REVIEW OF RESUSPENSION MODELS 221 



Since the power, P, is about 3 and the concentration over the heights from 0.7 to 2 m 

 deviates only about 20% from the 1-m reference velocity, one obtains, by combining the 

 above, 



F^-0.12u=,Xi (10) 



The data at GMX and Texas, respectively, give values for Xi of 



Xi=6.1u^«^ (11) 



and 



Xi=522u^3^ (12) 



For GMX and Texas, respectively, these values then result in fluxes of 



F = 0.73u^°^ (13) 



and 



F = 62.6u^3« (14) 



A tentative model of the upward dust flux was derived from profile and soil erosion 

 data from a number of locations. This was titled the Gillette-Shinn model and is 

 expressed by 



where F is the flux, the reference wind speed is 1 m/sec, Fq is a reference dust flux at 

 U:^ = 0, and 7 is the power in the dust profile. From a series of experiments by Gillette 

 and Goodwin (1974), a tentative relationship between the parameters in the Gillette- 

 Shinn model and the soil-erosion index was derived (Fig. 2). 



An initial attempt to assess resuspension from the ground was made by Healy and 

 Fuquay (1958) and Healy (1974) using data from Hilst (1955) and Hilst and Nickola 

 (1959) who were using zinc sulfide (ZnS) particles to estimate the effects of various 

 surfaces on wind erosion. At this time the high rate of increase with wind speed due to 

 breakup of aggregates was not known, and it was assumed that the rate increased as the 

 square of the wind speed. Later, the rates were converted to a cube relation with the wind 

 speed (Healy, 1977a), although it was noted that for these results the square appeared to 

 give less variance in the data. This indicated a pickup rate of 5 x 10~^ u^ per second. 

 Since the wind speeds were measured at a 2-m height (Hilst, 1955) and the Hanford area, 

 the site of the experiments, has a Zq of about 2 cm, this value would be about 4 x 10~^ ' 

 u* per second. This can be only a preliminary estimate, however, because of the 

 alteration of the natural roughness feature by the change in courses. 



Sehmel (1977b; 1977c) and Sehmel and Lloyd (1976a) have studied the resuspension 

 of a tracer, submicrometer calcium molybdate, sprayed as a suspension over a liglitly 

 vegetated area with a roughness height of 3.4 cm. The area sprayed was within a circle of 

 29-m radius with a sampling tower in the middle. The average surface concentration on 



