mine environment

1. Air Pollution in Mines: Causes and
Control
By
Prof. I.L. Muthreja
Dept. of Mining Eng.
Visvesvaraya National Institute of Technology,
Nagpur
1

2. AIR POLLUTION
Mining Pollutants
• Particulate
• Gaseous
2

3. Components of Atmosphere
Troposphere
Stratosphere
Mesosphere
Ionosphere (Reflecting radio
waves)
8Km
50 Km
80 Km
400 Km
Pole equator
16 Km
3

4. • Troposhere
– High CO2,N2,O2 (Clouds,fog and storms formed )
– Temp reduces with ht -50 deg at 10 Km
• Stratosphere
– Temp increases with height
– Low vapour content (no clouds formation)
– Layer of OZON found
– UV of Sun absorbed
– Temp increases to -10 degrees C
• Mesosphere
– Temp reduces with ht
• Ionosphere
– Density of air is low,
– electrically charged microscopic particles reflect electromagnetic
waves
• Exosphere
4

5. Particulate Matters:
• Any dispersed mater solid or liquid in which
the individual aggregates are larger than
single small molecule (0.0002 m m), but
smaller than 500 m m. Result of disintegration
of solids, if liable to remain in atmosphere,
may cause pollution
• Liquid droplets have similar effects, hence
included in this category
• Mining: excavation, comminution and
transport of solids cause dust pollution.
5

6. • DUST:
Solid particles caused by the breakup of larger
masses through grinding, crushing or blasting
operations
• Smoke:
Fine solid particles resulting from combustion of
organic particles. Size 0.5-1.0 m m
• Fumes:
Fine solid particles formed by condensation of
vapours of solid materials. Size- 0.03-0.3 m m
• Mist:
Liquid particles or droplets < 10 m m
If mist concentration is high enough to obscure
visibility, it is called as “Fog”
• Spray:
Liquid particles formed by atomizing of parent
liquids. Size 10-100 m m
6

7. WHAT IS MINE DUST AND WHY DOES IT NEED TO BE
CONTROLLED?
Dust is a generic term used to describe fine particles that are
suspended in the atmosphere.
The term is non-specific with respect to the size, shape and
chemical make-up of the particles.
Particles as small as a few nanometers and as large as 100
microns (μm) have been measured in the atmosphere.
Dust is formed when fine particles become entrained in the
atmosphere by the turbulent action of wind, by the mechanical
disturbance of fine materials, or through the release of
particulate-rich gaseous emissions.
The concentration of particles in the atmosphere can range
from a few micrograms to hundreds of micrograms per cubic
metre (μg/m3 ) in highly polluted areas.

8. • Dust associated with mining activity usually
occurs as a result of the disturbance of fine
particles derived from soil or rock.
• Dust formation is initiated by the disturbance
of particles through mechanical action eg
blasting, handling, transporting, in
combination with air movement.
• Where particles are small and light, with a
high surface area relative to their mass, the
upward forces exerted on particles by air
movement may exceed downward
gravitational forces, leading to the formation
of dust.
8

9. • Depending on factors such as climate,
geology and the method of mining, the
potential exists for greatly increased dust
levels in the environment surrounding a mine.
• Modern methods of open cut mining often
involve the mining, transport and handling of
huge tonnages of material, increasing the
potential for dust to be produced.
• The consequences may include visible
plumes and haze, the staining and soiling of
surfaces, aesthetic or chemical contamination
of water bodies or vegetation and, effects on
personal comfort, amenity and health.
9

10. • Mine dust may be qualitatively quite different
to other types of dust. In an urban
environment, dust commonly includes
sources from industry, transport, land clearing
and wood smoke.
• Mine dust is typically less complex in its
make-up, consisting mainly of particles from
exposed soil and rock.
• Mine dust can result in a serious nuisance
and loss of amenity for populations living in
the vicinity of a mine.
• This may be exacerbated by certain types of
dust, such as coal and iron ore dust, that are
highly visual and may result in a prominent
and unsightly coating over surfaces.
10

11. • Fortunately dust rarely presents a serious threat to the
wider environment.
• Dust concentrations, and hence deposition rates and
potential impacts, tend to decrease rapidly away from
the source.
• In the majority of situations dust produced by mining
operations is chemically inert, although exceptions may
occur where dust particles contain phytotoxic
substances such as cement dusts or fluorides
• Damage to vegetation and agriculture is possible
through mechanisms such as the blocking of leaf
stomata (and the inhibition of gas exchange), or
reduced photosynthesis due to smothered surfaces (or
in extreme cases lower ambient light levels).
• While such effects on vegetation are likely to be
localised and reversible, they can contribute to negative
public perceptions of the mining operation's
environmental performance.
11

12. • Nevertheless, there does exist the
potential for harmful and more
persistent contamination of the wider
environment from certain types of
material that may be exposed by
mining.
• Dust derived from ore types containing
asbestos, radioactive materials or heavy
metals, for example, are in this
category.
12

13. THE TERMINOLOGY OF DUST
Common terminology used to describe different
classes of dust includes:
1) Nuisance dust
• Nuisance dust is a term generally used to describe dust
which reduces environmental amenity without
necessarily resulting in material environmental harm.
• Nuisance dust comprises particles with diameters
nominally from about 1 mm up to 50 μm. This generally
equates with 'total suspended particulates' (TSP).
• The TSP range of dust particles is broad, and may be
produced from sources such as industrial and mining
processes, agricultural practices and, from wind erosion
of the natural environment.
• Impacts of mine dust on near neighbours is most often
due to nuisance dust.
13

14. 2) Fugitive dust:
• Fugitive dust refers to dust derived
from a mixture or not easily defined
sources.
• Examples of fugitive dust include dust
generated from vehicular traffic on
unpaved roads, materials transport
and handling, and unvegetated soils
and surfaces.
• Mine dust commonly is derived from
such non-point sources.
14

15. • Dust is considered to be any solid matter caused
by grinding/crushing/blasting operations, which
is borne by the air and in which the individual
aggregate is larger than single small molecules
(0.0002um in diameter, but smaller than 500
um).
• The surface mining activities are associated with
dust generation. Hence dust from workings is
often considered as significant nuisance. In
surface mine sites, dust is said to be one of the
major source of irritation. The problems related
to dust are not restricted to the mine
surroundings itself, but also to the people and
vegetation away from it.
• In surface mines dust can be emitted from stack
as a plume or it can be picked. up by the wind
from ground, the surface of a road or a stockpile.15

16. Characteristics of dust
A. Physical Characteristics
1) Size
2) Settling properties
3) Optical properties
B. Chemical Characteristics
16

17. A. Physical Characteristics:
1. Size
• Size is one of the most important physical properties of
the particulates. The particles of major interest range
from 0.01mm -10mm. Particles smaller than these
undergo random motion, and through coagulation
generally grow to larger sizes and settle out. Particles
larger than 10um settle quickly. A 10mm particle has a
settling velocity of approximately 20 cm/min.
• The dust particles that are picked up by wind and
carried over long distances tend to sort themselves out
to the sizes between 0.5 and 50mm.
• The dust particles less than 5mm are considered as
respirable dust.
17

18. • < 0.1 mm aerosol resulting from combustion
 undergo random motion (Brownian) and
never settle may coagulate by collision and
increase in size
• 0.1-1 mm  by condensation of vapours- not
affected by Brownian motion settling time
measured in months
• > 10 mm  resulting from abrasion of solids
have definite settling velocity
• Upto 200 mm  particles in suspension tend to
fall out at uniform speed in calm air (g is
countered by friction)
18

19. 19

20. 20

21. 2. Settling Properties:
• Settling characteristics of particulates are important In
the sense that settling is the major natural self-cleansing
process for removal of particulates from atmosphere.
The particulates can generally be classified as
Suspended or Settleable.
• The suspended particles vary in size from less than 1um
to approximately 20 mm. They remain suspended for
long periods of time.
• The settleable particles or dustfall are larger and heavier
and settle out close to their sources. They generally
greater than 10 mm in size.
21

22. Constt Speed V terminal velocity
• 150-200 mm  Newton’s law:
D= particle diameter
m1= specific mass of dust
m2= specific mass of air
• <150 mm : Stokes Law:
N= viscosity of air
5.0
2
1
).(..3/8 






m
m
DgVn
N
mmgD
Vs
.18
)(. 21
2


22

23. Falling speed of various sizes of
particulates
Size, micron Falling speed
200 1.2 m/s
100 0.3 m/s
50 70 mm/s
10 3 mm/s
5 0.7 mm/s
1 30 mm /s
0.5 7 mm /s
23

24. 3. Optical properties:
Reduction in visibility is one of the most
effect of dust pollution, and the scattering
of light by dust particles is primarily
responsible for that reduction. Particles in
the range of visible light( 0.38 to 0.76mm)
are effective in visibility reduction.
24

25. B. Chemical Properties:
• The effect of dust depends on its chemical
composition. It may consist of many
inorganic and organic compounds which
may have detrimental effects.
25

26. Effects of Dust
A. Effects on Material
B. Effects on vegetation and animals
C. Effects on Human health
D. Miscellaneous effects
26

27. A. Effects on Materials:
• Soiling clothings and textiles
• Corroding materials
• Eroding building surfaces
• Discolouring and destroying painted surfaces
B. Effects on vegetation and animals:
• The increased plugging of stomata reduces plant
growth
• Dust coating on leaves reduces photosynthesis
• Animals eating plants coated with particulates may
suffer some ill effects.
27

28. C. Effects on Human Health:
• Inhalation may lead to respiratory illness (asthama) (40%
of the particles between 1 & 2mm are retained in
bronchioles and alveoli)
• Irritation of eyes
Human defence mechanism
• > 10 mm =Hairs at the front of the nose remove all
particles over 10um
• 2-10 mm Movement of cilia sweeps mucus upward,
carrying the particles from windpipe to mouth where they
can be swallowed
• <2mm Lymphocytes and the phagocytes in the lung
attack some submicron particles
28

29. 29

30. D. Miscellaneous effects:
1) Visual effects: dust plumes, reduced visibility, coating and
soiling of surfaces leads to annoyance, loss of amenity
2) Need for cleaning surfaces
3) Mechanical/electrical faults
4) Abrasion of moving parts
5) Contamination of laboratory, quality control and standards
room and medical facilities
30

31. Legal Requirements:
• United Nations Conference on Human Environment, held in
Stockholm in June 1972, decisions were taken to initiate appropriate
steps for the preservation of natural resources of the earth which
include the steps for preservation of the quality of air and control of
air pollution
• The Air (Prevention and Control of Pollution) Act 1981 and the rules
made there under are the laws of the land that ensures the quality of
air we breathe.
• The Act defines 'Air Pollutant' as any solid, liquid or gaseous
substance present in the atmosphere in such concentration as may
be or tend to be injurious to human beings or other living creatures
or the plants or property or the environment. Subsequently, with
effect from 1st April 1988, Noise has also been declared as an air
pollutant. The Act , vide sec 19, has empowered the State Govt to
declare any area or areas within the State as “Air Pollution Control
Area”.
• The Act has imposed restrictions, vide Sec 21, to establish or
operate any industrial plant in such Air Pollution Control Areas
without prior consent of State Pollution Control Board.
31

32. On the basis of Land use and other factors the various
areas of a State may be classified into three categories:
a) Industrial and Mixed use areas
b) Residential and rural areas
c) Sensitive areas
Category (a) : having industrial activity in the area and is
bounded to have somewhat inferior quality of air compared to
other categories
Category(c) : covers hill stations, tourist stations, sanctuaries,
national parks, national monuments and other areas where
nation would wish to conserve it as clean environment even if
that implies some curbs on economic activity.
All areas not classified as a or c, will be classified as category (b)
32

33. • When monitored uniformly over 12 months
of a year with a frequency of not less than
once in a week, with a sampling time of 8
hrs for sample and analysed according to
procedure specified by Central Board, the
concentration of the different pollutants
shall be 95% of the time within the limit as
prescribed in following table
33

34. Pollutants Time-weighted
average
Concentration in ambient air Method of measurement
Industrial Areas Residential, Rural &
other Areas
Sensitive Areas
SulphurDioxide (SO2) Annual Average* 80 µg/m3 60 µg/m3 15 µg/m3 Improved West and Geake F4 - Ultraviolet
Fluorescence
24 hours** 120 µg/m3 80 µg/m3 30 µg/m3
Oxides of Nitrogen as (NO2) Annual Average* 80 µg/m3 60 µg/m3 15 µg/m3 - Jacob & Hochheiser Modified (Na-Arsenite)
Method
24 hours** 120 µg/m3 80 µg/m3 30 µg/m3 - Gas Phase Chemiluminescence
Suspended Particulate Matter
(SPM)
Annual Average* 360 µg/m3 140 µg/m3 70 µg/m3 - High Volume Sampling, (Average flow rate not less
than 1.1 m3/minute).
24 hours** 500 µg/m3 200 µg/m3 100 µg/m3
RespirableParticulate Matter
(RPM) (size less than 10
microns)
Annual Average* 120 µg/m3 60 µg/m3 50 µg/m3 - Respirable particulate matter sampler
24 hours** 150 µg/m3 100 µg/m3 75 µg/m3
Lead (Pb) Annual Average* 1.0 µg/m3 0.75 µg/m3 0.50 µg/m3 - ASS Method after sampling using EPM 2000 or
equivalent Filter paper
24 hours** 1.5 µg/m3 1.00 µg/m3 0.75 µg/m3 .
Ammonia1 Annual Average* 0.1 mg/ m3 0.1 mg/ m3 0.1 mg/m3 .
24 hours** 0.4 mg/ m3 0.4 mg/m3 0.4 mg/m3 .
CarbonMonoxide (CO) 8 hours** 5.0 mg/m3 2.0 mg/m3 1.0 mg/ m3 - Non Dispersive Infra Red (NDIR)
1 hour 10.0 mg/m3 4.0 mg/m3 2.0 mg/m3 Spectroscopy
* Annual Arithmetic mean of minimum 104 measurements in a year taken twice a week 24 hourly at uniform interval.
** 24 hourly/8 hourly values should be met 98% of the time in a year. However, 2% of the time, it may exceed but not on two consecutive days.
NOTE:
National Ambient Air Quality Standard: The levels of air quality with an adequate margin of safety, to protect the public health,, vegetation and property.
Whenever and wherever two consecutive values exceeds the limit specified above for the respective category, it would be considered adequate reason to institute regular/continuous
monitoring and further investigations.
The standards for H2S and CS2 have been notified seperately vide GSR No. 7, dated December 22, 1998 under Rayon Industry - for details please see Sl. No. 65 of this document.
[S.O. 384(E), Air (Prevention & Control of Pollution) Act, 1981, dated April 11, 1994 ]
[EPA Notification: GSR 176 (E), April 02, 1996]
1. Included vide Notification SO. 955 (E), Air (Prevention & Control of Pollution) Act, 1981 dated October 14, 1998)
34

35. Whenever and wherever, three
consecutive measurements spaced by
atleast the week apart, or any three out of
10 consecutive meaurements spaced
atleast one week apart, are found to
exceed limits, it would be considered
adequate reason to institute regular
weekly continuous monitoring and further
investigations
35

36. Generation of Dust
• There are a number of mechanisms which produce dust
in mlnes.
• It can occur naturally, as in sand or soil or it can be
produced by fracturing larger particles or aggregations.
• Small particles can be picked up by the wind from
exposed soil surfaces and carried long distances in
suspension.
• Wind over a stockpile or through a stream of falling
material, as off conveyor, can also remove fine particles.
A falling stream of material itself can create an air
current with a similar effect.
36

37. Three main dust sources in surface mines
1) Piont Source:
Drilling, blasting, loading, 'tipping, draglines, dozers,
chutes, crushers, screens, exhaust from dust control
systems, unsheeted trucks, conveyor transfer points.
2) Line source:
Well defined haul-roads, open conveyors
3) Area or Dispersed Source:
Top/soil stripplng and dumping when dry and friable,
mine floors, unsurfaced haul-roads, waste dumps,
stockpiles, spillages.
37

38. a) DRILLING:
This is one of the main source of dust production in
mines.
Dust production will be higher if:
i. Bits are not sharp enough.
ii. There is insufficient thrust on bits.
iii. Suitable arrangement for clearance of cuttings from the
hole is not provided.
Large diameter blast holes drilled in surface mines
produce huge quantity of fine dust which get dispersed
in the mine atmosphere and its neighboring places by
natural ventilation.
38

39. b) Blasting:
Heavy dust concentration is produced by blasting due to shattering
and disintegration of strata.
Amount of dust produced depends upon pattern of holes, quantity
and strength of the explosive used, brittleness characteristics of
rock, rock strength distribution etc.
A good proportion of dust is made up of particles below 5mm.
c) Loading ,unloading and transfer points:
Much amount of dust is raised by loading and unloading of dry
material.
Loading of coal/overburden in dumper/railway wagon/ conveyor
produces dust.
Similarly dust is raised by unloading and transfer points.
It is generally estimated that 0.02% of coal loaded for transportation
is converted into fugitive dust and similar percentage is converted
into fugitive dust at unloading points.
39

40. d) Hauling:
Often dust deposited on the floor of haulage road can become air-
borne by movement of men, mobile equipments, dumpers, vehicles
etc.
Chance of dust production is more with dry unsurfaced haul-roads.
e) Grading Roads and other surfaces:
Considerable amount of dust is produced by heavy earth moving
equipment, essentially when they are used for the purpose of
grading roads and other surfaces.
Dust produced depends on the moisture present in the material and
severity of wind.
f) Handling of dusty material
Portland cement and similar material are easily rendered airborne
during handling and batching.
40

41. g) Fixed plants:
ROM of mine is sent to crushing and
screening plant for required size reduction.
Because of crushing and vibratory motions
large amount of dust is produced.
The in-pit crushing system with conveyor
transport adds substantial amount of dust
to mine atmosphere.
41

42. h) Dust blow:
The refuse heap, stockpiles and overburden
dumps cause dust production due to wind.
High air velocity is contributing factor for
creating airborne dust clouds.
Once dust has been formed or in the event of
naturally fine particle materials such as clays
being present, the environmental nuisance from
dust depends upon the opportunity it has to
react with air flows of a velocity sufficient to carry
it from the point of origin.
42

43. Pick-up velocities of dry dusts
Particle
Size, mm
Air velocity, m/s
Coal Silica Granite
75-105 5 6 7
35-75 4 5 6
10-35 3 3 4
43

44. It is found experthan 5 m/s, dust of above 100
mm will be raised from stationary dry sufaces
and carried down wind for 250 m.
Wind speeds of 9 mls can transport dust over
800 m.
On haul roads velocity is imparted to the dust by
machinery and hence lower wind speeds suffice
to transport the dust and prevent rapid settling
out.
imentally that at wind speeds of more
44

45. Air pollution factors and air quality
data due to mining operation
The magnitude and significance of the environmental
pollution caused by mining operations depend on:
- Type of mineral
- Method of mining and beneficiation
- Smoke and gas from beneficiation plants
- Processing plant scale
- concentration of mining activity
- Geological and geomorphologic settings of the area
- Land use pattern before and after mining
- Natural resources existing in the area
45

46. Dust factors:
A. Overburden Excavation:
i. Scraper loading-
ii. Shovel excavation- 1.0-3.0 Kg/t
iii. Bucket wheel excavation- 0.7-2.0 Kg/t
iv. Loading in vehicles – 0.07-0.4 Kg/t
B. Transportation:
Conveyor Belt - 0.5-1.0 Kg/t(each transfer point)
Dumper - 1.5-3.0 Kg/Km of earthen dry surface
- 0.1 – 0.5 Kg/Km of soiled surface
46

47. C. Unloading :
Conveyor system -- 0.8-1.5 Kg/t
Dumper- Bull Dozer -- 1.5 – 4.0 Kg/t
D. Mineral Excavation:
Bucket wheel excavator- 0.5-1.0 Kg/t
Shovel - 0.8-1.5 kg/t
Loading conveyor belt- 0.05-0.1 Kg/t each
travel point
Loading Dumper - 0.07-0.3 Kg/t
47

48. E. Transport:
Conveyor Belt - 0.05-0.1 Kg/t each
transfer point
Dumper/truck - 1.5-3.0 Kg/Km travel
on dry surface
- 0.2-0.5 Kg/Km travel
on solid road
F. Stock Piling/Loading:
Conveyor - 1.0 – 2.5 Kg/t
Dumper/manual - 1.5-4.0 Kg/t
G. Size Reduction:
Jaw Crusher - 1.5-2.5 Kg/t
Screening - 2.5-5.0 Kg/t
Loading - 0.8-1.5 Kg/t
Stock piling/retrieval - 1.0-4.0 Kg/t
48

49. Dispersion of Dust
• Dust produced is mixed thoroughly with the surrounding
air and diluted by atmosphere dispersion. The
dispersion is due to turbulence and bulk air flow. The
adverse meteorological conditions may give rise to
problems of air pollution
• Factors Affecting Dispersion of Dust:
The following meteorological parameters may affect
dispersion of dust in atmosphere:
1. Rate of change of temperature with altitude (Laps rate)
2. Pressure
3. Wind
4. Moisture
49

50. 1. Rate of change of temperature with altitude:
The temperature change of atmosphere with altitude affects the plume
dispersion.
50

51. Looping plume condition will arise during unstable
atmospheric conditions. There will be rapid mixing of
dust and wind causing high eddies may carry the entire
plume to the ground causing high concentration of dust
close to the source before dispersion is complete.
In a Neutral plume, the plume may rise directly into
atmosphere. If wind velocity is more than 32 Km/hr and
when cloud cover blocks solar radiation by day and
terrestrial radiation by night, the neutral plume will be
converted into coning plume.
In stable atmospheric conditions also, there will be
Coning plume formation. In coning plume conditions
there is limited vertical mixing and probability of air
pollution problem in the area may be increased as the
fine dust particles will remain in the atmosphere for
longer duration.
51

52. 52

53. 2. Effect of Pressure:
• High pressure systems are related to clear
skies, light winds, atmospheric stability. If such
system prevails over an area for several days,
dust can build up to cause pollution problems.
• Low pressure systems are commonly
associated with unstable atmospheric conditions
and brings wind and rain. Hence contaminant
build up are less likely to occur under such
conditions. However in the absence of rain,
deposited dust will be raised and carried for
longer distances.
53

54. 3. Effect of wind
It is an important vehicle in the distribution,
transport and dispersion of dust in air. Hence
wind rose diagrammes are essential to know the
direction and speed of wind in an area over long
periods of time.
4. Moisture:
It has profound effect on air quality of the region.
With high humidity conditions dust problems are
less likely.
54

55. 55

56. Gaussian steady-state
dispersion model
56

57. It provides a steady-state solution to the transport and diffusion
equations (transport plus diffusion = dispersion).
The basic Gaussian diffusion equations assumes:
The degree of dilution is inversely proportional to the wind
speed.
 Pollutant material reaching the ground level is reflected
back into the atmosphere.
 The pollutant is conservative, i.e., not undergoing any
chemical reactions, transformation or decay.
57

58.  The accuracy of predicting the plume rise since that
affects the emission height used in the Gaussian
dispersion equation.
 The accuracy of the dispersion coefficients used in the
Gaussian dispersion equation
 Wind speed and wind direction are constant from the
source point to the receptor (for a wind speed of 2 m/s
and a distance of 10 km, 80 minutes of constant
conditions would be needed).
 Atmospheric turbulence is also constant throughout the
plume travel distance.
 Only vertical and crosswind dispersion occurs (i.e., no
downwind dispersion).
58

59. The model equations
The spatial dynamics of pollution dispersion is described by the
following type of equation in a Gaussian model:
C(x,y,z,t)= (Q/2πuσyσz ) *exp{-(y2/2σy
2 )}*exp{-(z+Heff)2/2σz
2)}
+exp{-(z+Heff)2/2σz
2}
where
C(x, y, z,t) :- pollutant concentration at point ( x, y, z );
u :- wind speed (in the x "downwind" direction, m/s)
σy, σz:- represents the standard deviation of the concentration in the y
and z direction, i.e., in the wind direction and cross-wind, in meters;
Q:- is the emission strength (g/s)
Heff is the effective stack height.
59

60. 60

61. Assessment & Monitoring
• Air quality monitoring  integral part of air
pollution control program
• Through monitoring current trends in air
quality can be evaluated by comparing the data
with the regulated standards
•  information so obtained is helpful in
implementing control measures for reducing
pollutant concentration to acceptable levels and
in assessing the effect of air pollution control
strategies
61

62. • Data to be collected:
– Meteorological data (Weather monitoring station)
• wind speed, turbulence and wind direction
• Temperature & Relative humidity
• Rainfall
• Pressure
• Sunshine
• Dust fall measurement
• Suspended Particulate matter & Respirable
particulate measurement
• Concentration (High Volume Samplers, Respirable Dust
Samplers)
• Size analysis (Particulate Size Analyser, Particulate
counters)
• Dust characterisation (mineralogical) (X-ray Diffraction)
62

63. SAMPLING:
1. Objectives:
The strategy for sampling the atmosphere and the
extent of a survey  governed by the objective,
which should be defined before planning and
undertaking a sampling program
a) To Assess Health Hazards
b) To Determine Background Pollution Levels
c) To Determine The Degree Of Air Pollution Control
d) To Identify Specific Source Of Air Pollution
e) To Collect Data For Formulation And Testing Of
Pollution Models
f) For Scientific investigations
63

64. 2. Preliminary information required for
planning the survey:
In addition to objective of a sampling
program, information to be collected:
– Local sources of dust
– Topography
– Population distribution
– Land use pattern
– Climatology
64

65. 3. Planning for survey
It includes:
a) Selection of sampling procedures
b) Location of samplers
c) Period of sampling, frequency of sampling
and duration of survey
d) Processing of data
e) Auxiliary requirements
65

66. a. Selection of sampling procedures:
Objective of any sampling program  to
obtain genuine and representative
sample
Sampling to be carried out long
enough and at a rate that allows
collection of an analytically measurable
sample.==> requires an appropriate
sampling procedure  High Volume
samplers (SPM or RDS)/ Particle size
analysers etc.
66

67. b. Location of sampling stations:
Factors governing location:
– Objectives
– Method/instrument to be used for sampling
– Resources available
– Physical access and security against loss or tempering
– Representativeness
– Should fulfill physical requirement
Objectives
i. Health hazard  as close as possible to specific
locations where effects are to be studied
• Population centre for healt hazards
• Critical areas- schools, hospitals etc
ii. Material damage  vegetation at foliage level (near
leaves)
iii. Background level determination grid form location &
sampling in all location simultaneously requires
considerable amount of effort, resources & manpower
Contribution from specific sources of pollution level
upwind and downwind locations 67

68. Sampling equipment:
To be provided with proper security against theft and
temper
Representativeness:
Site should be representative of the area
Physical requirement:
Availability of the site, accessibility, power availability
etc
Comparability:
Location to be standardized from the comparison point
of view ( 3-4 m above ground, 1-1.5 m from the
nearest vertical surface, HVS on the roof of low
buildings etc)
68

69. c. Period, frequency and duration of sampling:
Length of time over which a single sample or set of samples is
collected
Frequency: depending on objective of sampling: samples are
collected during a given time ( sampling of three hours – 8 times a
day)
Duration of sampling: total length of time for which entire sampling
program is carried out ( one year ( all seasons))
Period should be such that measurable quantities of dust are
trapped in the sample at the end of sampling
Period and frequency should be such that statistically reliable
averages over long periods or over the duration of sampling may
be obtained from the data.
One 24 hr sample collected daily, once weekly, once monthly will
give unreliable estimate of annual average
69

70. d. Processing of data
e. Auxiliary requirement
70

71. Control of dust:
- Forecasting the problem & avoiding them
- Preventing its escape into the
atmosphere
- Recapturing it once it is in the air
“TO AVOID CREATING IS EASIER THAN
SUBSEQUENT CONTROL”
71

72. 1) Dust blown from surface excavations,
dumps etc:
- simple water sprays at active locations
- revegetation or use of surface stabilisation
2) Drilling:
- Dry collection of dust (Cyclone & filter)
- Wet drilling (water or foaming agents)
- Use of sharp bits
- Use of proper thrust and flushing system
72

73. 73
The air and water flow during drilling operation to demonstrate water
flushing of the drill cuttings. The water flows through the center of the
drill steel and out the end of the drill bit to remove the cuttings from the
drill hole.

74. 74
Internal workings of a water separator sub.

75. 75
A basic dry dust collection system on a drill.

76. 76
Dust collector dump point prior to shroud installation (A). Two men
installing the shroud onto the dust collector dump point (B). The dust
collector dump point after installation of the shroud (C).

77. 77
Typical dust collection system used by small crawler or "buggy‖ drills.

78. 3. Haul Road Dust:
- To water all haul roads
- Tankers
- Water sprinkler system
Water alone may not be effective:
- Water retention on haul road is skin deep
- High heat, low humidity and high wind speed may affect retention of water on roads
- Dust binding capacity of water is poor
78

79. Alternative to water:
- Use of Hygroscopic salts
Retains water for long duration thus reduce water
requirements
Salt brines- effective but cause problems with
vegetation, ground water or surface water
Calcium/Magnesium Chloride powder
- Use of Oil-Water emulsions:
Help to consolidate dust but do not penetrate deep and
may cause slipping of equipment on roads
- Starch based absorbents:
More effective
- Absorbs water 100-150 times its weight
- Swells in water and gets immobilized on road
surfaces for a period of 3-6 months
79

80. 80
Example of haul road dust from a typical mine haul truck

81. 81
Cross section of haul road

82. 82
Water truck equipped with a front water cannon and rear water sprays

83. 83
Various types of manufactured fan spray nozzles for use on a water truck.

84. 84
Respirable dust concentrations measured from haul road after water
application occurred at 10:00 a.m.

85. 4. Transport:
- Use enclosed vehicles for dry material
- Use of rigid fiber glass covers/ tarpaulins
- Use of chemical binder sprays to form
resistant surface crust
85

86. 86
Types of fugitive dust emissions from conveyor belts.

87. 87
Typical dust curtain used at the entrance and exit of the chute
enclosure.

88. 5. Crushing, handling etc:
- Use of water sprays
- Reduce height of fall material
- Enclose transfer points
- Use of dust collectors: Principles of dust collection:
- Gravity
- Centrifugal force
- Inertia
- Filtration
- Electrostatic attraction
88

89. 89
Illustration of a wet dust control approach with partial enclosure at a crusher
dump loading operation. Note the blue "fan patterns" signifying water sprays.

90. 90
Illustration of a dry (exhaust) dust control system with a partial
enclosure at a crusher dump loading operation.

91. 91
Illustration of a dry (exhaust) dust control system at the discharge of a
jaw crusher onto a belt conveyor.

92. 92
Illustration of a dry (exhaust) dust control system on a vibrating
screen.

93. CONCLUSION:
• The nature of mining involves disturbing the ground,
removing and handling soil and rock, and the
subsequent transport, dumping, crushing and processing
of this material. At all stages there is some potential to
produce dust. Best practice environmental management
requires considering this issue during mine planning,
operations and at mine closure.
• The dual concerns of occupational health and the air
quality near the mine require careful management. For
mines located in dry or windy environments, the issue
becomes more challenging.
93

94. • In some situations the dust produced during mining may
contain hazardous substances and this clearly requires
special consideration. Even where dust does not contain
harmful constituents, it may still represent a potential
threat to the health of mine workers if concentrations in
the work environment are allowed to exceed certain
levels.
• From the standpoint of environmental impact, the main
concern is the potential of dust to be released off-site
and to affect the surrounding environment and general
environmental amenity. The impact on environmental
amenity is the most common issue relating to dust
generated from mining operations.
94

95. • In recent years, tools have become widely available that can greatly
assist in the control and management of dust. Modelling techniques
can predict dust impacts at the planning stage. The various mine
dust emission sources can be estimated quantitatively, thus allowing
control efforts to be applied systematically.
• Technological developments in monitoring techniques have
provided the means to accurately measure ambient dust levels. So-
called 'real-time' dust monitors are able to supply rapid feedback on
dust levels to the mine operators. This information can alert mine
personnel to high dust events in a timely manner, allowing
adjustments to mine operations. Such information can also be
directly linked to wind information, giving an indication of
contributing dust sources .
• Clearly, the level of effort and expense that is applied in the control
of dust will vary depending on circumstances. Each mine will have a
unique set of conditions, and the appropriate solutions are not
necessarily available 'off the shelf'. Nevertheless, success can be
achieved using a wide range of methods, and the range of available
of dust control techniques continues to develop and improve.
95