SOURCE APPORTIONMENT OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN SOILS WITHIN HOT MIX ASPHALT (HMA) PLANT VICINITIES

Abstract

Abstract
The composition of polycyclic aromatic hydrocarbons (PAHs) in soils within the vicinities of hot mix asphalt (HMA) production plants in Port Harcourt, Nigeria, was investigated. Soil samples were collected at an increasing distance of 10 m from two HMA plants, at surface (0-15 cm) and subsurface (15-30 cm) depths during dry and wet seasons. PAHs distribution in the soil samples were analyzed with gas chromatography equipped with flame ionization detector (GC-FID). PAHs concentrations during the dry season for HMA plant A ranged from 8.20 - 449.00 mg/kg and 5.66 - 271.00 mg/kg for surface and subsurface soils respectively. The concentrations in HMA plant B ranged from 219.00 - 378.00 mg/kg and 27.00 - 264.00 mg/kg for surface and subsurface soils respectively. The PAHs concentration in the wet season for HMA plant A ranged from 10.30 - 71.90 mg/kg and 4.11 - 38.50 mg/kg for surface and subsurface soils respectively while that of HMA plant B was between 28.70 – 106.00 mg/kg and 8.73 – 37.00 mg/kg for surface and subsurface soils respectively. PAH diagnostic ratios of Anthracene/Phenanthrene, Fluoranthene/Pyrene and Benzo[a]Anthracene/Chrysene indicated the dominant sources of PAHs within the HMA plant vicinities were pyrogenic with variable input from petrogenic sources due to petroleum fuels and oils from vehicle traffics, vehicle repair/maintenance in the plant area and runoffs during the wet season. Multivariate analysis of PAHs diagnostic ratios showed significant correlation (≥ 72.04%) in soil samples from both HMA plant vicinities and revealed similar PAHs profiles dominated by pyrogenic PAHs.

Full text

J. Chem. Soc. Nigeria, Vol. 41, No. 2, pp10-16 [2016]
SOURCE APPORTIONMENT OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN SOILS
WITHIN HOT MIX ASPHALT (HMA) PLANT VICINITIES
1*I. Ilechukwu, 2L.C. Osuji and 2M.O. Onyema
1Department of Industrial Chemistry, Madonna University, Elele Campus,
P.M.B 48 Elele, Rivers State, Nigeria.
2Department of Pure and Industrial Chemistry, University of Port Harcourt,
P.M.B 5323 Choba, Rivers State, Nigeria.
Accepted:04/08/2016
*Corresponding author: ifennai@yahoo.com
Abstract
The composition of polycyclic aromatic hydrocarbons (PAHs) in soils within the vicinities of hot mix asphalt
(HMA) production plants in Port Harcourt, Nigeria, was investigated. Soil samples were collected at an
increasing distance of 10 m from two HMA plants, at surface (0-15 cm) and subsurface (15-30 cm) depths
during dry and wet seasons. PAHs distribution in the soil samples were analyzed with gas chromatography
equipped with flame ionization detector (GC-FID). PAHs concentrations during the dry season for HMA plant
A ranged from 8.20 - 449.00 mg/kg and 5.66 - 271.00 mg/kg for surface and subsurface soils respectively. The
concentrations in HMA plant B ranged from 219.00 - 378.00 mg/kg and 27.00 - 264.00 mg/kg for surface and
subsurface soils respectively. The PAHs concentration in the wet season for HMA plant A ranged from 10.30 -
71.90 mg/kg and 4.11 - 38.50 mg/kg for surface and subsurface soils respectively while that of HMA plant B
was between 28.70 – 106.00 mg/kg and 8.73 – 37.00 mg/kg for surface and subsurface soils respectively. PAH
diagnostic ratios of Anthracene/Phenanthrene, Fluoranthene/Pyrene and Benzo[a]Anthracene/Chrysene
indicated the dominant sources of PAHs within the HMA plant vicinities were pyrogenic with variable input
from petrogenic sources due to petroleum fuels and oils from vehicle traffics, vehicle repair/maintenance in the
plant area and runoffs during the wet season. Multivariate analysis of PAHs diagnostic ratios showed
significant correlation (
≥
72.04%) in soil samples from both HMA plant vicinities and revealed similar PAHs
profiles dominated by pyrogenic PAHs.
Keywords: Asphalt, PAHs, soil, diagnostic ratio, multivariate analysis.
Introduction
The characterization and differentiation of
hydrocarbons from different sources is an essential
part of petroleum hydrocarbon pollution investigation
[1,2]. Hydrocarbons in the environment are either
from biogenic or anthropogenic source. Biogenic
hydrocarbons are generated by biological processes or
in the early stages of diagenesis in marine sediments.
Biological sources include land plants, phytoplankton,
animals, bacteria, macroalgae and microalgae [1,3].
There are two types of anthropogenic sources of
hydrocarbons; petrogenic and pyrogenic. Petrogenic
sources include petroleum and its products such as
kerosene, gasoline, diesel fuel and lubricating oil,
while pyrogenic sources are from incomplete
combustion of organic materials such as fossil fuels
used in industrial operations and power plants,
garbage incinerators, vehicle engines and forest fires
[4,5].
The growing demand for road construction and
expansion in Nigeria has led to a huge increase in
asphalt production [6]. The production of hot asphalt
cement is done in a hot mix asphalt (HMA) facility or
plant which is an assemblage of mechanical
equipment where aggregates (i.e. inert mineral
materials such as sand, gravel, crushed stones, slag,
rock dust or powder) are blended, heated, dried and
mixed with bitumen [7]. Asphalt production employs
the use of bitumen, a dark brown to black cement-like
semi-solid or solid or viscous liquid, produced by the
non-destructive distillation of crude oil during
petroleum refining. Bitumen contains aliphatic
hydrocarbons, cyclic alkanes, aromatic hydrocarbons,
heterocyclic compounds containing oxygen, nitrogen,
and sulphur as well as metals like nickel, vanadium
and iron [8].
HMA plants are numerous in Nigeria, especially in
southern Nigeria due to proximity to sea ports (for
bitumen importation), vibrant oil and gas industry and
large bitumen deposit in South Western Nigeria
[6,9,10].
Polycyclic aromatic hydrocarbons (PAHs) are a class
of diverse organic compounds with two or more
aromatic rings fused together. They are generated
during asphalt production and usage [11] and during
the combustion of petroleum products. They are
ubiquitous environmental contaminants found in air,
water, and soil. PAHs are difficult to degrade due to
the complexity and stability of their molecular
structures hence, they are classified among persistent
organic pollutants (POPs). PAHs are toxic to human
health [12]. The 4-6 ring PAHs are known
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J. Chem. Soc. Nigeria, Vol. 41, No. 2, pp10-16 [2016]
carcinogens (cancer-causing agents) while the 2-3
ring may act as synergists [13,14]. This study,
therefore aims to determine the sources of PAHs in
soils within the vicinity of two HMA plants in Port
Harcourt. It is expected to assist in adequate
environmental management during asphalt production
and usage.
Materials and Methods
Sampling
Two HMA plants were used for this study. HMA
plant A is located at Obigbo, latitude 4° 51′ 00″ N and
longitude 7° 04′ 55″ E, and HMA plant B is located at
Igwuruta, latitude 4° 55′ 04″ N and longitude 7° 02′ 30″
E, both in Rivers State, Nigeria. Soil samples were
collected in March (dry season) and August (rainy
season) at surface (0-15 cm) and subsurface depth.
Samples were collected at an increasing distance of 10
m from both plants using a stainless steel scoop. For
HMA plant A, samples were collected at 10m, 20m,
30m, 40m and 50m, while plant B samples were
collected at 10m, 20m, 30m and 40m. The control
samples were collected at 1 km away from both HMA
plants.
Sample extraction and chromatographic analysis
The soil samples (10g each) were extracted in a
soxhlet apparatus for 4 hours with dichloromethane.
The extracts were concentrated in a rotary evaporator
and then fractionated using glass chromatographic
column (15 cm x 1 cm) stocked with glass wool at the
lower end and packed with activated silica gel (100-
200 mesh) topped with 0.5 g anhydrous sodium
sulphate for water removal. Saturate hydrocarbons
were eluted with n-hexane while the aromatic
hydrocarbons were eluted with
hexane/dichloromethane (1:1 v/v). The aromatic
fractions which contain the PAHs were concentrated
in a rotary evaporator. Analysis of the aromatic
fraction of each sample extract was performed with
AGILENT 6890 gas chromatography (GC) equipped
with flame ionization detector (FID) and fitted to a
capillary column of length 25.0 m, diameter 320 µm,
stationary phase; phenyl methyl siloxane, film
thickness 0.17 µm. One microlitre (1µl) of each
sample extract was injected in splitless mode with
Helium used as the carrier gas and with the following
operational conditions: Flow rate (H2 35ml/min, air
350ml/min, N2 10ml/min); injection temperature
(initial 100oC, final 325oC). GC oven temperature was
programmed from 40oC to 320oC at a rate of 6oC/min
and held at 350oC for 15 minutes. Quantification was
determined by comparing the peak area of the internal
standard, perdeuterated n-tetracosane, to those of the
analytes.
Results and Discussion
Results of total polycyclic aromatic hydrocarbons
(PAHs) concentration from gas chromatographic
analysis of surface and subsurface soils within the
vicinity of HMA plants A and B are presented in
Table 1. For HMA plant A, PAHs concentrations
during dry season, ranged from 8.20 - 448.89 mg/kg
for surface soils and 5.66 - 270.78 mg/kg for
subsurface soils with no amount detected in the
control soil samples. In the wet season, PAHs
concentration ranged from 10.34 - 71.88 mg/kg for
surface soils and 4.11 - 38.45 mg/kg for subsurface
soils, while concentration in the control samples were
9.11 mg/kg and 1.61 mg/kg for surface and subsurface
soils respectively. For HMA plant B, the PAHs
concentration during the dry season ranged from
219.39 - 377.97 mg/kg for surface soils and 27.00 -
264.44 mg/kg for subsurface soils with no amounts
detected in the control soils. In the wet season, the
PAHs concentration was between 28.73 - 105.62
mg/kg and 8.73 - 37.33 mg/kg for surface and
subsurface soils respectively while concentration in
the control soil samples was 13.32 mg/kg and 1.93
mg/kg for surface and subsurface soils respectively.
The concentration of PAHs in HMA plants A and B
were lower during the wet season. This may be
attributed to reduction in asphalt production during
the wet season and runoffs during rainfall [6]. The
PAHs detected in the control soils from both plants
during the wet season may be from runoffs during
rainfalls. PAHs concentrations in soils from plants A
and B were higher at surface depth than at subsurface,
and the concentrations decreased with increasing
distance from both plants for dry and wet seasons.
This indicates that PAHs pollution in soils within the
vicinity emanated from surface soil close to both
HMA plants.
PAHs Source Determination
The distribution of PAHs in environmental media is
used to identify and differentiate hydrocarbon sources
and is very important for environmental damage
assessment [1]. Characteristic ratios of polycyclic
aromatic hydrocarbons (PAHs) have been employed
to unambiguously identify the sources of hydrocarbon
compounds in environmental samples as well as
differentiate between the sources [15,16]. Tables 2
and 3 show diagnostic ratios utilized for the
determination of the PAHs sources in soils within the
vicinities of HMA plants A and B respectively. The
ratio of low molecular weight (LMW) 2-3 rings PAHs
to high molecular weight (HMW) 4-6 rings PAHs
have been used to differentiate between sources.
LMW/HMW ratio greater than 1 (>1) signifies a
probable petrogenic origin for hydrocarbons while
ratios less than 1 (<1) are generally considered to
indicate a predominance of pyrogenic source [17].
Soils from the vicinity of the HMA plant A showed
predominance of the HMW PAHs over the LMW
PAHs at surface and subsurface depths for both
seasons (Table 2). The ratio LMW/HMW in soils
from HMA plant A was less than 1 during both
seasons. This indicates pyrogenic source as the most
11

I. Ilechukwu, L.C. Osuji and M.O. Onyema
significant source of PAHs within the vicinity. For
HMA plant B, ratios of LMW/HMW were less than 1
suggesting pyrogenic source, except for wet season at
surface soil with ratios of 6.69 and 1.08 at 10m and
20m respectively, which suggest petrogenic source
[18].
Table 1: Total Polycyclic Aromatic Hydrocarbons (PAHs) Concentrations in Soils within the Vicinity of
two HMA Plants.
Total PAH concentration at Dry Season (mg/kg)
Depth 10m 20m 30m 40m 50m Control
Plant A Surface
Subsurface 448.89
270.78 234.92
103.23 39.85
11.19 8.20
5.66 nd
nd nd
nd
Plant B Surface
Subsurface 377.97
264.44 368.23
27.00 219.39
227.38 269.66
139.56 -
- nd
nd
Total PAH concentration at Wet Season (mg/kg)
Plant A Surface
Subsurface 71.88
38.45 33.07
39.73 51.61
12.22 27.19
7.73 10.34
4.11 9.11
1.61
Plant B Surface
Subsurface 105.62
37.33 66.07
13.99 31.31
8.73 28.73
19.12 -
- 13.32
1.93
Surface (0-15cm), Subsurface (15-30cm)
Table 2: Source Diagnostic Ratios of PAHs in Soils within the Vicinity of Asphalt Plant A
Dist. Depth
An/(An+Phe)
Fl/(fl+pyr)
BaA/BaA + Chr
LMW/HMW
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Wet
10m
Surface
Subsurface
0.68
0.65
0.32
0.32
0.41
0.67
0.23
0.59
0.50
0.58
0.41
0.26
0.37
0.43
0.81
0.77
20m
Surface
Subsurface
nd
nd
0.64
nd
0.49
nd
Nd
nd
0.56
nd
0.47
0.52
0.21
0.18
0.26
nd
30m
Surface
Subsurface
nd
nd
1.00
nd
nd
nd
Nd
0.43
nd
nd
nd
nd
nd
nd
0.38
0.32
40m
Surface
Subsurface
nd
nd
nd
nd
nd
nd
Nd
nd
nd
nd
nd
nd
nd
nd
0.24
nd
50m
Surface
Subsurface
nd
nd
nd
nd
nd
nd
Nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
Cont.
Surface
Subsurface
nd
nd
nd
1.00
nd
nd
Nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
Petrogenic
pyrogenic
< 0.1
> 0.1
<0.4
>0.5
< 0.2
> 0.35
>1.00
<1.00
LMW; Low molecular weight PAHs = Σ 2 – 3 rings PAHs,
HMW; High molecular weight PAHs = Σ 4 – 6 rings PAHs,
An; Anthracene, Phe; Phenanthrene, Fl; Fluoranthene, Pyr; Pyrene, BaA; Benzo[a]Anthracene, Chr;
Chrysene, nd: cannot be determined because of the zero value of the nominator and/or denominator.
Petrogenic PAHs are related to non-combusted
petroleum while HMW PAHs are typical pyrogenic
products derived mainly from fossil fuel combustion,
a significant process in asphalt production [19,20].
This result indicates that hydrocarbons in soils within
the vicinity of the HMA plant B are mixture of
sources; a dominant pyrogenic source for PAHs and
petrogenic source input probably due to runoff during
wet season.
Diagnostic ratios of PAHs isomers have been used to
identify and differentiate hydrocarbon source types in
environmental samples as petrogenic or pyrogenic.
These ratios are based on the thermodynamics of
formation of the pyrogenic and petrogenic PAHs
isomers [21]. The kinetic or less stable isomers are
mainly generated during combustion at elevated
temperatures, while the thermodynamic or more stable
isomers dominate in the absence of combustion due to
long duration processes such as diagenesis or
catagenesis [22,23].
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J. Chem. Soc. Nigeria, Vol. 41, No. 2, pp10-16 [2016]
Table 3: Source Diagnostic Ratios of PAHs in Soils within the Vicinity of Asphalt Plant B
Dist. Depth
An/(An+Phe)
Fl/(fl+pyr)
BaA/BaA + Chr
LMW/HMW
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Wet
10m Surface
Subsurface nd
0.41 0.57
1.00 0.37
0.37 1.00
0.00 0.44
0.42 1.00
nd 0.39
0.39 6.69
0.30
20m Surface
Subsurface 0.48
nd 1.00
nd 0.43
nd 0.40
0.00 0.47
nd 0.22
nd 0.17
nd 1.08
0.23
30m Surface
Subsurface 0.33
0.36 1.00
nd 0.35
0.45 nd
nd 0.32
0.44 nd
nd 0.48
0.47 0.39
nd
40m Surface
Subsurface 0.35
nd nd
nd 0.58
nd nd
1.00 0.61
0.57 nd
nd 0.71
nd nd
0.96
Cont. Surface
Subsurface nd
nd nd
nd nd
nd nd
nd nd
nd nd
nd nd
nd nd
nd
Petrogenic
Pyrogenic
< 0.1
> 0.1
<0.4
>0.5
<0.2
>0.35
>1.0
<1.0
Anthracene/phenanthrene+anthracene (An/An+Phe)
ratios less than 0.1 signify probable petrogenic origin
for hydrocarbons, while ratios greater than 0.1 suggest
pyrogenic source (i.e. combustion sources).
fluoranthene/fluoranthene+pyrene (Fl/Fl+Pyr) ratios
less than 0.4 suggest petrogenic source and ratios
greater than 0.5 are generally considered as indicative
of a predominance of pyrogenic source. When ratios
of BaA/(BaA+Chr) are <0.2 or >0.35, petrogenic or
pyrogenic sources are suspected respectively [5,24].
The values obtained for these ratios indicate
pyrogenic sources as the dominant source of PAHs
within the asphalt plant vicinities. The
BaAn\/(BaA+Chry) values for subsurface sample 10
m in plant A (wet season) and surface samples 20 and
30 m (wet and dry season respectively) of plant B
showed petrogenic dominance. While that of plant A
may be attributed to a mixture of sources, that of plant
B may be due to the release of hydrocarbons as a
result of the articulated vehicles and equipment
maintenance that take place within the plant vicinity.
The values of Flu/(Flu+Pyr) for the samples showed
the PAHs in both plant vicinities was predominantly
due to combustion since Flu/(Flu+Pyr) < 0.4 indicates
petroleum spillage, between 0.4 and 0.5 implies liquid
fossil fuel combustion and > 0.5 is for biomass and
coal combustion [4]. The Flu/(Flu+Pyr) values for
plant A showed dominance of pyrogenic sources
except for surface sample 10 m in the wet season
while samples 10m at both depth and surface sample
30 m showed petrogenic dominance. The diagnostic
ratios for both plants showed the PAHs in the vicinity
of both plants were mostly of pyrogenic origin due to
combustion of fossil fuel.
Combustion in hot mix asphalt production is usually
applied during drying of the aggregates, heating the
bitumen and mixing both the aggregates and the
bitumen [7]. Furthermore, the exhaust emissions of
vehicles that load the hot mix asphalt (HMA) off the
production plants are also combustion products [25].
The petrogenic dominance in some sampling locations
indicates a probable mixture of sources. Some of these
petroleum products (e.g petrol) are employed in the
washing of equipment during maintenance and repairs
and in plant B where the vicinity serves as articulated
vehicles and construction equipment repair area, it is
not surprising that petrogenic sources were highly
suspected [15,18].
Multivariate correlation
Multivariate statistical analysis (PCA and HCA) of
the diagnostic ratios were used to determine the
relationship between soil samples from both HMA
plant vicinities and to provide information on the
contamination source(s). Principal component
analysis, PCA is a statistical method which derives a
set of variables, known as principal components
(PCs). Each component attempts to account for
variance in the data [26]. PCA provides an unbiased
comparison of samples based on graphical
interpretation of a complex data set. Samples that plot
nearest to the suspected source profile are most
similar in chemical composition and vice versa [27].
Petroleum products are well suited to such
explorations by PCA because their molecular
compositions result from a complex interaction of
biological, environmental, geological, and physical
processes working competitively and simultaneously
[26]. Principal component plots of diagnostic ratios
for plants A and B are presented in figures 1 and 2
respectively showing the correlation between samples
at both depths and seasons.
13

I. Ilechukwu, L.C. Osuji and M.O. Onyema
3210-1-2
2
1
0
-1
-2
-3
First Component (64.2%)
Second Component (17.3%)
ASS50W
AS50W ASS40W AS40W
ASS30W
AS30W
ASS20W
AS20W
ASS10W
AS10W
ASS50D
AS50D
ASS40D
AS40D
ASS30D
AS30D
ASS20D
AS20D
ASS10D
AS10D
A: HMA Plant A, SS: Subsurface sample, S: Surface sample,
D: Dry season sample, W: Wet season sample, ##: distance from the asphalt plant.
Fig 1: Principal Component Plot of Diagnostic Ratios for Soils within HMA Plant A Vicinity at Both
Seasons.
From the PC plot of diagnostic ratios for plant A, it
was observed that samples within 30m in both depths
and seasons, separated clearly. The first component
accounted for 64.2% (from -2 to +3) of the total
variance among the samples, while the second
component accounted for only 17.3% with most
samples clustered between -1 and +1. This suggest
PAHs contamination within the vicinity of HMA
plant A was similar and largely of pyrogenic source
(LMW/HMW < 1). However, increase abundance of
the LMW PAHs in soils at 10 m (higher LMW/HMW
ratio; table 2) suggests contamination from petrogenic
source. Therefore, the PAH contamination within the
vicinity of HMA plant A soils is mainly pyrogenic
sources with input from petrogenic sources.
543
210-1
-2
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
First Component (51.7%)
Second Component (24.8%)
BSS40W
BS40W
BSS30W
BS30W
BSS20W
BS20W
BSS10W
BS10W
BSS40D
BS40D
BSS30D
BS30D
BSS20D
BS20D
BSS10D
BS10D
Fig 2: Principal Component Plot of Diagnostic Ratios for Soils within HMA Plant B Vicinity at Both
Seasons.
The PC plot of diagnostic ratios for plant B, at both
depths and seasons, shows the first component
accounted for 51.7% of the total variance among the
samples, while the second component accounted for
24.8%. Soil samples from the wet season were
observed to be more scattered than those from the dry
season. Runoffs during the wet season may also be
responsible for this variability in hydrocarbon profile,
thus the increased scattering of the samples in the PC
plot.
The relationship between soil contaminations within
the vicinities of both HMA plants was determined
using hierarchical cluster analysis (HCA) of PAHs
diagnostic ratios and the result presented in figure 3.
14

J. Chem. Soc. Nigeria, Vol. 41, No. 2, pp10-16 [2016]
BS10W
BSS40W
ASS30W
BS40W
BSS30W
BSS20D
ASS50W
AS50W
ASS40W
ASS50D
AS50D
ASS40D
AS40D
ASS30D
AS30D
BSS20W
AS40W
ASS20D
BSS40D
ASS20W
BS10D
AS20D
BS20W
BSS10W
BS30W
AS30W
AS20W
BS40D
ASS10W
AS10W
BS20D
BS30D
BSS30D
BSS10D
ASS10D
AS10D
0.00
33.33
66.67
100.00
Samples
Similarity
Fig 3: Hierarchical Cluster Analysis (HCA) Dendogram of PAHs Diagnostic Ratios of Soils from Both
HMA Plant Vicinities
The HCA dendogram of PAH diagnostic ratios (fig 3)
showed all the soil samples from both HMA plant
vicinities, at both depths and seasons correlated
(similarity levels of 72.04% and above) with each
other except for the surface soil sample at 10 m from
plant B in the wet season, which showed no similarity
with the other samples. This reveals that both HMA
plants have similar PAHs profiles with predominance
of pyrogenic HMW 4-6 ring PAHs. The slight
differences in similarities observed among the
samples could be attributed to variation in petrogenic
LMW 2-3 ring) PAHs inputs from uncombusted
petroleum fuels and oils from vehicle traffics, vehicle
repair/maintenance in the plant area as well as runoffs
during the wet season. The surface soil sample at 10
m, from plant B in the wet season, which did not
correlate with the other samples is an indication that
asphalt production activities are not necessarily the
only source of PAHs contamination in soils within the
vicinities of the HMA plants.
Conclusion
This study showed the nature and degree of
hydrocarbons contributed to the soils by HMA
production plants in dry season as well as in the wet
season. The PAHs contamination in soils within the
vicinity of the two HMA plants showed dominance of
pyrogenic HMW PAHs with inputs from petrogenic
LMW PAHs. This study is expected to serve as a
template in taking environmental related decisions in
the management of HMA production plants and
considering that there are no regulatory guidelines
regarding soil pollution in many developing countries
such as Nigeria, the characterization of soil pollution
in relation to various industrial activities will assist in
setting up proper soil regulation guidelines for
sustaining a safe and balanced environment as well as
in protecting human health.
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