AIR CLEANSING BY CONVECTIVE STORMS
381
Insofar as the patterns of convection in the two observed cases of
diffuse convective rains are such that pockets of contaminated low-
level air are left between the relatively weak and isolated precipitation
cells, the irregular trends of contaminant concentrations observed in
these cases are entirely consistent with the previously stated hypothesis.
ACKNOWLEDGMENTS
This research was conducted under Public Health Service grants
E-1379 and AP-1, U. S. Atomic Energy Commission contract AT(11-1)-739, and Michigan— Memorial Phoenix project 245.
APPENDIX
For convenience, the following table has been prepared, giving the
common names and approximate diameters reported of all of the pol-
lens determined in rainwater. The diameters reported are the mean
of a small number of measurements made on the pollens found in
rainwater,
Pollen
Carya
Chenopodiaceae—
Amaranthaceae
Common name
Hick. -y
Goosefoots—
Pigweeds
Gramineae
Grasses
Picea
Tilia
Spruce
Linden
Juglans
Walnut
Approximate
diameter, yu
47
25
29
42
75
42
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580