FIELD TESTING AND EVALUATION OF DUST DEPOSITION AND ...

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will achieve equal deposition rates due to shadowing and other issues, the overall deposition velocity calculated using this area would be low. Logs of all the flat substrate samples and the artificial vegetation experiments, including samples not completely analyzed due to method or QA issues, are given in Table 3-2 and Table 3-3 respectively. This includes method development tests, samples where data were lost, samples that did not pass QA, and spare field samples that were not analyzed. The incremental cost of collecting spare field samples during the campaign was low compared to the cost of microscopy and image analysis. 3.2 Results: Deposition velocities measured by SEM and gravimetric techniques Microscopy counting of particles deposited on flat substrates gave a deposition velocity based on projected area ranging from 0.3 cm/s for submicron particles to 2 cm/s for 3 µm particles. The artificial vegetation suspended above a tub gave a deposition velocity based on horizontal surface area of about 10 cm/s. Deposition velocities by electron microscope particle counting of flat substrates and by gravimetric analysis of the deposits on artificial vegetation are presented in Figure 3-3. These values are also compared to predictions for dry deposition into a forest canopy in a theoretical study by Slinn (1982). The model prediction curve plotted in Figure 3-3 corresponds to a wind velocity of 5 m/s and a value of gamma (a measure of wind profile in the canopy) of 3.5, which represent the middle of the range considered by Slinn. A major difference is that Slinn's model calculates vertical flux from the atmosphere to a horizontal area of forest canopy while the data from this study are deposition from a horizontally moving cloud impinging on the projected area of a surface. Figure 3-4 gives the directional variation in the deposition velocities on flat surfaces (polycarbonate filter) normalized by the deposition velocity measured on the horizontal surface facing up (+z). The flux on the +z surface corresponds to the deposition velocity measured by Slinn. In addition, gravitational settling would be expected to deposit particles on this surface only. The vertical plane surfaces (-x, +y, -y) show enhanced deposition due to impaction caused by wind and vehicle wake whereas the deposition on surfaces facing down and away from the road (+x, -z) is presumed to be due to turbulence. Figure 3-5 shows the directional deposition velocities over the size range studied. Complete analysis was done on four samples (dry polycarbonate filters). They were SEM ID 12, 17, 18 and 19. SEM 17, 18 and 19 were 5 m away from the road and SEM 12 was 10 m away from the road. A grand average deposition velocity (17, 18, 19) curve versus each size bin plot is given in Figure 3-6. The particle concentration from the GRIMM measured coincident with the four SEM samples has been plotted in Figure 3-7. There appear to be systematic differences between the size distribution measured with a direct inlet (SEM 12) and the size distributions measured with an inlet tube. Particle losses increase the calculated deposition velocity, but data for d < 5 µm appear to be valid. Testing of alternative methods increased the chance of success for this experiment and provided data on materials and sampling strategies that can be used to design future 3-6
Table 3-2. Log of all flat substrate samples Date SEM ID # Location (x, y) # Of Trips Vehicle type 03/26/02 1N 10, 2 10 Chevy Impala Comments 03/26/02 1F 40, 2 20 Chevy Impala Very lightly loaded 03/27/02 2N 10, 2 10 Chevy Impala Only PM10 mass, no concentration by size 03/28/02 3N 10, 2 10 Chevy Impala Very lightly loaded 03/28/02 3F 40, 2 20 Chevy Impala Very lightly loaded 04/08/02 1– (+x, +y, +z) -100, 1 - Patriot Battery 04/08/02 2 5, 1 40 Voyager Missile 04/11/02 3 5, 1 17 Dodge Caravan 04/12/02 4 5, 1 20 Voyager 04/12/02 5 5, 2 20 Voyager Decided not to use oiled filters for counting Decided not to use oiled filters for counting -X filter lost, oiled base formed cake-like structure Decided not to use oiled filters for counting Decided not to use oiled filters for counting 04/12/02 8 5, 1 20 Voyager Very lightly loaded 04/13/02 1- (-x, -y, -z) -100, 1 - 1 hr upwind control 04/16/02 13 - - Voyager Not analyzed Decided not to use oiled filters for counting 13-1 - 0 - Filter pores clearly visible 13-2 - 0 - Oil forms a cracked cake-like base 13-3 (-x) 5, 1 1 - Very lightly loaded 13-4 (-x) 5, 1 5 - Loading greater than 13-3 13-5 (-x) 5, 1 5 - Cake base formed, Particles barely distinguishable 13-6 (-x) 5, 1 25 - Loading greater than 13-4 04/17/02 7 5, 1 50 2 ½ ton truck 04/17/02 14 5, 1 50 2 ½ ton truck Decided not to use oiled filters for counting Carbon tape seems to be a good substrate for future SEM experiments 04/17/02 12 10, 2.3 50 2 ½ ton truck Deposition velocity calculated 04/18/02 15 -100, 1 1 hr control Deposition velocity calculated 04/18/02 16 5, 1 5 Hemmet Spare – not analyzed 04/18/02 17 5, 1 25 Hemmet Deposition velocity calculated. 04/19/02 18 5, 2 15 04/19/02 19– (+x, +y, +z) 5, 1 15 04/19/02 20 50, 1.5 15 18 wheel Flatbed military truck 18 wheel Flatbed military truck 18 wheel Flatbed military truck Deposition velocity calculated. Deposition velocity calculated. Spare – not analyzed studies. Four different substrates were tested for flat surface sampling. The reported deposition velocities are based on SEM examination of dry polycarbonate filter membranes. The oiled filters developed a cracked surface film and it was difficult to distinguish the particles. The sample collected on carbon tape indicated that this might be a suitable substrate. The clear tape has high collection efficiency for large size particles, but it is difficult to distinguish the smaller size particles from artifacts on the adhesive surface. A comparison of particle counts done on a clear tape and a dry filter sample is given in Figure 3-8. 3-7
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 and 20: 1. INTRODUCTION 1.1 Background The
Page 21 and 22: 2.BACKGROUND Fugitive dust is emitt
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: In the laboratory, the deposited ma
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
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 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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