Environ Geol (2008) 56:11–18
DOI 10.1007/s00254-007-1135-6
ORIGINAL ARTICLE
Environmental research of groundwater in the urban
and suburban areas of Attica region, Greece
G. D. Bathrellos Æ H. D. Skilodimou Æ A. Kelepertsis Æ
D. Alexakis Æ I. Chrisanthaki Æ D. Archonti
Received: 27 July 2007 / Accepted: 12 November 2007 / Published online: 18 December 2007
Springer-Verlag 2007
Abstract In this study, 92 groundwater samples were
collected from the Attica region (Greece). Moreover,
geographical information system database, geochemistry of
groundwater samples and statistics were applied. These
were used for studying the chemical parameters (NO3,
Mg2+, Ca2+, Cl-, and Na+) and conductivity spatial distribution and for assessing their environmental impact. The
ranges of chemical parameters of the water samples (in
2+
mg L-1) are: NO2–293, Ca2+ 3–453, Cl3 1–306, Mg
+
5–1,988, and Na 4–475. The elevated concentrations of
sodium, Mg2+, Cl- are attributed to natural contamination
(seawater intrusion). On the other hand, NO3 elevated
concentrations are attributed to anthropogenic contamination (nitrate fertilizers). The results of the GIS analysis
showed that elevated values of Na+, Mg2+, Cl- are related
G. D. Bathrellos (&) H. D. Skilodimou A. Kelepertsis D. Alexakis
Faculty of Geology & Geoenvironment,
National & Kapodistrian University of Athens,
University Campus, Zografou, 15784 Athens, Greece
e-mail: gbathellos@geol.uoa.gr
H. D. Skilodimou
e-mail: hskilodimou@euof.uoa.gr
A. Kelepertsis
e-mail: kelepertsis@geol.uoa.gr
D. Alexakis
e-mail: dalexak@geol.uoa.gr
I. Chrisanthaki D. Archonti
Attica Region, 239 Mesogeion St, 11527 Athens, Greece
e-mail: i.hrisanthaki@attica.gr
D. Archonti
e-mail: darchodi@attica.gr
to shrubby and sparsely vegetated areas, while elevated
values of NO3 are connected with urban and agricultural
areas.
Keywords Environmental research Geostatistical analysis GIS Urban and suburban areas Greece
Introduction
In antiquity, the city of Athens, and in general the Attica
region were famous cultural centers of Greece. The study
area (Fig. 1) is characterized by extensive human interventions, intensive agricultural activities and a dense road
network. The intensive urbanization, small industries and
the uncontrolled building construction represent a considerable threat to the environment of Attica region.
In addition, western, northern as well as eastern parts of
Attica region are characterized by agricultural activities.
These activities combined with the extensive urbanization
resulted in a great demand for water. Besides, the quality of
the groundwater has been affected by human interventions.
In many cases the lack of wastewater treatment has led to
the degradation of groundwater (Stamatis et al. 2006).
Various studies (Kounis and Siemos 1987; McCartney
et al. 1997; Alexakis and Kelepertsis 1998; Stamatis et al.
2001; Alexakis 2002; Kelepertsis and Alexakis 2004;
Makri et al. 2006; Stamatis et al. 2006) carried out on the
quality of groundwater of the Attica region showed contamination and degradation in many areas due to natural
and human parameters.
In this study the quality of groundwater of the Attica
region was examined based on the various factors which
define the hydrogeological conditions of the study area.
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12
Fig. 1 Map showing the studied area
These factors include lithological parameters, water quality
indicators and statistical methods.
The main objectives of this study were:
Environ Geol (2008) 56:11–18
poorly developed due to morphology, geological and tectonic structure of the area as well as the urbanization
(Antoniou 2002; Skilodimou 2002). It is a mainly dendritic
drainage pattern and comprises streams with seasonal flow.
The main rivers that flow through the study area are: Kifisos
River, which end up to Saronikos Gulf and Biotikos Asopos
that ends up to Eubean Gulf (Fig. 1).
Generally, the climate of Attica belongs to the Mediterranean type, where the rainy period usually begins in
October and lasts until April. The mean annual precipitation in the study area is rather low and fluctuates from
286.4 to 483.1 mm (Skilodimou 2002).
The geological structure of the studied area is dominated
by alpine and post-alpine formations. The alpine formations belong to three main stratigraphic units, the subPelagonian unit, the autochthonous unit of Attica and the
nappe of Lavrio-Attica (Fig. 2). The sub-Pelagonian unit
is composed by clastic formations (arkose, greywacke,
phyllite, sandstone, and schist) limestones, dolomites
ophiolithic formations, transgression limestone, iron manganese ores and flysch. The autochthonous unit of Attica
comprises mainly schists, marbles and limestones, while
the nappe of Lavrio-Attica consists of phyllite, schist and
metalliferous ores. The Neogene deposits consist of marls,
clays, sandstone, conglomerates and travertine limestone.
Pleistocene continental deposits and Holocene deposits
include unconsolidated material with sand and pebbles,
(a)
to examine the spatial distribution of chemical parameters,
(b) to assess the most heavily contaminated areas,
(c) to correlate the contaminated areas with the urban
activities and in general the land use.
Study area
Geomophological and geological settings
The Attica region is situated at the southeastern part of
continental Greece (Fig. 1). It covers a total surface area of
2,920.89 km2 with altitudes varying from 0 to 1,413 m
above mean sea level (m.s.l.). The relief of the Attica
region is quite plain with mountains and hills, while 6% of
the area is covered by mountains, 30% by plains and 64%
by hills (Fig. 1). Also Fig. 1 shows the mountains and the
main plains of the Attica region.
The mountains of Gerania, Pateras, Kitheron, Parnis,
Penteli, Ymmitos, and Egaleo, form the relief of the area.
The main plains of the area are: Megara, Thriassio Field,
Athens, Marathon, and Mesogeia. The drainage network is
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Fig. 2 Geological map of the studied area (modified from Katsikatsos et al. 1986; Jacobshagen 1986; Migiros and Antoniou 2002)
Environ Geol (2008) 56:11–18
13
alluvial sediments debris cones and lateral deposits (Lepsius 1893; Marinos and Petraschek 1956; Katsikatsos et al.
1976; Gaitanakis 1982; Jacobshagen 1986; Katsikatsos
et al. 1986; Skilodimou 2002).
The polymetallic sulphide mineralization of the Lavreotiki Peninsula consists of Ag-bearing galena, sphalerite,
pyrite and many secondary minerals. The famous Pb-Zn
mines of Lavrion are located in the East Attica region
(Kelepertsis and Alexakis 2004).
Tectonically, the study area was affected mainly by
alpine thrusts and formed by post-alpine faulting (Fig. 2)
(Migiros and Antoniou 2002).
Hydrogeology
There are two major aquifers in the area of the western part
of Attica: a karstic formation of Mesozoic limestone and
dolomite, Neogene formations and Quaternary deposits in
which unconfined and confined aquifers are developed
(Kounis and Siemos 1991).
In the eastern Attica schists and phyllites as impermeable rocks, form a poor aquifer. The carbonate rocks,
limestones and marbles comprise the most important
aquifer of the area (Stamatis et al. 2006).
Fig. 3 Main towns and urban pattern of the studied area
Urbanization
The Attica region is mainly an urban area and 36% of the
total Greek population lives in it. The region is divided into
two subunits of urban areas. The first one comprises the
capital city of Athens including its suburbs and covers
11.2% of the total area (Fig. 3). The second subunit covers
88.8% of the total area and includes the city of Piraeus as
well as the western, northern and eastern Attica. Figure 3
illustrates the main towns of Attica and the urban pattern
including the road network.
Materials and methods
Sampling, sample preparation and chemical analysis
Fig. 4 Map showing the sampling location
A network of 92 sampling sites (drills and wells) distributed
evenly all over the study area was sampled once during
May–June 2006, covering an area of *2,920.89 km2.
Groundwater sample locations were recorded in the field by
using GPS (Fig. 4).
All possible precautions were taken during collection
and handling of samples to minimize contamination. The
groundwater samples were collected in polyethylene containers; 1,000 ml of sample was vacuum-filtered through
0.45 lm pore size membrane filters and stored in a polyethylene container. All the samples were preserved in a
refrigerator.
Nitrate and chloride were measured photometrically
using a Hach DR/4000 apparatus. Chemical analyses of
Mg2+, Ca2+, Na+ were performed at the Laboratory of the
Economic Geology and Geochemistry Section of the Geology Department of National and Kapodistrian University of
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Environ Geol (2008) 56:11–18
Athens. Mg2+ and Ca2+ were measured by atomic absorption
spectroscopy (AAS/Perkin Elmer 1100B) and Na+ was
measured by flame photometry (JENWAY PFP7). The data
quality was assured by the introduction of internal reference
samples and by analyzing the duplicates of two samples. The
electrical conductivity was measured in the field.
In order to measure the degree to which Na in irrigation
water replaces the adsorbed (Ca2+, Mg2+) in the soil clays
the sodium adsorption ratio (SAR), introduced by Richards
(1969), was calculated by the following formula:
meqNa
SAR ¼ qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi :
meqCa + meqMg=
2
A milliequivalent is one thousand of a compound’s or an
element’s equivalent weight; abbreviated meq, where:
mg of ion solution
meq ¼
atomic weight of ion
:
ion charge
Statistical analysis
Correlation analysis was used to define the underlying relationships of the elements and to link any relationships
between elements with geological or anthropogenic sources.
Interpolation of analytical data using GIS
types of land use were classified as follows: urban areas
(including continuous urban fabric, industrial, commercial
and transport activities, construction sites), agricultural
areas (including non-irrigated arable land, permanent crops
and heterogeneous agricultural areas) forest areas and
39.9% by shrubby and sparsely vegetated areas (Fig. 5).
About 15.2% of the total area of Attica is covered by urban
areas, 33.1% by agricultural areas, 11.8% by forest areas,
and 39.9% by shrubby and sparsely vegetated areas.
The evaluation of groundwater samples for drinking use
was carried out by comparing their parametric values given
by the Directive 98/83/EC (EC 1998). Table 1 summarizes
the maximum and minimum values of the studied chemical
parameters of the Attica groundwater in comparison with
the parametric values.
The NO3 content of the groundwater studied varies
from 0.2 to 306 mg L-1, while the parametric value given
by Directive 98/83/EC concentration of nitrate in drinking
water is 50 mg L-1. The high nitrate concentration
([50 mg L-1) in the area of Kifisia, Piraeus, Voula, Spata,
and Agia Paraskevi (Fig. 6) may be the result of the dissolution of fertilizers and the leakage of municipal sewage
rich in ammonia which subsequently oxidizes to nitrate.
The Mg2+ content of the studied water samples varies
from 5 to 393 mg L-1, while the parametric value given by
Directive 98/83/EC for concentration of magnesium in
drinking water is 50 mg L-1. Figure 7 shows three areas
with magnesium concentration [50 mg L-1. These areas
A GIS database was developed using ArcGIS Ver. 9.2
software. The following data layers were digitized and
saved in the database:
•
•
•
sampling locations with the analytical data,
land use,
drainage network, road network, towns, contours of the
area.
Using the geostatistical analyst extension of ArcGIS the
initial values of each parameter were interpolated in grid
layers with cell size 20 9 20m2. The inverse distance
weighted (IDW) was used for interpolation. The IDW is
similar to Kriging interpolation method (ESRI 2007), while
the application of the two methods led to the same results.
Moreover, the zonal statistics tool of ArcGIS was used
in order to calculate the percentage proportion of each land
use area lain on every zone of the spatial distribution of the
studied chemical parameters.
Results and discussion
The land use of the Attica region was derived by using the
program CORINE (Bossard et al. 2000). In addition, the
123
Fig. 5 Land use of the studied area
Environ Geol (2008) 56:11–18
15
Table 1 Chemical parameters and conductivity values of Attica
groundwater in comparison with parametric values (in mg L-1)
Minimum
value
Maximum
value
Parametric values
(Dir 98/83/EC)
NO3
1
306
50
Mg2+
2
393
–
Ca2+
Cl-
3
5
453
1,988
–
250
Na+
4
475
200
Conductivity
(lS cm-1)
292
9,100
2,500
Fig. 7 Concentrations of Mg2+ of the Attica groundwater
Fig. 6 Nitrate concentrations of the Attica groundwater
occur in the northern, western, and southeastern parts of the
studied area.
The Ca+2 content of the water samples of the studied
area ranges between 3 and 452 mg L-1. Figure 8 shows a
wide area occupying the half eastern part of the studied
area with some small complexes with Ca+2 values
exceeding 200 mg L-1.
The Cl- concentrations show a wide range (5–
1,988 mg L-1) with high concentrations ([250 mg L-1)
occurring in the area of Anavyssos, Lavrion, Piraeus,
Elefsis, and Megara (Fig. 9).
The Na+ content varies from 4 to 474 mg L-1, while the
parametric value given by the Directive 98/83/EC in
drinking water is 200 mg L-1. Figure 10 shows high
concentrations of sodium in the areas of Lavrion, Anavyssos, Voula, and Megara.
Fig. 8 Calcium concentrations of the Attica groundwater
Finally, the conductivity values range between 292 and
9,100 and are related to the total dissolved solids (Fig. 11).
Moreover, the Attica groundwater was classified in
terms of salinity hazard (conductivity) and sodium hazard
(SAR). The SAR of Attica groundwater samples ranges
from 0 to 11.5; while the mean value is 2.06. The Attica
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Fig. 9 Concentrations of Cl- of the Attica groundwater
Fig. 10 Concentrations of Na+ of the Attica groundwater
groundwater samples were classified according to SAR
categories as follows: C3–S1 (72.9%), C2–S1 (7.6%), C3–
S2 (6.5%), C4–S1(8.7%), C4–S2 (3.3%), and C3–S3(1.0%)
(Fig. 12).
According to correlation analyses (Table 2) the following parameters are intercorrelated: Mg2+, Na+, Cl- and
conductivity. The association of these parameters may be
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Environ Geol (2008) 56:11–18
Fig. 11 The spatial distribution of conductivity of the Attica
groundwater
attributed to the seawater intrusion in the area of Megara,
Elefsis, Piraeus, and Anavyssos (Fig. 13). The high conductivity and the total dissolved salts in some of the
groundwater samples and the association of Mg2+, Na+,
Cl- as basic constituents of seawater (Hem 1985; Alexakis
and Kelepertsis 1998; Alexakis 2002; Kelepertsis 2007)
certify the seawater intrusion.
Calcium shows a low positive correlation with sodium
(+0.38) and a medium positive correlation with NO3
(+0.48) suggesting a contribution from two sources; the
first source may be the wide extent of carbonate rocks
(limestones and dolomites) and their weathering products
and the second one is the seawater intrusion. The medium
correlation between calcium and nitrate may be attributed
to the wide extent of calcareous soils, covering the most
part of cultivated and fertilized areas.
There is not any correlation between NO3 and the elements Mg2+, Na+, Cl-, and this is an indication of the use of
fertilizers in the study area. According to Pachero et al.
(2001) if the correlation coefficient between NO3 and Cl is
greater than +0.35, this is an indication of a common origin of
these parameters such as industrial or civic wastes. Since the
correlation between NOis -0.04, there is no
3 and Cl
common origin of these elements in the studied area.
The results of geostatistical analyses showed the following relationship between Mg2+, Ca2+, Na+, Cl-,
conductivity, NO3 and the land use (Table 3).
From Table 3 it is obvious that the elements Na+, Mg2+,
Cl- and conductivity are highly positively intercorrelated
Environ Geol (2008) 56:11–18
17
Fig. 13 The spatial distribution of seawater intrusion zones of Attica
region
to 50 mg L-1 are mainly related both to agricultural
(36.7%) and shrubby and sparsely vegetated areas (36.7%),
while concentrations [50 mg L-1 are mainly related to
urban (39.2%) and agricultural (28.1%) areas. This is an
indication that nitrate pollution is mainly attributed to
urban and agricultural areas covered by calcareous soils.
Table 3 Comparison of elevated concentrations of chemical
parameters with the surface of land use (%)
Fig. 12 SAR-conductivity diagram of Attica groundwater samples
(n = 92)
and related to seawater intrusion. The associations of these
elements are mostly related to the shrubby and sparsely
vegetated areas. The Ca2+ contents varying between 100
and 200 mg L-1 are related mainly to shrubby and sparsely
vegetated areas, while concentration [200 mg L-1 are
mainly related to agricultural areas. Nitrate values from 25
Table 2 Correlation matrix of conductivity and chemical parameters
of Attica groundwater (n = 92)
Conductivity
Mg2+
Ca2+
Na+
ClNO3
2
Conductivity
Mg
1
0.74
1
2+
+
-
Ca
Na
Cl
0.41
0.06
0.49
0.51
0.93
0.72
1
NO3
0.04
0.04
0.38
0.19
0.48
1
0.84
0.20
1
-0.04
1
Chemical
parameters
Land use
Mg2+ (30–50 mg L-1)
Mg
2+
-1
([50 mg L )
Urban
areas
Agricultural
areas
Forest
areas
Shrubby
and
sparsely
vegetated
areas
15.8
30.4
12.8
41.0
12.5
35.6
10.5
41.4
Ca2+ (100–200 mg L-1)
22.0
31.6
10.4
36.0
Ca2+ ([200 mg L-1)
20.8
63.6
–
Na+ (200–400 mg L-1)
16.9
34.1
Na+ ([400mg/lt)
41.2
5.7
0.6
52.5
8.6
34.2
11.2
46.0
Cl- (250–500 mg L-1)
Cl- ( [500 mg L-1)
15.6
6.5
42.5
16.6
27.9
9.4
46.1
Conductivity
20.0
(2500–5000 lS cm-1)
28.6
8.7
42.8
Conductivity
([5000 lS cm-1)
24.2
40.1
17.4
18.3
8.7
36.7
14.9
39.7
39.2
28.1
8.1
24.6
-1
NO3 (25–50 mg L )
-1
NO3 ([50 mg L )
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Conclusions
Evaluating the results of this study the following
conclusions can be reached
The land use types of Attica Region, which were produced
by the program CORINE, were classified as follows: urban
areas (15.2%), agricultural areas (33.1%) forest areas
(11.8%) and shrubby and sparsely vegetated areas (39.9%).
The groundwater has been contaminated by seawater
intrusion (high concentrations of Na+, Mg2+, Cl-) and by
anthropogenic activities (elevated values of NO3 ). High
Ca2+ contents in some of the studied groundwater samples
are both related to nitrate fertilizers in calcareous soils and
to the seawater intrusion.
Only 1% of the Attica groundwater samples (Fig. 4:
sampling location no 62, town of Megara) demonstrated a
high sodium–high salinity hazard. The areas showing highconductivity values of groundwater relate spatially to high
SAR value areas.
The geostatistical analysis (GIS) showed that the elements Na+, Mg2+, Cl- are mostly related to the shrubby and
sparsely vegetated areas, while high nitrate values
([50 mg L-1) are mainly related to urban and agricultural
areas, which are mostly rich in calcareous soils. High concentrations of calcium ([200 mg L-1) are mainly related to
agricultural areas.
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