GeolCarp_Vol48_No1_63

GEOLOGICA CARPATHICA, 48, 1, BRATISLAVA, FEBRUARY 1997

63–68

TRACE ELEMENT DISTRIBUTION AMONG THE COMPONENTS

OF SOILS IN ŽITNÝ OSTROV REGION,

SOUTHWESTERN SLOVAKIA

SALEM YASEEN MEJEED

Department of Geochemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovak Republic

(Manuscript received May 14, 1996; accepted in revised form December 12, 1996)

Abstract:

Fifteen soil profiles were selected from agricultural areas in Žitný ostrov, and sixty one samples were

analysed for their total contents of several trace elements, viz. Ag, As, B, Ba, Be, Cd, Co, Cr, Cu, Ga, Hg, Ni, Pb, Sn,
Sr, V, Zn, and Zr. In addition, other soil characteristics have also been determined, viz. particle size, organic carbon,
carbonate, cation exchange capacity, and pH. The relations of trace elements with these characteristics were studied
using statistical multivariate analysis. Generally, most of the trace elements show strong association with the clays and
particularly the organic matter. Consequently, they exhibits strong positive correlation with the cation exchange
capacity. They also show strong inter-element relationships which reflect their common occurrence in the clays and
organic matter. Sr alone occurs in the carbonate fraction, and Zr in the sand fraction. Vertical distribution of all stud-
ied parameters within the soil profiles also proves these conclusions.

Key words:

trace elements, total contents, soil properties.

Introduction

Žitný ostrov is situated close to Bratislava in the south-west-
ern part of Slovakia enclosed between the Danube and Little
Danube rivers (Fig. 1). Economically, it is very important be-
cause it represents a very big water and food resource for the
country. It represents a very notable geochemical landscape
system due to its geological, hydrogeological, and hydro-
geochemical conditions.

Geologically, it is formed by Quaternary gravels which oc-

cur in different amounts, but locally reach 300 m thickness,
and are covered by Pleistocene and Holocene sediments of
different textures.

The groundwater of Žitný ostrov is supplied from the

Danube River, and flows through the permeable strata to-
ward the southeast almost parallel to the Danube River. The
water of the Danube is calcium bicarbonatic, weakly alka-
line, and slightly mineralized. Due to the interaction in the
soil–rock–water system the chemistry of groundwater gradu-
ally changes (Ca

, Mg

–Ca

, Mg

–Na

, HCO

3–

) with in-

creasing mineralization. Groundwater is also characterized
by its fluctuation in correspondence to the fluctuation in the
Danube River. Generally, it fluctuates during the year be-
tween 4–7 m in the upper part of the area, 2–4 m in the mid-
dle part, and 0–2 m in the lower part (Porubský et al. 1971;
Kalnová 1976). The zonal character in groundwater chemis-
try is reflected in soil chemistry, and the different hydromor-
phic influence leads to the evolution of different soil units
and hence the soil cover of the area is relatively variegated
(Fulajtár & Čurlík 1991). In the upper part of the region with
a deep groundwater table, automorphic soils prevail (repre-
sented by Calcaro-haplic Chernozem and Haplic Phaeozem).
In the middle part Phaeozems with the signs of former
(relict) or recent hydromorphic influence are present. In the

lower part more hydromorphic Fluvi-mollic Gley soils have
developed together with the highly alkaline and salt-affected
soils on places with highly mineralized groundwater.

The area is climatically hot and dry with an average annual

temperature of 9

C, precipitation of 570 mm, and potential

evaporation of 832 mm. Hence, evapotranspiration (potential
evaporation) exceeds precipitation creating a permanently
evaporative climatic regime. Consequently, mineral salts
(mainly carbonates) accumulate in the soil cover from the
groundwater.

Total trace element contents provide a useful but only pre-

liminary indication of the risk of toxicity as plant uptake de-
pends on the availability of the metals concerned, soil type,
and plant species. The present study tries to assess the influ-
ence of different soil properties such as particle size frac-
tions, organic C content, carbonate content, in addition to
other properties like pH and cation exchange capacity (CEC)
on the distribution of trace elements in the soil profile, based
on their total contents.

Fig. 1.

Žitný ostrov and the locations of the soil profiles investi-

gated.

64 MEJEED

Experimental procedure

Chemical analyses of total trace element contents

Fifteen soil profiles have been selected from the area of

Žitný ostrov (Fig. 1) and sixty one representative samples
have been chemically analysed for their total contents of
eighteen trace elements, viz. Ag, As, B, Ba, Be, Cd, Co, Cr,
Cu, Ga, Hg, Ni, Pb, Sn, Sr, V, Zn, and Zr. Analyses have
been carried out in the laboratories of the Geological Insti-
tute, Faculty of Natural Sciences, Bratislava. Different an-
alytical procedures have been applied for these analyses, and
basic parameters of precision, accuracy and detection limits
were determined for all used analytical methods (Medve et
al. 1992). Trace elements Ag, B, Ba, B, Co, Cr, Cu, Ga, Ni,
Pb, Sn, Sr, V, and Zr have been analysed by optical emission
spectroscopy (OES). Spectra were obtained by the excitation
of solid samples mixed with graphite powder and spectro-
chemical admixture of Li

in ratio of 3 : 6 : 1. They were

recorded on a grid spectrometer PGS 2 using a DC arc with
an intensity of 6 A during 90 seconds.

The atomic absorption spectrometry (AAS) has been ap-

plied for the analysis of As, Cd, Hg, and Zn, using PERKIN-
ELMER (USA) 380 spectrometer. Both As and Hg were
analysed using separate techniques. The absorption signals
of As were obtained by hydride techniques after dissolution
of the sample. Hg was determined from solid samples after
thermal evaporation in oxygen flow and its concentration in
an amalgamator. Cd and Zn were determined from solution
by atomization in an acetylene-air flame.

For the aim of these analyses a soil subsample (approxi-

mately 5 g) of the <0.056 mm (fine earth) air-dried fraction
of the soil was ground to a fine powder and homogenized in
an agate mortar. The samples were then dried at 28–30

before ignition at 650

C for two hours. The total dissolution

of soil samples was performed by a mixture of HNO

HClO

, and HF acids.

Other analyses

Forty seven samples have been chosen for several analyses

that determine some of the soil characteristics in order to en-
able comparison of their total trace element contents with the
different soil properties. All these analyses have been done in
the laboratories of the Soil Fertility Research Institute, Bra-
tislava.

The following particle size fractions were determined ac-

cording to the method described by Hraško (1962): medium
and coarse sand (2–0.25 mm), fine sand (0.25–0.05 mm),
coarse silt (0.05–0.01mm), fine silt (0.01–0.001mm), clayey
parts (<0.01 mm), and clay (<0.001 mm).

The electrometrical pH determination of H

-activity was

done by mixing one part of soil with two and half parts of
distilled water, and the pH of the obtained soil–water suspen-
sion is measured according to the method described by
Hraško (1962).

The method used for the determination of carbonate con-

tent is described by Hraško (1962). It depends on the destruc-
tion of the carbonate by 10 % HCl and gas volumetric deter-

mination with Janko’s calciometer. The organic carbon con-
tent has been determined according to the method of extrac-
tion by chromium sulphuric acid, described by Nikitin (1972,
in Sotáková 1988).

The total cation exchange capacity has been determined

according to the method described by Sotáková (1988).

Materials

The location of the soil profiles under investigation and

their general characteristics are listed in Table 1. These soils
are generally variegated and belong to different soil types,
Calcaric Fluvisol, Calcaro-haplic Chernozem, Fluvi-Haplic-
calcaric Phaeozem, Fluvi-gleyic-calcaric Phaeozem, and
Fluvi-mollic-calcaric Gleysol. All the soil profiles studied
are calcareous, with carbonates (both pedogenic and inherit-
ed) dispersed in the whole profile. They are slightly alkaline
with a pH range of 8–9. Their texture is very diverse but the
loamy (muddy) dominates. Their parent materials are light
to heavy calcareous alluvial sediments. The field areas from
which these soils were taken are currently agriculturally in-
tensively and diversely used for different crops, but mainly
for wheat, corn, sugar-beet, barley, sunflower, and soya-
bean. A lot of fertilizers and pesticides are applied in this
area, and added to its soils through the agricultural produc-
tion which could represent a further source of trace elements
in these soils.

Results

The average of total trace element contents together with

the other soil characteristics are listed in Table 2 and their
comparison in the soil profile is graphically illustrated in
Fig. 2. This figure shows the close relations among the
trends of most trace elements (decreasing downwards) and
the trends of clay and organic carbon, being concentrated in
surface horizons and depleted in lower horizons, which is
also expressed by the similar trend for CEC, while the sand
fraction shows an opposite trend. Carbonates show an in-
crease with depth in line with the Sr trend and pH.

Particle size

A strong association between particle size and trace ele-

ment concentrations often exists because the large surface
area per unit volume found in small particles accentuates ad-
sorption. Among the particle size fractions studied the clay
fraction (<0.001 mm), clayey part (<0.01mm), and fine silt
(0.01–0.001 mm) have significant positive correlations with
most of the trace elements investigated, namely B, Ba, Be,
Co, Cr, Cu, Ga, Ni, Pb, Sn, V and Zn (Table 3 and Fig. 3).
This indicates the affinity of these elements to be adsorbed
on the surfaces of clay minerals. It is worth mentioning here
that the quality of clay fraction in the studied soils is charac-
terized by illite + chlorite, in addition to small admixtures of
kaolinite and/or smectite (Mejeed & Čurlík 1992).

Only Zr shows a significant positive correlation with the

fine sand fraction (0.25–0.05 mm) which indicates the occur-
rence of Zr as an independent phase in zircon. Both Sr and

TRACE ELEMENT DISTRIBUTION AMONG THE COMPONENTS OF SOILS 65

carbonate contents show positive correlations of (0.50) and
(0.54) respectively with the coarse sand fraction (2–0.25
mm) which is attributed to the development of pedogenic
carbonate nodules in these soils usually of sand size.

Organic carbon

Humus (herein studied as organic carbon) content and par-

ticularly its quality belongs to the most important factors that
determine the content, availability, and distribution of trace
elements in the whole soil profile. In the present study reten-
tion of trace elements strongly correlates with the organic
carbon and this is obvious from the significant positive cor-
relations of the organic carbon with each of B, Ba, Be, Co,
Cr, Cu, Ga, Ni, Pb, Sn, V, and Zn suggesting their associa-
tion with the organic matter (Table 3 and Fig. 3). Hg is one of
the elements which did not show any significant correlation

Fig. 2.

Comparison of the average trace element contents and other soil characteristics in the different soil horizons.

Table 1:

General characteristics of the soils studied.

FAO soil classification:
Jc: Calcaric Fluvisol
Chc: Calcaro-haplic Chernozem
Hhcf: Fluvi-haplic-calcaric Phaeozem
Hgcf: Fluvi-gleyic-calcaric Phaeozem
Gmcf: Fluvi-mollic-calcaric Gleysol.

Parent materials:
A: mildly heavy calcareous alluvial sed-
iments

B: light calcareous alluvial sediments
C: loess
D: calcareous alluvial gravel-sand.

Texture:
1s: loamy sandy
l: loamy
lc: loamy clayey
c: clayey.

Table 2:

Average contents of trace elements (ppm), different

particle size fractions, organic carbon and CO

, cation exchange

capacity and pH.

-i

ír

-r

66 MEJEED

with any of the soil properties investigated. However, it has a
relatively close correlation (0.26) with the organic carbon on
one hand, and it also shows significant positive correlations
with the elements Cu, Ni, and Zn which are particularly
strongly bound to the organic matter in this study (Table 3

and Fig. 3). This may indicate that Hg is more or less associ-
ated with the organic matter.

Carbonate

Carbonates (calcite and dolomite) in the soils studied are

both of inherited and pedogenic origin (Mejeed, 1993). Pe-
dogenic carbonates are precipitated in the soil profiles from
the carbonatic groundwaters under the evaporitic climatic
conditions prevailing in the area. Sr is the only trace element
that is significantly positively correlated with this fraction
indicating that carbonates govern the distribution of Sr in the
soil profiles in this area (Table 3 and Fig. 3).

Cation exchange capacity (CEC)

This feature has the most marked influence and includes

all other soil characteristics, humus, particle size, and pH.
There is a significant positive correlation between CEC and
all the elements which are well correlated with both the clay
and organic fractions (Table 3), which affirms their adsorp-
tion on the surfaces of these fractions. The only significant
negative correlation was observed with Sr and Zr which are
not bound either to the clay or to the organic matter, or in
other words, they are not controlled by sorption processes.

It changes the chemical composition of the different soil

horizons and the availability and mobility of trace elements.
In this study, it has very significantly negative correlations to
all elements which are positively correlated with the clay and
organic matter (Table 3). The only significant positive corre-
lation was observed with the carbonate and consequently
with Sr. The negative correlations seem to be indirect. The
positive correlation with the carbonate indicates that the pH
in the soils studied (slightly alkaline) is attributed to hydroly-
sis of carbonates (Foth 1984), which indicates that the soil
pH increases as the carbonate content increases, and this
leads to dilution of the other major constituents including
clays and organic matter to which most of the trace elements
are attached and reflects in its turn the marked negative cor-
relation between pH and trace elements.

Element correlations

Significant correlation coefficients among elements are il-

lustrated in Fig. 4. The nature of these correlations is associ-
ated with the mineral phases to which the trace elements are
bound. The elements Ag, As, Cd, Zr, occur alone and never
show any common significant correlation with any of the
other elements. Sr only has significant negative correlations
with other elements because it occurs in the carbonate frac-
tion which is a major constituent and any increase or de-
crease in its amount influences the amount of other major
constituents such as clays and organic matter which govern
the distribution of most trace elements in the samples under
study. However, the majority of elements are significantly
positively correlated and this reflects their common occur-
rence in both the organic and clay fractions.

Fig. 3.

Significant relationships of trace elements to some soil

characteristics. Continuous lines represent the positive correla-
tions, and dashed lines represent the negative correlations.

Table 3:

Significant correlation coefficients of trace elements

with other soil characteristics (level of significance 0.05, sample
size 47).

TRACE ELEMENT DISTRIBUTION AMONG THE COMPONENTS OF SOILS 67

Discussion

From the obtained results it is obvious that both clays and

organic matter are the main contributors to most of the trace
elements in consistency with the literature. Esser et al.
(1991a, b) reported that most trace elements in soils in the
Indiana Dunes show elevated bulk concentrations in the
surface horizons and they attributed this accumulation to
pollution sources, vegetation density, organic matter and
clay contents. Le Riche (1973) attributed the high concentra-
tion of Cu in the surface horizons to organic matter. Berrow
et al. (1978) stressed the affinity of V to be adsorbed on the
clay. Murad & Fischer (1978) reported an enrichment of Pb
in surface soil layers and they attributed this to the affinity of
Pb for organic matter and, possibly to extraneous addition
as a result of environmental pollution. Jones et al. (1986) re-
corded a strong association between Ag and organic matter
and that Ag showed a marked surface enrichment in all cas-
es. Lund & Fobian (1991) attributed the retention of As, Cu
and Cr in the A horizon to high amounts of organic matter.
Beneš & Pabianová (1983, 1984, 1987) and Trnčík & Beneš
(1991) have also reported the significant correlations be-
tween trace element contents and the soil characteristics con-
cerned in this study and ascertained the big influence exerted by
all soil properties on the content and form of trace elements.

In spite of the fact that the elements Ag, As, and Cd exhib-

it no correlation to the remaining elements which may indi-
cate an independent occurrence, they do not show any asso-
ciation with any of the soil characteristics and so their occur-
rence remains questionable. This may happen probably due
to their low values especially for Ag and Cd which may con-
sequently yield unreal correlations. Esser et al. (1991a) re-
ported the presence of a significant correlation between As
and the content of primary iron oxides in the very fine sand
fraction and that As possibly occur in mineral inclusions
such as zircon, monazite, and sulfides within the Fe ox-
ides. Secondary Fe and Al-hydroxides play an important

role in the scavenging of trace elements that have been re-
leased by weathering (Jenne 1968; Koons et al. 1980). Ar-
senic of the present study shows its relatively strongest cor-
relation (0.20) with the fine sand fraction. The prevailance of
iron mottling in most of the soil profiles studied, as it is revealed
from the morphological description, may indicate that iron (and
manganese) oxides could significantly contribute to the distribu-
tion of trace elements in the soils studied.

However, the common occurrence of Ag, As, and Cd in

phosphate fertilizers can also throw the light on the possible
association of these metals with P. Jing & Logan (1992) con-
cluded that the somewhat better correlation of the Cd/P con-
tents of the sludges with sudax Cd uptake vs. that with
sludge Cd content supports the suggestions that sludge P
may reduce the solubility of sludge Cd by coprecipitating Cd
as various phosphates, in correspondence with similar sug-
gestions made by Logan & Feltz (1984).

Cluster analysis has also been used to determine the corre-

lations and groups which may be found among the different
trace elements. A dendogram based on the euclidean dis-
tance, single linkage, nearest neighbour method (Fig. 5) rep-
resents the results of grouping trace elements according to
their content. There is a primary separation which agrees
with our previous discussion about the different phases to
which trace elements are bound with the exclusion of Pb.
Eight groups have been identified, among them two are sub-
stantial which owned their existence to both the clay and or-
ganic matter, but the first includes Cu, Hg, Ni, and Zn which
are more inclined toward the organic matter. The second
group include the remaining elements shared by both the
clays and organic matter. The remaining groups represent el-
ements that are assumed to occur as independent phases like
Zr and Sr, or do not have clear relation with the other ele-
ments in the case of Ag, As, and Cd. However, even for Pb it
shows the supposed association with the two substantial
groups, but at higher distance level.

Fig. 5.

Dendogram showing the groups revealed by the trace ele-

ments under study.

Fig. 4.

Significant inter-element relationships. Continuous lines

represent positive correlations, and dashed lines represent nega-
tive correlations.

68 MEJEED

Conclusions

From the viewpoint of landscape geochemistry it could be

concluded that the majority of trace elements are concentrat-
ed in the upper part of soil profiles at the biogeochemical
barriers (humus horizon), which reflects the weak leaching
tendency in the soil profiles under the prevailing evapotrans-
pirative conditions.

Generally, they show tendency to be associated with clay

fraction and organic matter which suggests that their behav-
iour is mainly governed by sorption processes. From the
environmental viewpoint, it means that most of the followed
trace elements could be available to plants from the sorption
complex.

Sr represents the only element concentrated at the carbon-

atic evaporative geochemical barriers. This indicates its ad-
dition from the groundwater to the soil profile.

All obtained results indicate that the geogenic factor (par-

ent material) controls the distribution of trace elements in
the studied soils, but groundwater also play a significant role
by coprecipitating trace elements at the geochemical barri-
ers, which confirms the geochemical influence of ground-
water on soil cover in the Žitný ostrov region. A limited role
could also be played by the anthropogenic factor, particu-
larly the agricultural activities, as we pointed in a previous
work (Mejeed & Čurlík 1993).

Acknowledgement:

This work is a part of a Ph.D. thesis

submitted in the Department of Geochemistry, Faculty of
Natural Sciences, Comenius University, Bratislava. The
work was supported through the project of soil monitoring
carried out in the Soil Fertility Research Institute, Bratislava.
Thanks are due to Doc. Ján Čurlík the supervisor of the work
for his help and discussion.

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