On 6 June 1978, the Four Corners coal-fired power plant plume near Farmington, New Mexico, was sampled with an instrumented twin-engine Aero-commander 680E, up to 90 km downwind from the source. Measurements consisted of aerosol size distribution, condensation nuclei, various gases, individual particle chemistry using electron microscopy techniques and meteorological parameters.

A substantial formation of condensation nuclei took place downwind of the plant at a rate of 1.3 × 1016 s−1 in the first 0.3 h, 3.3 × 1017 s−1 up to 2.5 h, and 8 × 1017 s−1 in the 2.5–12.5 h plume travel time. The corresponding conversion rates were 0.15, 0.5 and 0.3% h−1, respectively. The conversion rate due to oxidation of SO2 on surfaces of fly ash particles was negligible. Dry removal of particles was very high and reached an estimated maximum of 36% during the first 2.5 h probably due to partial impingements of the plume to the ground.

Analysis of individual particles collected on nuclepore filters using a scanning electron microscope equipped with an x-ray energy dispersive analyzer, as well as particles collected on electron microscope screens for the detection of sulfate, show definitely that particles <0.5 μm are mostly sulfates, with 10–15% fly ash. In the larger size range most particles were identified as fly ash.

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