Research Journal of Environmental and Earth Sciences 4(4): 419-423, 2012
ISSN: 2041-0492
© Maxwell Scientific Organization, 2012
Submitted: December 16, 2011
Accepted: January 08, 2012
Published: April 15, 2012
Ambient Particulate Matter Monitoring - A Case Study at Tarkwa
Kenneth J. Bansah and Newton Amegbey
Mining Engineering Department, University of Mines and Technology, Tarkwa, Ghana
Abstract: Air pollution from airborne particulates remains a major concern of the communities within the
mining areas. In Ghana, little research has been done to ascertain the health implications of living around the
mine sites. This study studied ambient particulate matter less than 10 :m (PM10) pollution at Gold Fields
Ghana Limited (GFGL) mine residence in Tarkwa. A four-month PM10 monitoring was performed at GFGL
mine residence. The Gaussian Dispersion Model was also used to predict the concentration of PM10 in the
Tarkwa Township. The results show that 13% of the PM10 concentrations obtained exceeded the Ghana
Environmental Protection Agency’s threshold limit of 70 :g/m3. The dispersion model indicated that PM10
generated from GFGL attains a concentration of 68 :g/m3 when it reaches the Tarkwa Township.
Key words: Airborne particulates, air pollution, health implications, tarkwa, threshold limit
INTRODUCTION
selected as the study area. This study therefore, looks at
PM10 levels and the possible impacts on residents at Gold
Fields Ghana Limited mine site and the Tarkwa Township
as a whole.
Air pollution from airborne particulates is a major
concern of the communities within the mining areas. Gold
Fields Ghana Limited (GFGL), Tarkwa, Ghana operates
an open pit mine. The mining activities involve
overburden removal, drilling, blasting, loading, hauling
and ore crushing. These activities together with increased
vehicular movements on the untarred roads within and
around the mine sites introduce particulates into the
atmosphere. Particulates, when inhaled can evade the
system’s natural defences and lodge deep in the lungs,
leading to lung and heart diseases.
Zinatunor (1998), researched into pollution of
ambient air by particulate matter less than 10 :m (PM10)
at the Tarkwa Township in Ghana. During the period, a
six-month data was collected. The results show that 60%
of the PM10 concentrations obtained exceeded the
Environmental Protection Agency of Ghana (EPA)
threshold of 70 :g/m3. A conclusion drawn was that
“mining activities in Tarkwa pose a serious particulate
pollution threat to the Tarkwa Township”. Amegbey and
Ndur (2000) concluded that surface mining activities
around the Tarkwa town have contributed to increased air
borne particulate matter within the township. It also
recommended that further studies into particle pollution
in Tarkwa must be carried out. The studies must include
dispersion modeling and particulate analysis in order to
determine the sources contributing to the dust levels in the
Tarkwa Township.
In trying to solve particle pollution due to mining, in
the Tarkwa Township, Gold Fields Ghana Limited
(GFGL) residence which is most likely to be affected was
Location, relief, topography and climate of GFGL:
Gold Fields Ghana Limited, Tarkwa Mine, is located off
the Tarkwa-Bogoso highway, about 1.5 km from Tarkwa
in the Western Region of Ghana. Tarkwa Township has
a population of about 41000.
The topography of the mine comprises of ragged
ridges with peaks reaching a height of 335 m above mean
sea level in some areas, interspersed by undulating valley
bottoms and a true reflection of the pitching fold
structures of the Banket Series of the Tarkwaian System.
Elevation in the area ranges from approximately 60 to 225
m. The central area of the mine is low lying and flatter
and does not show the variations in elevation typical of
the south and eastern areas near Tarkwa and Akontansi
(Akurang, 2008).
The mining area falls within the western equatorial
climatic zone, with seasons primarily regulated by moist,
south-west monsoon winds from the South Atlantic Ocean
and dry dust-laden north-east trade winds, known as
Harmattan, which blows over the Sahara Desert from the
northern sub-tropical high pressure zone .
The inter Tropical Convergence Zone crosses the
mining area two times per year, causing hydrometeorological data including rainfall to peak during two
periods; April to June and October to November. The
mean annual rainfall is approximately 1933 mm; with a
range of 1100 to 2600 mm. Average monthly
temperatures range between 24 and 28°C, with the highest
Corresponding Author: Kenneth J. Bansah, Mining Engineering Department University of Mines and Technology, Tarkwa, Ghana
419
Res. J. Environ. Earth. Sci., 4(4): 419-423, 2012
120.000
EPA Guideline
100.000
Concentration (g/m 3 )
Concentration (g/m 3 )
Concentration (g/m 3 )
Concentration (g/m 3 )
120.000
80.000
60.000
40.000
20.000
EPA Guideline
100.000
80.000
60.000
40.000
20.000
f eb
2- M
4-M ay -08
a
6- M y - 08
a
8- M y - 08
a
10- y - 08
Ma
12- y - 08
Ma
14 y - 08
-M
16 ay -0
-M
a 8
18 y - 08
-M
20 ay -0
-M
8
22 ay -08
-M
24- ay -08
M
26- ay -0
Ma 8
28 y - 08
-M
30 ay -08
-M
ay 08
- 08
0.000
29 -
8
- 08
28 -
b- 0
-f e
27
f eb
8
- 08
26
-f e
b- 0
- 08
f eb
f eb
25 -
24 -
8
- 08
f eb
23 -
- 08
b- 0
f eb
-f e
21 -
22
8
8
-f e
b- 0
20
19
-f e
b- 0
0.000
Days of the month
Days of the month
Fig. 1: PM10 concentration profile for February 2008
Concentration ( g/m 3 )
100.000
Fig. 4: PM10 concentration profile for May 2008
Concentration ( g/m 3 )
EPA Guideline
characterized by dry weather conditions, although there
were few millimeters of rain. In all, 110 PM10 data were
collected using the PQ100 Air Sampler. Five of the
samples were discarded due to mishandling and
moistening of the filter membranes.
The procedure adopted for the particulate sampling
with the PQ100 Air Sampler is as follows:
80.000
60.000
40.000
20.000
1-M
a
3 - M r- 0 8
a
5 - M r- 0 8
a r7 - M 08
9 - M a r- 0 8
a
11 - r- 08
Ma
1 3 - r- 0 8
M
1 5 - a r- 0 8
M
1 7 - a r- 0
M 8
1 9 - a r- 0 8
Ma
2 1 - r- 0
Ma 8
2 3 - r- 0 8
Ma
2 5 - r- 0 8
M
2 7 - a r- 0 8
Ma
2 9 - r- 0 8
Ma
r- 0
8
0.000
C
Days of the month
C
Fig. 2: PM10 concentration profile for March 2008
Concentration (g/m )
3
Concentration ( g/m 3 )
120.000
C
EPA Guideline
C
100.000
80.000
60.000
C
40.000
20.000
C
1- A
pr
3- A - 0 8
p
5 - A r- 0 8
p
7 - A r- 0 8
pr
9- A - 0 8
p
1 1 - r- 0 8
Ap
1 3 - r- 0 8
Ap
1 5 - r- 0 8
Ap
1 7 - r- 0 8
Ap
1 9 - r- 0 8
A
2 1 - p r- 0 8
Ap
2 3 - r- 0 8
A
2 5 - p r- 0
Ap 8
2 7 - r- 0 8
A
2 9 - p r- 0
Ap 8
r- 0
8
0.000
A 47 mm Whatman filter is weighed with a
microbalance in a temperature and humidity
controlled filter weighing room and inserted in the
filter cassette.
The weighed filter is placed in the PQ100 Air
Sampler filtering unit.
With a flow rate of 16.7 Lpm, the pump of the
PQ100 is set to run for 24 h.
The filter with the particulate sample is removed
from the system and weighed after the 24 h sampling
duration.
The contaminant weight is determined by the
difference between the post and pre-sampling filter
weights.
With the contaminant weight, the sampling duration
and flow rate, the concentration of the particulate is
determined according to Eq. (1):
Concentration(:g/m3) = Contaminants Weight (1)
(mg)×1000/ Total Sample Volume (m3)
Days of the month
Fig. 3: PM10 concentration profile for April 2008
Contaminant weight is the difference between initial
filter weight and final filter weight in milligrams, and
Total sample volume is the volume of air passed through
the filter in cubic meters.
The PM10 concentrations obtained during the period
under review were plotted to determine whether these
concentrations exceeded the EPA guideline value. Figure
1, 2, 3 and 4 illustrate the monthly variations in PM10
concentrations at GFGL. While the maximum PM10
concentration was 110 :g/m3, the minimum concentration
temperatures recorded during February and March.
Annual evaporation is much less than the annual
precipitation, although evaporation losses from surface
water bodies can be significant during the few dry months
of the year (Akurang, 2008).
PM10 monitoring and results: A 24 h PM10 monitoring
was conducted for 110 days at GFGL residence. The
monitoring activity started from the 19th of February and
ended on the 7th of June 2008. This period was mainly
420
0.01
0.2
0.1
0.05
0.5
2
1
5
10
20
50
40
30
60
70
80
90
95
98
99
99.9
99.8
99.99
Res. J. Environ. Earth. Sci., 4(4): 419-423, 2012
1
9
8
7
6
5
4
3
EPA Guideline value
Geometric mean
1
9
8
7
6
5
4
3
2
99.99
99.9
99.8
99
98
95
90
80
60
70
40
50
30
20
10
5.0
2.0
0.5
1.0
0.01
0.05
0.1
0.2
1
9
8
7
6
5
4
3
Concentration (g/m 3 )
2
2
Probability
Fig. 5: Probability versus mass concentration
Concentration (g/m3)
was 1.3 :g/m3. These concentrations were respectively recorded on 120
12 and 18th April, 2008. The average PM10 concentration
100
over the period of study was calculated to be 27 :g/m3.
80
The PM10 concentrations were further grouped into
68
60
concentration ranges. The probability that a given
concentration will not be exceeded was calculated. A
40
graph of these probabilities versus the upper class limit
20
values of the concentration range was plotted on a log0
probability graph paper (Fig. 5). From the graph, the
6
0
1
3
8
2
5
4
7
Tarkwa
Distance (km)
probability that a given concentration will fall below the
EPA guideline value is read to be 87%. Thus the
Fig. 6: Distances versus PM10 concentrations
probability of obtaining a concentration higher than the
EPA guideline value is 13%. The geometric mean is also
z = Vertical distance from ground level, m
read to be 30 :g/m3.
H = Effective stack height, m
PM10 modeling and results: The Gaussian Dispersion
Model was used to predict the concentration of PM10 in
With a stack height of 30 m at the processing plant
the Tarkwa Township. The Model is given by Eq. (2)
and 1 m (assumed) for each of all other particulates
(Cooper and Alley, 2002):
emission sources, the effective stack height (H) was
calculated to be 16.5 m. This is as a result of the
2 
assumption that 50% of the emissions come from the

Q
H
(2)
C
exp 
processing plant while 50% come from other sources.
2
 y z
 2 z 
Other parameters include a wind speed (:) of 0.65 m/s,
emission rate (Q) of 306956 :g/s and a slightly stable
atmosphere. Modeling was performed over a distance up
where: C = steady-state concentration at a point (x, y, z),
:g/m3
to about 7 km. The result of the modeling is illustrated in
Fig. 6.
Q
= Emissions rate, µg/s
Fy, Fz = Horizontal and vertical spread parameters
DISCUSSION
respectively, m
µ
= Average wind speed at stack height, m/s
The minimum and maximum concentrations were 1.3
y
= Horizontal distance from plume centerline, m
and 110 :g/m3, respectively. While for 87% of the time
421
Res. J. Environ. Earth. Sci., 4(4): 419-423, 2012
Fig. 7: Relative positions of gold fields Ghana limited and tarkwa township
Figure 7 shows the relative positions of GFGL and
Tarkwa. A wind rose with predominant wind direction of
North-East over the study period has also been
superimposed on Fig. 7. Conventionally, a wind rose
shows the various directions from which the wind blows.
However, for easy interpretation of Fig. 7, the
superimposed wind rose indicates the directions to which
the wind blows. It could be seen from Fig. 7 that
particulates emitted from GFGL can be transported by the
wind towards the Tarkwa Township.
concentrations fell below the threshold limit value (TLV)
of 70 :g/m3 set by the Environmental Protection Agency
of Ghana, for 13% of the period of measurement
particulates concentration exceeded the EPA limit. Data
available from February to May 1998 indicates an average
PM10 concentration of 114 :g/m3 in the Tarkwa
Township (Zinatunor, 1998). However, during the period
under review, the average concentration was 30 :g/m3.
This reduction in PM10 concentration may be due to
increase dust suppression activities by GFGL. Moreover,
most of the roads within and around the Tarkwa
Township currently, have been tarred. It is interesting to
note also that the highest PM10 concentration of 110
:g/m3 was recorded only once, during the period of study.
This single highest concentration is lower compared to the
average PM10 concentration in 1998.
The results of particulates modeling show that PM10
concentration exceeded the 70 :g/m3 threshold set by
EPA, within a distance of about 1.3 km from the mine.
Also, PM10 generated from GFGL attains a concentration
of 68 :g/m3 when it reaches the Tarkwa Township. As
expected, the concentration of PM10 decreased as the
distance of transportation increased (Fig. 6). This occurs
due to the fact that, as particulates are transported, they
come into contact with each other, coagulate and fall by
gravity. Some particles may also react with other
substances to form secondary particulates, which can get
deposited by dry or wet deposition. Others may adhere
themselves to water droplets, increasing their
aerodynamic diameters as well as their settling velocity.
An increase in wind speed will also cause dilution of
PM10.
CONCLUSION
Analysis of data collected and subsequent study of
the results obtained, revealed that PM10 levels at Gold
Fields Ghana Limited mine residence exceeded the
Environmental Protection Agency’s threshold limit of 70
:g/m3, 13% of the time. Particulates emitted from GFGL
attain a concentration of about 68 :g/m3 on reaching the
Tarkwa Township.
ACKNOWLEDGMENT
The authors wish to acknowledge the support of Mr.
Steve Gyan and all the staff of the Environmental
Department of GoldFields Ghana Limited who
contributed to the success of this research.
REFERENCES
Akurang, J., 2008. A Study of the Drilling and Blasting
Practices at Goldfields Ghana Ltd. BSc. Project
Report, (Unpublished), University of Mines and
Technology, Tarkwa, Ghana, pp: 8-15.
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Res. J. Environ. Earth. Sci., 4(4): 419-423, 2012
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