Continuous observation of particulates during the General Motors sulfate dispersion experiment

During the General Motors Sulfate Dispersion Experiment of 1975, filter samples of particu-lafe matter were collected continuously and impactor samples intermittently for the first half of October. The sulfur background which varied by an order of magnitude was analyzed in detail and related to the weather situations. The three days of lowest background were selected for intensive analysis and indicate additions to the atmosphere during automobile runs of 1.0 μg/m3 for sulfur, 0.7 μg/m3 for calcium, and 0.3 μg/m3 for iron. These values correspond to generation rates per automobile of 10.1 ± 1.7 mg/km for sulfur, 7.0 ± 0.9 mg/km for calcium, and 2.9 ± 0.8 mg/km for iron. An air particulate sampler comparison of the dichotomous and "streaker" sampler measurements shows excellent agreement between the two devices.