Identifying the effect of individual emissions sources on particulate air quality within a photochemical aerosol processes trajectory model

A procedure is demonstrated that greatly expands the number of sources whose contribution to ambient particle levels can be followed separately within an aerosol processes trajectory model without significantly increasing the computational burden of the problem. Particles emitted from different sources within the same general class can be differentiated from each other with this technique; for example particles emitted by on-road diesel vehicles can be distinguished from particles emitted by diesel railroad locomotives, and particles emitted from identical sources at different locations can be distinguished from each other as well. The method developed is illustrated by application to the air quality situation in Southern California. The contributions of more than 50 types of air pollution sources to primary particle concentrations at Claremont, CA, are separated from each other by post-processing the output from the aerosol processes trajectory model for an externally mixed aerosol developed previously by Kleeman and Cass (1998, Atmospheric Environment 32, 2803–2816; 1999 Environmental Science and Technology, 33, 177–189).