FIELD TESTING AND EVALUATION OF DUST DEPOSITION AND ...

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value which was used up to the midpoint between the second and third measurement, and so on. 6.2.3 Calculation of Horizontal Flux The power law wind profile is appealing since analytical solutions exist for the integral of a power law for wind with either an exponential or a Gaussian function for dust concentration. For the exponential dust concentration case: F dust = C(z) u(z) dz = ∞ ( Ae − Bz) z u ref 0 z ref P − P Γ( P +1) dz = Au ref z ref B ( P+1) Equation 6-4 where Γ is the gamma function. Using a mathematical model that results in a converging definite integral avoids any uncertainty about the upper limit of integration, z max . The integral of a power law for wind, times a power law for dust concentration has an analytic solution, but does not converge. For this study, the horizontal dust flux was also calculated by trapezoidal rule numerical integration of Equation 6-1 using alternative interpolation equations to model the time averaged wind speed and concentration as a function of height. Variable step size (starting at ∆z = 0.1 m) was used to provide higher resolution near the ground where both concentration and wind speed change rapidly with height. 6.3 Results The data were collected during two vehicle activity periods between 01:00 and 02:30 Mountain Daylight Time on September 26, 2001. The clear sky, nighttime, desert conditions resulted in a stable atmosphere during the sampling period. Wind speed was generally between 1 and 5 m s -1 , which was sufficient to move the dust cloud, and the wind direction relative remained within 45° of perpendicular to the container array and road. General meteorological data are summarized in Table 6-2. Table 6-3 gives the wind speed and dust concentration mean and standard deviation. Table 6-2 Meteorological data from station DPG08, approximately 1 km south of test site, for September 26, 2002 01:00-03:00 MDT. Average Range Temperature 294 K 293 - 297 K Relative Humidity 23% 20-26% Barometric Pressure 866.54 mbar 24 hr- Precipitation 0 Wind at 10 m 3.0 m s -1 15 m s -1 gust Wind Direction from True North 98-186° 6-4
Table 6-3. Mean ± one standard deviation wind and concentration data for the entire 1.5 hr test period with 44 vehicle trips. Wind standard deviation based on variation between 15-minute averages. Concentration standard deviation based on variation between individual vehicle trips. Pulse area is the time-integrated concentration for the interval corresponding to one vehicle pass. Wind Height m Upwind m s -1 4 3.42 ± 0.51 2.22 ± 0.20 8 4.07 ± 0.50 3.44 ± 0.32 16 4.72 ± 0.52 4.59 ± 0.25 32 4.89 ± 0.31 Concentration Near Measurement 3 m from road Height m Pulse Area mg s m -3 per trip 32 m Tower m s -1 Peak Height mg m -3 Far Measurement 95 m from road Pulse Area Peak Height mg s m -3 per trip mg m -3 0.9 302 ± 171 38.9 ± 21 1.7 144 ± 92 19.9 ± 11 1.8 24.3 ± 17 0.72 ± 0.52 3.7 77.8 ± 56 10.3 ± 7.2 4.6 10.7 ± 7.2 0.41 ± 0.31 9.1 3.18 ± 3.1 0.21 ± 0.17 18.3 0.35 ± 0.1 0.019 ± 0.016 6.3.1 Wind Profile Figure 6-2 shows the wind speed versus height with the logarithmic and power law interpolation equations superposed on the 15-minute average data points. Both equations fit the upwind data within the variation of the measurements. Based on the field measurements, the fitted coefficients for Equation 6-2 upwind and at the center of the array are: Upwind Center of Array U ref at z ref, m/s 3.42 2.22 Z ref, m 4 4 P 0.234 0.414 6.3.2 Dust Concentration Typical dust concentrations versus time data are shown in Figure 6-3. Measurement locations are identified by the x, z coordinates in meters where x is downwind from the road and z is height above grade. Near-source dust clouds from individual vehicle trips appear as clearly defined spikes in the particle concentration 6-5
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FIELD TESTING AND EVALUATION OF DUS
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EXECUTIVE SUMMARY The Western State
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models. Countess (2001) summarized
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TABLE OF CONTENTS 1. INTRODUCTION 1
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TABLE OF FIGURES Figure 2-1. Develo
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Figure 4-6. The fraction of particl
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Figure 5-16. Comparison of fraction
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LIST OF TABLES Table 2-1. Parameter
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1. INTRODUCTION 1.1 Background The
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2.BACKGROUND Fugitive dust is emitt
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Planetary Boundary Layer (PBL) F =
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C D u* = ur The overall drag c
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St a vg u g = cA L * Equation 2
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Table 2-1. Parameters used in the S
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1E+01 1E+00 z0 = 4.4 cm z0 = 6.4 cm
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pathway for deposition for particle
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An alternative method for modeling
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3. MEASUREMENT OF DEPOSTION VELOCIT
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Department at the University of Uta
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In the laboratory, the deposited ma
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Table 3-2. Log of all flat substrat
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16 Normalized Deposition Velocity 1
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1.E+05 Deposition Velocity - cm/s 1
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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
Page 81 and 82: average wind speed measured at 12 m
Page 83 and 84: where the subscript i indicates tha
Page 85 and 86: k C int = peakend k C peeakstart d
Page 87 and 88: 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
Page 98 and 99: models analyzed in this study is su
Page 100 and 101: Table 6-1. Screen analysis of test
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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