Journal of Environmental Health Science and Engineering (2019) 17:657–669
https://doi.org/10.1007/s40201-019-00379-6
RESEARCH ARTICLE
Geochemical determination and pollution assessment of heavy
metals in agricultural soils of south western of Iran
Mehdi Ahmadi 1,2 & Razegheh Akhbarizadeh 3 & Neematollah Jaafarzadeh Haghighifard 1,2 & Gelavizh Barzegar 4 &
Sahand Jorfi 1,2
Received: 10 December 2018 / Accepted: 15 May 2019 / Published online: 6 June 2019
# Springer Nature Switzerland AG 2019
Abstract
Soil contamination with heavy metals due to the application of fertilizers and biocides in agricultural activities is a potential threat
for human health through the food chain. The present work was designed to study the spatial distribution of heavy metals,
pollution level and possible reasons for their contamination in agricultural soils of Aghili plain, Khuzestan, Iran. The median
concentrations of As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, V, Zn, and Hg were 2.90, 0.29, 8.10, 39.0, 17.75, 354.0, 0.97, 58.35, 5.90,
34.0, 42.0, and 0.01 mg/kg, respectively. The results revealed that average concentrations of all studied heavy metals with an
exception of Co, Cu, and Ni, were lower than background values. Analysis of source identification showed that Zn, Pb, and Cu
(P < 0.01, r > 0.9) and Co, Cr, Mn, Ni, and V (P < 0.01, r > 0.7) were mainly from anthropogenic. In addition, Cd probably was
originated from agricultural activities (application of manure and phosphorous fertilizers). Enrichment factor values of all metals
(except Ni), were in the range of non to moderate enrichment (EF < 5). According to the degree of contamination (Cd) and
ecological risk factor (ERF), all stations were categorized as low to moderate contaminated sites (4.5 < Cd < 17), and biological
communities in some locations may be at risk (ERF >65). Results indicate that application of fertilizers, herbicides and pesticides
in agricultural soils has led to soil contamination and special management and educational plans are needed for public and
farmers to prevent further adverse effects.
Keywords Agricultural soil . Pollution assessment . Heavy metals . Geochemical indices . Enrichment factor
Introduction
Soil as the main habitant of human and the main source of
food production via agriculture should be protected from
adverse effects of different contaminants [1, 2]. During previous decades, soil contamination became a global problem due
to rapid industrialization, increasing utilization of pesticides in
agriculture and global urbanization [3–5]. Since most of heavy
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s40201-019-00379-6) contains supplementary
material, which is available to authorized users.
* Sahand Jorfi
[email protected]
Mehdi Ahmadi
[email protected]
Razegheh Akhbarizadeh
[email protected]
1
Environmental Technologies Research Center, Ahvaz Jundishapur
University of Medical Sciences, Ahvaz, Iran
2
Department of Environmental Health Engineering, School of Health,
Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
3
Systems Environmental Health and Energy Research Center, The
Persian Gulf Biomedical Sciences Research Institute, Bushehr
University of Medical Sciences, Bushehr, Iran
4
Department of Environmental Health Engineering, Behbahan
Faculty of Medical Sciences, Behbahan, Iran
Neematollah Jaafarzadeh Haghighifard
[email protected]
Gelavizh Barzegar
[email protected]
658
metals are bound to soil in natural conditions, it acts as an
ultimate sink for discharged heavy metals [6, 7]. Previous
studies have proved the hazardous effects of soil pollution to
heavy metals [8]. Sources of heavy metals in soils are both
geogenic (derived from parent materials) and anthropogenic
(derived from human activities) [4, 9, 10]. Anthropogenic
sources of soil pollution are related to the manufacturing and
agricultural activities like mining, metallurgy, electroplating,
fuel combustion, waste disposal, long-term application of
sewage sludge, application of fertilizer and irrigation with
wastewater [11, 12]. Furthermore, agricultural related activities such as application of chemical fertilizers, pesticides and
herbicides followed by the washout of heavy metals and toxic
compounds into the soil and water resources can provide a
severe threat to the safety of soil and water, since these are
two important elements of hydrologic cycle that are directly
and indirectly related to each other [13]. Heavy metals accumulation in agricultural soils is a well-known phenomenon
and also a major concern, because of their high persistence,
toxicity, none-biodegradability, bio-accumulation and
biomagnification through the food chain [3, 10]. Entrance of
heavy metals into the food chain may pose serious threats to
ecosystems and humans [5, 14, 15]. In addition, animals and
human exposure to high quantities of heavy metals through
soil may pose a serious health risk by ingestion, inhalation and
dermal absorption [4]. Long-term application of fertilizers,
fungicides and metal-containing pesticides can lead to accumulation of heavy metals in agricultural soils [6, 16, 17]. It
should be noted that atmospheric deposition (wet and/or dry)
can further increase the levels of soils’ heavy metal [18]. The
most important parameters for controlling the deposition and
bioavailability of heavy metals in soils are physicochemical
and biological features of the soil, geochemical characteristics
of elements, soil mineralogy, and fertilizer application in agricultural lands and distance to manufacturing areas [18].
Localization of contamination sources and evaluation of agricultural soil according to the distribution of the heavy metals
concentration, are considered as effective tools to prevent and
control soil contamination [19, 20]. Geostatistical methods are
effective tools to discriminate natural sources of contamination from artificial ones [21, 22]. Geostatistical methods can
show the spatial distribution and variation of heavy metals in
the soil environment. Among various geostatistical methods,
Kriging interpolation analysis is a multidimensional method,
which can provide valuable data for interpretation of soil pollution level in combination with principal component analysis. It enables examination of the spatial correlation between
various variables at multiple scales and determination the
source of heavy metals based on the grouping results of the
principal component analysis [23–25]. Aghili plain is one of
the most critical agricultural centers in Khuzestan province,
south west of Iran, in which many industries such as cane
factory, metallurgical industries, and paper and pulp
J Environ Health Sci Engineer (2019) 17:657–669
manufacturing are located. Application of chemical fertilizers,
pesticides, and herbicides is a possible source of heavy metals
emission into the agricultural soil in study area. Since
Khouzestan province is a major source of agriculture
in Iran, containing several vast agricultural plains and
provides a variety of food crops for near 5,000,000
persons, it is very important to evaluate the safety of
soil and the agricultural crops in term of toxic elements
such as heavy metals. Therefore, investigation of spatial
distribution of heavy metals and related health risks is
necessary in potentially contaminated soils.
Consequently, an intensive observation was conducted
through current research for monitoring the concentrations of heavy metals in study area to perform Geostatistical analysis.
Material and methods
Study area and sample collection
Aghili plain, with 11,000 ha area, is located between 32°1′ to
32°7´ N and 48°52′ to 48°56′ E. The climate conditions of this
plain are hot and dry (semi-desert) with a rainfall of 326 mm/y
and an average temperature of 33 °C. Geologically, the study
area is widely characterized by quaternary unconsolidated alluvial sediment (Fig. 1) [26]. The main land use of study area
belongs to agricultural lands (80%) followed by national lands
with no special use (12%) and the remaining corresponds to
residential areas as well as some small industries. The samples
were collected by gridding the total area into equal squares, in
which one sample was taken per 200 ha. [26]. Afterwards, 54
topsoil samples (0–20 cm) were collected using a stainless
steel hand auger in March 2016 (dry season) (Fig. 1) [27]. In
each sampling point, a total of 1 ± 0.5 kg of soil was taken
from the mixed samples using a quartile method. The
collected soil samples were stored in polyethylene bags
and then carried to the laboratory [28]. Then, samples
were air-dried at room temperature and passed via a 2mm sieve. Finally, the dried soil samples were sent to
the MS analytical Laboratory (Langley, Canada). The
soil samples were digested using the Aqua Regia, and
the concentration of 12 potentially toxic elements
(PTEs) including (As, Cd, Co, Cr, Cu, Mn, Mo, Ni,
Pb, V, Zn, and Hg) were measured using inductively
coupled plasma mass spectrometry (ICP-MS, Model:
SPECTRO ARCOS, Germany).
Physicochemical characteristics of soil samples
Hydrometer method modified by [29] was applied for finding
the size of soil particles and the samples were categorized,
based on the amounts of sand, sil and clay. The amount of
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659
Fig. 1 Geological map of Aghili plain and sampling points in the study area
Quality assurance (QA) and quality control (QC)
total organic carbon (TOC) of the soil was measured via loss
on ignition (LOI) method [30]. In addition, acidity (pH) and
salinity of soil samples were determined using mixture of soil
and distilled water with 1:2.5 (g:mL) ratio which were shaken
during 15 min, prior to determining pH [31, 32].
Table 1
Analytical duplicates/replicates, standard reference material
(OREAS 24b, and GBM908–10), and blank reagents were
used for QA/QC. The average differences of the measured
Elemental concentrations in the agricultural soil of Aghili plain
Statistic
As
Cd
Co
Cr
Cu
Mn
Mo
Ni
Pb
V
Zn
Hg
Ref
Minimum (mg/kg)
Maximum (mg/kg)
1st Quartile (mg/kg)
Median (mg/kg)
3rd Quartile (mg/kg)
Mean (mg/kg)
Variance
Standard deviation
Skewness
Kurtosis
CV (%)
Background
0.08
6.20
1.60
2.90
3.65
2.77
2.08
1.44
0.18
−0.70
52.14
4.7
0.20
0.54
0.27
0.29
0.33
0.30
0.00
0.06
1.49
4.52
19.66
1.1
2.60
12.10
6.63
8.10
9.78
8.09
3.76
1.94
−0.14
−0.17
23.96
6.9
16.00
60.00
35.00
39.00
44.00
39.57
55.38
7.44
−0.27
1.17
18.80
42
7.70
34.40
15.80
17.75
20.28
18.39
20.20
4.49
1.44
4.21
24.44
14
176.00
468.00
308.25
345.00
401.00
348.13
3412.42
58.42
−0.28
0.00
16.78
418
0.37
2.72
0.75
0.97
1.18
1.01
0.18
0.43
1.49
3.79
42.26
1.8
23.90
87.10
49.23
58.35
67.50
58.66
179.18
13.39
0.02
−0.26
22.82
18
2.40
10.50
5.00
5.90
6.95
6.12
2.42
1.56
0.86
1.19
25.42
25
18.00
45.00
31.00
34.00
37.00
33.63
20.92
4.57
−0.56
1.48
13.60
60
13.00
68.00
36.00
42.00
49.00
43.09
104.24
10.21
0.21
0.95
23.69
62
0.01
0.03
0.01
0.01
0.02
0.01
0.00
0.01
1.36
0.87
49.60
0.1
[41]
*: Coefficients of variation
Note: The sample size: 54
660
J Environ Health Sci Engineer (2019) 17:657–669
Fig. 2 Spatial distribution of PTEs concentration (mg/kg) in soil samples
and certified values were around 10% variability. The validation parameters of the analytical procedure are presented in
Table S1.
Data analysis
All measured data were analyzed using Surfer 14, Excel,
XLSTAT, SPSS v.23 software for windows. The original
concentration data normality was evaluated using
Kolmogorov-Smirnov test (significance level was considered as P value ≤0.05). Spearman correlation analysis
was used in order to assess the correlation between
PTEs. The principal component analysis (PCA) was applied to explicate the relationship and sources of PTEs.
In the statistical analysis, those original concentrations
lower than the detection limit (DL) were presumed
equal to 0.75 of the DL.
Soil quality assessment
For determination of PTEs pollution level in agricultural soil
of Aghili plain, some geochemical assessment techniques including enrichment factor (EF), contamination factor (CF),
integrated ecological risk index (ERI) and monomial ecological risk factor (ERF) were used. EF is a common approach for
determining soil metal sources (anthropogenic or natural
events) by normalizing metal concentration, according to soil
textural properties and/or un-contaminated background levels
[33, 34]. In this study, due to the lack of non-contaminated
local background data, the average worldwide soil data
(Table 2) was used as reference baselines and Al was considered as a reference element.
EF (unitless) was calculated using following Eq. (1):
Enrichment factor ¼ ðC s =Al s Þ=ðC B =Al B Þ
ð1Þ
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661
Fig. 2 (continued)
Table 2
Concentrations of heavy metals in soil from other studies compared to current work
Study area
Average concentrations of heavy metals (mg/kg)
Ref
Cr
Ni
Cu
Zn
Cd
Pb
As
Hg
Yellow River basin, China
Qinghai-Tibet Plateau
Yerevan, Armenia
Changsha, Chaina
79.42
93.29
66.4
85.74
36.05
54.73
31.4
–
32.01
40.74
57.90
29.75
117.76
145.74
195
139.21
0.46
0.68
0.56
3.10
32.1
72.49
2.4
26.67
11.15
–
0.69
–
0.14
0.28
0.09
–
[35]
[36]
[37]
[18]
Krakow, Poland
Shushtar, Iran
9.9
39.58
6.50
58.66
13.40
18.39
56.80
43.09
0.80
0.30
33.9
6.12
–
2.77
–
0.01
[38]
Current work
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662
Table 3 Test of
normality for PTEs in
agricultural soil of Aghili
plain
Element
Kolmogorov-Smirnova
Table 5 Principal component analysis of PTEs in agricultural soil of
Aghili plain
Statistic
Heavy metal
As
df
Sig.
54
0.200*
54
0.043
Component
1
2
3
4
5
.069
Cd
.113
Co
−.003
−.078
−.033
Cu
.328
.911
.038
.066
−.094
Mn
Mo
.816
.204
.391
.034
−.115
−.181
.261
.950
−.001
−.008
Ni
.907
.234
−.016
.140
−.121
Pb
V
.357
.688
.902
.571
.067
.314
.151
.003
.002
.046
0.032
54
0.200*
54
0.019
54
0.200*
Zn
.393
.861
.255
−.087
−.044
54
0.010
Hg
−.080
−.057
−.005
−.004
.993
54
0.200*
Extraction Method: Principal Component Analysis.
54
0.200*
54
0.000
.059
Pb
.021
−.178
.176
−.056
54
.133
Ni
.639
.917
−.063
.223
0.200*
.083
Mo
−.491
.259
.335
.490
54
.126
Mn
.207
.027
.911
.822
0.200*
.085
Cu
.439
Cd
Co
Cr
54
.087
Cr
As
.140
V
.077
Zn
Rotation Method: Varimax with Kaiser Normalization.
.094
Hg
.387
where, CS, CB, are the concentrations of element in sample
and background (mg/kg), respectively. EF values of 0.5–1.5
and higher than 1.5 reveal the natural and anthropogenic
sources, respectively [3]. Furthermore, Enrichment factor
values were interpreted as: EF < 1 is no enrichment; 1 < EF
< 3 is minor enrichment; 3 < EF < 5 is moderate enrichment;
5 < EF < 10 is moderately sever enrichment, 10 < EF < 25
shows severe enrichment; 25 < EF < 50 indicate very severe
enrichment; and EF > 50 is extremely sever enrichment [39].
Table 4
The differences between metal concentrations in soil sample and its own values in background is contamination factor
(Cfi, unitless). Moreover, the degree of contamination (Cd,
unitless) shows the state of metal pollution in soil samples
and was calculated using Eq. (2):
C d ¼ ∑C f i ¼ ∑ðC s =C B Þ
ð2Þ
where, CS, CB, are the concentrations of element in sample
and background (mg/kg). Based on Hakanson’s classification,
Cfi < 1 and Cd < 7 show low degree of contamination; 1 < Cfi
< 3 and 7 < Cd < 17 imply moderate contamination; 3 < Cfi <
Spearman correlation matrix for PTEs in agricultural soil samples of Aghili plain
As
Cd
Co
Cr
Cu
Mn
Mo
Ni
Pb
V
Zn
Hg
As
Cd
Co
Cr
Cu
Mn
Mo
Ni
Pb
V
Zn
Hg
1.000
−.422**
1.000
.753**
−.003
1.000
.443**
.321*
.874**
1.000
.481**
.312*
.803**
.891**
1.000
.799**
−.062
.898**
.772**
.766**
1.000
.683**
−.354**
.438**
.180
.198
.481**
1.000
.683**
.022
.958**
.868**
.745**
.800**
.433**
1.000
.446**
.390**
.746**
.815**
.922**
.709**
.254
.675**
1.000
.330*
.461**
.739**
.906**
.882**
.710**
.137
.660**
.863**
1.000
.191
.439**
.608**
.803**
.910**
.538**
−.012
.555**
.906**
.852**
1.000
**correlation is significant at the 0.01 level (2-tailled)
*correlation is significant at the 0.05 level (2-tailled)
−.029
.020
−.156
−.115
−.142
−.118
.031
−.196
−.011
−.021
−.066
1.000
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663
Fig. 3 Enrichment factor of PTEs
in agricultural soil of study area.
6 and 14 < Cd < 28 indicate considerable degree of contamination; and Cfi > 6 and Cd > 28 show very high degree of
pollution in the sediment [40].
The integrated ecological risk index (ERI, unitless) and
monomial ecological risk factor (ERF, unitless) for heavy
metals in the sediments were determined using Eq. (3),
as follows:
ERI ¼ ∑if ER F i ¼ ∑if T ri C f i ¼ ∑if T ri C is =C in
ð3Þ
where, Tri is the biological toxicity factor for element i,
which is defined as Zn =1, Cr = 2, Cd = 30, As = 10,
Hg = 40 and Pb = Cu = Ni = 5 [40]. Cf is contamination
factor, and Cs and Cn are metal concentrations in sediments and background values of metal, respectively. The
five classes of ERF index are: ERF < 40- low risk; 40 ≤
ERF < 80- moderate risk; 80 ≤ ERF < 160- considerable
risk; 160 ≤ ERF < 320- high risk; and ERF ≥ 320- very high
risk. ERI values categorized as: ERI < 65- low risk; 65 ≤ ERI
< 130- moderate risk; 130 ≤ ERI < 260- considerable risk; and
ERI ≥ 260- very high risk [3].
Results and discussions
Grain size and soil characteristics in Aghili plain
According to the findings of hydrometer analysis, the mean
values of sand, silt, and clay contents of the studied soils were
18.29%, 42.56%, and 39.15%, respectively. The mean standard
deviation values of pH and EC of soil samples of Aghili plain
were 8.12 ± 0.52 and 1.69 ± 0.35 ms/cm, respectively.
Moreover, the mean standard deviation of TOC values was
8.24 ± 1.38. The relatively high organic contents of soil indicate
the low bioavailability of PTEs and high formation of organometallic complexes [39]. Moreover, the alkaline pH of the studied soil controls the bioavailability (desorption/adsorption and
precipitation) of heavy metals. Soil texture in term of grain size
can affect the availability of heavy metals. Usually soil with
high content of clay and silt tend to sequester heavy metals and
vice versa. In this regards, the silt content of 42.56% and clay
content of 39.15% demonstrate the high potential studied area
in sorption of heavy metals and detrition of soil quality.
Presence and spatial distributions of PTEs
The basic statistical characteristics of the concentrations of 12
PTEs (As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, V, Zn, and Hg) in
agricultural soil samples of Aghili plain are illustrated in
Table 1. The mean concentrations of PTEs followed this order: Mn > Ni > Zn > Cr > V > Cu > Co > Pb > As>Mo > Cd >
Hg. Moreover, the average concentrations of all considered
PTEs, except Co, Cu, and Ni, were lower than background
(Table 1). According to data observed for skewness, the biggest asymmetry was determined for Cd and Mo followed by
Cu, Hg, Pb and V. Based on the coefficient of variation (CV),
the anthropogenic import of Cd, Cr, Mn, and V in the study
area was low (CV < 20%). While, wide concentration ranges
and high CV percentage of the other studied metals, especially
As, Mo, and Hg, demonstrated that various anthropogenic
sources control soil PTEs contents in the study area. The spatial variation of PTEs in agricultural soils of Aghili plain is
J Environ Health Sci Engineer (2019) 17:657–669
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Table 6
Contamination factor (Cf) for heavy metals in agricultural soils of Aghili plain
Sample ID
Cf
As
Cd
Co
Cr
Cu
Mn
Mo
Ni
Pb
V
Zn
Hg
1
0.70
0.72
1.17
0.95
1.22
0.84
0.58
3.26
0.40
0.58
0.69
0.29
2
3
0.43
0.60
0.56
0.66
0.83
1.06
0.69
0.88
0.94
1.14
0.62
0.76
0.46
0.58
2.34
2.99
0.31
0.38
0.47
0.55
0.52
0.65
0.29
0.14
4
1.32
0.54
1.49
1.02
1.56
1.12
0.52
3.11
0.63
0.68
0.87
0.14
5
6
0.62
0.36
0.68
0.56
1.14
0.84
0.93
0.74
1.26
1.01
0.84
0.69
0.61
0.51
3.14
2.42
0.39
0.33
0.57
0.48
0.71
0.58
0.11
0.14
7
8
0.62
0.02
0.72
0.52
1.45
0.38
1.12
0.38
1.47
0.55
1.02
0.42
0.53
0.39
3.78
1.33
0.50
0.16
0.67
0.30
0.84
0.21
0.14
0.11
9
10
0.43
0.64
0.68
0.64
1.13
1.17
1.05
1.05
1.44
2.46
0.88
0.88
0.55
0.70
3.21
3.26
0.39
0.70
0.63
0.60
0.76
1.08
0.11
0.14
11
0.30
0.58
0.90
0.74
1.05
0.72
0.57
2.47
0.32
0.50
0.53
0.14
12
0.74
0.60
1.19
0.90
1.28
0.74
0.58
3.47
0.50
0.57
0.71
0.29
13
14
0.45
0.28
0.94
0.70
1.59
0.94
1.43
0.81
1.90
1.13
0.99
0.72
0.22
0.54
4.19
2.71
0.59
0.33
0.75
0.53
1.10
0.66
0.11
0.14
15
0.30
0.62
1.03
0.93
1.24
0.77
0.33
2.90
0.39
0.57
0.68
0.14
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
0.64
0.34
0.15
0.17
0.49
0.55
0.34
0.43
0.15
0.57
0.13
0.21
0.26
0.51
0.19
0.26
0.64
0.64
0.60
0.58
0.56
0.58
0.70
0.68
0.60
0.70
0.54
0.56
0.68
0.70
0.42
0.64
1.08
0.72
1.17
0.93
0.87
0.81
0.81
1.22
1.04
0.91
1.19
0.96
0.68
1.13
1.19
1.01
0.93
0.99
1.36
1.02
0.83
0.74
0.74
0.79
1.02
0.88
0.86
1.14
0.81
0.57
1.07
1.07
0.90
0.86
0.93
1.12
2.44
1.13
1.09
1.08
1.08
1.41
1.19
1.27
1.40
1.14
0.80
1.39
1.33
1.14
1.15
1.29
1.57
0.88
0.70
0.64
0.63
0.78
0.84
0.74
0.70
0.75
0.88
0.57
0.76
0.76
0.78
0.71
0.78
0.96
0.65
0.47
0.41
0.41
0.42
0.88
0.41
0.49
0.21
0.43
0.43
0.24
0.24
0.62
0.32
0.23
0.44
3.27
2.72
2.51
2.37
2.04
3.41
3.02
2.65
3.55
2.34
2.07
3.23
3.47
2.77
2.77
2.82
3.49
0.70
0.35
0.32
0.32
0.33
0.47
0.39
0.40
0.43
0.35
0.25
0.40
0.42
0.35
0.34
0.41
0.51
0.60
0.53
0.47
0.47
0.52
0.63
0.55
0.53
0.63
0.57
0.40
0.62
0.62
0.57
0.53
0.55
0.67
1.08
0.60
0.61
0.65
0.50
0.79
0.68
0.82
0.89
0.58
0.40
0.74
0.81
0.60
0.68
0.74
0.92
0.14
0.29
0.14
0.14
0.43
0.29
0.11
0.14
0.29
0.14
0.43
0.14
0.14
0.14
0.14
0.11
0.43
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
0.51
0.13
0.68
1.06
0.74
0.64
1.02
1.13
0.66
1.09
0.81
0.72
1.04
0.74
1.00
0.50
0.52
0.64
0.42
0.58
0.64
0.50
0.54
0.50
0.40
0.42
0.62
0.54
0.58
0.60
0.97
0.84
1.26
1.09
1.49
1.62
1.51
1.65
1.12
1.49
1.20
1.57
1.75
1.20
1.41
0.81
0.79
1.02
0.83
1.12
1.24
1.12
1.19
0.76
1.00
0.90
1.12
1.21
0.95
0.98
1.04
1.09
1.46
1.26
1.32
1.60
1.55
1.41
1.11
1.50
1.13
1.60
1.71
1.11
1.45
0.74
0.72
0.96
0.83
0.98
0.89
1.00
1.06
0.79
1.00
0.82
0.95
1.03
0.94
0.98
0.62
0.34
0.53
0.32
0.79
0.40
0.55
0.66
0.49
0.87
0.68
0.46
0.66
0.55
1.51
2.53
2.42
3.09
3.05
4.23
4.84
4.29
4.68
3.06
3.76
3.43
4.23
4.68
3.53
3.69
0.32
0.32
0.47
0.31
0.40
0.45
0.47
0.41
0.33
0.52
0.32
0.49
0.59
0.37
0.51
0.50
0.50
0.63
0.48
0.62
0.63
0.58
0.63
0.45
0.58
0.52
0.60
0.65
0.52
0.60
0.55
0.56
0.82
0.56
0.66
0.84
0.79
0.71
0.55
0.76
0.53
0.87
0.94
0.58
0.71
0.29
0.14
0.29
0.14
0.11
0.11
0.29
0.14
0.11
0.14
0.29
0.11
0.14
0.29
0.14
J Environ Health Sci Engineer (2019) 17:657–669
665
Table 6 (continued)
Sample ID
Cf
As
Cd
Co
Cr
Cu
Mn
Mo
Ni
Pb
V
Zn
Hg
48
1.02
0.54
1.46
1.05
1.47
0.97
1.13
3.97
0.45
0.62
0.71
0.14
49
50
0.79
0.89
0.48
0.50
1.29
1.51
0.93
1.02
1.18
1.42
0.82
1.04
0.68
0.74
3.73
4.18
0.33
0.42
0.52
0.55
0.55
0.73
0.11
0.14
51
52
0.83
0.89
0.56
0.44
1.33
1.16
0.93
0.83
1.23
1.11
0.91
0.80
0.67
0.87
3.81
3.31
0.37
0.35
0.53
0.48
0.58
0.55
0.11
0.11
53
0.83
0.56
1.42
1.02
1.29
0.96
1.06
4.11
0.41
0.58
0.66
0.29
54
0.74
0.52
1.48
1.07
1.32
0.94
0.65
4.27
0.37
0.58
0.66
0.11
illustrated in Fig. 2. The obtained results demonstrated that the
west and northwest parts of the study area have lower contents
of PTEs. Similar spatial distribution trends for Co, Cr, Mn, V
and Ni; Pb, Zn, and Cu indicated the same sources for mentioned PTEs in each group. Cr, Co, Mn, V, and Ni are mainly
from natural sources. Animal manure, commercial fertilizers,
fungicides and pesticides contain high amounts of Zn, and Cu
[4, 39]. Moreover, fuel combustion of agricultural machinery
could also be considered as another source of Pb, Zn, and Cu
in the study area. According to Fig. 2, the spatial variation of
16
Fig. 4 a Variations of degree of
contamination (Cd) of heavy
metals in different samples of
agricultural soils (b) spatial
distribution Cd in study area and
a
14
12
Cd
10
8
6
4
2
0
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53
Sample code
b
J Environ Health Sci Engineer (2019) 17:657–669
666
Table 7 The integrated ecological risk index (ERI) for heavy metals in
agricultural soils of Aghili plain
Table 7 (continued)
Stations
Stations
ERI
ERI
Zn
Cr
Cd
1
0.69
1.90
21.60
2
3
0.52
0.65
1.38
1.76
4
0.87
5
6
As
Hg
Pb
Cu
7.02
11.43
2.00
6.11
16.28
16.80
19.80
4.26
5.96
11.43
5.71
1.57
1.90
4.71
5.71
11.72
14.97
2.05
16.20
13.19
5.71
3.17
7.82
15.56
0.71
0.58
1.86
1.48
20.40
16.80
6.17
3.62
4.29
5.71
1.97
1.67
6.32
5.04
15.69
12.08
7
0.84
2.24
21.60
6.17
5.71
2.50
7.36
18.92
8
9
0.21
0.76
0.76
2.10
15.60
20.40
0.16
4.26
4.29
4.29
0.80
1.97
2.75
7.21
6.64
16.06
10
1.08
2.10
19.20
6.38
5.71
3.50
12.29
16.31
11
0.53
1.48
17.40
2.98
5.71
1.60
5.25
12.36
12
13
14
0.71
1.10
0.66
1.81
2.86
1.62
18.00
28.20
21.00
7.45
4.47
2.77
11.43
4.29
5.71
2.50
2.97
1.63
6.39
9.50
5.64
17.36
20.94
13.56
15
16
17
18
19
0.68
1.08
0.60
0.61
0.65
1.86
2.05
1.67
1.48
1.48
18.60
19.20
18.00
17.40
16.80
2.98
6.38
3.40
1.49
1.70
5.71
5.71
11.43
5.71
5.71
1.97
3.50
1.73
1.60
1.60
6.21
12.21
5.64
5.43
5.39
14.50
16.33
13.61
12.53
11.83
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
0.50
0.79
0.68
0.82
0.89
0.58
0.40
0.74
0.81
0.60
0.68
0.74
0.92
0.55
0.56
0.82
0.56
0.66
1.57
2.05
1.76
1.71
2.29
1.62
1.14
2.14
2.14
1.81
1.71
1.86
2.24
1.62
1.57
2.05
1.67
2.24
17.40
21.00
20.40
18.00
21.00
16.20
16.80
20.40
21.00
12.60
19.20
32.40
21.60
15.00
15.60
19.20
12.60
17.40
4.89
5.53
3.40
4.26
1.49
5.74
1.28
2.13
2.55
5.11
1.91
2.55
6.38
5.11
1.28
6.81
10.64
7.45
17.14
11.43
4.29
5.71
11.43
5.71
17.14
5.71
5.71
5.71
5.71
4.29
17.14
11.43
5.71
11.43
5.71
4.29
1.63
2.37
1.97
2.00
2.17
1.73
1.23
2.00
2.10
1.73
1.70
2.03
2.53
1.60
1.60
2.37
1.53
2.00
5.39
7.07
5.96
6.36
7.00
5.68
4.00
6.93
6.64
5.68
5.75
6.46
7.86
5.18
5.46
7.29
6.32
6.61
10.22
17.06
15.11
13.25
17.75
11.72
10.33
16.14
17.33
13.86
13.86
14.11
17.47
12.64
12.08
15.47
15.25
21.14
38
39
40
41
42
43
44
45
46
0.84
0.79
0.71
0.55
0.76
0.53
0.87
0.94
0.58
2.48
2.24
2.38
1.52
2.00
1.81
2.24
2.43
1.90
19.20
15.00
16.20
15.00
12.00
12.60
18.60
16.20
17.40
6.38
10.21
11.28
6.60
10.85
8.09
7.23
10.43
7.45
4.29
11.43
5.71
4.29
5.71
11.43
4.29
5.71
11.43
2.27
2.33
2.07
1.67
2.60
1.60
2.43
2.97
1.87
8.00
7.75
7.04
5.57
7.50
5.64
8.00
8.57
5.54
24.19
21.44
23.42
15.31
18.78
17.17
21.17
23.39
17.64
Zn
Cr
Cd
As
Hg
Pb
0.71
0.71
0.55
0.73
0.58
0.55
0.66
0.66
1.95
2.10
1.86
2.05
1.86
1.67
2.05
2.14
18.00
16.20
14.40
15.00
16.80
13.20
16.80
15.60
10.00
10.21
7.87
8.94
8.30
8.94
8.30
7.45
5.71
5.71
4.29
5.71
4.29
4.29
11.43
4.29
2.53
2.23
1.67
2.10
1.83
1.73
2.07
1.83
Cu
Ni
Ni
47
48
49
50
51
52
53
54
7.25
7.36
5.89
7.11
6.14
5.57
6.46
6.61
18.47
19.83
18.67
20.89
19.06
16.53
20.56
21.36
Hg, Cd, As and Mo completely differed from the others. Since
the hotspot of Hg is close to the residential area, human activities could be the sources of Hg in the study area. Moreover,
Cd, usually presents in all agricultural soils, due to wide application of manure and phosphorous fertilizers [42]. Table 2
presents the concentrations of heavy metals in soil obtained
for other sites in the world like China, Poland and Armenia
compared to current work. As can be seen, the concentrations
vary widely depending on the kind of heavy metal and also
study area. But, some similarities can be seen in the trends of
variations between the kinds of heavy metals. For example the
most values belong to Zn and the least to the Hg, almost for all
samples from different studies.
Source identification of PTEs in soil
The results of Kolmogorov-Smirnov test showed that Cd, Cu,
Mo, Pb, and Hg were not normal (Table. 3). Hence, for finding
the correlation between PTEs and their probable origin, the
non-parametric spearman correlation analysis was done
(Table. 4). A strong positive relationship between Zn, Pb,
and Cu (P < 0.01, r > 0.9) indicated the same sources of contamination (mainly anthropogenic). Moreover, the significant
positive relationship was discovered between Co, Cr, Mn, Ni,
V (P < 0.01, r > 0.7), Mo and As (P < 0.01, r > 0.6) that indicated the similar sources. Cd shows a relatively moderate
positive correlation with Vand Zn (P < 0.01, r < 0.5) and weak
positive correlation with Cu, Pb, Cr (P < 0.01, r < 0.4).
Furthermore, the relationship between Cd, As and Mo, was
negative (P < 0.01, r = −0.422 and r = 0.354, respectively).
Finally, an insignificant relationship was observed between
Hg and the other PTEs (P > 0.05).
In order to find more information about the relationship
between heavy metals and their sources, principal component
analysis (PCA) was carried out (Table 5). The results of applied PCA were completely in line with correlation analysis.
The five principal components (PCs) showed 94.65% of the
variance within the data set. The first factor displayed 34.97%
J Environ Health Sci Engineer (2019) 17:657–669
667
of the total variance including Co, Cr, Mn, Ni, and V. The
grouping of Ni and V mostly indicates the crude oil sources
as well as transportation [33, 43]. This group of elements
suggests mixed sources of contamination (both anthropogenic
and natural). The second PC accounting for 28.21% of the
total variance indicates loading of Pb, Cu, and Zn, showing
the role of anthropogenic sources (combustion of fossil fuels
and fertilizers). Proximity of two highway and several local
ways contribute in emission of heavy metals such as lead due
to combustion of fossil fuels [39, 44]. The third group shows
12.2% of the total variance and dominated by As and Mo
(mainly from natural sources). Factor 4 displays 9.69% of
the total variance and defined by Cd. Phosphorous fertilizers,
pesticides and municipal solid wastes are the main sources of
Cd in agricultural soil [4, 16, 39, 42]. Finally, the fifth PC was
accounted for 8.50% of the total variance includes Hg (both
human activities and natural sources). Hence, the natural and
chemical fertilizers and human activities are the most important sources of soil pollution in the study area. It should be
noted that the majority of land use in study area was agricultural soil and application of herbicides and pesticides as well
as chemical fertilizers have the highest contribution in land
pollution to heavy metals. Of course, other pollution sources
such as industrial plants and transportation should not be
neglected [44].
Quality of the agricultural soil
Figure 3 demonstrates the calculated EF values of PTEs in
agricultural soil of Aghili plain. The EF values of all
studied elements in either all or some stations were
higher than 1.5, indicating the influence of human activities in the study area. However, EF values of all
metals, except Ni, were in the range of non to moderate
enrichment. While, EF values for Ni, in most stations,
indicated sever enrichment (10 < EF < 25). The probable
reason for soil enrichment with oil-associated elements
(Ni, Mn, V, Zn, and Co) in the study area is the application of kerosene as herbicides.
The calculated values of Cf are presented in Table 6.
Results indicated that Cf values of As, Cd, Cr, Mn, Mo, Pb,
V, Zn and Hg, in most stations, were within the range of low
degree of contamination (Cf < 1). While, Cf values of Co and
Cu were in the range of moderate contamination (1 < Cf < 3)
and Cf value of Ni was in the range of considerable contamination (3 < Cf < 6). Moreover, the variations of Cd in different
sample points is presented in Fig. 4a. As is shown in Fig. 4b
and based on calculated values of Cd, all stations were categorized as low to moderate contaminated sites (4.5 < Cd < 17).
Based on the calculated values of the ERI (Table 7), the
agricultural soils of Aghili plain were classified as low potential ecological risk (ERI <40). However, considering the ERF
values (Fig. 5), the biological communities in some stations
may be at risk (ERF >65). Results are in accordance with
study by Jorfi et al., 2017 on heavy metals pollution in
Mianab plain, Dezful city, Iran [34].
Conclusion
Spatial distribution of some important heavy metals were investigated in agricultural soils of Aghili plain, in south weste
of Iran. In this regards, soil quality assessment was performed
using geochemical indices. The EF values of higher than 1.5
proved the influence of human activities. Principal component
analysis (PCA) indicated that the chemical fertilizers, transportation, drainages containing herbicides and pesticides are
the most important sources of heavy metals emission to soil.
ERI values indicated that the agricultural soils of Aghili plain
were classified as low potential ecological risk, but, the biological communities in some stations may be at risk (ERF >
65). This demonstrated the serious requirement for planning
and conducting management strategies in order to maintain
the soil quality and mitigate the adverse effects of human
80
Fig. 5 Monomial ecological risk
factor (ERF) for heavy metals in
agricultural soils of Aghili plain
70
60
ERF
50
40
30
20
10
0
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53
Sample point
J Environ Health Sci Engineer (2019) 17:657–669
668
activities in terms of heavy metals entrance to agricultural
soils as well as subsequent human health risks associated with
exposure to heavy metal through contaminated soils and agricultural crops. Training plans for farmers, replacing chemical
fertilizers and pesticides with harmless ones, implementation
of perfect environmental impact assessment for industries and
periodical sampling programs would be effective in keeping
and promoting soil quality.
Acknowledgments The funding of the present research has been provided by the Environmental Technologies Research Center, Ahvaz
Jundishapur University of Medical Sciences (Grant No. ETRC-9620).
11.
12.
13.
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
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