Source apportionment of organic and light-absorbing carbon using receptor modeling techniques

An intensive field-monitoring program designed to attribute visibility reducing aerosols to their sources or source regions was carried out in the western half of Washington state. Because of the perceived concern over the contribution of carbonaceous material from prescribed and wildfires to visibility impairment, this paper focuses on attribution of organic and light-absorbing carbon to known sources and source regions. A variety of receptor-oriented models was successfully exercised and reconciled with each other. It is shown that much of the organic and light-absorbing carbon is associated with urban emissions of the Seattle-Tacoma area. Fire tracers were not strongly linked to either organic or light-absorbing carbon; however, the fire-related tracers were shown to be primarily associated with transport from south of the Washington-Oregon state border.