FIELD TESTING AND EVALUATION OF DUST DEPOSITION AND ...

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counting by scanning electron microscopy (SEM) the number of particles deposited on polycarbonate membranes which were exposed using a three-axis support stand (Figure 3-1). Six samples corresponding to the stream-wise, crosswind and vertical directions (+x, -x, +y, -y, +z, and –z) could be exposed simultaneously. The +x direction was downwind perpendicular to the road and the +z direction was vertical upward. The substrates were exposed to dust from vehicles driving on the test road at speeds from 5 to 50 mph. Alternative locations, exposure durations, and substrate materials were tested as discussed in method development, below. The best results were obtained on polycarbonate substrates (Millipore type GTTP, Fisher Scientific) located 5 m downwind of the road and exposed for 15 vehicle trips. 6-Direction Passive Deposition Polycaronate Polycarbonate membrane on on Carbon Tape Petri Dish Detail Typical for 6 Support Stand with Clamps Grimm Figure 3-1 The experimental setup of the passive deposition on flat surfaces for examination by electron microscopy. Three-axis (corresponding to the stream-wise, crosswind, and vertical components of wind direction i.e. +x, +y, +z, -x, -y and –z directions) passive collection substrates were mounted on a ring stand. Standard right hand coordinates are used with the positive x-axis downwind perpendicular to the road. A GRIMM inlet was placed right next to it to monitor the dust concentration. The substrates were placed 1 or 2m high and 5 or 10m away from the unpaved road. The size and number of particles deposited on the flat substrates were determined by quantitative electron microscopy. The flat substrates were mounted on double-sided carbon tape in a disposable 50 mm diameter Petri dish. Different substrate types were tested side by side in a single Petri dish. After exposure in the field the Petri dish covers were replaced and the set of samples was boxed for shipment to the laboratory. To prepare for microscopy, a section of the substrate assembly was cut from the dish and the bottom layer of conductive double-sided carbon tape was used to mount the sample on an aluminum SEM stub (Hitachi S-450®, Redding, CA) for gold coating. All samples were evaluated qualitatively for dust loading using the Hitachi S3000N® scanning electron microscope (Hitachi, Pleasanton, CA) located in the Material Science and Engineering 3-2
Department at the University of Utah. The selected filters that passed QA underwent full quantitative microscopy to provide the images for particle counting. SEM images for counting were taken in a non-overlapping structured grid pattern at three magnifications (100X, 500X, 2500X). By combining data from multiple magnifications both the infrequent, large, high-mass particles and the ubiquitous, less massive sub-micron particles could be quantified. Particles d>20 µm were measured on 100X images, particles 5
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: 3. MEASUREMENT OF DEPOSTION VELOCIT
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
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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