Elemental carbon concentrations: Estimation of an historical data base

While recent advances in instrumentation permit routine determination of elemental carbon concentrations in atmospheric aerosol samples, historical data on elemental C concentrations are absent. Two methods are available for the estimation of an historical data base for elemental C concentrations: calibration of reflectance-based tape samplers and analysis of archived high volume sampler filters. These methods are described and applied to the problem of reconstructing an historical data base for elemental C concentrations in Los Angeles. Twenty-four year average elemental C concentrations at seven monitoring sites in the Los Angeles area are estimated to range from 6.4 μg m^-3 at Downtown Los Angeles to 4.5 μg m^-3 at West Los Angeles. At most monitoring sites studied, elemental C concentrations were lower in recent years than during the late 1950s and early 1960s.