Accession Number : ADA576087


Title :   Black Carbon Aerosol over the Los Angeles Basin during CalNex


Descriptive Note : Journal article


Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA


Personal Author(s) : Metcalf, A R ; Craven, J S ; Ensberg, J J ; Brioude, J ; Angevine, W ; Sorooshian, A ; Duong, H T ; Jonsson, H H ; Flagan, R C ; Seinfeld, J H


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a576087.pdf


Report Date : 20 Apr 2012


Pagination or Media Count : 25


Abstract : Refractory black carbon (rBC) mass and number concentrations were quantified by a Single Particle Soot Photometer (SP2) in the CalNex 2010 field study on board the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter in the Los Angeles (LA) Basin in May, 2010. The mass concentrations of rBC in the LA Basin ranged from 0.002 0.530 micro g m(expn -3), with an average of 0.172 micro g m(expn -3). Lower concentrations were measured in the Basin outflow regions and above the inversion layer. The SP2 afforded a quantification of the mixing state of rBC aerosols through modeling the scattering cross-section with a core-and-shell Mie model to determine coating thickness. The rBC particles above the inversion layer were more thickly coated by a light-scattering substance than those below, indicating a more aged aerosol in the free troposphere. Near the surface, as the LA plume is advected from west to east with the sea breeze, a coating of scattering material grows on rBC particles, coincident with a clear growth of ammonium nitrate within the LA Basin and the persistence of water-soluble organic compounds as the plume travels through the outflow regions. Detailed analysis of the rBC mixing state reveals two modes of coated rBC particles; a mode with smaller rBC core diameters (90 nm) but thick (200 nm) coating diameters and a mode with larger rBC cores (145 nm) with a thin (75 nm) coating. The weekend effect in the LA Basin results in more thickly coated rBC particles, coinciding with more secondary formation of aerosol.


Descriptors :   *AEROSOLS , *LIGHT SCATTERING , *SOOT , AIR QUALITY , ALTITUDE , BASINS(GEOGRAPHIC) , BLACK(COLOR) , CARBON , CLIMATE CHANGE , LAGRANGIAN FUNCTIONS , LOS ANGELES(CALIFORNIA) , MIE SCATTERING , PARTICLES , PHOTOMETERS , TEMPERATURE


Subject Categories : Physical Chemistry
      Optics
      Air Pollution and Control


Distribution Statement : APPROVED FOR PUBLIC RELEASE