Concentration fluctuations and plume dispersion within 100 m of an isolated source during stable conditions

Few data exist to characterize plume behavior on instantaneous time scales under stable conditions. This paper describes recent field experiments conducted at night during July of 1999 among rural terrain in Washington State. Sulfur hexafluoride gas was released as a point source near ground level, and concentration fluctuations were measured with a fast-response analyzer at downwind distances ranging from 30 m to 100 m. In addition, 30-min average concentrations were collected with an array of syringe samplers. Meteorological conditions were monitored throughout the experiments with uvw anemometers and a 10-m tower equipped with temperature and wind sensors at two heights. Results from the study will consist of concentration fluctuation statistics with plume spread parameters for stable conditions on instantaneous and average time frames.