ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY & ENVIRONMENT
AZOJETE, September 2019. Vol. 15(3) 678-691

Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria.
Print ISSN: 1596-2490, Electronic ISSN: 2545-5818

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678

ORIGINAL RESEARCH ARTICLE

SEASONAL VARIATION IN RATES OF DUST FALL AT MOTOR PARKS OF UNIVERSITY
OF ILORIN, ILORIN, NIGERIA

F. O. Nwosu1*, O. D. Olayinka1 and C. O. Akoshile2

(1Department of Industrial Chemistry, University of Ilorin, P.M.B 1515 Ilorin, Nigeria
2Department of Physics, University of Ilorin, P.M.B. 1515 Ilorin, Nigeria)

* Corresponding author’s email address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng

ARTICLE INFORMATION

Submitted 22 November, 2018
Revised 7 March, 2019
Accepted 10 March, 2019

Keywords:
Insoluble Dust
Soluble Dust
Ash
Volatile Matter
Wet Season
Dry Season

ABSTRACT
The enormous vehicular activities on the commercial motor parks of
University of Ilorin, Nigeria called for concern as a result of noticeable
level of particulate matter in the atmosphere of the area. This study was
carried out to indicate the seasonal variation in the rate of dust fall at
three motor parks in the permanent site of the University campus by
using the single bucket sampling method. The study was carried out for
five months each of wet and dry season periods. The sampling sites were
First Motor Park (PK1), New Motor Park (PK2) and Clinic Area (Cl).
Gravimetric method was used to quantify the soluble, insoluble, volatile
matter and ash content of the dust. Volatile matter and ash were the
component of insoluble dust and the highest rate of insoluble dust
deposition was observed in January (2043.12 ± 41.4 and 284.1 ± 35.5
mg/m2/day) for PK2 and Cl and in November (1282.7 ± 64.9 mg/m2/day)
for PK1 when their respective traffic density (1509.5 ±72.1, 29.8 ± 1.2 and
1000.8 ± 48.3 vehicles per hour) was highest. The highest (32713.0 ±
1290.1 mg/m2/day) and lowest (70.6 ± 6.9 mg/m2/day) rate of soluble
dust deposition in the study were observed at PK1 for September and
February respectively which was suspected to be due to increase and
decrease in the amount of rain fall. The Pearson Correlation showed that
increases in traffic density were correlated with increases in the rate of
insoluble dust fall at various sites and the relationship was in the stronger
order of PK2 > PK1 > Cl. The motor parks ambient air was highly
contaminated with soluble dust in the wet season and insoluble dust in
the dry season their being values are more than the recommended 133
mg/m2/day.

© 2019 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved.

1.0 Introduction
Air pollutants can either be particles, liquids or gaseous in nature. Pollutants may come from
natural sources or caused by human activities (anthropogenic) such as use of motor vehicles,
domestic activities, industry and other economic activities (Jimoda, 2012). Particulate matter is
used to describe contaminant particles like dust found in the air (Yahi et al., 2014; Nwosu et al.,
2016). There could be environmental degradation and hazard on the health status of human and
animal due to presence of particulate matter in the air (Kamble, 2015). Particulate matter in the
form of dust is usually in the size range from about 1 to 10μm in diameter, and they settle slowly

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Arid Zone Journal of Engineering, Technology and Environment, September, 2019; Vol. 15(3):678-691. ISSN 1596-2490;
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679

under the influence of gravity (Espinosa et al., 2001). The ones greater than 10μm that settle to
surfaces from the air are the main component of dust fall (Sami et al., 2006; Alahmr et al., 2012)
and are too heavy to remain suspended in the air for any period of time. The potential
environmental impacts of dust fall were described by Piechota et al. (2002) to include surface
and groundwater quality deterioration, soil contamination, toxicity to soil and water Its toxicity
to humans, air pollution and changes in hydrologic characteristics of the soils cannot be over
emphasized. A number of medical conditions can be traced to the impact of dust, and the
effects of fine wind-borne particles on human health (Garrison et al., 2003, Polizzi et al., 2007,
Alahmr et al., 2012). The most health-damaging dust particles are those lesser in size with a
diameter less than 10 microns (10µ ≤ PM). Humans mostly at risk are elderly and children with
symptoms of asthma, heart or cardiovascular disease as stated by Kamble (2015). The presence
of dust in the ambient air is very noticeable in the areas where there are more vehicular activities
and the composition varies in complex mixture of soluble and insoluble forms of organic and
inorganic substances suspended in the air (Polizzi et al., 2007). The enormous vehicular activities
on the commercial motor parks of University of Ilorin, Nigeria called for concern as a result of
noticeable level of particulate matter in the atmosphere of the area due to continuous increase
of students and other users of the parks. Therefore, the objective of this study is to assess the
seasonal variations and traffic effect on the rate of soluble, insoluble, volatile matter, ash and
total dust fall at three different parks in the permanent site of the University of Ilorn.

2. Materials and Method
2.1 Study Area
The dust samples were collected at three different motor parks within the permanent site of
University of Ilorin, Kwara State, Nigeria. There were two parking locations for commercial
vehicles within the campus of the permanent site of University of Ilorin between 2016 and 2017
during the period of this study. The first motor park is located behind Lagos Boys’ Hostels of the
school, another park; the New Park is by the Sky Chicken restaurant in the permanent site of the
University campus. The Clinic Area of the University is about 150 m away from the location of the
New Park and is a parking lot for the clinic staff and their visitors. Figure 1 shows the sampling
point locations. It should be noted that none of the parks was paved during the period of the
study.

Figure 1: Google Map of University of Ilorin (permanent site) showing the Park locations
The nomenclature of sampling points and description of geographical coordinates are given in
Table 1.

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Nwosu and Olayinka: Seasonal Variation in Rates of Dust Fall at Motor Parks of University of Ilorin, Ilorin, Nigeria.
AZOJETE, 15(3):678-691. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 680

Table 1: Description of sampling points and their geographical location.
Sampling Points Location Point Coordinates
PK1 First Motor Park 8°47’94.2’’N 4°67’06.9’’E
PK2 New Motor Park 8°48’13.8’’N 4°66’84.0’’E
Cl Clinic Area 8°48’27.5’’N 4°66’90.3’’E

2.2 Material Preparation
All the sampling buckets were usually washed thoroughly with soap and water, followed by
dilute nitric acid and then deionised water before drying properly. Also, all the sampling
apparatus were cleansed by subjecting them to acid wash and then rinse with distilled water
before use. Analytical grade stock solutions were used for the preparation of samples and
standards.

2.3 Sampling Method
The dust fall (bulk type) was sampled using the method of open bucket system according to IS
5182 (2006) and ASTM (2010) standard procedures. This involved the use of a cylindrical
sampling bucket with height (h), radius (r) and surface area (A) of 0.342 m, 0.138 m and 0.05983
m2 respectively as employed by. Annegarn and Scorgie, (2002); Moja and Mnisi, (2013); Kamble,
(2015) and Nwosu et al., (2016) in their various studies. The 20 L bucket was filled with a known 5
L of distilled water, opened and exposed on a rigid stand to trap the dust fall sample. The rigid
stand of 2 m long comprised of a ring supported by four stabilizing bars above the base plate to
prevent the sample from contamination by perching birds. The openings of the buckets were
covered with insect net so as to only collect dust of smaller size which is most hazardous to
health. Although there was rapid evaporation due to exposure of sampling bucket, the 5 L
distilled water in the bucket was sufficient to remain and trap dust sample during each sampling
period. Also, it usually do not overflow due to rainfall during sampling period. Figure 2 shows
one of the rigid stands with bucket used for the sampling. The stands were buried into the earth
to a depth of about 0.5 m according to some criteria laid by ASTM D 5111 Standards (ASTM,
1996) such as locating the sampler towards the predominant wind direction and considering the
distance from obstacles that could interfere in sampling. The sampling buckets were exposed at
the various sites for a month and the sampling buckets were replaced with new ones of the
same dimensions following the same process. The study was carried out for a total of ten
months to include five months of rainy season period (September and October, 2016; April to
June, 2017) and five months of dry season period (November and December 2016, January to
March, 2017).

Figure 2: One of the Sampling Stands at the First Park

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2.4 Traffic Density
The estimation of the traffic density was conducted by counting the number of vehicles that
went in and out of the park during the periods of heavy traffic, usually about 3h in the morning
and 3h in the afternoon. The average of morning and afternoon counts was the traffic count for
a day. Two different daily counts were obtained during the sampling period of each month
throughout the study. The average of the daily counts was used to determine the traffic density
for each month (number of vehicles per hour) according to Adekola and Oloruntoba (2000).

2.5 Determination of Insoluble Particle Fall Out Rate
A dried pre-weighed ashless filter paper number 42 was placed in the filter unit according to IS
5182 (Part 1) (2006). The bucket content was then carefully poured through the filtration set up
to obtain a filtrate and residue. The residue, an insoluble component of the dust fall, was
weighed after drying in an oven at 105°C for 2 hrs. The rate of insoluble dust fall was estimated
in duplicate following the method stated by IS 5182 (Part 1) (2006) and Norela et al. (2009)
based on number of days and the surface area of the bucket, calculated as in equation (1):

where:
Cidf = Concentration of Insoluble dust fall (mg/m2/day),
Mf = Weight of loaded filter (mg),
Mb = Weight of blank filter (mg),
A = Surface area of the bucket (m2),
T = Sample duration (days).

2.6 Determination of Total Soluble Particle Fall Out Rate
A known volume of filtrate (soluble matter) obtained from 2.3 was concentrated in a pre-
weighed evaporating dish and dried in an oven at 105°C for 2h as stated by Latif and Rozali
(1999). It was cooled in a desiccator before being weighed. The rate of soluble dust fall was
calculated as given in the equation (2):

Css (mg/m2 )/day =
�� −��

��
�2

AT
………….(2)

where:
Css = Concentration of soluble solids,
M3 = Weight of evaporating dish without the soluble matter (mg),
M4 = Weight of soluble matter with the weight of the evaporating dish (mg),
V1 = volume of filtrate (all the water in the sampling bucket) (mL),
V2 = Volume of filtrate used for analysis (30 mL),
A = Bucket surface area (m2),
T = Sampling period (days).

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Nwosu and Olayinka: Seasonal Variation in Rates of Dust Fall at Motor Parks of University of Ilorin, Ilorin, Nigeria.
AZOJETE, 15(3):678-691. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 682

2.7 Determination of Total Dust Particle Fall Out Rate
Total dust particle was computed in duplicate by the addition of concentration of the insoluble
and soluble dust fall together according to the AQMM (2016) and IS 5182 (Part 1) (2006) as
shown in equation (3):

TDF (mg/m2/day) = Cidf +Css ………… (3)
where:

TDF = Total dust fall rate (mg/m2/day),
Cidf = Concentration of Insoluble dust fall (mg/m2/day),
Css = Concentration of soluble solids (mg/m2/day).

2.8 Determination of Ash Particle Fall Out Rate
A known mass of the homogenised dried insoluble matter from 2.3 above was collected into an
ashless filter paper. This was then put in a pre-weighed porcelain crucible. The porcelain crucible
was placed in a muffle furnace and fired at 550 ºC for 4 h. The sample was cooled to constant
weight. The amount of ash was determined in duplicate using the equation (4) due to Norela et
al. (2009):

AshRate mg/m2/day =
(Mfa − Mco)

AT ………….(�)

where:
Mfa = Weight of porcelain crucible with ash after incineration (mg),
Mco = Weight of porcelain crucible only (mg),
A= Surface area of the sampling bucket (m2),
T= Sampling period (days).

2.9 Determination of Volatile Particle Fall Out Rate
This was estimated in duplicate using equation (5) due to Al-Harbi (2015) and Kamble (2015).

VM (mg/m2/day) = Cidf – Ash rate …………….(5)
where:

VM =Volatile matter,
Cidf = Rate of Insoluble PM in mg/m2/day

2.10 Meteorological data
Meteorology data of rain fall, wind speed, humidity and temperature were obtained from the
Atmospheric Research Laboratory, Physics Department, University of Ilorin, Ilorin, Nigeria. This
department have the appropriate instruments that measured the various meterological factors.

3.0 Results and Discussion
3.1 Traffic Density
Table 2 shows the average rate of various dust depositions with traffic density at the three sites.
The highest traffic density at PK1 was 1000.8 ± 48.3 vehicles per hour in November while the
least traffic density at PK1 was 3.0 ± 0.5 vehicles per hour in April. The highest traffic density at
PK2 was in January (1509.5 ± 72.1 vehicles per hour) while the least (43 ± 3.3 vehicles per hour)
was in September. The traffic density at Cl was highest (29.8 ± 1.2 vehicles per hour) in January
while lowest (16.5 ± 0.7) in September. The least value of traffic density in this study was
observed in April (3 ± 0.5 vehicles per hour) at PK1 during the period of inter-semester break

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and when it was not really active as Motor Park. Though, the school resumed in October, it
seemed most students and staff resumed fully to school or more visitors entered into the school
campus in January. This accounted for the highest traffic density in this study to be in January
(1509.5 ± 72.1 vehicles per hour) at PK2. Also PK2 was the most active park during this January
period. Nwosu et al. (2016) reported a similar observation on a motor park in the same
University.

Table 2: Average and Standard Deviation of Soluble, Insoluble, Ash, Volatile and Total Dust Fall in
mg/m2/day with Traffic Density (Number of vehicles per hour) (n = 2).
Month Sample Insoluble Soluble Ash Volatile

Matter
Total Dust
Fall

Traffic
Density

Sep PK1 340.8 ± 3 32713.03 ±
1290

94.4 ± 1.4 246.1 ±
4.3

33053.5 ±
1287

305 ± 22.6

PK2 208.9 ± 0 27579.6 ±
732

82.7 ± 1.2 126.2 ±
1.2

27788.5 ±
732

43 ± 3.3

Cl 154.6 ± 5.9 19706.2 ±
442

116.3 ±
3.9

38.3 ± 2.0 19860.8 ±
448

16.5 ± 0.7

Oct PK1 355.1 ± 5.9 18094.8±
928

124.4 ±
14.6

230 ± 8.7 18094.8 ±
928

387.8±
22.4

PK2 305.4 ± 6.5 17012.1 ±
666

136.1 ±
17.03

169 ± 23.5 17317.5 ±
672

51.2 ±2.1

Cl 213.1 ± 5.9 13780.4 ±
826

170.1 ±
15.5

43 ± 9.6 13993.5 ± 8 18.3 ±0.9

Nov PK1 1282.7 ±
64.9

4671.5 ± 454 690.1±
16.8

592.6 ±
48.1

5954.2 ± 389 1000.8 ±
48.3

PK2 630.9 ±
17.7

1848.5 ± 102 503.7 ±
66.4

127.2 ±
48.7

2479.4 ± 120 58.5 ±3.1

Cl 238.6 ±
29.5

1314.4 ± 199 179.4 ±
29.4

58.8 ± 0.3 1552.5 ± 228 25.7 ± 1.9

Dec PK1 129.5 ± 5.9 2372.3 ± 466 40.9 ± 4.6 88.7 ± 1.3 2501.8 ± 460 3.5 ± 0.7
PK2 2013.9 ±

118.2
891.1 ± 31.2 431.02 ±

27.2
1582.8 ±
91

2905 ± 87 1428.7 ±
388

Cl 309.2 ±
11.8

727.7 ± 26.6 227.7 ±
16.3

81.5 ± 4.5 1036.84 ±
14.8

25.8 ± 2.6

Jan PK1 259.0 ±
11.8

825.9 ± 33.2 213.5 ±
11.7

45.5 ± 0.1 1085 ± 21.4 5.3 ± 0.9

PK2 2043.1 ±
41.1

1247.3 ±
39.5

1865.8 ±
30.4

177.3 ± 11 3290.4 ±1.9 1509.5
±72.1

Cl 284.1 ±
35.5

983.5 ± 12.1 266.2 ±
34.5

17.9 ± 0.9 1267.6 ±
47.6

29.8 ± 1.2

Feb PK1 254.9 ±29.5 70.6 ± 6.9 179.8
±21.1

75.0 ± 8.5 325.5 ± 22.7 4.3 ± 0.9

PK2 1654.6
±23.6

134.9 ±15.6 363.3
±10.3

1291.2 ±
13.4

1789.1 ± 8 1506
±144.2

Cl 267.4 ±11.8 281.5 ± 25.7 192.3 ±
9.9

75.1 ± 1.9 548.9 ± 13.8 29.7 ± 2.8

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Nwosu and Olayinka: Seasonal Variation in Rates of Dust Fall at Motor Parks of University of Ilorin, Ilorin, Nigeria.
AZOJETE, 15(3):678-691. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 684

Mar PK1 208.9 ±
11.8

297.5 ± 41.4 88.6 ± 2.4 120.3 ±
14.2

506.4 ± 29.5 3.8 ± 0.2

PK2 1261.8 ±
11.8

500.6 ± 15.3 554.6 ± 1 707.2 ±
10.8

1762.4 ± 3.5 930 ± 59.4

Cl 263.2 ± 5.9 446.4 ± 10.8 115.8 ±
0.12

147.4 ±
5.79

709.6 ± 4.92 21.8 ± 1.2

Apr PK1 254.9 ± 5.9 502.6 ± 1.4 76.4 ± 4.8 178.5 ±
10.7

757.5 ± 4.6 3 ± 0.5

PK2 292.5 ±
11.8

886.0 ± 64.6 104.7 ±
1.5

187.8 ±
13.3

1178.5 ±
52.8

528 ±
169.7

Cl 288.3 ± 5.9 690.4 ± 9.7 170.1 ±
0.6

118.2 ±
6.5

978.7 ± 3.8 17 ± 1.9

May PK1 167.1 ±
11.8

4129.4 ±382 60.5 ± 8.2 106.6 ±
3.6

4296.5 ±
370.2

3.7 ± 0.9

PK2 259.0 ±
11.7

2541.6 ±10.0 239.7 ±
16.4

19.3 ± 4.6 2800.6 ±
21.9

1164 ±
67.9

Cl 228.1 ± 3.6 2219.2 ±208 189.3 ±
0.3

38.8 ± 3.8 2447.3±
211.9

26.3 ± 0.9

Jun PK1 271.6 ±
17.7

3416.3 ± 364 68.0 ± 8.9 203.5 ±
8.9

3687.8 ± 381 992 ± 18.4

PK2 196.4 ±
17.7

3326.1 ± 174 37.4 ± 0.9 158.9 ±
16.9

3522.5 ±
156.7

1057.5 ±
31.8

Cl 346.8 ±
17.7

3813.5 ± 299 154.8 ±
21.3

191.9 ±
3.6

4160.3 ± 281 24.5 ± 0.7

(±) standard deviation

3.2 Insoluble, Soluble Dust and Traffic Density
The lowest insoluble dust was observed at PK1 in the month of December (129.5 ± 5.9
mg/m2/day) which could be due to low traffic density (3.5 ± 0.7 vehicles per hour) observed at
this park during the month as shown in Table 2. The highest (2043.12 ± 41.4 mg/m2/day)
insoluble dust was observed at PK2 for the month of January which may be attributed to the
highest traffic density (1509.5 ±72.1 vehicles per hour) observed at the park in that month. The
highest insoluble dust was observed in January (2043.12 ± 41.4 and 284.1 ± 35.5 mg/m2/day) for
PK2 and Cl respectively; PK1 in November (1282.7 ± 64.9 mg/m2/day) when their respective
traffic density (1509.5 ±72.1, 29.8 ± 1.2 and 1000.8 ± 48.3 vehicles per hour) was highest. The
same observation was reported by Khan et al., (2002), Khan et al. (2013), Norela et al. (2009),
Malokootia et al. (2013), Tyagi et al., (2014) and Nwosu et al., (2016) in their separate studies.
That is, the rate of insoluble dust deposition increased as the traffic density increased. This
means that movement of vehicles and passengers are key factors in the generation of insoluble
dust. The soluble dust had no regular pattern of relationship with the traffic density. Thus, some
other factors may be responsible for its deposition.

3.3 Ash Matter, Volatile Matter and Traffic Density
Generally, the highest (1865.8 ± 30.4 mg/m2/day) ash matter was observed at PK2 for January
and the lowest (40.9 ± 4.6 mg/m2/day) was obtained at PK1 for December as given in Table 2.

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The traffic density was highest (1509.5 ±72.1 vehicles per hour) at PK2 in the month of January.
Also, PK1 which had the lowest ash in December had a very low traffic density (3.5 ± 0.7 1
vehicles per hour). Thus, it seemed that the major cause of the ash component is dependent on
the traffic activities. During the period of this study, the highest (1582.8 ± 91 mg/m2/day)
volatile matter was observed at PK2 for December which was not the month of its highest traffic
density. Volatile matter was lowest (17.9 ± 0.9 mg/m2/day) for January at Cl when it had its
highest traffic density as 29.8 ± 1.2 vehicles per hour. This seemed that volatile matter did not
necessarily depend on the traffic density. That is, vehicular activities were likely not the major
cause of volatile matter but probably the combustion of oil, refuse and tiny decaying leaves shed
from the trees around the areas of study (Kamble, 2015).

3.4 Dust fall at various sampling points
As can be seen from Table 2, the soluble dust generally decreased monthly from September to
February and increased from March to May at all the sampling points such that the highest
(32713.0 ± 1290.1 mg/m2/day) and lowest (70.6 ± 6.9mg/m2/day) soluble dust in the study were
observed at PK1 for September and February respectively. The decrease in the soluble dust must
be due to decrease in the amount of rain fall from September to February while the increase
must be due to increase in rain fall and precipitation from March to May. This was in line with
the findings of Norela et al. (2009) and Kamble (2015) who said that the soluble dust was always
more than the insoluble dust in the wet season. Therefore, the major cause of the soluble dust
may be components of aerosols which are usually washed down from the atmosphere in larger
quantity by rain during wet seasons.
On the other hand, the insoluble dust increased from September to January and decreased from
February to May for PK2 and Cl. At PK1, the insoluble dust increased from September to
November before the park became inactive in December. The increase in the insoluble dust was
likely due to decrease in the amount of rain fall from September to January. AL-Harb (2015)
reported that insoluble dust increases as the rain fall decreases. This is because when there is no
heavy rain fall to wet the ground and wash away the top soil, the traffic activities would be able
to lift more dust into the atmosphere.

3.5 Seasonal Comparison of the three sampling points and other studies
The average rate of parameters of each season was obtained by taking the average of monthly
concentrations for each season. Table 3 presents seasonal comparison of average insoluble,
soluble, volatile, ash and total dust fall.

3.5.1 Wet Season
The results in Table 3 for wet season shows that rate of soluble dust was highest
(11771.2mg/m2/day) at PK1 followed by PK2 (10269.1mg/m2/day) and then Cl
(8041.9mg/m2/day). There was probably high amount of soluble particles in the suspended
particulate that was washed down by rain fall at PK1 than PK2 and Cl. The observed amount for
the rate of soluble dust in the present study at all the sampling sites during the wet season
period was higher than observed by Norela et al. (2009) (216.11 mg/m2/day) and Alahmr et al.
(2012) (78.41 mg/m2/day). This may be because the study of Norela was at a residential area and
that of Alahmr et al. (2012) was at a Semi-Urban Area both of which have less amount of soluble
aerosol or suspended particulate matter washed down by the rain fall or the rain falls were not
heavy enough to wash down the suspended matter. The insoluble dust at all sampling points
were very close in the wet season with PK1 having the highest (277.9mg/m2/day), followed by

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AZOJETE, 15(3):678-691. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 686

PK2 (252.4 mg/m2/day) and then Cl (246.2 mg/m2/day). The insoluble dust at all the sampling
points in this present study during the period of wet season were more than that of Norela et al.
(2009) (37.83 mg/m2/day) and Alahmr et al. (2012) (53.08 mg/m2/day). This may be attributed to
the two studies conducted in areas of less traffic densities and low generation of dust.

Table 3: Seasonal Comparison of Average Insoluble, Soluble, Ash, Volatile and Total Dust fall
(mg/m2/day) in this study and previous studies

(*) Not available

The total dust fall at PK1 was highest (12049.1 mg/m2/day) followed by PK2 (10521.5 mg/m2/day)
and then Cl (8288.1 mg/m2/day) according to Table 3. That means the rate of dust deposition at
PK1 was higher than PK2 and Cl in the wet season period. The observed amounts of total dust

Study Research
Site Area

Season Traffic
Density

Soluble Insoluble Volatile
Matter

Ash Total
Dust
Fall

DOE,
2005

This
study,PK1

Motor Park Wet
Season

338.3 hr-1 11771.2 277.9 193.1 84.7 12049.1 133

Dry
Season

203.5 hr-1 1647.6 427 184.4 242.6 2074.6

This
study,PK2

Motor Park Wet
Season

568.7 hr-1 10269.1 252.4 132.3 144.4 10521.5

Hot
Season

1086.5 hr-1 924.5 1520.8 543.2 974 2445.3

This
study,Cl

Motor Park Wet
Season

20.5 hr-1 8041.9 246.2 85.3 167.6 8288.1

Dry
Season

26.6 hr-1 750.7 272.4 76.1 196.3 1023.1

Nwosu et
al., (2016)

Unilorin
Motor Park

Dry
Season

300 day-1 * 1122.2 * * *

Kwasu
Motor Park

Dry
Season

103.2 day-1 * 627.7 * * *

Unibadan
Motor Park

Dry
Season

273.4 day-1 * 316.3 * * *

Alahmret
al., (2012)

Semi-
Urban Area
(Kajang
and Bangi,
Malaysia)

Wet
Season

* 78.41 53.08 * * 131.50

Norela et
al., (2009)

Residential
Area
(Negeri
Malaysia)

Wet
Season

* 216.11 37.83 * 106.96 253.95

Al-Harbi,
2015

Urban
area,
(Shuwaikh,
Kuwait)

Dry
Season

* * * * 944.23 *

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687

fall in this study at all the sampling stations were higher than observed by Norela et al. (2009)
(253.95 mg/m2/day) and Alahmr et al. (2012) (131.50 mg/m2/day). This may be because the
study of Norela was at a residential area and that of Alahmr was at a Semi-Urban Area, both of
which may have lesser amount of settling dust. The volatile matter component was highest
(193.1mg/m2/day) at PK1 followed by PK2 (132.3 mg/m2/day) and then Cl (85.2mg/m2/day) in
the wet season. Volatile was higher than ash in the months of the wet season while low in the
months of the dry season for PK1. It was probably because PK1 had been a motor park quite a
time before this study. Rainfalls could have washed down suspended matter generated as a
result of combustion of oil, refuse and tiny decaying leaves shed from the trees around the area.
The volatile matter was higher than ash in the months of the wet season for PK1. The ash matter
in the wet season as presented in Table 6 shows highest value (167.5mg/m2/day) at Cl followed
by PK2 (144.4 mg/m2/day) and PK1 (84.7mg/m2/day). This high value at Cl could mean that the
top sandy soil at Cl was rich in soil mineral than in PK1 and PK2 areas in the wet season period.
The top soil could be blown up by rainy season wind to become settling dust. All the values
obtained for ash in this study during wet season period were higher than (106.96mg/m2/day)
obtained by Norela et al, (2009).

3.5.2 Dry Season
Table 3 also presents the results obtained in the dry season period. Soluble component was
highest (1647.6 mg/m2/day) at PK1 followed by PK2 (924.4mg/m2/day) and then Cl
(750.7mg/m2/day). The highest value at PK1 could be as a result of deposition of soluble
particles lifted from the ground. The insoluble component was highest (1520.8mg/m2/day) at
PK2 followed by PK1 (427mg/m2/day) and then Cl (272.4mg/m2/day) in the dry season as
presented on Table 3. This must have resulted from their respective obtained traffic density
(1086.5, 203.5, 26.6 vehicles per hour) in the season. The insoluble dust obtained for PK2 in the
dry season of this present study was more (1743.3mg/m2/day) than that obtained by Nwosu et
al. (2016) (1122.2 mg/m2/day) at a motor park in the same university environment. The higher
average traffic density (1086.5 vehicles per hour) observed for dry season at PK2 during this
present study compared to that of Nwosu et al. (2016) (300, 103.2 and 273.4 vehicles per day) in
the same dry season must have contributed to the increase in the insoluble dust. Total dust fall
at PK2 was the highest (2445.3mg/m2/day) followed by PK1 (2074.5mg/m2/day) and then Cl
(1023.1 mg/m2/day) in the dry season. The high traffic density (1086.5 hr-1) and hauling
movement of people on the dry unpaved area of land at PK2 must have greatly contributed to
this high value. Volatile matter component was highest at PK2 (543.2 mg/m2/day) followed by
PK1 (184.4 mg/m2/day) and then Cl (76.1mg/m2/day) in the dry season as shown in Table 3. The
soil around PK2 could contain more of volatile dust than other sites in this study. It might be
because it was formerly a grass land before it was recently adopted as a motor park. Therefore, it
was easier for traffic activities and hauling movement of people to have contributed to lifting of
soil reach in organic matter in the area. The ash matter component presented on Table 6 was
highest (974 mg/m2/day) at PK2 followed by PK1 (242.5mg/m2/day) and Cl (196.3mg/m2/day) in
the dry season. That is the insoluble dust collected at PK2 during the dry season contains more
of ash than Cl which has the highest in the rainy season. Also, ash component at PK2 in the dry
season was more than that obtained (944.23 mg/m2/day) by Al-Harbi 2015 in an urban area of
his study.

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3.5.3 Comparison between Dry and Wet Seasons
Figures 4-6 show the seasonal comparison of dust fall and components at all sampling sites. It
was observed that at all the sampling points in this study; the total dust in the wet season period
was more than that in the dry season period which could be attributed to the washing down of
more suspended particulate matter in the rainy season than dry season. According to Alahmr et
al. (2012), wet deposition is the main process which brings down particles from the air. Soluble
component obtained during the wet season period was found to be more than that of the dry
season period. That is, rain fall do contribute to the washing of the atmosphere thereby
depositing aerosol and other particulate matter most of which are probably dissolved in water.
Chate and Pranesha (2004) reported that heavy rain could capture aerosol particles and wash it
down from the atmosphere. The insoluble matter was lower in the wet season period than in the
dry at all the sampling points. Glavas et al. (2008) and Al-Harbi (2015) reported that heavy rain
fall causes wetting of the ground and wearing away of the top soil which cause reduction in
insoluble matter during wet season. That is, insoluble dust increases from wet season period to
the dry season period.

Figure 4: Seasonal Comparison of Total Dust Fall and Components at PK1 (Tdf = total dust fall,
Sol = soluble dust, Ins = insoluble dust, Vol = volatile matter and Ash)

Figure 5: Seasonal Comparison of Total Dust Fall and Components at PK2 (Tdf = total dust fall,
Sol = soluble dust, Ins = insoluble dust, Vol = volatile matter and Ash)

This is according to the findings of Kamble (2015) and Ifeanyi et al. (2016) that reported dust fall
increases during the dry season because of low humidity conditions which enables easy lifting of
dry soil by hauling movement and traffic activities. Volatile matter was lower in wet season

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689

period than in the dry season period at PK2, while the opposite was the case at PK1 and Cl.
Rainfalls could have washed down suspended matter generated as a result of combustion of oil,
refuse and tiny decaying leaves shed from the trees around the PK1 and Cl. Kamble (2015) also
observed that increase in volatile matter may be from combustion of oil, coal or refuse. Ash
matter was also lower in wet season period than in dry season period at all the sampling points.
The observation suggested that the surface dust found around all the sampling points may be
rich in minerals which have been blown into the container by traffic and wind activities.

Figure 6: Seasonal Comparison of Total Dust Fall and Components at Cl (Tdf = total dust fall, Sol
= soluble dust, Ins = insoluble dust, Vol = volatile matter and Ash)

3.6 Influence of Meteorological parameters on Dust Fall Level
Table 4: Meteorological Data
Parameter Wet Period Dry Period
Temperature (ºC) 28.02 ± 2.18 31.51 ± 1.67
Relative humidity (%) 59.57 ± 11.07 44.02 ± 8.49
Rainfall (mm) 0.73 ± 1.02 0
Wind speed (km/h) 2.04 ± 0.69 1.76 ± 0.7

Table 5: Pearson Correlation Sig (2-tailed) for Comparison of Dust fall, Traffic Density and Rainfall
Pearson Correlation Coefficient (r)
Sites Insoluble/Traffic Density Insoluble/Rainfall Soluble/Traffic Density Soluble/Rainfall
PK1 0.687 -0.018 0.178 0.988
PK2 0.707 -0.432 -0.641 0.991
Cl 0.557 -0.757 -0.633 0.978
Correlation is significant at the 0.05 level

The meteorological data supported the discussion so far. There was a lower average
temperature (28.02 ºC), higher relative humidity (59.57 %) average higher rainfall (0.73 mm) and
an average higher wind speed (2.04 km/h) in wet season than their dry season corresponding
value as shown in the Table 4. The lower temperature and higher humidity favour the binding of
aerosol particles in the atmosphere while the higher rainfall contribute in increasing the washing
down of these aerosol particles which are majorly soluble in water in rainy season. Although the
wind speed was lower in the dry season, the increase in the level of insoluble dust must have
been caused by the hauling movement and traffic activities in the studied sites. Also, increase in

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temperature, decrease in relative humidity, and decrease in rainfall activities favour the lifting of
soil particles into the collecting containers (Mkoma et al. (2010), Kamble (2015) and Ifeanyi et al.
(2016).

3.7 Pearson Correlation
A Pearson product-moment correlation coefficient was computed to assess the relationship
between the levels of insoluble and soluble dust generated with traffic density and rainfalls at
various sites. The closer the coefficient (r) to 1, the stronger the relationship while the closer it is
to 0, the weaker the relationship. The results are shown in the Table 5. There was a positive
correlation for monthly data of insoluble/traffic density at various sites such that increases in
traffic density were correlated with increases in the level of insoluble dust at various sites. The
relationship was strongest at PK2 (r = 0.707), followed by PK1 (r = 0.687) and the Cl (r = 0.557).
However, there was a negative correlation for monthly data of insoluble/rainfall at various sites.
That is, as either of them increases, the other decreases. The monthly level of soluble dust
showed a weak positive correlation (0.178) with traffic density at PK1 while it was negative at PK2
(r = -0.641) and Cl (r = -0.633). Also, level of soluble dust showed a very strong correlation with
amount of rainfall at all sites, PK1 (r = 0.988), PK2 (r = 0.991) and Cl (r = 0.978). This also
suggests that increases in the amount of rainfall correlated with increases in the level of soluble
dust fall.

4.0 Conclusion
This study had observed that the highest total dust fall and soluble dust fall were obtained in the
month of September while that of insoluble dust was in the month of January for PK2 and Cl
while in November for PK1. Also, the rate of soluble dust and total dust deposition decreases
from wet season to dry season while that of insoluble dust and ash deposition increases from
the wet season to dry season. These variations were observed to be majorly as a result of traffic
density and were supported with meteorological data. The observed total dust fall in dry and wet
seasons at various sites is more than the recommended 133 mg/m2/day of Malaysian
Department of Environment. It was also above the South African permissible limit (600 – 1200
mg/m2/day) for dust in heavy commercial and industrial area (SANS 1929, 2005). Therefore, the
motor parks ambient air was highly contaminated with soluble dust in the wet season and
insoluble dust in the dry season. It is therefore advisable for the University Community and other
appropriate authority that have unpaved motor parks all over the nation to take necessary
control measurements such as proper paving or regular wetting of the park.

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