Mixing ratios of 15 carbonyls and BTEX (benzene, toluene, ethyl benzene, xylenes) were measured for the first time in ambient air of Kolkata, India at three sites from March to June 2006 and their photochemical reactivity was evaluated. Day and nighttime samples were collected on weekly basis. Formaldehyde was the most abundant carbonyl (mean concentration ranging between 14.07 microg m(-3) to 26.12 microg m(-3) over the three sites) followed by acetaldehyde (7.60-18.67 microg m(-3)) and acetone (4.43-10.34 microg m(-3)). Among the high molecular weight aldehydes, nonanal showed the highest concentration. Among the mono-aromatic VOCs, mean concentration of toluene (27.65-103.31 microg m(-3)) was maximum, closely followed by benzene (24.97-79.18 microg m(-3)). Mean formaldehyde to acetaldehyde (1.4) and acetaldehyde to propanal ratios (5.0) were typical of urban air. Based on their photochemical reactivity towards OH. radical, the concentrations of the VOCs were scaled to formaldehyde equivalent, which showed that the high molecular weight carbonyls and xylenes contribute significantly to the total OH-reactive mass of the VOCs. Due to the toxic effect of the VOCs studied, an assessment for both cancer risk and non-cancer hazard due to exposure to the population were calculated. Integrated life time cancer risk (ILTCR) due to four carcinogens (benzene, ethyl benzene, formaldehyde and acetaldehyde) and non-cancer hazard index for the VOCs at their prevailing level were estimated to be 1.42E-04 and 5.6 respectively.

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An extensive aerosol sampling program was conducted during January-December 2006 over Kolkata (22º33′ N and 88º20′ E), a mega-city in eastern India in order to understand the sources, distributions and properties of atmospheric fine mode aerosol (PM 2.5 ). The primary focus of this study is to determine the relative contribution of natural and anthropogenic as well as local and transported components to the total fine mode aerosol loading and their seasonal distributions over the metropolis. The average concentrations of fine mode aerosol was found to be 71.2±25.2 μgm -3 varying between 34.5 μgm -3 in monsoon and 112.6 μgm -3 in winter. The formation pathways of major secondary aerosol components like nitrate and sulphate in different seasons are discussed. A long range transport of dust aerosol from arid and semiarid regions of western India and beyond was observed during pre-monsoon which significantly enriched the total aerosol concentration. Vehicular emissions, biomass burning and transported dust particles were the major sources of PM 2.5 from local and continental regions whereas seasalt aerosol was the major source of PM 2.5 from marine source regions.

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[1] A comprehensive size-segregated characterization of the chemical properties (watersoluble inorganic fraction) of the sea-salt aerosol originated from the surf zone at the landocean boundary of Sundarban Mangrove forest, NE coast of Bay of Bengal, and an analysis of the relevant meteorological parameters revealed how the combined effect of anthropogenic gases and aerosol advected to the virgin mangrove forest and micrometeorological conditions could change the marine character of the aerosol before the onset of SW monsoon. The average aerosol mass concentration was 99.94 ± 41.9 mg m À3 with production rate of 0.19 mg m À2 s À1 (during January) to 4.29 mg m À2 s À1(during April) and dry deposition rate of 0.019 mg m À2 s À1 (during January) to 13.21 mg m À2 s À1 (during June). 72.35% of the total aerosol mass was leachable by water, and relatively large concentrations of phosphorus were observed. More chloride depletion from the coarse (2.0 < d p < 10 mm) and nucleation (d p < 0.4 mm) modes compared to the accumulation mode (0.4 < d p < 2.0 mm) was observed in winter (Cl/Na = 0.6023 ± 0.1798), and a reverse trend was observed in summer (Cl/Na = 0.644 ± 0.262). A significant positive correlation was obtained for chloride loss with non-sea-sulphate and nitrate for particles > 2.0 mm. , and PO 4 3À in different size modes were considered to collate their source apportionment. The proximity of Calcutta and Haldia metropolis to the mangrove forest could influence the forest air quality and depositional processes.

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