Fine particulate matter, i.e., PM2.5, is one of the U.S. EPA’s National Ambient Air Quality Standard (NAAQS) criteria air pollutants. Two of the major contributors to PM2.5 in California are elemental carbon (EC) and organic carbon (OC). Chemical Mass Balancing (CMB) is an approach to assessing the sources of OC and PM2.5 using chemical tracers that are indicative of a specific source. For example, the difference in fuel composition and combustion temperature in gasoline engines as compared with diesel engines results in a different profile of chemical tracers in their exhaust. The Miller-Schulze Laboratory is developing methodology to quantify tracers of PM2.5 the San Joaquin Valley to investigate the impact of wind-blown agricultural dust on OC and PM2.5 levels using samples collected at sites in Fresno and Bakersfield. This project is in collaboration with researchers at the University of Wisconsin, Madison.