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DOE's Gasoline/Diesel PM Split Study

DOE's Gasoline/Diesel PM Split Study was conducted to assess the sources of uncertainties in quantifying the relative contributions of tailpipe emissions from gasoline-powered and diesel-powered motor vehicles to the ambient concentrations of fine particulate matter (PM2.5) in the urbanized region of Southern California using an organic compound-based chemical mass balance model (CMB). The study, conducted from May-September 2001, involved several groups working cooperatively on sample collection and quality assurance aspects of the study, but working independently, on chemical analysis and data analysis. Groups participating in the study included California's Bureau of Automotive Repair, South Coast Air Quality Management District, U.S. Environmental Protection Agency, Ralph's Groceries, Clean Air Vehicle Technology Center, West Virginia University, the University of Wisconsin at Madison, and the Desert Research Institute. Vehicle testing included 59 light-duty vehicles (including 2 diesel vehicles) and 34 heavy-duty diesel vehicles. Twenty-four hour ambient samples were collected for twenty-eight consecutive days at air monitoring stations in downtown Los Angeles and Azusa. Ambient samples were also collected from a mobile sampling van at several regionally representative sites and at locations with expected higher proportions of PM emissions from diesel trucks (e.g., Terminal Island, truck stop, highway truck routes) and from gasoline vehicles (e.g., congested freeways during commuter rush hour, surface streets during weekends, a parking lot at a major sporting event).

In addition to the source apportionment effort, researchers examined the variations in relative abundances of key marker compounds in the source-dominated ambient samples relative to corresponding variations in the samples from regional air quality monitoring sites by day of week.

Results from the Gasoline/Diesel PM Split Study will be presented by webcast from the California Air Resources Board on September 7, 2005. Information on the webcast is found at http://www.arb.ca.gov/research/seminars/doe/doe.htm.

You can access the data acquired during the study below on this site (the DBF files below can be opened using Microsoft Excel):

At the present time, we do not recommend that the mobile source profile data from this study be used for any other source apportionment studies or for source attribution in locations outside of southern California during summertime conditions, unless it can be demonstrated that emissions profiles for those areas are similar to those developed in this study. The presence of high emitters, ambient temperatures (especially influencing the cold start), fuels and engine lubricating oil greatly affect vehicle fleet emissions; the significance of these effects must be thoroughly evaluated when mobile source emissions profiles are being developed.