Search Results
Abstract
Pollen transport and dispersion from generalized area sources was studied by 29 flights to distances of 100 km and heights of 3 km using an aircraft-mounted isokinetic sampler. Tree pollens and ragweed pollen served as tracers. Four types of flights were made to study various aspects of pollen transport: 1) ascents over a fixed location to investigate vertical distribution; 2) flights over a source-free area to document change of concentration with distance, 3) east-west flights along Long Island to study the influx of pollen from the mainland with westerly winds; and 4) vertical ascents and horizontal flights during sea breeze flows to determine their effect on pollen concentrations.
It was found that large quantities of pollen are transported in orderly fashion from their source regions but pollen often travels in large, discrete clouds. Pollen is transported to Long Island from the mainland in some quantity. Sea breeze flows greatly decrease low-level concentrations but pollen is carried aloft at the sea breeze front and recirculated in the return flow aloft. Vertical distribution is reasonably well related to lapse rate although secondary concentration peaks which often occur below elevated inversions cannot be explained by the data obtained.
Abstract
Pollen transport and dispersion from generalized area sources was studied by 29 flights to distances of 100 km and heights of 3 km using an aircraft-mounted isokinetic sampler. Tree pollens and ragweed pollen served as tracers. Four types of flights were made to study various aspects of pollen transport: 1) ascents over a fixed location to investigate vertical distribution; 2) flights over a source-free area to document change of concentration with distance, 3) east-west flights along Long Island to study the influx of pollen from the mainland with westerly winds; and 4) vertical ascents and horizontal flights during sea breeze flows to determine their effect on pollen concentrations.
It was found that large quantities of pollen are transported in orderly fashion from their source regions but pollen often travels in large, discrete clouds. Pollen is transported to Long Island from the mainland in some quantity. Sea breeze flows greatly decrease low-level concentrations but pollen is carried aloft at the sea breeze front and recirculated in the return flow aloft. Vertical distribution is reasonably well related to lapse rate although secondary concentration peaks which often occur below elevated inversions cannot be explained by the data obtained.
Abstract
Dispersion and deposition of ragweed pollen released naturally from circular area sources of four sizes (5–27 m in diameter) and artificially from point sources were studied at Brookhaven National Laboratory. Concentrations were measured by wind-impaction samplers mounted on 20° radii at four heights (0.5–4.6 in) and four or five distances from the sources to a maximum of 69 m. Deposition was measured by greased microscope slides on the ground. Differences in dispersion patterns between point and area sources are analyzed. Normalized centerline concentrations, cross-wind integrated concentrations, plume widths, plume heights and mass flux 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 2–6 cm sec−1 but values close to area sources were much greater. Loss of airborne particles between sampling circles is compared to deposition over the same distances. Results are compared to those of previous dispersion and deposition studies and to theory.
Abstract
Dispersion and deposition of ragweed pollen released naturally from circular area sources of four sizes (5–27 m in diameter) and artificially from point sources were studied at Brookhaven National Laboratory. Concentrations were measured by wind-impaction samplers mounted on 20° radii at four heights (0.5–4.6 in) and four or five distances from the sources to a maximum of 69 m. Deposition was measured by greased microscope slides on the ground. Differences in dispersion patterns between point and area sources are analyzed. Normalized centerline concentrations, cross-wind integrated concentrations, plume widths, plume heights and mass flux 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 2–6 cm sec−1 but values close to area sources were much greater. Loss of airborne particles between sampling circles is compared to deposition over the same distances. Results are compared to those of previous dispersion and deposition studies and to theory.
