DETERMINATION OF HEAVY METALS IN SOILS USING
XRF TECHNIQUE*
ANTOANETA ENE1, ALINA BOŞNEAGĂ1, L. GEORGESCU2
1
“Dunarea de Jos” University of Galati, Faculty of Sciences, Physics Department,
111 Domneasca St, 800201 Galati, Romania
E-mail: [email protected]
2
“Dunarea de Jos” University of Galati, Faculty of Sciences, Chemistry Department,
111 Domneasca St, 800201 Galati, Romania
Received September 14, 2009
In this work X-ray fluorescence (XRF) technique was used to evaluate the soil
pollution with heavy metals (As, Cr, Cu, Ni, Pb, V and Zn) in the vicinity of Iron and
Steel Works at Galati, Romania, which is one of the most important metallurgical
complexes in the South-East of Europe. The investigated soil samples were collected
in open places at different depths, at different distances from the metallurgical plant.
XRF analyses were carried out at the Laboratory of European Excellence Centre for
the Environment, Faculty of Sciences, Dunarea de Jos University of Galati, using a
handheld Thermo Scientific XLTj-793 NITON energy-dispersive XRF analyzer. The
experimental results indicate that the concentrations of heavy elements decrease with
the distance from the metallurgical works and they are greater than the levels detected
in a control soil collected from a zone situated far from traffic and industrial activity.
For the majority of metals, pronounced maximum concentrations for all depths were
detected in the sites located in influence zones of industrial objective with ferrous
processing activities. Anthropogenic releases give rise to higher concentrations of the
metals relative to the normal background values and in some locations their levels
exceed the alert level admitted by the Romanian guideline.
Key words: X-Ray Fluorescence (XRF) technique, heavy metals, soil pollution,
industrial plant.
1. INTRODUCTION
The main objective of this paper is to determine the level of soil pollution
with heavy metals, in the vicinity of Iron and Steel Integrated Works (ISIW) at
Galati, Romania, whose activity lasted from 1965, being one of the most important
metallurgical complexes in the South-East of Europe and representing a great
potential of environmental contamination [1–4]. Galati is a city in Eastern part of
*
Paper presented at the 10th International Balkan Workshop on Applied Physics, July 6–8,
2009, Constanta, Romania.
Rom. Journ. Phys., Vol. 55, Nos. 7–8, P. 815–820, Bucharest, 2010
816
Antoaneta Ene, Alina Boşneagă, L. Georgescu
2
Romania (Moldavia region) with a total population of 291,354 (in 2009), on the
banks of the Danube, very close to Braila county.
The most important sources of heavy metals in the environment are the
anthropogenic activities such as mining, smelting procedures, steel and iron
industry, chemical industry, traffic, agriculture as well as domestic activities [5–7].
Chemical and metallurgical industries are the most important sources of heavy
metals in soils [3, 5, 9]. The presence of heavy metals in soil can affect the quality
of food, groundwater, micro-organisms activity, plant growth etc [8, 10–12].
The attractiveness of non-destructive methods and the ability to perform
simultaneous multi-elemental determinations has led to an extensive application in
industrial and research laboratories of accurate, precise and sensitive atomic and
nuclear analytical techniques for the investigation of different types of materials
(industrial, geological, archaeological, biological, environmental etc), such as
neutron activation analysis (NAA) [1, 4, 5, 10, 13], X-ray fluorescence (XRF) [10,
14–16] and particle-induced X-ray emission (PIXE) [7, 12, 17]. For the analysis of
environmental samples XRF has the advantage of being a rapid and inexpensive
method with a simple sample preparation. Quantitative and qualitative analyses are
performed without acid digestion processes and a great number of elements can be
determined simultaneously in a short time.
The main goal of the present research was to use XRF technique in order to
assess the heavy metals distribution in some areas near the industrial complex of
Galati and to compare the soil heavy metal concentrations with the maximum
values admitted by the Romanian guideline [18]. This study is part of a partnership
project funded by National Plan of Research, Developing and Innovation, of
implementation of high precision and sensibility methods for the bio-monitoring of
the environmental pollution in South, South-East and Central regions of Romania
(Project PNCDI2 No. 72–172/2008).
2. EXPERIMENTAL
The soils investigated in this experiment were sampled from the vicinity of
the contaminated area from the Iron and Steel Integrated Works (ISIW) at Galati,
Romania, from a district of Galati town (site 4) and three communes: Vadeni –
sites 1a, 1b and 1c; Sendreni (localities: Sendreni – sites 2a and 2b; Movileni
village – site 2c) and Smardan (localities: Smardan – site 3a; Mihail Kogalniceanu
village – sites 3b). Geographic areas included into the study are presented in Fig. 1.
Control soils were taken from an unpolluted region located far from traffic in
the north of Galati county, in Adam village, Draguseni commune (site 5).
Soils were collected in open areas from different depths (0 cm and 5 cm)
from fields located at different directions and distances from the ISIW (from the
administrative building, labeled as W in Fig. 1). The actual functional steel plant
3
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Determination of heavy metals in soils using XRF technique
No. 1, blast furnaces Nos. 3 and 4 and coke-making plant of ISIW are approximately
situated at 600 m – 2 km South of W building. Smardan commune is closer to the steel
plant No. 3 which was closed in the autumn of 2008 and Vadeni and Sendreni are
closer to the functional plants.
Fig. 1 – Geographical areas included into
the study.
Soil pH was determined using soil-water ratio of 1:5 using a Consorte C862
benchtop conductivity/pH/DO meter. The pH values of the soil samples collected
from Galati region are presented in Table 1 indicating that the soils collected
around ISIW of Galati are alkaline (pH in the range 8.41–8.85) and the control soil
of Galati county is slightly acid (pH=6.18).
Table 1
pH values for the investigated soil samples
Soil
No.
pH
1a
1b
1c
2a
2b
2c
3a
3b
4
5
8.442
8.846
8.662
8.484
8.396
8.837
8.557
8.373
8.409
6.185
The soil samples were dried, homogenized and sieved at 250 µm particle
sizes. XRF analyzes were carried out at the Laboratory of European Excellence
Centre for the Environment, Faculty of Sciences, Dunarea de Jos University of
Galati, using a handheld Thermo Scientific XLTj-793 NITON energy-dispersive
XRF analyzer having as excitation source a miniaturized 30 kV X-ray tube. By
automatically adjusting for matrix effects, NITON XRF analyzers are able to
determine the content of soil samples typically in seconds, without any requirement
for instrument users to input empirical, sample specific calibrations. The sample
818
Antoaneta Ene, Alina Boşneagă, L. Georgescu
4
name, spectrum and elemental composition are stored in a dedicated library. Each
soil sample was analyzed five times for 240 s using two X-ray filters, one for
elements from K to Cu and the second for elements from Zn to Sb.
3. RESULTS AND DISCUSSION
XRF results for the collected soil samples evidentiated the existence of the
following major and minor elements: Ca, Fe, K, Mn, Ti (major) and As, Cr, Cu,
Hg, Ni, Pb, Rb, Sc, Sr, V and Zn (minor). The average concentrations of heavy
metals As, Cr, Cu, Ni, Pb, V and Zn for five measurements of each of the soil
samples are given in Table 2. For the elements Ag, Cd, Hg, Sb, Se and Sn the XRF
results have not been reported because their concentrations were below the
detection limits of 35 mg/kg, 45 mg/kg, 3 mg/kg, 150 mg/kg, 3 mg/kg, 125 mg/kg,
respectively, with the exception of Se in one sample (site 2c; 4.2 mg/kg) and of Hg
in three samples (sites 2a, 3a, 3b) in the range 4.9–5.7 mg/kg, all the values being
greater than the alert level in the less sensitive area for Hg (4 mg/kg) specified in
Romanian guideline [18].
From the experimental results presented in Table 2 and the map from Fig. 1 it
can be seen that in general the concentrations of heavy elements decrease with the
distance from the ISIW factories and they are greater than the levels detected in the
control soil collected from a zone situated far from traffic and industrial activity in the
North of the Galati county (control sample No. 5), with the exception of chromium.
There was a large variation in the quantities of V and Zn determined in the
investigated soils, for all depths. As and Ni concentrations are greater than the
normal values (5 mg/kg for As and 20 mg/kg for Ni [18]) for all studied sites
(including the control site) and depths; Pb concentrations are greater than the
normal value (20 mg/kg [18]) for six sites at 0 cm and five sites at 5 cm, including
Galati district, and exceed the alert level in the sensitive area (50 mg/kg [18]) for
one location (Movileni, the nearest point from the blast furnaces) corresponding to
0 cm depth. Zn concentrations are greater than the normal value (100 mg/kg [18])
for two sites at 0 cm and one site at 5 cm. Cu concentrations are greater than the
normal value (20 mg/kg [18]) for all studied sites and depths with the exception of
control site. Cr concentrations are greater than the normal value (30 mg/kg [18])
for all studied sites (including the control site) for 0 cm and 5 cm depths and
exceed the alert level in the sensitive area (100 mg/kg [18]) for two locations
(Movileni, Smardan) corresponding to 0 cm depth and one location (Smardan) for
5 cm depth. V concentrations are greater than the normal value (50 mg/kg [18]) for
all studied sites and depths and the alert level in the less sensitive area (100 mg/kg
[18]) in four locations near ISIW, including the district of Galati town (site 4).
5
819
Determination of heavy metals in soils using XRF technique
Table 2
Heavy metal content in the investigated soils
Soil
No.
Depth
(cm)
1a
0
5
0
5
0
5
0
5
0
5
0
5
0
5
0
5
0
5
0
5
1b
1c
2a
2b
2c
3a
3b
4
5
As
Cr
Cu
Ni
(mg/kg) (mg/kg) (mg/kg) (mg/kg)
8.51
9.09
10.07
8.81
10.1
8.54
9.05
9.5
9.44
9.19
9.89
10.3
9.81
10.03
8.76
9.81
12.06
10.99
5.94
7.19
86.86
85.35
74.13
82.05
71.57
74.04
88.91
83.73
100.6
90.15
53.00
52.91
77.42
95.16
101.26
99.19
79.78
95.08
84.90
69.32
32.79
32.02
25.06
30.54
30.03
52.78
21.74
23.68
21.02
21.85
31.38
29.89
24.7
23.64
21.78
25.13
24.24
24.61
< 15
18.38
60.51
61.41
48.32
53.3
57.36
61.5
42.13
51.64
52.39
58.7
50.65
65.55
47.38
60.33
60.88
62.67
54.18
56.46
41.93
44.71
Pb
(mg/kg)
27.74
23.87
18.71
17.84
15.48
17.11
21.59
18.9
23.31
20.82
52.24
30.37
19.97
15.46
29.07
25.63
40.07
36.51
11.63
11.02
V
Zn
(mg/kg) (mg/kg)
93.80
110.74
82.91
84.38
81.36
84.06
68.45
84.77
78.87
76.14
98.19
85.28
101.15
98.35
76.64
106.08
88.75
106.08
59.50
62.67
100.2
92.8
79.46
70.63
63.11
102.6
52.60
51.40
60.88
62.03
121
71.48
58.81
54.59
72.69
61.62
86.19
72.45
35.1
34.07
4. CONCLUSIONS
XRF technique has been employed in order to evaluate the pollution of soil with
heavy metals (As, Cr, Cu, Ni, Pb, V and Zn) in the vicinity of Iron and Steel Integrated
Works (ISIW) at Galati, Romania. This is one of the first published studies on soil
pollution realized in this region related with the industrial activity. The experimental
results indicate that the concentrations of heavy elements decrease with the distance
from the metallurgical works and they are greater than the levels detected in the control
soil collected from a zone situated far from traffic and industrial activity. For the
majority of metals, pronounced maximum concentrations for all depths were detected
in the sites located in influence zones of industrial objective with ferrous
processing activities. Anthropogenic releases give rise to higher concentrations of
the metals relative to the normal background values and in some locations their
levels exceed the alert level admitted by the Romanian guideline.
820
Antoaneta Ene, Alina Boşneagă, L. Georgescu
6
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