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Major Factors of Wind Erosion and Road Dust

Major Factors of Wind Erosion and Road Dust. Robert Surrago. Background. Fugitive/natural sources make up the majority of PM-10 and PM-2.5 emissions Two main fugitive/natural sources are wind erosion and road dust (mainly from unpaved roads). Wind Erosion - Factors. Wind speed

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Major Factors of Wind Erosion and Road Dust

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  1. Major Factors of Wind Erosion and Road Dust Robert Surrago

  2. Background • Fugitive/natural sources make up the majority of PM-10 and PM-2.5 emissions • Two main fugitive/natural sources are wind erosion and road dust (mainly from unpaved roads)

  3. Wind Erosion - Factors • Wind speed • Wind gusts are more important than average wind speed - best indicator is fastest mile • Used in conjunction with reference height to calculate the friction velocity (u = (u*/0.4) ln(z/zo))

  4. Wind Erosion - Factors • Erosion potential (P) • A function of the friction velocity (u*) & the threshold friction velocity (ut*[observed experimentally]) • If u* < ut*, then there is no chance of wind erosion (cannot overcome friction) • Each event must be treated separately

  5. Road Dust - Factors • Mean vehicle weight - the average weight of all the vehicles that traverse a given road • The more weight, the more force acting on the road  more dust can be created • Surface material silt content - dust emissions vary directly with the % of silt in the road surface material • Varies with geographic location

  6. Road Dust - Factors • Moisture content - more moisture = more particle cohesiveness  less dust created • Can be affected by precipitation • Mean vehicle speed/mean # of wheels • Faster = more force applied to surface = more dust created • More wheels = more opportunities to create more dust • Both are minor factors

  7. Wind and Road Relations • Both emission types have ways to account for frequency of disturbances • Wind - total P is sum of all disturbances • Road - mean vehicle conditions • Both types take into account material properties • Wind - threshold friction velocity • Road - silt and moisture contents

  8. Summary • Factors are similar for fugitive dust emissions • Different applications of factors yields different equations/constants • What does the future hold? • Apply to present data? • Generate emissions projections? • Questions/comments/suggestions

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