Modeling - Field Sampling: Principles and Practices in Environmental Analysis - page 187

Windows-friendly and is unconventional in its use of keys for moving through the
program and obtaining the data needed to make a calculation. It has some interesting
features, but will take some time to figure out if real use is to be made of it [9].
There is a similar equation for wind erosion. This equation takes the form
E= f (ICKLV)
It states that the amount of soil eroded by wind E is a function f of I soil erodability, C
climate, K soil ridge roughness, L width of field, and V vegetative cover factors. In this
case these factors are not simply multiplied together but are calculated using the
appropriate equation. This is the wind erosion equation (WEQ), and there is also a
revised wind erosion equation (RWEQ). Calculations using WEQ are carried out using a
computer program [11, 12].
Wind erosion can complicate field sampling by depositing or removing contaminants,
thus as with the USLE and RUSLE, the WEQ and RWEQ can be used to estimate where
contaminants are being exposed or buried by windblown soil. It is common for
contaminants from manufacturing to be carried in air. These contaminants can be
deposited on a field by simply falling out of the air or with rain when it occurs. Erection
of windbreaks to stop wind erosion will also allow pollutants to fall out of suspension.
This continuing source of contaminants can complicate the sampling and analysis of field
samples if not taken into account.
7.5. MODELING MOVEMENT OF PARTICLES THROUGH THE
ENVIRONMENT
Calculation or modeling the movement of particles in air may seem relatively simple, but
can be complex. There is a complex interaction of wind, field, and particle concentration.
There is also the question of the type of movement being considered. Is it by saltation or
suspended transport? Add to this the complexity of turbulent flow, and the system
becomes complex. In spite of this it is often the case that time in the air and distance
moved is relatively easy to determine. The glide path of a particle can be calculated once
the characteristics of the particle are known. This involves not only the pull of gravity but
also the shape of the particle. A flat particle will have a longer glide path than a round
particle and will take longer to reach the ground. Mass also comes into play in that as the
particle size increases the time in the air decreases until it reaches a value of 0 with
particles larger than sand.
Movement of suspended particles depends on wind speed and direction. High wind
speeds will keep particles in suspension for long distances. The direction of the wind will
determine the direction of movement of the particles, thus where the particles are
deposited will depend on both these factors, which are relatively easy to determine.
In many ways the movement of particles in water is similar to their movement in air.
The speed of particles settling will depend on their shape and mass and the flow of the
water they are suspended in. One difference is that some particles will be heavier than
water and settle; others can be less dense than water and thus float. Some particles will be