The atmospheric dispersion and subsequent deposition of corn (Zea mays L.) pollen emitted from plants in two 18‐m diameter plots were studied in 39 tests at Brookhaven National Laboratory to compare the spread of this large pollen to that of smaller pollens studied previously. Concentrations were measured by wind‐impaction samplers mounted at four heights (0.5 to 4.6 m) and at five distances from the source on 20‐degree radii. Deposition was measured by greased microscope slides on the ground.
Data were analyzed in terms of current meteorological dispersion theory. Normalized centerline concentrations, crosswind integrated concentrations, plume widths and heights, and mass flux are presented as functions of distance and compared to similar data from ragweed (Ambrosia) and timothy (Phleum pratense) sources of comparable size. Normalized centerline and crosswind integrated deposition and velocity of deposition are also presented as functions of distance and are compared to ragweed and timothy pollen data. The study shows that corn pollen is not transported as far by the wind as smaller pollens, does not disperse as widely in either the horizontal or the vertical direction and settles to earth more quickly, much of it within the source itself.
The dispersion of corn pollen is influenced by its large size and rapid settling rate. At 60 m from the source in the downwind direction, concentrations average about 1% of those at 1 m. Width of the pollen plume at 60 m is less than that of smaller pollens under similar conditions. The rate of settling opposes the rate of upward dispersion so that the height of the pollen plume does not increase continuously with downwind distance. At 60 m from the source concentrations integrated in the crosswind direction average from 3 to 6% of those at 1 m. The total amount of pollen remaining airborne at 60 m is 5% of that at 1 m.
Total deposition within the source plot is greater than that outside. Deposition per unit area at 60 m downwind is only 0.2% of that near the source. Crosswind integrated deposition at 60 m varies from 0.5 to 0.8% of that at 1 m. The velocity of deposition at 32 m from the source averages about 33 cm/sec.
Hourly measurements of pollen emission were made from cultivated plots of Ambrosia, Phleum, Zea, and Ricinus over the course of several pollination seasons as part of a study of pollen dispersion from known sources. A characteristic diurnal emission pattern was found for each genus. Ambrosia pollen emission normally begins an hour or two after sunrise, peaks a few hours later, and decreases through the afternoon. Phleum starts during the night, peaks about 2 hr after sunrise, and declines slowly through the day. Zea emits pollen fairly uniformly during the period from 2 hr after sunrise to about sunset, while Ricinus pollen was collected from several hours after sunrise to late afternoon with a peak in mid‐morning. Daily patterns often vary from the seasonal mean in response to changing meteorological conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.