FIELD TESTING AND EVALUATION OF DUST DEPOSITION AND ...

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1.4 Report Organization This report is divided into six main Chapters. Chapter 2 reviews the literature with respect to models for particle deposition and turbulent dispersion. Pilot-scale measurement of deposition to surrogate surfaces and comparison of results with theory are summarized in Chapter 3. In Chapter 4, the three models considered in this report are introduced and analyzed. The assumptions of the Box Model and the characteristics of the ADE and ISC are examined in this Chapter. The Ft. Bliss field experiments are presented in Chapter 5. In addition to the horizontal flux and particle concentration profiles, this Chapter details the measurement of vehicle-induced turbulence and its effect on particle removal downwind of the source. Model predictions are compared with measurement and used to characterize the effect of the “injection height”. We summarize The Dugway Proving Ground experiments in Chapter 6 and analyze the related model results. A summary of findings and major conclusions is provided in Chapter 7. 1-2
2.BACKGROUND Fugitive dust is emitted from an unpaved road when a vehicle passes and disturbs the soil. A cloud of dust is raised behind the vehicle and begins to travel downwind. Initially, the dust cloud is very dense, sometimes to the point of being opaque, but with travel downwind, the cloud is dispersed by mechanical mixing at the ground and by buoyant eddies in the atmosphere. Particles suspended in the cloud can be removed by interaction with the vegetative cover in the downwind fetch of the unpaved road. Figure 2-1 schematically illustrates the progression of a dust plume emitted behind a vehicle and advected downwind over a vegetative cover. In the region (A) where the dust cloud first meets the vegetation, dust particles may be removed by individual vegetation elements. Though possibly significant, none of the models or measurements discussed in this report is geared towards quantifying the extent of removal in this “impact zone”. Some work in the area of particle removal by windbreaks may be applicable to this region (Raupach and Leys, 1999), though the specific formulation would have to be adjusted for vegetative covers with a long fetch (as opposed to a windbreak that is only several meters deep). Region C: Far Downwind 50 m < x < ∞ Region B: Near Source 5 m < x < 200 meters Region A: Impact Zone 0 < x < 20 m Point of Emission Figure 2-1. Development of a dust plume downwind of an unpaved road Very far downwind (Region C in the figure), the dust plume approaches a steady concentration profile that does not change very much with transport downwind. In between the “impact zone” and the “Far downwind” region, the concentration profile of dust particles is changing with transport distance; specifically, the dust plume is expanding in the vertical direction. The models discussed in this report are most concerned with this region, where it is necessary to simulate the expansion of the dust plume in the vertical direction simultaneously with the removal of particles at the ground by the vegetative cover. These two processes are turbulent dispersion and dry deposition, respectively. 2-1
Page 1: FIELD TESTING AND EVALUATION OF DUS
Page 5 and 6: EXECUTIVE SUMMARY The Western State
Page 7 and 8: models. Countess (2001) summarized
Page 9 and 10: TABLE OF CONTENTS 1. INTRODUCTION 1
Page 11 and 12: TABLE OF FIGURES Figure 2-1. Develo
Page 13 and 14: Figure 4-6. The fraction of particl
Page 15 and 16: Figure 5-16. Comparison of fraction
Page 17 and 18: LIST OF TABLES Table 2-1. Parameter
Page 19: 1. INTRODUCTION 1.1 Background The
Page 23 and 24: Planetary Boundary Layer (PBL) F =
Page 25 and 26: C D u* = ur The overall drag c
Page 27 and 28: St a vg u g = cA L * Equation 2
Page 29 and 30: Table 2-1. Parameters used in the S
Page 31 and 32: 1E+01 1E+00 z0 = 4.4 cm z0 = 6.4 cm
Page 33 and 34: pathway for deposition for particle
Page 35 and 36: An alternative method for modeling
Page 37 and 38: 3. MEASUREMENT OF DEPOSTION VELOCIT
Page 39 and 40: Department at the University of Uta
Page 41 and 42: In the laboratory, the deposited ma
Page 43 and 44: Table 3-2. Log of all flat substrat
Page 45 and 46: 16 Normalized Deposition Velocity 1
Page 47 and 48: 1.E+05 Deposition Velocity - cm/s 1
Page 49 and 50: are deposition from a horizontally
Page 51 and 52: single element that is intended to
Page 53 and 54: 4. MODELS USED TO STUDY PARTICLE RE
Page 55 and 56: κu ( ) * z 8 fz K zz = exp −
Page 57 and 58: C = −6 ( 1× 10 ) QV 2π u s σ
Page 59 and 60: oad. M is the mass of particles in
Page 61 and 62: By making the approximation that dm
Page 63 and 64: diameters less than 10 microns. Dis
Page 65 and 66: of such a height is somewhat arbitr
Page 67 and 68: 1 0.9 0.8 1 0.9 0.8 Fraction remain
Page 69 and 70: Fraction of Particles Remaining in
Page 71 and 72:
gravitational settling. Stable cond
Page 73 and 74:
though it is expected to improve at
Page 75 and 76:
5. DETERMINATION OF PARTICLE REMOVA
Page 77 and 78:
PM 10 measured by the DustTrak must
Page 79 and 80:
100% 90% 80% Relative Frequency (pr
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average wind speed measured at 12 m
Page 83 and 84:
where the subscript i indicates tha
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k C int = peakend k C peeakstart d
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Height z (m) 14 12 10 8 6 T1_data T
Page 89 and 90:
Horizontal fluxes of PM 10 measured
Page 92 and 93:
Table 5-2 enumerates the speed-depe
Page 94 and 95:
6 Ratio of AP-42 Emission Factor to
Page 96 and 97:
to the ground) giving an approximat
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models analyzed in this study is su
Page 100 and 101:
Table 6-1. Screen analysis of test
Page 102 and 103:
value which was used up to the midp
Page 104 and 105:
measured at 3,1. Downwind the dust
Page 106 and 107:
trips, the average readings for the
Page 108 and 109:
Fraction of particles of stated siz
Page 110 and 111:
the ground, where particles have a
Page 112 and 113:
particles through the top of the bo
Page 114 and 115:
deposition. Much of the decrease in
Page 116 and 117:
7-8
Page 118 and 119:
Gifford, F.A. (1961). Use of Routin
Page 120:
Venkatram, A. (1993). The Parametri
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