Sources of Urban Contemporary Carbon Aerosol

Abstract

Emissions from the major sources of fine carbonaceous
\naerosol in the Los Angeles basin atmosphere have been
\nanalyzed to determine the amounts of the ^(12)C and ^(14)C
\nisotopes present. From these measurements, an inventory
\nof the fossil carbon and contemporary carbon particle
\nemissions to the Los Angeles atmosphere has been created.
\nIn the winter, more than half of the fine primary
\ncarbonaceous aerosol emissions are from sources containing
\ncontemporary carbon, including fireplaces, charbroilers,
\npaved road dust, cigarette smoke, and brake lining dust,
\nwhile in the summer at least one-third of the carbonaceous
\nparticle emissions are contemporary. Using a mathematical
\nmodel for atmospheric transport, predictions are made
\nof the atmospheric fine particulate fossil carbon and
\ncontemporary carbon concentrations expected due to
\nprimary source emissions. Model predictions are in
\nreasonable agreement with the measured radiocarbon
\ncontent of the fine ambient aerosol samples. It is
\nconcluded that the high fraction of contemporary carbon
\nmeasured historically in Los Angeles is not due to local
\nemission sources of biogenic material; rather, it is due to
\na combination of local anthropogenic pollution sources
\nand background marine aerosol advected into the city.