Black Carbon Aerosol over the Los Angeles Basin during CalNex
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 20, 2012
- Accession Number
- ADA576087
Entities
People
- A. R. Metcalf
- A. Sorooshian
- H. H. Jonsson
- H. T. Duong
- J. Brioude
- J. H. Seinfeld
- J. J. Ensberg
- J. S. Craven
- R. C. Flagan
- W. Angevine
Organizations
- Naval Postgraduate School