1. Air Pollution Engineering (EAT 301)
AIR POLLUTION CONCENTRATION MODEL

2. Air Pollution (AP) Concentration Models
Fixed-box models
Diffusion models
Gaussian plume models
Plume rise

3. Why do we need AP modeling ?
Polluted air can adversely affect humans, plants, animals and buildings.
Major pollution events can cause illness and death.
Chronic pollution, even at low levels can cause and exacerbate respiratory illness.
Pollution may arise from industry, domestic and commercial heating, agriculture and transport.
Major problems are now being created by motor vehicles, despite technological improvements.

4. What is air pollution modeling ?
Air pollution modeling are mathematical and numerical techniques to simulate the physical and chemical processes that affect air pollutant as they disperse and react in the atmosphere.
Based on inputs of source information (e.g. emission rates, stack height) and meteorological data.
They are used to:
Compliance with DOE referring to EIA.
(Health) risk analysis.
Emergency planning.

5. Type of AP modeling Fixed-box models Dispersion (diffusion) models
Single and multiple box models, with and without chemical reactions
Dispersion (diffusion) models
Single and multiple point sources
Receptor models
3 types of models.

6. Types of Models Meteorological model Emission model Chemical model
AIR QUALITY/
AIR POLLUTANT
MODELS
Source dispersion
model
Receptor
model

7. Continue….. Emission model Meteorological model Chemical model
Estimates temporal and spatial emission rates based on activity level, emission rate per unit of activity and meteorology.
Meteorological model
Describes transport, dispersion, vertical mixing and moisture in time and space.
Chemical model
Describes transformation of directly emitted particles and gases to secondary particles and gases; also estimates the equilibrium between gas and particles for volatile species.
Source dispersion model
Uses the outputs from the previous models to estimate concentrations measured at receptors; includes mathematical simulations of transport, dispersion, vertical mixing, deposition and chemical models to represent transformation.
Receptor model
Infers contributions from different primary source emissions or precursors from multivariate measurements taken at one ore more receptor sites.

8. Classification of AP models
Developed for a number of pollutant types and time periods
Short-term models – for a few hours to a few days; worst case episode conditions.
Long-term models – to predict seasonal or annual average concentrations; health effects due to exposure.
Classified by
Non-reactive models – pollutants such as SO2 and CO.
Reactive models – pollutants such as O3, NO2, etc.
Classified by coordinate system used
Grid-based
Region divided into an array of cells
Trajectory
Follow plume as it moves downwind
Classified by level of sophistication
Screening: simple estimation use preset, worst-case meteorological conditions to provide conservative estimates.
Refined: more detailed treatment of physical and chemical atmospheric processes; require more detailed and precise input data.

9. USEPA AP models

10. AP balance equation
The general balance equation applies to some specified set of boundries can de defined as follows:
Accumulation
rate
All flow
rates in
All flow
rates out = -
Creation
rate
Destruction
rate + -

11. Fixed-box model
Simple box model of rectangular city

12. Fixed-box model Simple fixed-box model for a rectangular city:
c – pollutant concentration in air living box
b – pollutant concentration in entering air
q – pollutant mass emission rate per unit area in the city (area source)
L – length of box in direction of wind
u – wind speed
H – mixing height

13. Fixed-box model
The city is a rectangle with dimension W and L and one side is parallel with wind direction.
Complete atmospheric turbulence is produced and total mixing of pollutants up to H and no mixing above this height.
The turbulence is strong enough in the upwind direction that the pollutant concentration is uniform in the whole volume of air over the city and not higher at downwind side than upwind side.
The wind blows in x direction with velocity u. This velocity is constant and is independent of time, location or elevation above the ground (steady state condition). We use average u between at the ground (z=0) and at H.
To compute the air pollutant concentration using Box Model the following major assumptions must be made:-

14. Continue….
The concentration of pollutant entering the city (at x = 0) is constant and is equal to b (background concentration). The units are g/m³ or µg/m³.
The air pollution rate of the city is Q (g/s). This is usually given as emission rate per unit area, q, g/s.m².
Q = qA
This emission rate is constant and unchanging with time (in steady state condition)
No pollutant enters or leaves through the top or side of the box.
The pollutant is long-lived in the atmosphere (destruction rate = 0).
A = WxL.

15. Continue….
With all these assumption and using the general mass balance, the equation is simplified as below:
All flow
rates in
rates out = -
All flow
rates in
rates out =
A = WxL.
Accumulation
rate
All flow
rates in
rates out
Creation
Destruction = - +

16. Fixed box model – All flow rate in
Upwind side of city
Flow rate in = uWHb
Where:
uWH – volume/time
b – mass/volume
Therefore:
Flow rate in = mass/time

17. Fixed box model – All flow rate out
Pollutant emitted by the city
Flow rate in = Q = qWL
Where:
q – mass/time.area
WL – area
and
Flow rate in = mass/time
According to the assumption,
the concentration of entire city
is a constant and equal to c.
Therefore:
Flow rate out = uWHc

18. Continue….
Substitute these expression into E1:
E.1

19. Fixed-box model – Example 1
A city with dimension W  L  H (7 km  13 km  1.5 km) had a wind velocity of 4 m/s. The upwind concentration of SO2 is 10 µg/m3. The emission rate for the city is 4.5 x 10-6 g/s.m2. What is the concentration of SO2 over the city?

20. Example 1 - Answer W = 7 km L = 13 km H = 1.5 km u = 4 m/s
b = 10 µg/m3
q = 4.5 x 10-6 g/s.m2

21. Fixed-box model – Example 2
A city with dimension W  L  H (5 km  15 km  1 km) had a wind velocity of 3 m/s. The upwind concentration of CO2 is 5 µg/m3. The emission rate for the city is 4.0 x 10-6 g/s.m2. What is the concentration of CO2 over the city?

22. Example 2 - Answer W = 5 km L = 15 km H = 1 km u = 3 m/s b = 5 µg/m3
q = 4.0 x 10-6 g/s.m2

23. Fixed-box model
The model indicates that the upwind concentration for a long lived pollutant is additive to the concentration produced by the city.
From the pollutant concentration in the air living box (see equation), the concentration (c) increases with q and L and decreases with u and H.
Most of the models predicts concentrations for only one specific meteorological condition.
To calculate the annual average concentration of some pollutant, we need to calculate the concentration for each meteorological condition and then multiply by the frequency of occurrence for that meteorological condition.

24. Continue…. =  Annual average concentration Concentration for that
meteorology
Frequency of
occurrence of that
meteorology
= 
Over all
meteorologies

25. Fixed-box model – Example 3
For the city in Example 1, the meteorological conditions described (u = 4m/s, H = 1.5 km) occur 34% of the time. For the remaining of time, the wind blows at right angles from the direction shown in figure at velocity of 8 m/s and the same mixing height. What is the annual concentration of CO in this city?

26. Example 3 - Answer
Find the concentration for another meteorology condition:
W = 7 km
L = 13 km
H = 1.5 km
u = 8 m/s
b = 10 µg/m3
q = 4.5 x 10-6 g/s.m2

27. Continue…. =  Therefore: Annual average concentration Concentration
for that
meteorology
Frequency of
occurrence of that
meteorology
= 
Over all
meteorologies

28. Fixed-box model – Example 4
For the city in Example 1, the meteorological conditions described (u = 3 m/s, H = 1 km) occur 40% of the time. For the remaining 60%, the wind blows at right angle to the direction shown in figure at velocity of 6 m/s and the same mixing height. What is the annual concentration of CO in this city?

29. Example 4 - Answer
Find the concentration for another meteorology condition:
W = 5 km
L = 15 km
H = 1 km
u = 6 m/s
b = 5 µg/m3
q = 4.5 x 10-6 g/s.m2

30. Continue…. =  Therefore: Annual average concentration Concentration
for that
meteorology
Frequency of
occurrence of that
meteorology
= 
Over all
meteorologies

31. Fixed-box model – Example 5
A city consist of 3 parallel strips, located perpendicular to the wind. For all of the strips the wind velocity is 5 m/s. The background concentration of NOx entering the upwind suburbs is 1.4 mg/m3. The properties of each of the strips are describe below. Estimate the concentration of NO2 at the downwind edge of the city. ?
Name of trips
Length (km)
Emission rate (g/s.km2)
Mixing height (m)
Upwind suburbs 6
150
380
Downtown
2.5
550
450
Downwind suburbs 5
120
410

32. Fixed-box model – Example 5C B A

33. Example 5 - Answer 1st Section L = 6 km H = 380 m u = 5 m/s
b = 1.4 mg/m3
q = 150 g/s.km2

34. Example 5 - Answer 2nd Section L = 2.5 km H = 450 m u = 5 m/s
b = 1.87 mg/m3
q = 550 g/s.km2

35. Example 5 - Answer 3rd Section L = 5 km H = 410 m u = 5 m/s
b = 2.48 mg/m3
q = 120 g/s.km2

37. Diffusion models – Gaussian plume
Objectives
To develop dispersion model for point source using Gaussian plume model.
Highlight the main parameters that influence the accuracy of the model.
Explain briefly the algorithms used in the model

38. Evolution of air quality models (AQM)
1st generation AQM (1970s s)
Dispersion Models (e.g., Gaussian Plume Models-ISC)
Photochemical Box Models (e.g. OZIP/EKMA)
2nd generation AQM (1980s s)
Photochemical Grid Models (e.g., UAM, RADM)
3rd generation AQM (1990s s)
Community-Based ‘One-Atmosphere’ Modeling System (e.g., U.S. EPA’s Models-3/CMAQ)

39. First generation AQM Gaussian Dispersion Model ISC3, CALPUFF, AERMOD
(for primary pollutants)
Photochemical Box Model
OZIP/EKMA
(for ozone)

40. Second generation AQM
Eulerian Grid Models
UAM, RADM, REMSAD, ROM

41. Third Generation AQM – One-Atmosphere Modeling: Models-3/CMAQ
Mobile
Sources
Ozone
NOx, VOC,
PM, Toxics
(Cars, trucks, planes,
boats, etc.) PM
Industrial
Sources
Acid Rain
Chemistry
Meteorology
NOx, VOC,
SOx, PM,
Toxics
Visibility
(Power plants, refineries/
chemical plants, etc.)
Air Toxics
Area
Sources
Atmospheric
Deposition
NOx, VOC,
PM, Toxics
Climate Change
(Residential, farming
commercial, biogenic, etc.)

42. Diffusion models – Gaussian plume
It is a material balance model.
Most widely used techniques for estimating the impact of non-reactive pollutants.
Source of air pollutants
Point sources (e.g. stack)
Line sources (e.g. roads)
Area sources (e.g. treatment ponds)
Volume sources (e.g. buildings)
Most of the emission releases into the atmosphere are point sources.

43. Diffusion models – Gaussian plume
z (z = to H on plume centerline) h h H
x (wind direction) y
h = plume rise
h = stack height
H = effective stack
height
H = h + h
Plume centerline
The plumes normally rise higher above the smoke stack because they are emitted at higher temperature than atmosphere and with vertical velocity.
For Gaussian plume calculations the plume is assumed to be emitted from a point with coordinated 0,0,H.
2. The smoke emitted at the point source is assumed to be a nonbuoyant pollutant at emission rate Q (g/s) and blows in x direction with velocity u that independent of time, elevation or location.
3. The problem is to compute the concentration due to this source at any point (x, y, z) for x>0
x=y=z=0 at base of stack

44. Gaussian plume Assumptions:
The plume is assumed to be emitted from a point with coordinated 0,0,H.
The smoke emitted at the point source is assumed to be a nonbuoyant pollutant at emission rate Q (g/s) and blows in x direction with velocity u that independent of time, elevation or location.
The problem is to compute the concentration due to this source at any point (x, y, z) for x>0.
This approach tries to calculate the average value without making any statement about instantaneous values.

45. Plume shapes and typical velocity

46. AP balance equation
The general balance equation applies to some specified set of boundries can be defined as follows:
Accumulation
rate
All flow
rates in
All flow
rates out = -
Creation
rate
Destruction
rate + -

47. Gaussian plume
To find out how the contaminated air expands by turbulent mixing, we need to perform material balance around some small cube of space near the center of the plume. Assume that neither material is created nor destroyed in the atmosphere z y x

48. Accumulation rate = (all flow rates in) – (all flow rates out)
Gaussian plume
Accumulation
rate
All flow
rates in
All flow
rates out = -
Creation
rate
Destruction
rate + -
Therefore:
Accumulation rate = (all flow rates in) – (all flow rates out)

49. Gaussian plume
The accumulation rate is the time derivative of the amount contained that is concentration and volume.
But the volume of the cube is not changing with time.
There will be no bulk flow (e.g. convection) into or out of the cube because the cube is moving with the local wind velocity.
However, there are flows through all the surfaces of the cube due to turbulent mixing.

50. Continue….
The flux of material being mixed across any surface is given by
where:
c – concentration
n – distance in the direction (normally x, y or z)
K – turbulent dispersion coefficient

51. Continue…. Flux, must have units of mass/time.area (g/s.m2).
c/n, has a dimension of mass/length4.
K (eddy diffusitivity), must have dimensions of length2/time (e.g. m2/s).
–ve, indicate that the flow is from higher concentration to low.
Gradient transport or K theory or first order closure approach.

52. Continue…..
The cube has 2 faces that look in x direction (y and z). So, the net flow into the cubes in the x direction is
Since there are 6 faces involving y and z, these 6 faces (of the box) represent the flows in or out by turbulent mixing.
Flow in
Flow out z y x

53. Continue….
E.1
E.2
Accumulation rate = (all flow rates in) – (all flow rates out)
E.3
Therefore:
Substitute E.1 and E.2 into E.3 and divided both sides with x y z…….

54. Continue….

55. Continue….
But……
So that if we take the limit of an infinitesimally small cube, it becomes….
Since experimental data indicates that for turbulent diffusion in the
atmosphere the values of K in the 3 directions are not the same, therefore

56. Continue…..
The Gaussian plume equation is regularly applied to pollutant spreading in 1, 2 or 3 dimensions.
By using equation below,
the 1, 2 or 3 dimensions are as follows:

57. Continue…..
One dimension:
Two dimension:
Three dimension:

58. Gaussian plume – 2-D spreading
To use the 2 dimensions equation for problems solving, the material balances and substitutions had been made as follows:
Where:
c - mean concentration of diffusing substance (kg/m3)
y and z are called horizontal and vertical dispersion coefficients (m)
Q - contaminant emission rate (g/s); lateral dispersion coefficient function (m); vertical dispersion coefficient function (m)
y – crosswind distance (m)
u - mean wind velocity in downwind direction (m/s)
z - vertical distance above ground (m)
H - effective stack height (h + h)
The general equation to calculate the steady state concentration of an air contaminant in the ambient air resulting from a point source is given by….

59. Continue…… Plume boundary
The general equation to calculate the steady state concentration of an air contaminant in the ambient air resulting from a point source is given by….
Plume boundary

60. Continue….
If we set y = (z - H) = 0, then exp 0 = 1. This shows the concentration on the centerline of the plume.
The two  values show that this centerline concentration decrease with the downwind distance. Hence, the concentration decreases as the plume move in the horizontal and vertical directions.
The general equation to calculate the steady state concentration of an air contaminant in the ambient air resulting from a point source is given by….

61. Example 1
A factory emits 34 g/s of SO2 at height H. The wind speed is 5 m/s. At a distance of 1 km downwind, the values of y and z are 24 m and 37 m, respectively. What are the concentration of SO2 at the centerline of the plume, and at a point 60 m to the side and 20 m below the centerline?

62. Answer 1
Q = 34 g/s
u = 5 m/s
y = 24 m
z= 37 m

63. Gaussian plume – 2-D spreading
The basic Gaussian plume equation predicts a plume that is symmetrical with respect to y and z and ignoring the ground level effect (H).
Different values of y and z mean that the spreading in the vertical and horizontal directions is not equal. Usually y > z.
The horizontal dispersion coefficient (y) forms a family of a straight lines (for various atmospheric conditions) with slope of
The vertical dispersion coefficient (z) forms a fan- shaped pattern for various atmospheric conditions.

64. Horizontal dispersion coefficient (y).
Horizontal dispersion coefficient as a function of downwind distance from the source for various stability categories.
The lines labeled A to F is correspond to different levels of atmospheric stability.

65. Vertical dispersion coefficient (z)
Vertical dispersion coefficient as a function of downwind distance from the source for various stability categories..
The lines labeled A to F is correspond to different levels of atmospheric stability.

66. Continue…. Clear and hot weather with low wind speed
The air near the ground is heated by the sun causing the air to rise and thus cause the pollutant to mix.
The atmosphere is unstable thus the values of y and z will be larger.
Cloudless cold night
The ground is cooled by radiation and thus cooled the air near the ground.
The air are in inversion layer, making the atmosphere stable and inhibit the pollutant the values of y and z will be small.

67. Continue….
The horizontal (y) and vertical (z) dispersion coefficient along with Gaussian plume 2-D equation are able to predict downwind concentrations from the point source.
This is the most widely used method for routine calculations of air pollutant dispersion from the point source.
These plots are based on measurements for x1. The values beyond that are based on extrapolations.

68. Atmospheric stability classes
5-6 C
C-D D
 6

69. Example 2 Answer 2 Stability category – C y – 70 m z – approx. 45 m
Estimate the values of y and z at a point of 0.7 km downwind from a pollutant source on a bright sunny day with the wind speed 6 m/s.
Answer 2
Stability category – C
y – 70 m
z – approx. 45 m

70. Example 3
An industrial boiler is burning at 12 tons of 2.5% sulfur coal/hr with an emission rate of 151 g/s. The operation was conducted during night time with thick clouds. The following exist : H = 120 m, u = 2 m/s. Determine the.….
i. Stability class ?
ii. y ?
iii. sz ?
iv. Concentration of SO2 at the centerline of the plume and at a point 1 km to the side and 10 m below the centerline ?

71. Answer 3 i. Stability class D. ii. y is approx. 70m. iii. z is 35 m.
iv. C = 2.37  g/m3

72. Gaussian plume – Ground level
The up and downwards random atmospheric motion that spread the plume in vertical direction cannot penetrate the ground. Hence, the vertical spreading terminate at z=0.
It is assumed that the pollutant is reflected upward as if the ground is a mirror.
To compute the concentration that consider the ground effect, the equation is similar to the previous one accept for additional of mirror image plume, (z+H)2.

73. Gaussian plume – Ground level

74. Gaussian plume – Ground level
If z=H, the main plume has a high concentration (in the air). Whereas the mirror-image plume has a small number [exp -½ (2H/z)2].

75. Example 4
A factory emits 20 g/s of CO at height (H) of 20 m. The wind speed is 5 m/s at distance 0.5 km downwind for C stability. What are the CO concentration at a point of 25m to the side and 2 m above the ground ?
H = 20 m
Q = 20 g/s
u = 5 m/s
Stability C
y = 50 m
z= 30 m

76. Answer 4

77. Gaussian plume – Ground level
When z=0, the main plume and the mirror-image plume have the same value (at the ground level).
When y=0 and z=0, which correspond to the line on the ground directly under the center of the plume
Important because human may be exposed to this level.

78. Ground level cu/Q for C stability

79. Example 5
A large copper smelter has a stack of 150 m high and a plume rise of 75 m. It is currently emitting 1000 g/s of SO2. Estimate the ground level concentration of SO2 from this point source at a distance of 5 km directly downwind when the wind speed is 3 m/s and the stability class is C?
h = 150 m
Q = 1000 g/s
u = 5 m/s
Stability C
y = 400 m
z= 250 m

80. Answer 5

81. Plume rise
Thermal power plants, petrochemical industries and factories (e.g. oil palm mill) releases emissions into the atmosphere.
These emissions will rise from the stack the a plume will occurred which moves horizontally.
Plume rise buoyantly because:
They are hotter than the surrounding air.
They exit the stack with vertical velocity.
They stop rising because as they mix with the surrounding air, they lose the velocity and cool by mixing.
Finally, the plume will settled in the atmosphere when the temperature is the same with atmosphere.

82. A dispersion model with virtual source at an effective stack height H
Cont….
A dispersion model with virtual source at an effective stack height H

83. Cont….. To calculate the plume rise: h - plume rise (m)83
To calculate the plume rise:
h - plume rise (m)
Vs = stack exit velocity (m/s)
D = stack diameter (m)
u = wind speed (m/s)
P = pressure (milibars)
Ts = stack gas temperature (K)
Ta = atmospheric temperature (K)

84. Example 6
Estimate the plume rise for a 2 m diameter stack whose the exit gas has a velocity of 34 m/s when the wind velocity is 4 m/s, the pressure is 1 atm and the stack and surrounding temperatures are 85 OC and 33 OC respectively.
Vs = 34 m/s
D = 2 m
u = 4 m/s
P = 1 atm (1013 milibar)
Ts = 85oC (358 K)
Ta = 33oC (306 K)

85. Answer 6

88. Gaussian Dispersion Models
Most widely used
Based on the assumption
plume spread results primarily by molecular diffusion
horizontal and vertical pollutant concentrations in the plume are normally distributed (double Gaussian distribution)
Plume spread and shape vary in response to meteorological conditions X Z Q u Y H 88
12/28/2018 88

89. Model Assumptions
Gaussian dispersion modeling based on a number of assumptions including
Steady-state conditions (constant source emission strength)
Wind speed, direction and diffusion characteristics of the plume are constant
Mass transfer due to bulk motion in the x-direction far outshadows the contribution due to mass diffusion
Conservation of mass, i.e. no chemical transformations take place
Wind speeds are >1 m/sec.
Limited to predicting concentrations > 50 m downwind 89
12/28/2018 89

90. Atmospheric Stability Classes
Gaussian Dispersion Equation
Why isn’t x in the equation?
Atmospheric Stability Classes
Table 7.4 90
12/28/2018 90

91. Dispersion Coefficients: Horizontal
Fig 7.12 91
12/28/2018 91

92. Dispersion Coefficients: Vertical
Fig 7.13 92
12/28/2018 92

93. Gaussian Dispersion Equation
If the emission source is at ground level with no effective plume rise then
Plume Rise
H is the sum of the physical stack height and plume rise. 93
12/28/2018 93

94. Plume Rise
For neutral and unstable atmospheric conditions, buoyant rise can be calculated by
Buoyant plume: Initial buoyancy >> initial momentum
Forced plume: Initial buoyancy ~ initial momentum
Jet: Initial buoyancy << initial momentum
Vs: Stack exit velocity, m/s
d: top inside stack diameter, m
Ts: stack gas temperature, K
Ta: ambient temperature, K
g: gravity, 9.8 m/s2
where buoyancy flux is 94
12/28/2018 94

95. (heat emission rate, kJ/s)
Carson and Moses: vertical momentum & thermal buoyancy, based on 615 observations involving 26 stacks.
(heat emission rate, kJ/s)
(stack gas mass flow rate. kg/s)
When pollutants are dispersed to the ground level, how should we handle the situation? 95
12/28/2018 95

96. What if the surface is absorbing?
Wark & Warner, “Air Pollution: Its Origin & Control”
What if the surface is absorbing?
How should the concentration profile look like w/ reflection? 96
12/28/2018 96

97. Ground level concentration97
12/28/2018 97

98. Maximum Ground Level Concentration
Under moderately stable to near neutral conditions,
The ground level concentration at the center line is
The maximum occurs at
Once sz is determined, x can be known and subsequently C. 98
12/28/2018 98

99. Example
An industrial boiler is burning at 12 tons (10.9 mton) of 2.5% sulfur coal/hr with an emission rate of 151 g/s. The following exist : H = 120 m, u = 2 m/s, y = 0. It is one hour before sunrise, and the sky is clear. Determine downwind ground level concentration at 10 km.
Stability class =
sy =
sz =
C(10 km, 0, 0) =
Stability class: F
y = 230 m
z = 53 m
C (10 km, 0, 0) = 121 ug/m3 99
12/28/2018 99

100. Exercise
If emissions are from a ground level source with H = 0, u = 4 m/s, Q = 100 g/s, and the stability class = B, what is downwind concentration at 200 m?
At 200 m:
sy =
sz =
C(200 m, 0, 0) =
At 200 m: y = 31 m,  z = 21 m, C(10 km, 0, 0) = 12.2 mg/m3
100
12/28/2018
100

101. Example
Calculate H using plume rise equations for an 80 m high source (h) with a stack diameter = 4 m, stack velocity = 14 m/s, stack gas temperature = 90o C (363 K), ambient temperature = 25 oC (298 K), u at 10 m = 4m/s, and stability class = B. Then determine MGLC at its location.
F =
h plume rise =
H =
sz =
sy =
Cmax =
F = 98 K, h plume rise = 152 m, H = 232, z = 164 m, y = 170 m Cmax = 33.4 ug/m3, x = 2 km downwind.
Residents around Florida Rock Cement Plant are complaining its emission being violating its allowed level. The plant has its facility within 0.5 km diameter. Its effective stack height is 60 m. You are a FLDEP environmental specialist. Where are you going to locate your air quality monitors? Why?
101
12/28/2018
101

102. Chemical Mass Balance Model
A receptor model for assessing source apportionment using ambient data and source profile data.
Available at EPA Support Center for Regulatory Air Models - 8 1 2
3,4,5,12 6 7 9 10 11 13 14
PM10 emissions from permitted sources in Alachua County (tons) (ACQ,2002)
2000 Values
1. GRU Deerhaven 144.2
2. Florida Rock cement plant 34.35
3. Florida Power UF cogen. plant 3.19
1997 Values
4. VA Medical Center incinerator 0.2
5. UF Vet. School incinerator 0.2
6. GRU Kelly 1.9
7. Bear Archery 9.5
8. VE Whitehurst asphalt plant 4.9
9. White Construction asphalt plant 0.7
10. Hipp Construction asphalt plant 0.3
11. Driltech equipment manufacturing 0.2
Receptor Sites
12. University of Florida
13. Gainesville Regional Airport
14. Gainesville Regional Utilities (MillHopper)
102
12/28/2018

103. Cij = Σ(aik×Skj) Principles
Mass at a receptor site is a linear combination of the mass contributed from each of a number of individual sources;
Mass and chemical compositions of source emissions are conserved from the time of emission to the time the sample is taken.
Cij = Σ(aik×Skj)
Cij is the concentration of species ith in the sample jth measured at the receptor site:
aik is the mass fraction of the species in the emission from source kth, and
Skj is the total mass contribution from source kth in the jth sample at the receptor site.
103
12/28/2018
103

104. Example
Total Pb concentration (ng/m3) measured at the site: a linear sum of contributions from independent source types such as motor vehicles, incinerators, smelters, etc
PbT = Pbauto + Pb incin. + Pbsmelter +…
Next consider further the concentration of airborne lead contributed by a specific source. For example, from automobiles in ng/m3, Pbauto, is the product of two cofactors: the mass fraction (ng/mg) of lead in automotive particulate emissions, aPb, auto, and the total mass concentration (mg/m3) of automotive emission to the atmosphere, Sauto
Pbauto = aauto (ng/mg) × Sauto (mg/m3air)
104
12/28/2018
104

105. Assumptions
Composition of source emissions is constant over period of time,
Chemicals do not react with each other,
All sources have been identified and have had their emission characterized, including linearly independent of each other,
The number of source category (j) is less than or equal to the number of chemical species (i) for a unique solution to these equations, and
The measurement uncertainties are random, uncorrelated, and normally distributed (EPA, 1990).
105
12/28/2018
105