Magnetic, geochemical and mineralogical properties of sediments from
clean karstic and flysch rivers of Croatia and Slovenia
Stanislav Frančišković-Bilinski1*, Robert Scholger2, Halka Bilinski1 and Darko Tibljaš3
1
Institute «Ruđer Bošković», Division for marine and environmental research, POB 180, 10002 Zagreb, Croatia
2
Montanuniversität Leoben, Department of applied geosciences and geophysics, Peter-Tunner-Straße 25, 8700
Leoben, Austria
3
University of Zagreb, Faculty of Science, Department of Geology, Institute of Mineralogy and Petrology,
Horvatovac 95, 10000 Zagreb, Croatia
*Corresponding author, E-mail: francis@irb.hr; Phone: +385 1 4561081; Fax: +385 1 4680242
Abstract
The aim of the present work was to investigate links between the low-field magnetic
susceptibility (MS) of sediments from several Croatian and Slovenian rivers and their
chemical and mineral composition, as well as possible anthropogenic influence. MS
measurements are a fast and simple method, which serves as a proxy for the estimation of
pollution in different environmental systems. As far as we know, it is the first time applied on
stream sediments in the studied region.
The investigated rivers are predominantly unpolluted rivers from Croatian and Slovenian
karstic and flysch areas, which belong to the Adriatic or the Black Sea watersheds: the
Dragonja, the Mirna, the Raša, the Rižana, the Reka, the Rak, the Cerknišnica, the Unec and
the Ljubljanica rivers. It was assumed, that due to their mostly unpolluted status, they could
serve as a database for natural MS background values for this region. For comparison, several
rivers and a lake from the Celje old metallurgic industrial area (Slovenia) were also
investigated: the Savinja, the Hudinja, the Voglajna and the Slivniško Lake. They form a subbasin of the Sava River drainage basin.
Sediments of the clean karstic and flysch rivers showed extremely low MS values, with mass
susceptibility values ranging from 0.5*10-7 to 5.11*10-7 m3/kg, and isothermal remanent
magnetism (IRM) values ranging from 0.7 to 7.88 A/m. In the Celje industrial area, river
sediments showed much higher MS values, with mass susceptibility values ranging from
1.31*10-7 to 38.3*10-7 m3/kg and IRM values ranging from 0.91 to 100.42 A/m. The highest
MS value was found in the Voglajna River at Teharje-Štore, a point which showed a
significant number of anomalies of toxic metals in earlier investigations. Semiquantitative
determination of relations between grain-size and concentration of magnetite was performed
using the Thompson-Oldfield method.
XRD mineralogical analysis showed that sediments of the Celje area have mostly quartz as
major mineral, with relatively small amount of carbonate minerals, while in sediments of
karstic rivers carbonate minerals prevail.
Statistically significant correlations were obtained between MS and Cr, Mn, Fe, Co, Ni, Cu,
Zn, Cd and Ba in the Slovenian karstic region, and between MS and Cr, Fe, Co, Ni and Zn in
flysch drainage basins. On the contrary, no correlation of MS and Hg content was obtained.
Keywords
karstic and flysch rivers; Croatia; Slovenia; magnetic susceptibility; trace elements; heavy
metals; sediments; mineralogy; anthropogenic influence
1
1. Introduction
Magnetic susceptibility is the ease with which material can be magnetized in an external
magnetic field. Determination of volume susceptibility is a cheap and fast method and it is
possible to use it as an indicator of anthropogenic contamination with certain metals.
The development of magnetic measurements application in environmental research begun in
the eighth decade of the twentieth century. The application of this method to sediments was
initiated by Thompson and Oldfield (1986) and a whole series of authors have been using it
for different investigations in geosciences. Shortly after that, the application of magnetic
measurements as proxies and indicators for expensive and complicated chemical analyses
became one of the main research topics in contamination research (Oldfield et al., 1985;
Strzyszcz,1993; Strzyszcz et al.,1996; Hay et al., 1997; Heller et al., 1998; Scholger, 1998;
Plater et al., 1998; Kapička et al., 1999; Petrovsky et al., 2000; Hanesch and Scholger, 2002;
Hanesch et al., 2003; Boyko et al., 2004; Fialova et al.,2006; Shoumkova et al., 2006; Botsou
et al., 2011 Novakova et al. 2012). Investigations performed in industrial areas have also
shown, that the distribution of magnetic susceptibility in soils is closely connected with
deposition of industrial dust and, that magnetic measurements could be used as a method for
detection of heavy metals in soils. A detailed overview of magnetic monitoring methods in
pollutant research was given by Petrovský and Ellwood (1999).
The majority of the authors are in accordance with the conclusion, that this method is
promising and confident for the discrimination of polluted areas. Because this method is fast
and cheap, it is possible to handle a dense network of sampling sites and construct magnetic
susceptibility maps, which enable an efficient selection of the most important points on which
chemical analyses will also be performed. This procedure cuts significantly the costs of heavy
metal screening in the environment and contributes significantly to the quality of
environmental research.
Until recently, magnetic susceptibility measurements of stream sediments have not been used
with the purpose of environmental quality assessment in Croatia. First such measurements in
Croatia have been performed by Frančišković-Bilinski (2008a) on the samples from the Kupa
River watershed. The area with the highest values of magnetic susceptibility was found to be
the lower flow of the Mrežnica River. It was shown that this anomaly originates from
uncareful coal burning products disposal. Increased values of magnetic susceptibility were
observed in stream sediments of the upper flow of the Dobra River, which are suggested not
to be of anthropogenic influence (Frančišković et al., 2014).
To our knowledge, in Slovenia there were no investigations of magnetic susceptibility in
surface sediments to assess the quality of rivers.
The aim of the present work was to perform measurements of the low-field magnetic
susceptibility (MS) of stream sediments from several Croatian and Slovenian rivers and to
find links with their chemical and mineral composition, as well as with possible
anthropogenic influence. The results could serve as a database for natural MS background
values for two presumably relatively clean regions (Slovenian karstic rivers; flysch and
alogene rivers of Croatia and Slovenia) in comparison with those from the Celje industrial
region with intensive metal manufacturing processes.
2. Study area
The study area is composed of three regions in Slovenia and Croatia (Figure 1). The first, with
16 sampling points, is the Celje industrial region (Slovenia) drained by the Voglajna, Hudinja
and Savinja rivers (Figure 2). The second (Figure 3) is a karstic region in Slovenia with
karstic rivers (the Rak, Cerknišnica, Unec and Ljubljanica) belonging to the Sava River
drainage basin, represented by 8 sampling stations. The third region comprises drainage
2
basins of rivers that flow through flysch (the Reka from Brkini Hills with 8 sampling stations;
the Rižana, Dragonja, Mirna and Raša from Istria, with 23 sampling points) (Figure 4).
a)
Details about the study area of the Savinja, Voglajna and Hudinja drainage basins are
given in Frančišković-Bilinski et al. (2006). This area is located in the eastern part of
Slovenia. The studied area represents a young tectonic basin, which is filled with Quaternary
deposits of the Savinja, Voglajna and Hudinja rivers. In the northern part, there are
Pleistocene clays, quartz gravel and sand. In the SE part, Miocene sand, sandstone, marly
limestone and lithothamnian limestone are also exposed as part of the Celje syncline. The
oldest rocks (Triassic dolomite and limestone, as well as andesite and their tuff and
Carboniferous and Permian shale, sandstone and conglomerate) crop out in the southern part.
These rivers were poorly studied in terms of geochemistry; even though they are significantly
affected by metallurgical industry around Celje.
b)
The investigated system of Slovenian karstic rivers stretches from the Cerkniško Lake
in the south to the Ljubljanica River in the north. The most distant source branch of this
system is the Trbuhovica, which springs on Prezid Polje in Croatia. Two main branches which
are feeding the periodic Cerkniško Lake are the Obrh and Stržen. The Cerkniško Lake has an
area of 38 km2 when it is full, the maximal depth is 10 m, and it is 10.4 km long and 4.7 km
broad. The Rak River drains the lake area and it flows through the famous Rakov Škocjan
valley and canyon and then underground until the Planinska Jama cave. Within this cave it
unifies with the Pivka River and reaches the surface as Unica. This river sinks and, when it
again reaches the surface near Vrhnika at Močilnik spring, it has the name Ljubljanica. It
flows to Ljubljana, where it inflows the Sava River. The hydrology of this karstic system is
explained by distribution of areas built of the Triassic semi-permeable dolomites and
permeable Jurassic and Cretaceous limestones (Gams, 2004). Ljubljanica River was described
earlier by Frančišković-Bilinski (2008b).
c)
Flysch and alogene rivers of Croatia and Slovenia which were studied within this
paper are located in the Istria peninsula, the Raša and Mirna in its Croatian part, the Dragonja
at or close to the Croatian-Slovenian border and the Rižana in Slovenian part. Another studied
river (the Reka) is located in nearby Brkini hills flysch area in SW Slovenia. The flysch of the
Istrian peninsula is one of the three main flysch areas in the outer Dinarides, the other two
occurring in the northern Dalmatian and Split areas. The flysch units in Istria have been
considered as Middle to Late Eocene in age (Babić et al., 2007). From these rivers, Raša was
studied earlier by Sondi et al. (1994; 1995), with respect to trace metal transport and
sedimentation processes. Some results of contamination status of the Rižana, Dragonja, Mirna
and Raša Rivers were earlier reported in two brief conference papers by Frančišković-Bilinski
et al. (2003; 2007).
3. Materials and methods
3.1. Sampling and sample preparation
Sampling of 57 stream sediments sites from Croatian and Slovenian rivers was performed
during three years (2001-2003), in the frame of a Croatian-Slovenian bilateral project, in
which geochemistry and mineralogy of river sediments was studied. Sediments were air dried
and dry sieved (standard sieves, Fritsch, Germany). Sieved samples were pulverized using a
mortar grinder Pulverisette 2 (Fritsch, Germany). Samples were used for different purposes
within the above mentioned project and the rest material was stored for possible further
research in the future. In the present paper, their magnetic susceptibility and isothermal
remanent magnetism (IRM) were measured for the first time.
3.2. Measurements of magnetic susceptibility and isothermal remanent magnetisation
3
For measurements of mass susceptibility (χ in m3/ kg), samples were placed in a standard
cylindrical sample container (10 cm3) and weighed. A multifunction kappa-bridge MFK1-FA
(AGICO, Brno, Czech Republic, Field 200 A/m, Frequency 976 Hz) was used. The procedure
was earlier described in Hanesch et al. (2003).
A direct magnetic field of 1T was introduced, using a Pulse Magnetizer Model 660 (2G
Enterprises, Ca, USA). After the magnetisation step, IRM was measured on a DC-Squid
Magnetometer (2G Enterprises, Ca, USA).
3.3. Mineralogical analysis using XRD
The mineral composition of the sediments (fraction <63 μm) was determined by X-ray
powder diffraction using a Philips X-Pert MPD diffractometer (Cu tube, graphite
monochromator, generator settings: 40 kV, 40 mA, range scanned 4-63 º2θ). Crystalline
phases were identified by comparison with Powder Diffraction File (1997) using the computer
program X’Pert High score (Philips, 2001).
3.4. ICP-MS analysis of sediment fraction <63 μm
Chemical analysis was performed by ACTLABS commercial laboratories, Ontario, Canada,
in the fraction <63 μm, using ICP-MS (Inductively Coupled Plasma Mass Spectroscopy) and
“Ultratrace 2” software. The procedure was as follows: 0.5 g of sample was dissolved in aqua
regia at 90 ºC in a microwave digestion unit. The solution was diluted and analyzed using a
Perkin Elmer SCIEX ELAN 6100 ICP-MS instrument. The reference materials ( USGS GXR1, GXR-2, GXR-4 and GXR-6) were analyzed at the beginning and after analysis of each
series of samples.
Although this digestion is not total, its use is justified because the international standard
methods for determining action limits are based on aqua regia leach (Salminen and Tarvainen,
1997).
3.5 Statistical procedure for determination of anomalous values
Basic statistical parameters and correlation analysis were performed using STATISTICA 8.0.
(StatSoft, Inc., 2007). Anomalous values of magnetic susceptibility and IRM were obtained
from the experimental data in Table 1 using the two dimensional scatter box diagrams (Tukey,
1977; Reimann et al., 2005). The same procedure was used for assessing anomalous
concentrations of toxic elements in Region 2 and Region 3 from the data in Table 2 while
anomalies for the elements in Region 1, determined using same statistical approach, are taken
from Frančišković-Bilinski et al. (2006).
4. Results
4.1. Measurements of magnetic susceptibility and isothermal remanent magnetisation
(IRM)
Results of the measurements of mass susceptibility and isothermal remanent magnetisation
(IRM) are divided in three regions/datasets and, for each of them, mean values for every
measured parameter are presented (Table 1). As expected, the highest values of all parameters
are observed in the Celje industrial region, with mass susceptibility values ranging from
1.31*10-7 to 38.3*10-7 m3/kg and IRM values ranging from 0.91 to 100.42 A/m. Sediments of
the clean karstic and of flysch and alogene rivers showed extremely low MS values, with
mass susceptibility values ranging from 0.5*10-7 to 5.11*10-7 m3/kg and IRM values ranging
from 0.7 to 7.88 A/m. Rivers from this clean region were divided into two groups; those from
4
Slovenian karst showed a bit higher values than flysch and alogene rivers of Croatia and
Slovenia.
Semiquantitative determination of relations between grain-size and concentration of magnetite
was performed using the Thompson-Oldfield method (1986) (Figure 5). In this diagram,
magnetic volume susceptibility (abbreviation: MS, dimensionless in SI units) is plotted vs.
IRM-intensity (A/m). The diagram shows, that the concentration of magnetic phases varies
largely between rivers. The values of magnetite concentrations spread approximately from
0.003% to 0.3%. In region 3 the values are the lowest and in region 1 are the highest.
“Magnetic grain” sizes range between 1 and 16 µm in most samples of regions 1 and 2. Most
samples from region 3 have grain sizes above 16 µm. The use of magnetic susceptibility vs.
IRM as magnetic grain size indicator rests on many assumptions, therefore the results can be
considered only as tentative ones.
4.2. Mineral composition of stream sediments
The mineral composition of river sediments (fraction <63 μm) of the Celje industrial region
was earlier presented in details (see Table 1, Frančišković-Bilinski et al., 2006). Quartz was
found as a major mineral in all sediment samples. Among other major minerals, albite was
found in locations 1 and 3; muscovite in locations 2, 79, and 82; calcite in locations 4, 5, 6
and 82; dolomite in locations 6 and 81. Depending on locations there are several minor
minerals and also several trace minerals, some of which contain Fe- ion in the structure.
In stream sediments from the Slovenian karstic region quartz, calcite and dolomite are present
in different proportions. Quartz predominates in samples 8, 9, 38, 39 and 17; calcite
predominates in samples 58 and 10; while dolomite predominates in sample 11. There are also
some traces of feldspars, muscovite and of chlorite.
In all samples from the Reka River, quartz is a dominant constituent. Feldspar (presumably
albite ordered) is present as the second abundant mineral in samples 53 and 54 and as a minor
constituent in samples 12, 15, 16 and 56. Calcite is present in all samples as minor
component, except in sample 12, where it is not present.
In sediments of the Mirna, Raša, Rižana and Dragonja Rivers (Figure 4) quartz and calcite are
the major minerals with slightly different proportions. Feldspars and muscovite are present as
trace minerals.
Magnetite was not detected by XRD in any sample, which can be attributed to the generally
low concentrations indicated by MS measurements.
4.3. Elemental composition of sediments
Concentrations of 38 elements were determined in sediments of regions 2 and 3 in the present
work. From them only concentrations of 12 potentially toxic elements (Fe, Cr, Mn, Co, Ni,
Cu, Zn, As, Cd, Cd, Ba, Pb and Hg), which are included in the list of existing sediment
criteria issued by SMSP and FALCONBRIDGE NC SAS (2005) are shown in Table 2, in
addition to macrocomponents (Mg, Al, Ca, S and K). For concentrations of elements and their
anomalies in the Celje Region, we refer to our earlier paper (Frančišković-Bilinski et al.
2006), which showed that stream sediments of the Celje region are still contaminated,
although industrial pollution decreased during the last decades. The most significant
contaminants in the Celje region are Zn and Cd. In two locations within the town of Celje,
serious toxic effects are possible due to several elements. In other locations, only minor toxic
effects are possible. Descriptive statistics was used to obtain basic statistical parameters
shown in Tables 3a and 3b. For each element the values are given for the arithmetic mean,
geometric mean, median, minimal and maximal concentrations, variance, standard deviation,
skewness and kurtosis. The value for the arithmetic mean ± standard deviation can be
considered as baseline value for each element studied here. Comparison of mean
5
concentrations of potentially toxic elements with sediment quality criteria (SMSP and
FALCONBRIDGE NC SAS, 2005) is presented in Tables 4a and 4b, for regions 2 and 3,
respectively. In Region 2 mean concentrations of Cu and Zn are below the level for the lowest
toxic effects. Mean concentrations of Cr, Fe, Ni, As, Cd, Pb and of Hg are above the values
that could cause the lowest toxic effects. Mean concentrations of Mn and of Ba are above the
value capable for causing significant toxic effects. In Region 3 mean concentrations of Cd
and Pb are below the level for the lowest toxic effects. Mean concentrations of Cr, Mn, Fe,
Cu, Zn and of As are above the values causing the lowest toxic effects. Mean concentrations
of Ni, Ba and of Hg are above the values causing significant toxic effects. The highest values
of Ni and of Hg are observed in the Reka River. Increased concentrations of Cu in samples
53, 54 and 56 could be due to intensive fruit growing in this region (field observation of D.T.,
one of authors of the current paper).
Concentrations of total Hg are elevated in several samples: in samples 38, 39 (Region 2) and
in 13, 15, 53 and 54 of the Reka River, the values are higher than 2 ppm, the value reported
as capable of causing significant toxic effects. The values of Hg concentrations are the highest
in sample 15 (Region 3) and in sample 38 (Region 2). These concentrations of total Hg are
almost comparable with Hg concentrations of lower stretch of the Idrijca, and Soča Rivers
(see Table 2 and Table 4, in Frančišković-Bilinski et al., 2005).
Anomalies in concentrations of selected elements and of magnetic susceptibility in sediments
of regions 1-3 were determined by the boxplot method (Table 5). (In other sediments, which
are not included in Table 5, anomalies were not found.
Comparison of the measured element concentrations with the available quality criteria for
fresh water sediments (SMSP and FALCONBRIDGE NC SAS 2005) indicate that some of
the investigated sediments contain several elements in concentrations that could have the
lowest (e.g. Cr, Fe, Ni) or even significant toxic effects (Ba, Hg) i.e. such comparison indicate
possible pollution of investigated sediments. But careful analysis of such elevated
concentrations for several elements show that they are most probably the result of natural
processes and that they do not indicate any pollution. A typical example is Ba in sediments
from the flysch region rivers. Sandstones from this region contain from 50 to 3600 ppm of Ba,
the highest values have been observed in the samples from the Pazin flysch basin (Mikes et
al., 2006). These values are in accordance with the fact that authigenic barite is one of the
most abundant heavy minerals found in marls of the central Istria flysch (Magdalenić, 1972).
The fact that sediment samples with the highest recorded Ba concentrations (99, 100, 107)
were taken precisely in the streams which drain areas in which marls and sandstones contain
authigenic barite support the conclusion that Ba is naturally present in investigated sediments.
Similar conclusions could be reached for Cr whose concentrations are lower in stream
sediments than in flysch sandstones. The highest measured Cr concentrations are in the Reka
river sediments that drain the Brkini area in which sandstones generally have higher Cr
values. Cr is concentrated in chromium spinel, a key mineral in ophiolitc detritus which was
more abundant in Brkini sandstones than in sandstones from other NW External Dinarides
flysch basins (Mikes et al., 2006). Elevated concentrations of Ni, another element that indicate
ultramafic-mafic detritus origin, in the Reka river sediments are also in accordance with that.
The only element which has elevated concentrations in some sediment samples, which could
not be explained by natural processes, is mercury. Analyses of two marls collected upstream
of Ilirska Bistrica showed that their Hg content is very low: 90 and 25 ppb, respectively.
Apart from that there is no available data on Hg concentration in source rocks, but in the soils
from the surroundings of nearby town Rijeka values higher than 170 ppb were only rarely
observed, and the median value for Croatian soils is 60 ppb (Halamić & Miko, 2009).
Therefore it can be presumed that some of the highest measured values (i.e. sample 15)
indicate some pollution especially due the fact that sediments taken closer to the river sources
6
(i.e. sample 12) have significantly lower Hg concentrations. Possibly the elevated
concentrations are the result of agriculture, in which it is used among other ways as a foliar
spray against plant diseases.
Such conclusions raise a question about usage of the available quality criteria for fresh water
sediments (SMSP and FALCONBRIDGE NC SAS 2005). In our case obviously unpolluted
river sediments, and even rocks from which they have been derived have some element
concentrations that are supposed to have possibility to cause even significant toxic effect. Use
of such criteria which are based merely on (questionable) concentrations and not taking in
account the bioavailability of elements should be done with judiciousness.
5. Discussion of magnetic properties of sediments in context of their geochemical and
mineral composition
In the current discussion we refer to our earlier papers (Frančišković-Bilinski et al., 2003;
Frančišković-Bilinski et al., 2006 and Frančišković-Bilinski et al., 2007), in which
geochemistry and mineralogy of here studied sediments was described.
Earlier investigations in the Celje area (Frančišković-Bilinski et al., 2006) described in details
the contamination of river sediments with following toxic metals for which are given their
maximal measured values: Zn (1040 µgg-1), Cd (7 µgg-1), Cu (138 µgg-1), Ni (82 µgg-1), Pb
(133 µgg-1), Ag (3 µgg-1), Hg (1086 ngg-1) and As (30 µgg-1). An extreme MS value is
observed in Voglajna River at Teharje-Štore, the point which showed significant number of
anomalies of toxic metals (Mo, Sb, P, Cr, Cu, Re, Pb, Bi, W). Another outlier MS value was
measured in Voglajna River at Celje at the point which showed numerous anomalies (B, Na,
Co, Zn, Sc, Zr, Cd, In, Pb, Tl)
XRD mineralogical analysis showed that sediments of the Celje area have mostly quartz as
major mineral, with relatively small amount of carbonate minerals, while in sediments of
karstic rivers carbonate minerals prevail.
According to Frančišković-Bilinski et al. (2007) high concentration of toxic elements Cd, Sb,
Pb and Hg in sample 18 in upper flow of the Rižana River could be of concern, therefore
more sampling upstream can be suggested. Magnetic susceptibility of these samples show
values only slightly above the mean values for the investigated flysch and alogene rivers.
Therefore, low value of MS does not always mean that there is no contamination with some
elements. Raša, Mirna and Dragonja represent clean environments according to most of MS
results. But, sample 112 in the lower flow of the Raša River showed increased value of IRM
(6.40 A/m), what could be due to the influence of nearby Plomin coal power-plant. Coal
combustion products which enter river systems are known to cause increased magnetic
susceptibility of river sediments, what was investigated in details on the case of Mrežnica
River, Croatia (Frančišković-Bilinski, 2008 a).
Correlation analysis is presented in Table 6a (Region 2) and in Table 6b (Region3).
Significant correlations were obtained between MS and Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and
Ba in Region 2; between MS and Cr, Fe, Co, Ni and Zn in Region 3. No correlation of MS
and Hg was obtained; therefore the magnetic method is not applicable to detect all pollution
sources, particularly of mercury. In the polluted Celje industrial region, correlations of MS
and IRM were obtained only with Cr, Cu and Pb.
6. Conclusions
Magnetic susceptibility measurements as fast and simple method for estimation of pollution
with numerous toxic elements in different environmental systems were for the first time
applied on stream sediments from several karstic and flysch rivers of Croatia and Slovenia.
The presented results led to following conclusions:
7
-
-
-
The highest values of all measured parameters are present in the Celje industrial
region with mass susceptibility values ranging from 1.31*10-7 to 38.3*10-7 m3/kg and
IRM values ranging from 0.91 to 100.42 A/m;
Sediments of the clean karstic and flysch rivers showed extremely low MS values,
ranging from 0.5*10-7 to 5.11*10-7 m3/kg and IRM values ranging from 0.7 to 7.88
A/m. Th studied rivers were divided into two groups, the Slovenian karstic rivers
(Region 2) showed slightly higher MS values than flysch and alogene rivers of Croatia
and Slovenia (Region 3);
The results could serve as a database for the pollution state of sediments with respect
to toxic elements, although not with Hg.
Significant correlations were obtained between MS and Cr, Mn, Fe, Co, Ni, Cu, Zn,
Cd and Ba in Region 2; between MS and Cr, Fe, Co, Ni and Zn in Region 3.
No correlation of MS and Hg was obtained; therefore magnetic method is not
applicable to detect all pollution sources in the area, particularly of mercury.
Acknowledgements
Field work was organized within the Croatian-Slovenian bilateral project (2001-2003),
principal investigators H. Bilinski and D. Hanžel. Magnetic measurements were performed at
the Montanuniversität Leoben and at its Paleomagnetic Laboratory in Gams. A short stay of
S. F-B. in Austria was covered from the Croatian-Austrian bilateral project (2010-2011),
principal investigators S. Frančišković-Bilinski and T. Hofmann. Additional expenses were
covered from projects of Croatian Ministry of Science Education and Sport No. 098-09829342720 (Principal investigator I. Pižeta) and No. 119-1191155-1156 (Principal investigator D.
Balen).
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Figure captions
Figure 1. Location of three study areas within Slovenia and Croatia
Figure 2. Celje industrial region (Slovenia) drained by the Voglajna, Hudinja and
Savinja rivers: simplified geological map with position of sampling locations
Figure 3. Karstic region in Slovenia drained by the Rak, Cerknišnica, Unec and
Ljubljanica rivers, belonging to the Sava River drainage basin: simplified geological
map with position of sampling locations
Figure 4. Flysch areas of Croatia and Slovenia drained by the Reka from Brkini Hills
and the Rižana, Dragonja, Mirna and Raša from Istria: simplified geological map with
position of sampling locations
Figure 5. Diagram according to Thompson-Oldfield (1986), presenting semiquantitative
determination of relations between grain-size and concentration of magnetite: magnetic
volume susceptibility (abbreviation: MS, dimensionless in SI units) is plotted vs. IRMintensity (A/m).
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