where:

v

_{g}=is the gravitational settling velocity (m/s),U

_{r}=is the approach wind speed at 10m (m/s),α =is the proportionality constant in the relationship between flux from the pit and the product of U

_{r}and concentration in the pit (Thompson, 1994).The gravitational settling velocity, v

_{g}, is computed as described in Section 1.3.2 for each particle size category. Thompson (1994) used laboratory measurements of pollutant residence times in a variety of pit shapes typical of actual mines and determined that a single value of α = 0.029 worked well for all pits studied.The adjusted emission rate (Q

_{i}) for each particle size category is then computed as:where Q is the total emission rate (for all particles) within the pit, φ

_{i}is the original mass fraction for the given size category, and ε is the escape fraction calculated from Equation (1-68). The adjusted total emission rate (for all particles escaping the pit), Q_{a}, is the sum of the Q_{i}for all particle categories calculated from Equation 1-69. The mass fractions (of particles escaping the pit), φ_{ai}, for each category is:Because of particle settling within the pit, the distribution of mass escaping the pit is different than that emitted within the pit. The adjusted total particulate emission rate, Q

_{a}, and the adjusted mass fractions, φ_{ai}, reflect this change, and it is these adjusted values that are used for modeling the open pit emissions.

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APLICACIONES castellano: DIS CUS DES RAD english: DIS CUS DES RAD

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