Review of Resuspension Models 



J. W. HEALY 



Resuspension has been recognized as a potential mode of human exposure to 

 contaminants in the soil for a number of years. However, methods for expressing the 

 resulting concentrations quantitatively have been crude; in most cases, the resuspension 

 factor was used. In this chapter we distinguish three main types of resuspension: 

 wind-borne, mechanical disturbance, and local. The three main models for estimating 

 concentrations (resuspension factor, resuspension rate, and mass loading) are described, 

 and the data applicable to each are reviewed. 



The studies of wind erosion of desert sands and of agricultural soils liave provided 

 much of the information available on the mechanisms involved in wind resuspension. 

 However, such a body of evidence is not available for mechanical disturbance of the soil, 

 although recent experiments have provided some data. Information on concentrations in 

 the vicinity of the individual causing the disturbance is still poor. 



Considerable progress has been made in the past few years on wind resuspension. For 

 both wind and mechanical resuspension, scientists are on the verge of providing improved 

 estimates using the resuspension rate at specific locations. However, for generic studies 

 the mass-loading approach is recommended. 



Resuspension from soils and subsequent inhalation of the resuspended material has long 

 been considered the chief source of exposure to transuranium elements deposited in soils. 

 In spite of the obvious importance of this pathway, research has been limited; thus it is 

 difficult to obtain a reasonable prediction of the resulting concentrations and inhalation. 

 In fact, Slinn (1978) indicates that he does not trust resuspension factors, rates, or 

 velocities to within many orders of magnitude. In the following text we will review the 

 data available and attempt to arrive at as reasonable an answer as possible. 



Types of Resuspension Considered 



The overall resuspension problem can be divided into three types for conceptual 

 understanding and calculations (Healy, 1977a; 1977b): (1) wind-driven resuspension, (2) 

 mechanical resuspension, and (3) local resuspension. For wind resuspension the energy 

 required to dislodge the particles arises from the wind, and the particles then disperse 

 downwind, depositing on surfaces at a rate depending on the aerodynamic properties of 

 the particles and the nature of the terrain. Both mechanical resuspension and local 

 resuspension result from mechanical disturbance of the soil. However, in the mechanical 

 resuspension case the concern is with concentrations downwind following dispersion and 

 deposition. Local resuspension, on the other hand, describes the exposure in the 

 immediate vicinity of the individual before dispersion occurs. 



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