Elemental and organic carbon particle concentrations: A long-term perspective

Long-term trends in organic and elemental carbon particle concentrations can be explored by establishment of new routine air monitoring programs, by analysis of archived filter samples, and by calibration of reflectance-based tape samplers to read in terms of equivalent elemental carbon concentrations. These methods have been combined to study the long-term history of organic and elemental carbon particle concentrations at Downtown Los Angeles. Particulate elemental and organic carbon concentrations both peak during winter months, a behavior characteristic of primary traffic-derived pollutants like CO and lead. The ratio of total carbon to elemental carbon present in fine particles in Downtown Los Angeles shows little seasonal dependence, and averages 2.6:1 over an annual cycle, a composition that approximates the ratio of total to elemental carbon in primary source emissions.