Chemical composition and optical properties of the aerosol in the free troposphere PDF Download

Author: Peter Hoffmann
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Category :
Languages : de
Pages : 16

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Aerosol, optical properties, chemical-analytical strategy.

Author: James M. Rosen
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Category : Aerosols
Languages : en
Pages : 0

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Author: Jiumeng Liu
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Category : Aerosols Optical properties
Languages : en
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The chemical and optical properties of particulate organic compounds remain unclear, which leaves large uncertainties in the estimation of global radiative transfer balance. Gas and find particle (PM2.5) phase formic acid concentrations were measured with online instrumentation during separate one-month studies in the summer of 2010 in Los Angeles (LA), CA, and Atlanta, GA, and the gas-particle partitioning behavior was investigated and compared with that of water-soluble organic compounds (WSOC). The diurnal profiles clearly indicated that the photochemistry production serves as a strong source for the formation of organics, while the correlation between the gas and particle phase suggested that another partitioning route, the aqueous reactions, is also very important. Later, the optical properties of light-absorbing organic compounds were examined. Little is known about the optical importance of light absorbing particulate organic compounds (brown carbon), especially its extent and absorption relative to black carbon throughout the tropospheric column. Mie theory was applied to size-resolved spectrophotometric absorption measurements of methanol and water-extracts from cascade impactor substrates collected at three surface sites around Atlanta, GA, including both urban and rural. These results were applied to similar measurements of brown carbon in extracts from aircraft bulk filter samples collected over central USA. At the surface sites predicted light absorption by brown carbon relative to total absorption (brown carbon plus pure black carbon) was about 10% and 30% at 350 nm, versus 1 and 11% at 450 nm, for water and methanol extracts, respectively. The relative contribution of brown carbon was greater in the free troposphere and significantly increased with altitude. Although this approach has limitations, it demonstrates the ubiquity and significant potential contribution of brown carbon.

Author:
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Category :
Languages : en
Pages : 13

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In two balloon flights over Laramie, Wyoming, simultaneous measurements of aerosol backscatter and total aerosol scatter were successfully obtained. The data have been analyzed and used to directly measure the extinction-to-backscatter ratio under the assumption that the aerosols are relatively non-absorbing (small imaginary component to the index of refraction). The results are consistent with previous estimates of the extinction-to- backscatter ratio, although very little information is available relevant to direct measurements of this important parameter. It is concluded that the new instruments and techniques employed here will provide a practical method of obtaining a wealth of new information concerning the extinction-to-backscatter ratio of tropospheric aerosols.

Author: James M. Rosen
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Category : Aerosols
Languages : en
Pages : 17

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Author:
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Category :
Languages : en
Pages : 348

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Author: Mariya M. Shcherbyna
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Category : Atmospheric aerosols
Languages : en
Pages : 350

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Author: Mansour Zakikhani
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Category : Troposphere
Languages : en
Pages : 208

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Author:
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Category :
Languages : en
Pages :

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Author: Ryan Christopher Moffet
Publisher:
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Category :
Languages : en
Pages : 340

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Knowledge of aerosol physical, chemical, optical properties is essential for judging the effect that particulates have on human health, climate and visibility. The aerosol time-of-flight mass spectrometer (ATOFMS) is capable of measuring, in real-time, the size and chemical composition of atmospheric aerosols. This was exemplified by the recent deployments of the ATOFMS to Mexico City and Riverside. The ATOFMS provided rapid information about the major particle types present in the atmosphere. Industrial sources of particles, such as fine mode particles containing lead, zinc and chloride were detected in Mexico City. The rapid time response of the ATOFMS was also exploited to characterize a coarse particle concentrator used in human health effects studies. The ATOFMS showed the ability to detect changes in particle composition with a time resolution of 15 min during short 2 hour human exposure studies.