The Carbon Containing Component of the Los Angeles Aerosol: Source Apportionment and Contributions to the Visibility Budget

Abstract

Source resolution of the organic component of the fine fraction of the ambient aerosol (dp < 3.5 fim) has been carried out by combining source information from the inorganic component with thermal analysis and local emission inventories. The primary and secondary carbon containing components were identified using a source fingerprint thermogram. The primary carbon emitted from automobiles was calculated using the ambient lead concentration and a recent estimate of the lead to carbon ratio for this source. The remaining primary carbon was apportioned to the other sources according to the local emission inventory. Source apportionment of the secondary component was performed by scaling the secondary carbon to a recent emission inventory for reactive organic gases (ROG) neglecting biogenic contributions and assuming equal potential for aerosol formation for the various ROG. The method was applied to data collected at Lennox and Duarte on 10/23/80. The major source at both sites was automobiles which were responsible for 68% and 36% of the carbon containing component of the fine aerosol at Lennox and Duarte respectively. Industrial sources made a relatively higher contribution at Duarte, 26%, than at Lennox 12%. Good correlation was found between ozone and secondary carbon. However, a weaker correlation was found between sulfates and secondary carbon. Contributions to the visibility budget by various chemical species were calculated at Lennox and Duarte on 10/23/80 using an appropriate regression model. It was found that the carbon containing component was responsible for 27% and 44% of the incident light extinction at Lennox and Duarte, respectively.