal contact pathway. The ILCR values ranged from 10-11 to 10-6, and a higher cancer risk was observed for children and adults in comparison to infants. PAH concentrations emitted from biomass emissions shows a direct correlation with mutagenesis to humans, indicating a higher potential for the frameshift mutation as compared to base-pair mutation for dung, bituminous coal, charcoal, Dalbergia sissoo, Psidium guajava, Ziziphus mauritana, Polyalthia longifolia, and Ailanthus trithesa.

Characterization of ambient PM1 at a suburban site of Agra: chemical composition, sources, health risk and potential cytotoxicity.

The present study was conducted at a University campus of Agra to determine concentrations of crustal and trace elements in submicron mode (PM1) particles to reveal sources and detrimental effects of PM1-bound metals (Cr, Cd, Mn, Zn, As, Co, Pb, Cu and Ni) in samples collected in the foggy (1 December 2016-17 January 2017) and non-foggy periods (1 April 2016-30 June 2016). Samples were collected twice a week on preweighed quartz fibre filters (QM-A 47 mm) for 24 h using Envirotech APM 577 (flow rate 10 l min-1). Mass concentration of PM1 was 135.0 ± 28.2 and 54.0 ± 18.5 µg/m3 during foggy and non-foggy period, respectively; crustal and trace elements were 13 and 4% during foggy and 11 and 3% in the non-foggy period. Source identification by PCA (principal component analysis) suggested that biomass burning and coal combustion was the prominent sources in foggy period followed by resuspended soil dust, industrial and vehicular emission, whereas in non-foggy period resuspended soil dust was dominant followed by biomass burning and coal combustion, industrial and vehicular emissions. In both episodes, Mn has the highest Hq (hazard quotient) value and Cr has the highest IlcR (Incremental Lifetime Cancer Risk) value for both adults and children. In vitro cytotoxicity impact on macrophage (J774) cells was also tested using MTT assay which revealed decreasing cell viability with increasing particle mass.

Chemical fractionation of heavy metals in fine particulate matter and their health risk assessment through inhalation exposure pathway.

Samples of PM2.5 were collected from an urban area close to a national highway in Agra, India and sequentially extracted into four different fractions: water soluble (F1), reducible (F2), oxidizable (F3) and residual fraction (F4) for chemical fractionation of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni) and lead (Pb). The metals were analyzed by inductively coupled plasma optical emission spectroscopy in each fraction. The average mass concentration of PM2.5 was 93 ± 24 µg m-3.The total concentrations of Cr, Pb, Ni, Co, As and Cd in fine particle were 192 ± 54, 128 ± 25, 108 ± 34, 36 ± 6, 35 ± 5 and 8 ± 2 ng m-3, respectively. Results indicated that Cd and Co had the most bioavailability indexes. Risk Assessment Code and contamination factors were calculated to assess the environmental risk. The present study evaluated the potential Pb hazard to young children using the Integrated Exposure Uptake Biokinetic Model. From the model, the probability density of PbB (blood lead level) revealed that at the prevailing atmospheric concentration, 0.302 children are expected to have PbB concentrations exceeding 10 µg dL-1 and an estimated IQ (intelligence quotient) loss of 1.8 points. The predicted blood Pb levels belong to Group 3 (PbB < 5 µg dL-1). Based on the bioavailable fractions, carcinogenic and non-carcinogenic risks via inhalation exposure were assessed for infants, toddlers, children, males and females. The hazard index for potential toxic metals was 2.50, which was higher than the safe limit (1). However, the combined carcinogenic risk for infants, toddlers, children, males and females was marginally higher than the precautionary criterion (10-6).

Chemical partitioning of fine particle-bound As, Cd, Cr, Ni, Co, Pb and assessment of associated cancer risk due to inhalation, ingestion and dermal exposure.

The bioavailability and human health risks of As, Pb, Ni, Co, Cr and Cd in fine particulate matter (PM2.5) at an urban site on a National highway in Agra, India were investigated. Inductively coupled plasma-optical emission spectrometer was used for metal analysis in sequentially extracted samples to ascertain the highly mobile, reducible, bioavailable and immobile fractions of the metals. Cancer risk resulting from inhalation, dermal and ingestion exposure to each metal in these fractions was calculated according to US EPA models. The average mass concentration of PM2.5 was 87.16 ± 62.51 µg/m3. Cr, Ni and Pb were the most abundant metals. The results showed that Pb and Cr were higher in the mobile fraction. Cd and Co had high bioavailability. Ingestion is the major exposure pathway for all heavy metals except Cr to infants, children and adults followed by inhalation and dermal contact. The cumulative risk for Cr(VI) due to dermal and inhalation routes exceed the maximum acceptable limit for children of age 1-7 years, 8-15 years and adults when total concentration is considered, but the estimated risks are within the acceptable limit when the bioavailable, water soluble and mobile fraction are taken into account. Hence the study shows that children and adults living in the vicinity of this site are more susceptible, hence more attention should be paid to protect them from pollution hazards. The study indicates the importance of metal speciation in assessing associated human health risks.

Chemical characteristics and mutagenic activity of PM2.5 at a site in the Indo-Gangetic plain, India.

Airborne fine particulate matter PM2.5 was collected from May 2010 to December 2012 at Agra, a semi-urban site in north-central India. PM2.5 samples were chemically characterized for 16 polycyclic aromatic hydrocarbons by gas chromatography. PM2.5 values varied between 8.4 and 300 µg m(-3) with 55% of the values exceeding the 24h average NAAQ (National Ambient Air Quality) standard of 65 µg m(-3). Particle associated total PAHs ranged between 8.9 and 2,065 ng m(-3) with a mean value of 880.8 ng m(-3) during the sampling period, indicated an alarming level of pollution in Agra. Strong relationship was observed between PM2.5 and total PAHs (r=0.88), suggesting an increasing PAHs concentration with increasing PM2.5 mass. On a mass basis 3-ring and 4-ring compounds were dominant. Seasonal variation in mass concentration of PAHs was observed with high concentration in winter followed by post monsoon, summer and monsoon. This seasonal pattern could be attributed to differences in source strength and climatic conditions. PAHs concentration were also observed to be negatively correlated with the meteorological parameters i.e. temperature, solar radiation, relative humidity and wind speed. Molecular diagnostic ratios revealed vehicular emissions and combustion of wood and coal as the probable sources. The estimated carcinogenicity of PAHs in terms of benzo(a)pyrene toxic equivalency (B[a]PTEQ) was assessed and confirmed that benzo[a]pyrene was the dominant PAH contributor (3.64%). Health risk of adults and children by way of PAHs was assessed by estimating the lifetime average daily dose (LADD) and corresponding incremental lifetime cancer risk (ILCR) using USEPA guidelines. The assessed cancer risk (ILCR) was found to be within the acceptable range (10(-6)-10(-4)). The particulate samples indicated the presence of both base pair and frame shift mutagens using TA98 and TA100 strains of Salmonella typhimurium. Enhanced mutagenic response was observed in the presence of enzyme activation.

Characterization of polycyclic aromatic hydrocarbons in emissions of different mosquito coils.

Emission rates and emission factors of particulate matter and polycyclic aromatic hydrocarbons (PAHs) were determined in the emissions of three prevalent mosquito coil brands available in the market in India, under controlled conditions in an environmental chamber. The emission rates varied between the brands and ranged between 2.0 ± 1.9 to 27.1 ± 1.5 µg h(-1) for brand A, 3.4 ± 1.1 to 32.3 ± 1.2 µg h(-1) for brand B and 3.1 ± 1.0 to 72.2 ± 1.1 µg h(-1) for brand C for different compounds. Five and six ring PAHs were not detected, however four and three ring PAHs dominated. Three ring PAHs contributed 24 %, 42 % and 29 %, while four ring compounds contributed 53 %, 35 % and 61 % to total PAHs in the three brands. Carcinogenic PAH compounds were also present in the emissions, indicating the potential risks associated with the inhalation of coil smoke.

Comparison of BTX profiles and their mutagenicity assessment at two sites of Agra, India.

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 µgm(-3), 8.1 ± 1.2 µgm(-3), 2.1 ± 0.8 µgm(-3), and 5.1 ± 1.2 µgm(-3), respectively. At the petrol pump, the mean concentrations of benzene, toluene, o-,m-xylene and p-xylene were 19.5 ± 3.7 µgm(-3), 12.9 ± 1.1 µgm(-3), 3.6 ± 0.5 µgm(-3) and 11.1 ± 1.5 µgm(-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.

Severe haze events in the Indo-Gangetic Plain during post-monsoon: Synergetic effect of synoptic meteorology and crop residue burning emission.

In recent years, the frequent occurrence of haze events in the Indo-Gangetic Plain (IGP) during crop residue burning period has caused a serious reduction in atmospheric visibility and deteriorated air quality. The present study is carried out to investigate the haze event observed in IGP in Nov 2017 using ground-based observations, satellite data and synoptic meteorology to understand the possible factors responsible for haze formation. PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5 µm) concentrations and Air Quality Index (AQI) at two sites (Agra and Delhi) situated in the central Indo-Gangetic Plain (CIGP) showed a sudden increase in PM2.5 concentrations and deteriorated air quality during 7-14 Nov. To monitor the variation of particulate matter (PM) in IGP, PM2.5 and PM10 (particulate matter with aerodynamic diameter ≤ 10 µm) concentrations were monitored at 22 stations in 12 cities of IGP during 1-15 Nov which also showed an increase in PM concentrations during haze event (7-14 Nov). Crop residue burning activities in north-west Indo-Gangetic Plain (NW-IGP) were observed during haze event. Synoptic weather conditions of IGP identified using geopotential height and wind at 700 hPa showed high-pressure systems and low winds in IGP favoring stagnant conditions during haze event. A detailed analysis of the variation of pollutants and meteorology was carried out at Agra. Ozone (O3), carbon monoxide (CO), sulphur dioxide (SO2) and nitrogen oxides (NOx) showed higher concentrations during haze event along with lower temperature, low wind speed and high relative humidity. Aerosol ionic composition showed a higher contribution (~84%) of Cl-, NO3-, SO42- and NH4+ to total soluble ions suggesting secondary aerosol formation during haze event.

First observation-based study on surface O3 trend in Indo-Gangetic Plain: Assessment of its impact on crop yield.

Tropospheric ozone (O3) is an important air pollutant which causes substantial losses in crop production. Increasing O3 levels in India particularly in Indo-Gangetic Plain (IGP) is a major issue as it is reducing the crop yield. The present study is an attempt to determine the O3 and its precursor trend using continuous ground-based observations at a suburban site in IGP. The study focuses on the overall characteristics of annual, monthly, diurnal and hourly measurements of O3. Annual mean values of O3 have shown an increment of 19.2% from 2010 to 2015. Similarly, nitrogen oxide (NOx) levels increased by 30.2%. O3 levels at the study site showed a significant increasing trend of 0.7 ppb/yr. The observed O3 trend was analyzed in terms of changes in NOx levels and meteorological parameters. No significant difference in meteorological parameters was observed during 2010-15, however, NOx levels have shown an increasing trend of 0.9 ppb/yr. Further to quantify the impact of increasing O3 on crops, ozone-related crop yield losses for rice and wheat crop were determined for the period 2010-15. AOT40 (accumulated ozone exposure over a threshold of 40 ppb) and M7 (mean 7-h O3 mixing ratio from 09:00 to 15:59 LT) O3 exposure metrics were used to calculate the reduction in crop yield during major crop growing seasons: Rabi and Kharif.

Seasonal and spatial variability of secondary inorganic aerosols in PM2.5 at Agra: Source apportionment through receptor models.

The present study was conducted at sub-urban and rural site of Agra. The main aim of this study was to characterize WSII in terms of spatial, seasonal and formation characteristics and identify the major sources responsible for the pollution of WSII in PM2.5 particles using different source apportionment models. Since biomass burning is one of the most important sources of PM2.5 pollution in Agra, a case study was also conducted at rural site to investigate the contribution of biomass burning from cooking activities using different types of fuels. PM2.5 mass concentrations were higher at sub-urban site (91.0 ±â€¯50.8 µg/m3) than at rural site (77.1 ±â€¯48.6 µg/m3). WSII contributed 50.0% and 45.8% of annual average PM2.5 mass at both sites. The aerosols were ammonium rich and were therefore alkaline in nature. Aerosol acidity characteristics studied using AIM-II model showed that the aerosols were slightly less acidic at rural site than at sub-urban site. SO42-, NO3- and NH4+ were the major contributors of WSII and their formation was favoured mainly in winter. Although, WSII showed slight variations in seasonal and spatial characteristics, the major sources of pollution were found to be similar. Four sources were identified as biomass burning (29.1% and 27.4%), secondary aerosols (26.2% and 22.5%), coal combustion (22.3% and 26.9%) and soil dust (22.4% and 23.1%) at sub-urban and rural sites. The results of case study showed that among different types of biomass fuels cow dung cakes showed maximum PM2.5 emissions while LPG showed minimum PM2.5 emissions.

Larvicidal activity of Artemisia annua L. callus culture against Anopheles stephensi larvae.

The emergence of resistance by both Plasmodium falciparum and Anopheles stephensi made the search for an alternative environmentally safe plant based insecticide inevitable. Artemisia annua is a well known antimalarial. Present study is an attempt to induce callus production from young leaves of Artemisia annua plant and study its larvicidal activity against larvae of Anopheles stephensi. Callus was initiated by using different concentrations of auxins and cytokinins. A suitable culture media was standardized for optimal growth of callus. Healthy callus cultures were obtained in the slightly modified Murashige and Skoog's medium +NAA and BAP (0.03 and 0.2 mg l(-1) respectively) + Sucrose 20 gm l(-1) +Agar 8 gm l(-1) within 28 days of inoculation. Callus was successively extracted in order of increasing polarity of solvents. Larvicidal activity, in terms of lethal concentration (LC50) of the callus extract in chloroform was calculated to be 18.45 +/- 0.75 ppm after72 hr against third instar larvae of A. stephensi.

Larvicidal activity of an indigenous plant, Centratherum anthelminticum.

Crude extracts of fruits and leaves of Centratherum anthelminticum in different solvents were tested for larvicidal activity against Anopheles stephensi, the vector of malaria. The petroleum ether crude extract of both fruits and leaves exhibited significant larvicidal activity against III instar larvae with LC50 values of 162.60 ppm and 522.94 ppm, respectively after 24 hr. The petroleum ether extract of fruit was 11.66, 2.15 and 1.32 times more toxic than that of leaf extract after 24, 48 and 72 hr, respectively at LC90 level. However at LC50 level the corresponding values were 3.22, 1.83 and 1.19, respectively. The petroleum ether extract of C. anthelminticum fruits is a promising source for the control of Anopheles larvae.

Atmospheric concentrations and gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs at Indo-Gangetic sites.

Aerosol samples in the dual-phase (gaseous and particulate) were collected simultaneously for the first time in Agra at a rural and a traffic dominated site during post-monsoon and winter seasons to investigate the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs). The samples were collected using a high volume sampler on quartz micro-fiber filter papers and polyurethane foam plugs for particulate and gas phases respectively. The samples were extracted in a mixture of DCM and n-hexane. 16 priority PAHs and two nitro-PAHs were analyzed using gas chromatograph-mass spectrometry. The total concentration of PAHs (gas + particulate) was 4015 and 624 ng m-3 at the traffic and rural sites respectively. Two and three ring PAHs were dominant in the gas phase while four, five and six ring PAHs were abundant in the particle phase. A statistically significant correlation (r2 = 0.69-0.98, p < 0.001) for log Kpvs. was obtained for individual PAHs at both sites where slopes varied between -2.83 and -0.04 at the traffic site and from -3.15 to -0.06 at the rural site. Regression statistics of Clausius-Clapeyron plots suggest that the concentration of highly volatile PAHs in the atmosphere is influenced by temperature. The gas-particle partitioning coefficient Kp in its logarithmic form correlated with 1/T (r2 = 0.5-0.95, p < 0.001) and a positive slope for individual PAHs was found. In health risk assessment DbA was found to be the most carcinogenic and mutagenic as compared to other PAHs followed by BaP. 1-NPyr had a larger contribution to BaP-TEQ than 3-NFla.

Evaluation of dry deposition of acidifying N compounds to vegetation.

This papers deals with direct measurements of dry deposition flux of total acidifying N species (gaseous HNO3 and particulate NO3(-)) and theoretically by parameterization method to vegetation (leaf surfaces) over a semiarid region in India. Annual average experimental dry deposition of NO3(-) to leaf of Cassia is 0.65 ± 0.61 mg m(-2) day(-1). Ambient concentrations of HNO3 vapor and particulate NO3(-) are 1.53 and 1.24 µg m(-3), respectively. Theoretically obtained dry deposition velocity of HNO3 and NO3(-) are 0.74 cm s(-1) for both while calculated dry deposition flux of total NO3(-) is found to be 1.3 ± 0.33 mg m(-2) day(-1). The measured dry deposition flux of NO3(-) to Cassia leaf is in the range of theoretically obtained flux. The annual input of N as nitrate is 3.8 mmol m(-2) year(-1) which is lower than the other forest site in China which is probably because of low pollution than China.

Characterization of major pollution events (dust, haze, and two festival events) at Agra, India.

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, Ca(2+), Cl(-), NO3 (-), and SO4 (2-) were the most abundant ions and Ca(2+) 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.

Assessment of PAH toxicity and mutagenicity in emissions from coal and biofuel combustion.

Emissions from combustion of coal, wood and cowdung cakes in domestic cookstoves were sampled through a Stack Monitor on Glass Fibre thimbles. 16 PAH compounds were quantified in the samples extracted in dichloromethane by Gas Chromatography using FID detector. The toxic potencies of the quantified PAHs were determined by Toxicity Equivalence (TEF) Approach and their mutagenecities were tested by using Ames Plate Incorporation Method. All the 16 PAHs were determined in the emission of wood, including genotoxic compounds: carcinogens (BaA, Chy, BbF, BkF, BaP, DbA and IP) and co-carcinogens (Fla, Pyr, BghiP). In coal smoke, only 12 compounds were detected, while in cowdung cake 15 PAHs were detected except Phenanthrene. Emission factors on a fuel weight basis are highest for cowdung cake (120.23 mg/kg), followed by wood (48.97 mg/kg) and coal (28.85 mg/kg). Most of the contribution to the total PAH concentrations was from the high molecular weight compounds. Considering the genotoxic PAHs, the emission factor ranking order was from cow dung cake (115.85 mg/kg) to wood (43.03 mg/kg) and lowest for coal fuel (25.97 mg/kg). The emission factor for BaP was highest for cowdung cake (78.83 mg/kg) followed by coal (5.53 mg/kg) and wood fuel (4.47 mg/kg). Calculation of toxic potencies reveals that the carcinogenic contribution from low molecular weight PAHs is relatively much lower than high molecular weight PAHs for each tested fuel. Cow dung cake extracts did not show mutagenic activity in the Ames Salmonella test probably due to lower concentration of the direct-mutagens like Pyr, Chy. In contrast, the extracts of coal and wood had higher concentrations of direct-mutagens like Pyr, Chy, so positive results were obtained.

Field measurements of aerosol particle dry deposition on tropical foliage at an urban site.

This paper presents dry deposition of major ions on tropical foliage (leaves of Ashok (Polyalthia longifolia) and Cassia (Cassia siamea)) at St. John's, Agra, an urban site of tropical India on nonrainy, nondewy, and nonfoggy days. The deposition flux was higher on Cassia leaf than Ashok leaf probably due to a rougher surface as shown by scanning electron microscopy. Dry deposition of cations varies from 0.46 to 12.16 mg m(-2) day(-1) while anions vary from 0.04 to 3.24 mg m(-2) day(-1). The percentage contribution of alkaline components is greater than that of acidic components, indicating the alkaline nature of dry deposition. Two-way analysis of variance results reveal significant seasonal variation only for K+, SO4(2-), and F-; however, values varied season to season for Na+, Ca2+, Mg2+, Cl-, NO3-, and NH4+ also. The large seasonal variation in deposition flux may be due to meteorological conditions, diameter of particles, and variation in atmospheric level. SO42- and NO3- show significant correlation, indicating their origin from similar sources while significant correlation between Ca2+ and Mg2+ implies their origin from soil. Poor correlation between Ca2+ and SO4(2-), Ca2+ and NO3-, and Mg2+ and SO4(2-) indicates that in addition to soil other sources also contribute to dry deposition. Low dry deposition fluxes of SO2- and NO3- compared to Ca2+ and Mg2+ may be due to low mass medium diameters of SO4(2-) and NO3- and may be due to uptake through the stomatal pores abundant on leaf surfaces. Factor analysis was employed to identify the sources. F-, Cl, SO4(2-), NO3-, and K+ are grouped together in the first factor, indicating their probable contribution from combustion, Ca2+, Mg2+, and NH4+ are grouped in factor II, which may be attributed to road dust and soil, and factor III includes mainly Na+ and F-, probably contributed from brick-kiln industries. Atmospheric concentrations of F-, Cl-, NOs-, SO4(2-), Na+, K+, Ca2+, Mg2+, and NH4+ were found to be 0.38, 2.28, 1.31, 2.74, 0.44, 0.59, 1.21, 1.2, and 2.29 microg m(-3), respectively.