Soil moisture was measured gravimetrically at random selected locations

within 50 m of the equipment installation to a depth of 2.5 cm mentioned
Dust samples from the Bagnold sampler were dried at 100 C.
earlier.

for 24 hours prior to mechanical sieving through a sonic sifter to

estimate fractions above and below 53 um diameter.

RESULTS

The reduced data for precipitation, soil moisture, windspeed, and temperature are presented in Table 1.
Bagnold data, summarized in Tables 2
and 3, were expressed as dust flux (ug/em2/day) and Pu concentrations
(pCi/g dry dust); the values represent estimated integral averages for
each time interval.
Table 4 also includes the fraction of the dust
particles collected with diameters greater than 53 ym to compare with

soil sampling results at the site (Nyhan et al., 1976).

Dust flux was

also estimated separately for ground creep events (C_), saltation pro-

c

cesses (Cl); and for total flux (C,).

Multiple and simple linear and curvilinear regression analyses were
applied to the dust flux data assuming a soil erosion relationship
stating that the local wind erosion factor varies directly with the cube
of the wind velocity, and inversely with the cube of the soil moisture

content (Chepil and Woodruff, 1963).

Additionally, the model includes

an effect of air temperature near the ground on dust flux based on the
relationship between heat flux from soil to air and soil moisture content

via evapotranspiration (Geiger, 1965; Change et aZ., 1965; Baver, 1964).
Heat flux from soil to air was assumed to be proportional to the fourth
power of the absolute temperature of air near the ground because of its
relationship to soil temperature at the surface of the ground, which is
so dependent.

Precipitation was assumed to affect dust flux through its effect on soil
moisture status, soil crustal formation and dissolution, raindrop
impact energy, and sheet water erosion in the lower collectors (Baver

et al., 1972).

Our initial hypothesis was that dust flux would be related to the parameters described above by a relationship of the form (Baver et al.,

1972; Wischmeier et al., 1958):
~3,.3
Cog p _7 DyPT 4, MU

(1)

where

C. st dust flux for specified collectors (ground creep (c),
7“
saltation (s), and total (t)) ug/em2/day (Table 2)

by

= proportionality constant (regression coefficient)

683

Select target paragraph3