Journal of Research in Environmental Science and Toxicology (ISSN: 2315-5698) Vol. 1(10) pp. 267-274, November 2012
Available online http://www.interesjournals.org/JREST
Copyright ©2012 International Research Journals
Full Length Research Paper
Transfer coefficients of some toxic and trace elements
into Siam weed along highways in Ado-Ekiti, Nigeria
*1
Falusi Bamidele Ayodeji and 2Olanipekun Edward Olorunsola
1
Department of Chemistry, Federal College of Education (Special), P.M.B. 1089, Oyo, Oyo State, Nigeria
2
Department of Chemistry, Ekiti State University, P.M.B. 5363, Ado-Ekiti,
Nigeria
Accepted November 13, 2012
Transfer coefficients of the trace and toxic elements: arsenic, cadmium, mercury, lead, and zinc into
Siam weed collected along Nigerian highways have been determined with the view to quantify the
differences in bio-availability to the plant species. The samples were acid-digested and analyzed by
flame atomic absorption spectrophotometry. TCs of the elements along the low traffic road (LTR) and
high traffic road (HTR) respectively ranged as follows: As (0.00 – 3.20, 0.75 – 2.40), Cd (1.13 – 2.79, 0.88
– 1.59), Zn (1.11 – 1.42, 1.25 – 1.45), Hg (0.27 – 1.51, 0.48 – 1.65) and Pb (0.63 – 1.16, 1.05 – 1.23).
Whereas Cd and Zn were within the expected ranges, other values far exceeded the normal values (i.e. 1
– 10 for Cd and Zn; and 0.01 – 0.10 for As, Hg and Pb respectively), which was indicative of the rather
elevated levels of these elements in the top soil along the highways. Transfer coefficients are a key
component of human exposure to metals and metalloids through consumption of food and or
traditional medicines. The findings suggest that plant samples sourced along the highways should not
be used for therapeutic purposes.
Keywords: Transfer coefficients, Siam weed, therapeutic purposes, physico-chemical parameters, Ado-Ekiti.
INTRODUCTION
Roadside soils have been shown to contain high
concentrations of metallic contamination (Jaradat and
Momani, 1999). The bioavailability and environmental
mobility of the metals vary with the forms in which they
exist within the soil. Trace metal concentrations of Cd,
Cu, Zn and especially Pb, in surface soils have been the
focus of major investigations (Jaradat and Momani, 1999;
Sutherland, 2000). The volume of traffic affects the
accumulation of these metals in topsoil, introducing a
number of toxic metals into the atmosphere (Wixon and
Davies, 1994). The lead in roadside soil is mainly found
in the form of lead sulphate (Jaradat and Momani, 1999).
Metals such as Cu, Fe, Zn, and Cd are essential
components of many alloys, wires, tyres and many
industrial processes, and could be released into the
roadside soils as a result of mechanical abrasion and
normal wear, and subsequently be absorbed by plants
*Corresponding Author E-mail: deledoncattle@yahoo.com
(Ferguson and Kim, 1991). The heavy metal pollution of
soils can have serious health implications especially
through consumption of crops grown in the soils
(Nyagababo and Hamya, 1986; Birley and Lock, 1999).
Plant material such as fungi, lichens, tree bark, tree
rings and leaves of higher plants have been used as
indicators of the deposition, accumulation and distribution
of metallic pollution. Lower plants, especially, mosses
and lichens, in view of their higher capacity for metal
accumulation, are probably the organisms most
frequently used for monitoring such pollution in urban
environments (Markert, 1993; Al-Shayeb et al., 1995;
Aksoy and Sahin, 1999). Leaves of higher plants have
been used for the biomonitoring of heavy metals since
the 1950s (Al-Shayeb, et al., 1995). In recent decades,
there has been increased use of higher plant leaves as
indicators of heavy metal pollution in the terrestrial
environment (Djingova and Kuleff, 1993; Aksoy and
Ozturk, 1996; Aksoy and Ozturk, 1997).
Siam weed (Chromolaena odorata) has many reported
medicinal values, particularly among Africans (Akubue,
1986; Gill, 1992; Omotayo, 2000; Chamratpan and Hom-
268 J. Res. Environ. Sci. Toxicol.
Chuen, 2002; Obuekwe and Obuekwe, 2002). For
instance, crushed fresh leaves of the plant, when added
to alum and chewed and applied on wounds have been
used as an antidote for snake bite (Chamratpan and
Homchuen, 2002). The leaves when chewed alleviate
headache and toothache and have been proven to have
antimicrobial and anti-coagulant properties (Akubue,
1986). The infusion of the leaves is a remedy for
dysentery; and the decoction of the leaves with
Azadirachta indica is used for the cure of malaria (Gill,
1992). The juice of the leaves can stop bleeding (Gill,
1992). The plant is a febrifuge, reduces backache, is a
styptic for bleeding, and can be used as a poultice for
wounds and sores (Omotayo, 2000). The leaves of the
plant taken with some other leaves (Occimum
gratissimum and Vernonia amygdalina) and local chalk
have been used traditionally to treat diarrhea (Obuekwe
and Obuekwe, 2002). Siam weed has antifungal
properties. The presence of oxalates and tannins is said
to be responsible for the anticoagulant properties
(Omotayo, 2000). Active constituents of Siam weed
include essential oil (terpenoids),
abeled s-pinene,
limonene, cardinene and oxygenated sesquiterpenoids
(Okogun, 1986); flavonoids and oxalates (Bose et al.,
1973).
These benefits however depend on clean sources.
Siam weed collected within the vicinity of highways has
been shown to be unsuitable for therapeutic purposes,
because of high metal burdens (Falusi and Olanipekun,
2011). Metals such as Cd, Pb and Hg are not essential to
living organisms and their accumulation over time in
mammals can cause serious illnesses (Hawkes, 1997).
Consequently this study was conducted with the following
aims:
(1) To investigate the concentrations of five elements; As,
Cd, Hg, Pb, and Zn in the plant and soil samples
collected at different sites along two highways of different
traffic densities in Ado-Ekiti, Nigeria
(2) To determine the transfer coefficients of the elements
from the soil into the plant so as to quantify the relative
differences in bio-availability of the elements to the plant
species.
MATERIALS AND METHODS
Sample collection
A total of fourteen soil samples (~100g), and fourteen
plant leaf samples (also~100g), were collected along two
highways in Ado-Ekiti, Nigeria (Lat. 26.50°S, Long.
12.70°W). Samples were collected at distances of 2.0 m,
5.0 m, 10.0 m, 15.0 m and 20.0 m on roadsides away
from the highways. Top-soil samples were collected at
depths of 0–15 cm using a stainless steel hand trowel,
which was cleaned between sampling points. The soil
and plant samples were packaged in polythene bags and
clearly abeled. They were transported immediately to
the laboratory for processing and preservation. Only fresh
leaves of Siam weed in prime condition were collected in
order to produce good quality dried products (Audu and
Lawal, 2005).
Digestion and analysis of soil samples
The soil samples were air-dried, mechanically ground for
30 minutes using a ball mill and sieved to obtain a
fraction with a particle size < 2 mm. This fraction was
used to determine pH (1:5 soil-water extract), electrical
conductivity (EC) (1:5 soil-water extract), and particle size
analysis using standard laboratory methods (Rayment
and Higginson, 1992). Smaller samples of 20–30 g were
drawn from the same fraction and reground using mortar
and pestle to obtain a sample with particle size < 200 µm.
This material was used to determine organic matter
(OM), cation exchange capacity (CEC) and total metal
concentrations. The OM was determined by the modified
Walkley and Black method (Mc Leod, 1973); the CEC
was determined by the silver thiourea method (Rayment
and Higginson, 1992).
An adapted technique (Berrow and Ure, 1981;
Paveley and Davies, 1988) was employed for analysis.
One-gram samples of dried and sieved soil materials
were ashed in a muffle furnace; the weighed ash was
digested in 10 mL aqua regia in an Erlenmeyer digestion
tube (300 mL) on a heating block for a total of 9 h with
the sequence and duration of temperatures: 2 h each at
25 ºC, 60 ºC, and 105 ºC, and finally 3 h at 125 ºC. All
digested samples were centrifuged and made up to
volume with 1% HNO3. Triplicate digestions of each
sample together with blank were carried out.
Digestion and analysis of plant leaf samples
The samples were thoroughly washed under the tap and
distilled water and dried in an oven at 105 ºC for 24 h
until they were brittle and crisp. The dried samples were
finely ground using clean-acid washed mortar and pestle.
A described method (Al-Shayeb et al., 1995) was used
for digestion. One-gram samples of dried and ground
plant material were ashed; the weighed ash was digested
in concentrated HNO3 and evaporated to near dryness on
a hot plate. Digested samples were centrifuged and
brought up to the mark with 1% HNO3. Triplicate
digestions of each sample as well as blanks were carried
out.
Concentrations of As, Cd, Pb, and Zn were
determined directly in soil and plant material using a
Shimadzu flame atomic absorption spectrophotometer
(model AA-6200). Hg levels were determined using cold
vapour generation ICP-AES (Varian Liberty Series II).
Validation of digestion methods was done using certified
Ayodeji and Olorunsola 269
Table 1. Concentration of elements [mg/kg] (mean ± SD, N =14) in soil
samples along the two highways.
Code
SL1
SL2
SL3
SL4
SL5
SL6
SL7
SH1
SH2
SH3
SH4
SH5
SH6
SH7
As
1.00 ± 0.10
0.00 ± 0.00
0.00 ± 0.00
0.00 ± 0.00
0.00 ± 0.00
0.50 ± 0.04
1.60 ± 0.10
0.50 ± 0.03
0.65 ± 0.07
1.00 ± 0.60
1.25 ± 0.03
1.68 ± 0.12
1.56 ± 0.13
2.00 ± 0.84
Cd
0.18 ± 0.02
0.13 ± 0.01
0.12 ± 0.02
0.10 ± 0.01
0.03 ± 0.01
0.10 ± 0.02
0.42 ± 0.03
0.60 ± 0.14
0.49 ± 0.11
0.50 ± 0.06
0.41 ± 0.01
0.34 ± 0.05
0.85 ± 0.14
0.77 ± 0.18
Hg
0.15 ± 0.01
0.13 ± 0.01
0.12 ± 0.03
0.11 ± 0.03
0.08 ± 0.02
0.55 ± 0.08
0.36 ± 0.07
0.25 ± 0.03
0.22 ± 0.10
0.15 ± 0.03
0.14 ± 0.00
0.12 ± 0.02
0.75 ± 0.10
0.89 ± 0.07
Pb
104 ± 10
97.1 ± 9.7
80.9 ± 7.5
74.3 ± 8.6
68.9 ± 7.6
142 ± 20
159 ± 23
307 ± 25
302 ± 24
299 ± 26
286 ± 22
271 ± 28
346 ± 40
388 ± 42
Zn
53.9 ± 7.2
53.8 ± 6.1
52.8 ± 6.1
52.7 ± 6.1
52.6 ± 5.7
54.8 ± 6.5
54.5 ± 6.4
53.9 ± 7.1
52.9 ± 6.5
52.9 ± 6.4
52.8 ± 6.1
52.7 ± 6.2
55.5 ± 8.2
55.3 ± 7.2
Note- L1 and H1 = 2.0 m; L2 and H2 = 5.0 m; L3 and H3 = 10.0 m; L4 and H4
= 15.0 m; L5 and H5 = 20.0 m away from the roadside; L6 and H6 = dumpsite;
L7 and H7 = road junction; L = low traffic highway; H = high traffic highway and
S = soil.
Table 2. Comparison of mean concentrations of metals (mg/kg) in soils with other studies worldwide.
As
6.00
0.10–40.00
–
–
–
–
–
0.00–2.00
Cd
0.06
0.01–2.00
1.97–9.80
0.21
0.75
1.10
0.36–0.82
0.03–0.85
Hg
0.03
0.01–0.50
–
–
–
–
–
0.08–0.89
Pb
10.00
2.00–300.00
15.28–76.92
34.70
188.80
991.00
16.04–80.34
68.90–388.00
Zn
50.00
1.00–900.00
41.66–237.96
42.60
121.70
663.00
20.91–61.07
52.70–55.50
Reference
WAL, London (BN)
Glasgow (HG)
Kaduna, Nigeria (OK)
Spain (RJ)
Amman (JM)
Hong Kong (JM)
Akungba, Nigeria(OL)
Present Study
Note: BN = Bowen, 1996; HG –Holdgate, 1997; OK = Okunola et al., 2007; RJ = Rojo, 2004; JM = Jaradat
and Momani, 1999; OL = Olanipekun et al, 2008; WAL = WAL
reference materials: CRM 142 R (soil) and SRM
1547 (peach leaves). The recoveries for soil were
96.6, 90.0, 97.8, 95.7 and 96.2% for As, Cd, Hg, Pb
and Zn,
respectively.
The corresponding
recoveries for plant samples were 90.0, 92.8, 102.2, 96.8
and 98.2%.
RESULTS AND DISCUSSION
Levels of metals in soil samples
Table 1 shows the concentration (mean ± standard
deviation) in mg/kg of As, Cd, Hg, Pb and Zn in soil
samples collected along the low traffic road (LTR) and
the high traffic road (HTR).
It can be observed that the concentrations of the
elements along the LTR and HTR respectively ranged
as follows: As (0.00 – 1.60, 0.50 – 2.00); Cd (0.03 – 0.42,
0.34 – 0.85); Hg (0.08 – 0.55, 0.12 – 0.89); Pb
(68.9 – 159, 271 – 388) and Zn (52.6 – 54.8,
52.7 – 55.5). Maximal concentrations of all the
elements were recorded in the samples collected
along the HTR while the lowest concentrations of all
the metals occurred in the samples collected
along the LTR. The trend of occurrence of the
elements in the study areas was in the order: Pb > Zn >
As > Cd > Hg. Positive correlations (p<0.05) exist
between pairs of all elements in the soil
samples indicating common sources, most likely
automobiles.
Table 2 compares the results of our study with those
270 J. Res. Environ. Sci. Toxicol.
Table 3. Physico-chemical properties of soils samples along the two highways
Codes
pH
SL1 6.23±0.43
SL2 6.15±0.38
SL3 6.04±0.42
SL4 5.98±0.36
SL5 5.86±0.31
SL6 6.44±0.42
SL7 6.54±0.34
SH1 6.58±0.56
SH2 6.51±0.42
SH3 6.52±0.44
SH4 6.27±0.38
SH5 6.23±0.41
SH6 6.92±0.67
SH7 6.74±0.68
OM (%)
2.80±0.18
2.76±0.22
2.84±0.28
2.64±0.32
2.52±0.12
3.00±0.28
3.10±0.30
3.60±0.41
3.40±0.38
3.00±0.42
2.98±0.40
2.72±0.25
3.68±0.26
2.90±0.27
CF (%)
11.56±0.78
11.80±0.24
11.89±0.72
12.04±0.82
11.98±0.68
12.86±0.26
12.77±0.25
12.50±0.78
12.78±0.82
13.40±0.75
12.94±0.67
13.75±0.84
14.28±0.62
14.86±0.87
EC (µScm-1)
368±34
366±27
361±33
359±41
272±42
375±40
389±28
426±25
417±28
406±24
399±36
372±42
434±26
443±33
CEC (mmolkg1)
144±38
146±27
142±23
139±30
133±26
147±28
148±40
155±28
150±34
147±29
148±30
144±42
153±31
156±39
Note- SL1 – SL7 and SH1 – SH7 have same notations as those in Table 1; EC =
Electrical conductivity; CEC = cation exchange capacity; OM = organic matter; CF=
clay fractions.
Table 4. Concentration of elements [mg/kg] (mean ± SD, N =14) in plant samples
along the two highways.
Code
PL1
PL2
PL3
PL4
PL5
PL6
PL7
PH1
PH2
PH3
PH4
PH5
PH6
PH7
As
0.50 ± 0.02
0.08 ± 0.00
0.00 ± 0.00
0.00 ± 0.00
0.00 ± 0.00
1.60 ± 0.04
1.86 ± 0.07
1.00 ± 0.06
1.56 ± 0.07
1.62 ± 0.06
1.72 ± 0.05
1.82 ± 0.03
2.00 ± 0.04
3.00 ± 0.06
Cd
0.35 ± 0.01
0.25 ± 0.02
0.15 ± 0.00
0.11 ± 0.00
0.08 ± 0.00
0.15 ± 0.03
0.56 ± 0.04
0.85 ± 0.03
0.78 ± 0.02
0.71 ± 0.04
0.59 ± 0.02
0.49 ± 0.01
0.75 ± 0.03
0.87 ± 0.04
Hg
0.20 ± 0.03
0.19 ± 0.01
0.15 ± 0.02
0.12 ± 0.01
0.02 ± 0.00
0.15 ± 0.02
0.40 ± 0.02
0.37 ± 0.01
0.30 ± 0.02
0.25 ± 0.00
0.21 ± 0.01
0.19 ± 0.02
0.35 ± 0.01
0 .68 ± 0.02
Pb
120 ± 12
103 ± 12
89.7 ± 11.5
83.3 ± 10.9
72.3 ± 11.1
89.8 ± 10.9
145 ± 24
378 ± 24
345 ± 22
323 ± 26
321 ± 20
311 ± 26
389 ± 32
406 ± 30
Zn
59.9 ± 8.2
65.6 ± 7.8
63.3 ± 7.5
66.2 ± 8.2
73.1 ± 8.7
72.3 ± 8.4
77.4 ± 8.7
69.1 ± 7.6
66.2 ± 7.7
70.8 ± 8.1
76.5 ± 8.6
70.1 ± 8.3
76.6 ± 8.6
69.1 ± 8.4
Note- L1 - H1 = 2.0m; L2 and H2 = 5.0m; L3 and H3 = 10.0m; L4 and H4 =
15.0m; L5 and H5 = 20.0m away from the roadside; L6 and H6 = dumpsite; L7
and H7 = road junction; L = low traffic highway; H = high traffic highway and P = plant.
found at some other places. Concentration of ‘As’
recorded here was lower than levels recorded in
London (Bowen, 1996) and Glasgow (Holdgate, 1997).
Cd had an average concentration that compared
favourably with those r ecorded in Amman (Jaradat and
Momani, 1999),
London (Bowen, 1996), Glasgow (Holdgate, 1997),
Spain (Rojo et al., 2004), and Akungba, Nigeria
(Olanipekun et al., 2008) but was lower than levels
recorded in Hong Kong (Jaradat and Momani, 1999),
Nigeria (Okunola, et al., 2007). The levels of Hg recorded
in our study compared favourably with results from other
places (Bowen, 1996; Holdgate, 1997). Furthermore, the
concentration of Pb recorded in this study was lower than
in Hong Kong (Jaradat and Momani, 1999) but higher
than in Amman (Jaradat and Momani, 1999), London
(Bowen, 1996), Glasgow (Holdgate, 1997), Kaduna,
Nigeria (Okunola et al., 2007), Spain (Rojo et al., 2004)
and Akungba, Nigeria (Olanipekun et al., 2008).
Zn levels recorded in this study were higher than those
Ayodeji and Olorunsola 271
Table 5. Comparison of mean concentrations of metals (mg/kg) in plant samples with other studies
worldwide.
As
0.20
0.0 –7.00
–
–
–
5.00–20.00
0.00–3.00
Cd
0.60
0.10–2.40
4.88–14.93
ND
0.06 – 0.31
5.00–30.00
0.08–0.87
Hg
Pb
Zn
0.015
2.70
100.00
0.0005–0.17 0.20–30.00
1.00–400.00
–
0.00–32.37
27.78–185.19
–
7.30
98.70
–
0.40 – 4.26
8.15 – 14.53
1.00–3.00
30.00–300.00 100.00–400.00
0.02–0.68
72.30–406.00 59.90–77.40
Reference
(BN)
WAL, London
(HG)
Glasgow
(OK)
Kaduna, Nigeria
(JM)
Amman
(OL)
Akungba, Nigeria
(HG)
Critical levels
Present Study
Note: BN = Bowen, 1996; HG = Holdgate, 1997; OK = Okunola et al., 2007; JM = Jaradat and Momani,
1999; OL = Olanipekun et al., 2008; ND = Not detected
Table 6. Correlation coefficients
between
concentrations
of
elements in soil and plant samples
along the two highways.
Metals
As
Cd
Hg
Pb
Zn
RHSP
0.8757
0.7256
0.8459
0.9029
0.9983
RLSP
0.8021
0.9585
0.4174
0.7325
0.5730
Note – RHSP = Correlation
coefficients between concentrations
of elements in soil and plant
samples along the HTR.
RLSP = Correlation coefficients
between
concentrations
of
elements in soil and plant samples
along the LTR.
recorded in London (Bowen, 1996), Spain (Rojo et al.,
2004) and Akungba, Nigeria (Olanipekun et al., 2008) but
lower than those recorded in other places (Holdgate,
1997; Jaradat and Momani, 1999; Okunola et al.,
2007).
Table 3 shows that the soils have a wide range of
values of measured properties. Soil pH in water
varied from 5.9 – 6.5 and 6.2 – 6.9 respectively along
the LTR and the HTR. The pH values indicate that the
soils were mildly acidic. The values of electrical
conductivity (EC) along the LTR and HTR respectively
ranged as follows: 272 – 389 and 372 – 443 µScm-1.
These suggest non-saline growing conditions in the
regions studied. The OM lay in the range 2.5 – 3.1%
along the LTR and 2.7 – 3.7% in the soil samples
collected along the HTR. The clay fractions (CF) of the
soil samples collected along the LTR and the HTR
respectively ranged as follows: 11.6 – 12.9 % and 12.5 –
14.9 %. The CEC recorded in the soil samples collected
-1
along the LTR ranged 133 – 148 and 144 – 156 mmolkg
along the HTR.
Levels of elements in plant leaf samples and their
transfer coefficients
Table 4 shows the mean concentration of elements (As,
Cd, Hg, Pb and Zn) in the samples of Siam weed
(Chromolaena odorata) collected along the LTR and the
HTR.
From the results, it can be observed that the general
trend of the concentrations of the elements in the plant
samples followed the order Pb > Zn > As > Cd > Hg.
Highest concentrations of all the elements were recorded
in plant samples collected along the HTR while lowest
concentrations of all the elements occurred in samples
collected along the LTR.
The concentrations of the elements recorded in our
study compared to other studies, as contained in Table 5,
show that most elements with the exception of Pb, have
similar concentrations.
Positive significant (p<0.05) correlations existed
between concentrations of all the elements in the
soils and plant samples along both the LTR and HTR as
272 J. Res. Environ. Sci. Toxicol.
Figure 1. Transfer Coefficients of elements from the soils to the plant samples along the LTR.
Figure 2. Transfer Coefficients of elements from the soils to the plant samples along the HTR.
shown in Table 6. These positive correlations reflect
similar sources of the elements in the plant tissues and
soil samples.
The transfer coefficients (TC) of the five elements from
the soils to the plant tissues in Ado-Ekiti (Nigeria) are
calculated using equation 1 (Kloke et al., 1984; Alloway,
1995; Kachenko and Singh, 2004; Awode et al., 2008;
Falusi et al., 2010). Figures 1 and 2 present the results
for the LTR and HTR respectively.
TC = CP / CS --------------------------- (1)
where TC = transfer coefficient; CP = concentration
of element in plant tissues above ground and CS = total
elements concentration in the soil.
The TCs were determined for the elements (As, Cd,
Hg, Pb and Zn) to quantify the relative differences in their
bioavailability to the plant species and to identify the
efficiency of the plant species to accumulate the
elements. These coefficients were based on the root
uptake of the elements and discount foliar absorption
of atmospheric metal deposits (Alloway, 1995; Kachenko
Ayodeji and Olorunsola 273
and Singh, 2004; Awode et al., 2008; Falusi et al., 2010).
TC ranges of 0.00 – 3.20 and 0.75 – 2.40 were
recorded for ‘As’ along the LTR and HTR respectively.
TCs of other elements along the LTR and HTR
respectively ranged as follows: Cd (1.13 – 2.79, 0.88 –
1.59), Zn (1.11 – 1.42, 1.25 – 1.45), Hg (0.27 – 1.51, 0.48
– 1.65) and Pb (0.63 – 1.16, 1.05 – 1.23). Most of the
sites
investigated
have higher TCs than those
suggested in reference (Kloke et al., 1984), i.e., 1 – 10 for
Cd and Zn; and 0.01 – 0.10 for As, Hg and Pb
respectively.
The high numbers of samples exceeding the
suggested TC range of As, Hg and Pb in our study
reflects the elevated topsoil concentrations of the
elements found along the two highways. The soil
physico-chemical properties may have further influenced
the soil-plant transfer of the elements. Low organic matter
content, acidic nature of soil, low cation exchange
capacity, low clay fractions, and non saline growing
conditions (as reflected by values of electrical
conductivity) have been reported to enhance
bioavailability of elements for plant uptake (Kachenko
and Singh, 2004; Awode et al., 2008; Falusi et al., 2010).
Positive correlations that were recorded between the
concentrations of the elements in the soils and the
physico-chemical parameters of the soils along the two
highways corroborated these findings. The TC has been
reported to be one of the major key components of
human exposure to trace and toxic elements through the
food chain (Awode et al., 2008; Falusi et al., 2010). As a
result, we would recommend that Siam weed leaves
picked from plants growing along highways should not be
used for therapeutic purposes. This is to minimize the
effect of health hazards associated with ingestion of toxic
elements.
ACKNOWLEDGEMENT
The contributions of Mrs. Bamidele-Falusi, D.O. of the
Department of Nursing, Federal Medical Centre, Ido-Ekiti
(Nigeria) and Mr. Ladeji A. L. of the Federal Science and
Technical College, Usi Ekiti (Nigeria) in regard to this
research are greatly appreciated.
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