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List of Abstracts 198and highly industrialized regions (e.g. the Po valley). The specific megacities in this study are chosen toprovide a global sample. From this, the differences due to the location of the megacities can be investigated.The remote responses away from megacity perturbations are considered in addition to local effects. Aerosoltypes investigated include sulphate, nitrate, black carbon and organic carbon.P-Observations 2.64 ID:4334 10:30Characterization of solvent-extractable organics in urban aerosols using a high resolution time-offlightaerosol mass spectrometer and a hygroscopicity tandem differential mobility analyzerToshiyuki Mihara 1 , Michihiro Mochida 21 Graduate School of Environmental Studies, Nagoya Univ., Nagoya, 464-8601, Japan2 Institute for Advanced Research, Nagoya Univ., Nagoya, 464-8601, JapanContact: mihara.toshiyuki@d.mbox.nagoya-u.ac.jpTo investigate the characteristics of atmospheric particulate organics with different polarities, aerosolsamples collected in the urban area of Nagoya, Japan, in spring and summer 2009 were extracted with waterand organic solvents and subjected to the analyses using a high resolution time-of-flight aerosol massspectrometer (HR-ToF-AMS) and a hygroscopicity tandem differential mobility analyzer. The aerosolsamples were collected on quartz fiber filters (50% cut-off diameter: 0.95 µm) and extracted with water,methanol and ethyl acetate. Particles introduced to the instruments were generated by atomization of theextracts. The absolute concentrations of the solvent-extractable organics were determined from additionalHR-ToF-AMS analyses for particles generated from the extracts with known amounts of phthalic acid. Theconcentrations of the organics extractable with water, methanol and ethyl acetate were in the ranges of 1.9–5.4, 2.6–7.1, and 1.4–5.0 µg m -3 , respectively. Further, the oxygen-to-carbon ratios were determined to be inthe ranges of 0.51–0.71 (water), 0.31–0.48 (methanol), and 0.27–0.32 (ethyl acetate) from the millimassspectra. The quantification of water soluble fractions in ethyl-acetate extractable organics using the HR-ToF-AMS and the comparison with the organic carbon concentrations measured using a carbon analyzer suggestthat a major part of the organics is extractable with water and/or ethyl acetate. From the hygroscopic growthmeasurements of water and ethyl acetate extracts, the κ values of the extracted organics were calculated,with the consideration of the water uptake by inorganic salts using the AIM model(http://www.aim.env.uea.ac.uk/aim/aim.php). By excluding the samples with large nitrate fractions tominimize a possible artifact caused by the evaporation, we determined κ of extracted organics to be from0.00 to 0.16 at 85% relative humidity (RH). The aerosol water retained by these organics was estimated tocomprise up to 70% of the total aerosol water at 85% RH.P-Observations 2.65 ID:4262 10:30Chemical Composition of aerosols over the marine environments of Bay of Bengal and Arabian SeaPrabha R. Nair 1 , Susan K. George 2 , Imran Asatar Girach 1 , Salu Jacob 31 Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram, India2 National Physical Laboratory, New Delhi3 Vikram Sarabhai Space Centre, Thiruvananthapuram, IndiaContact: prabha_nair@vssc.gov.inAerosols in the marine atmosphere primarily compose of in situ generated sea-salt particles and non-sea-saltparticles, formed from oceanic biogenic activities or transported from continental regions. This paperpresents the results of the ship-based measurements conducted as part of the Integrated Campaign forAerosols, gases and Radiation Budget (ICARB) under the Geosphere Biosphere Programme of Indian SpaceResearch Organization (ISRO-GBP). Aerosol sampling has been carried out during the premonsoon monthsof March to May 2006 over Bay of Bengal(BoB) and Arabian Sea(AS) and during winter months ofiCACGP-IGAC 2010 14 July, 2010