Premium
Changes of ns‐soot mixing states and shapes in an urban area during CalNex
Author(s) -
Adachi Kouji,
Buseck Peter R.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50321
Subject(s) - soot , aerosol , particle (ecology) , absorption (acoustics) , materials science , particulates , particle size , megacity , carbon fibers , sea salt , ultrafine particle , mineralogy , chemistry , nanotechnology , meteorology , physics , combustion , composite material , geology , oceanography , economy , organic chemistry , composite number , economics
Aerosol particles from megacities influence the regional and global climate as well as the health of their occupants. We used transmission electron microscopes (TEMs) to study aerosol particles collected from the Los Angeles area during the 2010 CalNex campaign. We detected major amounts of ns‐soot, defined as consisting of carbon nanospheres, sulfate, sea salt, and organic aerosol (OA) and lesser amounts of brochosome particles from leaf hoppers. Ns‐soot‐particle shapes, mixing states, and abundances varied significantly with sampling times and days. Within plumes having high CO 2 concentrations, much ns‐soot was compacted and contained a relatively large number of carbon nanospheres. Ns‐soot particles from both CalNex samples and Mexico City, the latter collected in 2006, had a wide range of shapes when mixed with other aerosol particles, but neither sets showed spherical ns‐soot nor the core‐shell configuration that is commonly used in optical calculations. Our TEM observations and light‐absorption calculations of modeled particles indicate that, in contrast to ns‐soot particles that are embedded within other materials or have the hypothesized core‐shell configurations, those attached to other aerosol particles hardly enhance their light absorption. We conclude that the ways in which ns‐soot mixes with other particles explain the observations of smaller light amplification by ns‐soot coatings than model calculations during the CalNex campaign and presumably in other areas.