Dispersion and deposition of timothy pollen emitted naturally from circular area sources 18–37 m in diameter and artificially from point sources were studied in 64 tests at Brookhaven National Laboratory. Concentrations were measured by wind-impaction samplers mounted at four heights (0.5–4.6 m) and five or six distances from the source on 20° radii. Deposition was measured by greased microscope slides on the ground.

Data are analyzed in terms of current dispersion theory. Normalized centerline concentrations, crosswind integrated concentrations, plume widths and heights, mass flux and the size of areas having concentrations above selected values are presented as functions of distance and related to source size and meteorological variables. Deposition data are also related to distance and source size. Most deposition velocities ranged from 10 to 14 cm/sec but many values close to the source were much higher. Loss of airborne particles between sampling circles is compared to deposition over the same distances. Results are compared to previous dispersion and deposition experiments, including a large number of similar ragweed pollen tests, and to theory.