International Journal of Geosciences, 2011, 2, 84-97
doi:10.4236/ijg.2011.22009 Published Online May 2011 (http://www.SciRP.org/journal/ijg)
Trace Elements Distribution in Red Soils under Semiarid
Mediterranean Environment
José A. Amorós Ortiz-Villajos1*, Francisco J. García Navarro1,2, Carlos Jesús Sánchez Jiménez2,
Caridad Pérez de los Reyes1, Rosario García Moreno3, Raimundo Jiménez Ballesta4
1Escuela Universitaria Ingeniería Técnica Agrícola, Ciudad Real, Spain
2Instituto Tecnología Química y Medioambiental, Ciudad Real, Spain
3Departamento de Ciencias da Navegación e da Terra, Facultad de Ciencias, Universidade da Coruña,
A Coruña, Spain
4Departamento de Geología y Geoqu ímica, Facultad de Ciencias, Un i v er sidad Autónoma d e Madrid,
Madrid, Spain
Received March 17 , 20 1 1; revised April 17, 2011; accepted May 3, 2011
Abstract
This study states the potential trace elements (TE’s) conten t of red soils located at the centre region of Spain,
characterized by low rainfall and slight acidity over prolonged weathering periods. For this purpose, three
soil profiles from a catena were described, sampled and analyzed. The most notable characteristics are the
low organic matter content and the predominantly acidic pH. Illite and kaolinite are the predominant clay
minerals. The fertility of the soils is sufficient to provide most of the nutrients required, with very suitable
potassium levels. The geochemical characters of this soil are: only few elements remain almost invariable
across the profiles and over time, however the majority of them were directly linked with the clay content.
These soils are characterized by relatively low levels of some trace elements such as Sr (64.35 mg·kg–1), Ba
(303.67 mg·kg–1) and Sc (13.14 mg·kg–1); high levels of other trace elements such as V (103.92 mg·kg–1), Cr
(79.9 mg·kg–1), Cu (15.18 mg·kg–1), Hf (10.26 mg·kg–1), Ni (38 mg·kg–1) and Zr (337 mg·kg–1); while the
levels for rare earth elements (REE’s) such as La (48.36 mg·kg–1), Ce (95.07 mg·kg–1), Th (13.33 mg·kg–1)
and Nd (42.65 mg·kg–1) are significantly high. The distribution of mayor and trace elements was directly re-
lated to weathering processes, parent material and anthropogenic activities.
Keywords: Trace Elements, Castilla-La Mancha Region, Red Soils, Soil Geochemistry
1. Introduction
Red Mediterranean soils are common in the semiarid
regions of Spain, but are also broadly distributed world-
wide. The name “red soil” refers to the characteristic
colour found in the B horizon. Their hue is redder than 5
YR, and their chroma is over 5 [1]. Bech et al. [2] iden-
tified the following specific properties of Mediterranean
red soils: their chroma exceeds 3.5, they possess a Bt
horizon and they are independent of their parent material.
Their characteristics can be associated with four cir-
cumstances: high anthropogenic influence, specific cli-
mate, orographic regions higher than 300 m in altitude,
and presence of Saharian fine dust from the desert [1].
The common red colour of these soils has been attrib-
uted to hematite [3-5]. However, these soils are formed
by a large number of different kinds of soil with different
parent materials. This fact increases the geochemical va-
riety attributable to location. Different anthropogenic ac-
tivities are important as well.
In the region of Castilla–La Mancha, the existing red
Mediterranean soils constitute 16.7% and represent the
second most abundant soil type. They are exceeded in
abundance only by the soils originating from Tertiary
sediments (Miocene) [6]. These soils, formed over Or-
dovician-Silurian rocks, originate from the erosion and
weathering of the old Hercinic socket. They are classi-
fied as Luvisols, with rhodic or chromic character, owing
to the presence of iron oxides [7]. The main materials
found over the Hercinic socket result from the weather-

J. A. AMORÓS ET AL.85
ing and erosion of quartzite and materials from the schist-
greywacke complex [8].
The main economic use of these soils in the region is
the production of premium-quality wines. These soils
represent 27.2% of the total regional area dedicated to
the cultivation of the wine grape [6,9].
Several studies have been carried out on red soils from
Mediterranean regions and areas of influence because of
their different origins, parent material and characteristics
[10-15]. Indeed, recently published studies have ad dr essed
the area under consideration [16,17]. However the soils
from the region of Ciudad Real have been poorly studied,
particularly in relation to their con tent of trace and major
elements. This specific area of the region is very impor-
tant because it includes a large percentage of the total
producti on of wine grape [18] .
Trace elements are defined as those elements that
are present in a rock at concentrations below 0.1% or
1000 mg·kg–1 [19]. The distribution and content of these
chemical elements in soils depend on several factors:
nature of the parent material, weathering processes and
human activity [20]. Trace elements occur naturally in
soils. Some of these elements are essential nutrients for
plant growth as well as for human and animal health.
However, at elevated levels some trace elements become
potentially toxic, therefore acting as soil sinks for these
compounds [21]. To give an idea of naturally occurring
concentrations, Table 1 shows the mean content of trace
elements for the Castilla-La Mancha region [22] and in
the world [23].
Marques et al. [24] noted that trace elements that ac-
cumulate during weathering are either pentavalent (Nb5+),
tetravalent (Ti4+, Zr4+ and Th4+) or trivalent (Sc3+, V3+,
Cr3+, Ga3+, Y3+, La3+, Ce3+) in soils that have acidic pH
and are well-aerated. However, elements that are mono-
valent (Rb+) or divalent (Mn2+, Co2+, Ni2+, Cu2+, Zn2+,
Sr2+, Ba2+ and Pb2+) are depleted at acidic pH.
Tetravalent cations crystallise into minerals that are
very resistant to weathering and thus persist and accu-
mulate (such as zircon, ZrSiO4). Zr is probably the most
immobile of all trace elements [25], even less so than Ti.
Nb can replace Zr and Ti in clay structure [24,26]. Ti and
Zr (Al and Si as major elements) are classed as residual
elements after long weathering periods [27]. However,
several other experiments provide evidence for the mo-
bility of Zr [28].
In this context, threshold levels are not yet defined by
law in Castilla-La Mancha. Because of the high level of
industrial and agricultural activities, anthropogenic input
of trace elements into the natural environment in the re-
gion represents a potential hazard [17]. The aforemen-
tioned trace elements can be absorbed by plants [23,29]
and fungi [30] in different amounts and can accumulate
Table 1. Mean concentrations for trace elements in Cas-
tilla-La Mancha region [22] and in the world [23].
Concentrations (mg·kg–1)
Trace element Castilla - La Mancha World
As 7.4
Ba 390 527
Ce 57.7 55
Co 5.8 10
Cr 54.8 67
Cs 7.7
Cu 10.3 24
Ga 11.1 17
Hf 4.9
La 23.6 31
Mo 0.9
Nb 8 16
Nd 21.6
Ni 16.9 24
Pb 19.3 29
Rb 86.2 73
Sc 23.6 9
Sn 4
Sr 380 190
Ta 2.2
Th 9.6 8
U 3.8 4
V 49.9 100
W 3.2
Y 17.9 18
Zn 35.7 67
Zr 167 307
in different structures (roots, leaves, fruits). They can
then pass into the human food chain from these plants
and fungi.
The goals of this study are to evaluate potential prob-
lems in wine production associated with these soils and

J. A. AMORÓS ET AL. 86
to formulate recommendations for improved manage-
ment. Accordingly, the study sought to provide pedolo-
gical data from a typical red soil catena of the region and
to study the associated geochemical properties in order to
describe the distribution and content of trace elements in
relation to other geochemical composition. The results of
the study would then serve to evaluate potential risk to
human health through agricultural production.
2. Materials and Methods
2.1. Site Description
The sampling area was located near the Almagro-Carrión
de Calatrava road (3 km from Almagro). The area is in
the centre of the province of Ciudad Real (Figure 1),
around 12 km southeast of the capital (UTM coordinates:
38˚55'44"N; 3˚43'30"W). Samples were carefully taken
from each profile and horizon with a small shovel (Fig-
ure 2). The soil samples were taken from 3 profiles (to-
posequence) exposed by a machine along the slope of the
hill called “Cerro Molino” (Figure 3). The selected soil
profiles were identified and described morphologically
according to FAO Guidelines [7].
Profile 1 (P1) was taken near the 680 m summit (Fig-
ure 2). The site is used as a temporary sheep pasture.
Profile 3 (P3) was taken near the piedmont of the same
hill, about 500 m down the slop e at an altitude of 650 m.
A A’
P
1
P
2
P
3
Figure 1. Geographical location of the profiles. From I.G.N. E.1:25000, Sheet 785-I “Base de Almagro” (UTM coordinates:
38˚55'44"N; 3˚43'30"W).

J. A. AMORÓS ET AL.87
Figure 2. Location of profiles P1, P2 and P3 along the slope of Cerro Molino and their agricultural uses.
Figure 3. Sampling area.

J. A. AMORÓS ET AL. 88
The site is used for the culture of woody crops (olive tree
and wine grape). Profile 2 (P2) was taken at an interme-
diate point between P1 and P3. This location is tradition -
ally used for dry farming (cereal-fallow).
Selected climatic information is given in Figure 4,
based on data supplied by the Meteorological Station of
Ciudad Real. This station is located near the sampling
area. The mean temperature and rainfall throughout the
year were sampled from 1970 to 2009. A Mediterranean
climate modified by altitude is evident and is typical of
the central high plateau of Spain. This area has low mean
rainfall (410 mm/year), especially in summer when a
xeric period occurs from mid-June to the end of Sep-
tember. The evapotranspiration is negative (average
400 mm/year). The mean temperature is 14.4˚C and ex-
hibits a wide range between winter and summer.
2.2. Analytical Procedures
All the analytical determinations were carried out ac-
cording to SCS-USDA [31]. All samples were extracted
and analysed in triplicate.
Specifically, soil texture was determined using the h y-
drometer method [32]. Soil pH was measured in H2O and
in 0.1 M KCl using a 1:2.5 soil/solution ratio. Electrical
conductivity was measured in a 1:5 soil:water extract.
The method of Olsen et al. [33] was used to estimate
available P. The soil organic matter was quantified by
the Walkley and Black wet oxidation method [34]. Ex-
changeable cations were determined using an ammonium
acetate extraction method [35]. Exchangeable Na, K, Ca
and Mg were determined by atomic absorption spec-
trometry. Total nitrogen content was determined by the
Kjeldahl method [36].
Semi-quantitative mineralogical analyses were carried
out by X-ray diffraction (XRD) techniques. About 2 g of
sample was hand-milled to below 53 m in an agate
mortar and used for the bulk mineralogy determination
(random powder method). For the detailed study of
phyllosilicates, 100 g of sample was treated to remove
components that prevent complete dispersion (e.g. car-
bonates, sulphates, organic matter). The clay fraction (<
2 m) particles were extracted by sedimentation tech-
niques and analysed on “thick” glass slides by XRD ac-
cording to Moore and Reynolds [37]. Samples were
chemically treated [(a) ethylene glycol to detect expand-
able minerals and (b) dimethyl sulphoxide to differenti-
ate chlorite and kaolinite] and thermally treated (550˚C
for 2 h, to study the behaviour of phyllosilicates). The
samples were analysed using a CuK
 radiation source
(Philips-Panalytical X-PERT diffractometer) with a
graphite monochromator, 40 kV and 40 mA, and a sensi-
tivity of 2.103 cps. The ranges measured were 2 - 75˚ or 2
- 50˚ 2
 , goniometer speed of 0.04 or 0.05 and time con-
stant of 0.4 or 1 second for random powder or glass
slides, respectively.
Figure 4. Mean temperatures (Tm ,˚C, in bars) and monthly rainfall (mm in line) throughout the year (meteorological station
f Ciudad Real, Spain, 1970 - 2009). o

J. A. AMORÓS ET AL. 89
The trace element content of whole samples was de-
termined using an X-ray fluorescence spectrometer (PHI-
LIPS PW 2404) in solid mode.
2.3. Statistical Analysis
The software packages XLSTAT_Pro version 7.5 (©
1995-2006 Addinsoft) and XLSTAT_3DPlot version 3.0
(©1995-2006 Addinsoft) were used for statistical and
PCA analyses.
3. Results and Discussion
3.1. Profile Description, Granulometric and
Mineralogic Properties
The characteristics of the three profiles (P1, P2 and P3)
in terms of depth, texture, stoniness and boundaries be-
tween studied profiles are included in Table 2, detailed
by horizon. The main differences among the profiles
concern the thickness of each horizon and the boundaries
between them. The plow layer (Ap) has almost the same
thickness in each case, a result consistent with the use of
soil. The Bt1 horizon shows the same behaviour, but Bt2
increases in depth towards the foot of the hill.
The textures of the profiles tend to be rich in clay, es-
pecially at depth. This property will increase the Cation
Exchange Capacity (C.E.C.) and the potential water re-
tention [12,38]. This clayey character of soils from the
sequence increases their adsorptive properties.
The Bt1 horizon has a level of clay about 15% higher
than that of the layer above. The layer thickness in all
three cases is very similar, a value of about 30 cm that
increases slightly at the bottom of th e slope (P3). Finally,
in horizon Bt2 the clay content reaches 60% (P2). At the
foothill site, the profile is much deeper (more than 140 cm
depth).
In each case the stoniness is high and increases with
depth. The boundaries between the horizons Ap/Bt1 are
gradual and irregular (G.I.) and gradual and undulated
(G.U.). The limit is net and plane (N.P.) between Bt1/Bt2
owing to the higher compactness of the Bt2 horizon.
The mineralogy of the finer and clay fractions is rep-
resented in Figure 5. The high content of phyllosilicates
(more than 70% in all horizons) is noteworthy. Illite is
predominant, with lower amounts of Kaolinite (15 to
20%). Illite usually provides significant amounts of na-
tive potassium [38]. Smectite was not detected, and this
finding is consistent with the lack of vertic character.
3.2. Chemical Characteristics and Soil
Classification
The main chemical characteristics of the profiles studied
are given in Table 2. Trace element content is consi-
dered in the next section. As indicated in Table 2, the pH
is slightly acidic.
Only in the case of P3 does the Bt2 horizon possess a
slightly higher pH. This property is probably the result of
migration of calcium carbonate from some source mate-
rial (Miocene) below or at the same level. The neutral or
slightly acidic pH induces the availability of certain ele-
ments (mainly Fe, Mn and Zn), whose migration is
blocked in calcareous soils [10,39,40].
The C.E.C. values of the soils under investigation are
over 20 cmol·kg–1 (Table 2). This result is consistent
with results obtained in surrounding areas [16] and in
other regions in Spain [12] that have Mediterranean
character and similar types of soil. The low pH - BS rela-
tion in the surface layers can be attributed to a possible
effect of nitrification as a result of intensive nitrogen
fertilization. Salinity problems were not detected in the
profiles studied.
It is worth noting that organic matter content is low,
ranging from 0.4% - 2.4%. The organic matter content is
only substantial in the Ap horizon and drops significantly
in Bt (to around 1% in fine earth). The observ ed values of
organic matter content are mainly the result of the warm
climate and tillage management of ploughed land.
The available P levels are given in Table 2. The am-
ounts found in these profiles show that the P is exo-
genous in origin (fertilisers and O.M. mineralisation).
The exchange complex is not saturated (BS%), espe-
cially in the Ap horizon, owing to leaching and removal
of crops (dystric character). In the Bt1 horizon, a greater
degree of saturation is observed, with values above 60%
(eutric character) that increase to 100% in the Bt2 horizon
of P3. Such variation has been reported for similar soils
and environments [12].
The exchange cations are dominated by calcium, par-
ticularly in the Bt horizons. The magnesium and potas-
sium levels are normal and balanced according to levels
reported by Lanyon et al. [41]. The levels of sodium
were not significant.
The three soils under investigation are classified as
Typic Rhodoxeralf [31]. In terms of the F.A.O. (2006)
classification, these soils are poorly developed Luvisols
(prefix Haplic for P1), highly coloured (Rhodic second
suffix), with a clear and sharp contact with bedrock near
the surface in P1 and P2 (Ruptic first suffix) and high
stoniness in P3 (Skeletic first suffix).
The contents of nine major elements were analysed.
The results are reported in Table 3. From the content
obtained for each element, the following behaviour pat-
terns wer e ob served:
1) Some elements, such as Al, Fe, Ca and Mg, tend to
ncrease with depth in relation to the content of the clay i

J. A. AMORÓS ET AL. 90
Table 2. Soils characteristics between studied profiles (P1, P2 and P3) detailed by horizon (P is given in mg·kg–1 and C.E.C., Ca2+, Mg2+, K+ and Na+ is given in cmol·kg–1).
*G.I.: Limit
g
radual and irre
g
ular
;
G.U.: Limit
g
radual and undulated
;
N.P.: Limit net and
p
lane
;
N.I.: Limit net and irre
g
ular
;
D.I: Limit diffuse an d i rre
g
ular.

J. A. AMORÓS ET AL.91
Figure 5. Mineralogy of finer and clay fractions. Top: percentage of minerals <2 µm. Bottom: Percentages of major clay
types detected (smectite was not detected).

J. A. AMORÓS ET AL. 92
fraction. K, Ti and Si do not vary with depth, and only a
small increase is observed in the intermediate horizo n Bt1.
The other elements, such as Mn and Na, become de-
pleted with depth.
2) Slight enrichment in Mn was found at the sur face in
the three profiles. This result suggests an allochthonous
origin for Mn.
3) Finally, variations in the levels of the major ele-
ments within a given toposequence are related to the
parent material, slope gradients and vegetation cover.
3.3. Trace Element Content
The results for trace elements are reported in Table 4. In
comparison with the values shown in Table 1, the con-
tent of trace elements in this particular red soil in La
Mancha was within the range of background values for
Castilla-La Mancha and is comparable to average values
worldwide. The most obvious variations with respect to
average levels are discussed in this section in order to
show that trace element content can serve as a fingerprint
of the studied soil catena. In general, when the concen-
tration is less than 5 mg/kg (detection threshold) only
inconsistent conclusions can be drawn. Such was the
case for U, Ta, W, Sn and Mo.
Ti, Nb and Th content remained constant in all prof iles
and horizons. The permanence observed at the surface
for Zr and Hf content is consistent with the direct linkage
of these elements with sand content.
Zr minerals are linked to sand particle size and were
more abundant in Ap horizons, as noted in other studies
[42,43]. These elements showed higher content in the
soil under investigation than in the average values re-
ported for Castilla-La Mancha (Table 1).
The behaviour of trivalent elements is more complex
because of their ionic radius (similar to that of Al and Fe).
This behaviour allows them to be incorporated into the
structures of kaolinite, hematite and goethite, which
make up most of the clay fraction. In the samples, this
fraction increased with depth in the Bt1 and Bt2 horizon s.
This finding is consistent with results reported by
Marques et al. [24] and is also the case for the values
found for Sc, V, Cr and Ga.
Lanthanides, also known as rare earth elements
(REEs), have an affinity to oxygen as trivalent cations.
Their presence can be a strong indicator of pedological
processes. We found a uniform distribution of REEs
within profiles and horizons. No enrichment as a func-
tion of depth was evident. It can be concluded that the
studied profiles have the same origin and that no litho-
logical discontinuity ex ists.
In contrast, lithological discontinuity has been found
in other soils in Castilla-La Mancha (Malpica) [44] and
in other regions [45] based on examination of REE dis-
tributions. Moreover, the relatively high content of La,
Ce, Nd and Th represents part of the fingerprint of these
soils in comparison with others from Castilla-La Mancha
that are calcareous, volcanic or igneous in origin [9,17,46].
Zn and Ni levels were relatively high (46 mg·kg–1), as
expected, given that the original rock was quartzite. In
our case, slightly acidic soils without smectite (Figure 2)
yielded lower Ca, Mg, Ba and overall Sr content (3 or 4
times less) compared with the average values found in
soils in Castilla-La Mancha (Table 1). Ca is the most
important element in change complex saturation. In the
case described here, it almost never reached sufficiently
high levels to influence th e depletion of REE. Sr is more
abundant in the gypsum and calcium carbonate-rich soils
of Castilla-La Mancha [22]. Rb content was relatively
low in comparison with leve ls in soils that originate over
granitic rocks.
In order to enhance our understanding of the distribu-
Table 3. Major elements (in alphabetic order) in oxide form given in % from all the horizons.
P1 Ap P1 Bt1 P2 Ap P2 Bt1 P2 Bt2 P3 Ap P3 Bt1 P3 Bt2 Mean
Al2O3 14.42 19.01 14.89 19.30 24.82 13.42 20.93 23.99 18.85
CaO 0.28 0.46 0.33 0.48 0.71 0.35 0.60 0.80 0.50
Fe2O3 4.08 5.49 4.11 5.32 8.02 3.64 5.82 7.73 5.53
K2O 2.51 2.73 2.59 2.91 2.77 2.17 2.47 2.16 2.54
MgO 0.82 1.14 0.87 1.14 1.41 0.69 1.05 1.30 1.05
MnO 0.07 0.05 0.08 0.06 0.04 0.06 0.06 0.03 0.06
Na2O 0.22 0.18 0.25 0.19 0.11 0.24 0.14 0.08 0.17
SiO2 71.97 64.09 71.19 63.59 51.48 73.60 60.98 51.77 63.58
TiO2 0.87 0.89 0.84 0.94 0.82 0.76 0.84 0.78 0.84

J. A. AMORÓS ET AL.93
Table 4. Trace element content for horizons belonging to the three profiles studied. Average content in mg·kg–1.
P1 Ap P1 Bt1 P2 Ap P2 Bt1 P2 Bt2 P3 Ap P3 Bt1 P3 Bt2 Average Concentration
As 12.1 13 11.6 14.1 17.3 10.6 13.2 16 13.48 ± 2.10
Ba 304.4 304.3 316.6 352.7 304.3 258.7 295.7 292.7 303.67 ± 24.44
Ce 97.4 103.9 103.3 98.7 96.9 88.7 87.7 84 95.07 ± 6.93
Co 9.1 11.4 10.1 12.6 11 9.4 12.5 12.4 11.06 ± 1.31
Cr 68.5 70.2 64.8 78.6 102.3 60 86.4 108.4 79.90 ± 16.60
Cs 4 8.7 6.8 7.3 12.3 2.2 6.6 11.6 7.43 ± 3.22
Cu 13.5 15.4 15.3 16.4 17.5 11.1 14 18.3 15.18 ± 2.16
Ga 9.3 13.3 10 13.1 20.5 8.9 14.3 21.3 13.83 ± 4.48
Hf 12.7 11.6 13.5 9.8 8 10.8 7.8 7.9 10.26 ± 2.10
La 42.9 50.7 46.8 53.2 56.5 40.4 48.6 47.8 48.36 ± 4.88
Mo 0.4 0.2 0.6 0.5 0.7 0.4 0.3 0.9 0.50 ± 0.21
Nb 15 16.5 15.8 17.1 17.5 14.4 16.2 17.8 16.28 ± 1.11
Nd 40.1 46.3 43.2 42.2 47.6 40.4 41 40.4 42.65 ± 2.68
Ni 26.3 32.9 28.3 34.6 49.6 27.5 43.1 61.7 38.00 ± 11.73
Pb 19.9 18.5 20.6 19.6 21.3 21.7 21 20.1 20.33 ± 0.96
Rb 61.9 77.9 67.1 81.7 95.7 55.9 73.7 89.4 75.41 ± 12.69
Sc 9.6 13.5 9.9 12.9 18.9 8.4 14.3 17.6 13.14 ± 3.53
Sn 0.7 0.9 0.2 1.5 1.8 0.6 1.1 1 0.97 ± 0.47
Sr 57.6 67.4 61.1 68.8 74.6 56.2 60.5 68.6 64.35 ± 6.01
Ta 1.6 1.7 0.9 1.1 2.5 1.6 1.1 1.6 1.51 ± 0.46
Th 13.6 14.2 13.5 14.4 13.6 12 12.4 13 13.33 ± 0.77
U 3 3 3.2 3.6 2.8 3.3 2.5 2.8 3.02 ± 0.31
V 76.7 101.9 79.7 100.3 147.8 70.6 109.6 144.8 103.92 ± 27.57
W 1.4 1.2 1.9 2.8 1.1 2 1.8 2.7 1.86 ± 0.59
Y 21.9 21.5 22.6 23.4 20.4 20.5 20 18.9 21.15 ± 1.37
Zn 36.3 45.5 39.7 46.9 63.2 32.5 46.4 60.7 46.40 ± 10.17
Zr 434.5 346.9 444.5 373.2 234 368.8 286.4 212.1 337.55 ± 80.81
tion of trace elements (Table 4), a Principal Compo-
nents Analysis (PCA) was performed on the data (Figure
6). Each horizon was considered to be a vector with 26
variables (trace element content). Of the seven principal
components given by the program, F1 and F2 explained
76.89% of the total variance. Thus, the best representa-
tion was that in which the X axis corresponded with F1
(56, 74%) an d the Y axis corresponded with F2 (20, 15).
Several relationships between trace elements can be
inferred from the correlation matrix (Table 5). Zr was
highly correlated with Hf (0.92), and both accumulate in
surface horizons. However, the elements that are de-
pleted correlate with each other [for example Sr corre-
ates with Rb (0.96), As (0.9), Zn (0.89), Cu (0.88), V l

J. A. AMORÓS ET AL. 94
Table 5. Correlation matrix. (Highlighted in black significant values; alpha = 0.050 (bilateral probe)).

J. A. AMORÓS ET AL. 95
(0.83), Ga (0.81) and Cr (0.72)].
Figure 6 indicates that when elements accumulate
near the surface, they appear on the left of the y axis.
Examples are Zr and Hf. Elements that accumulate at
depth are grouped on the right of the y axis. Elements
that appear in the centre of the graph and near to the y
axis are not well represented in this PCA. It is difficult to
draw any conclusions about them (Y, Ce, Th, Ba, Pb).
4. Conclusions
The results of this study indicate that the distribution of
trace elements in the red soil sequence studied under
semiarid conditions in the province of Ciudad Real can
provide specific composition of this Mediterranean red
soil.
This distribution is affected mainly by the following
factors:
1) The specific parent material yields residual ele-
ments which are resistant to weathering. This is the case
for Ti, Zr, Hf and Th.
2) The pedogenetic process, which explains the accu-
mulation of clay at depth, allows the existence of nu-
merous associated elements in the studied profiles, such
as Fe, Ca, Sc, V, Cr and Ga.
3) The profiles have a significant degree of evolution.
The semiarid environment can explain this fin ding. Lith-
ological discontinuities were not observed.
4) In general, the three profiles have similar character-
ristics with respect to their main geochemical and pe-
dological properties. The most notable characteristics are
the low organic matter content and the predominantly
acidic pH. Illite and kaolinite are the predominant clay
minerals. The fertility of the soils is sufficient to provide
most of the nutrients required, with very suitable potas-
sium levels.
Figure 6. Variable representation of the PCA carried out on data from Table 5 with the two first principal components
F1 (X axis) and F2 (Y axis).

J. A. AMORÓS ET AL. 96
5) Finally, the relatively low influence of human ac-
tivity is indicated by the absence of surface enrichment
of trace elements considered to be pollutants, namely Cu,
Pb, Ni, Cr or Zn.
In general, the geochemical characteristics for this soil
are:
1) Low levels of some trace elements such as Sr
(64.35 mg·k g–1), Ba (303.67 m g·kg–1) and Sc ( 13.14 mg ·kg–1)
and major elements like Ca and Mg.
2) High levels of some trace elements such as V
(103.92 mg·kg–1), Cr (79.9 mg·k g–1), Cu (15.18 mg·kg–1),
Hf (10.26 mg·kg–1), Ni (38 mg·kg–1) and Zr (337 mg·kg1)
and major elements like Fe.
3) High levels of REEs such as La (48.36 mg·kg–1), Ce
(95.07 mg·kg–1), Th (13.33 mg·kg–1) an d Nd (42. 65 mg·kg–1).
In general, the results show that the textur e of the soils
and their stoniness can allow the development of crops as
long as these crops do not have to compete for water. In
particular, these soils can be used for the cultivation of
high-quality grapes. To ensure the settling of the crop
and as well as water-holding capacity, 1 m of soil must
be left to accommodate the roots.
Finally, it is important to mention that the data ob-
tained in this study can serve as a pattern for extended
agro-edaphic areas (almost 20% from Ciudad Real pro-
vince and more than 10% from Toledo province). The
study data are potentially useful for evaluating potential
uses of the soils in accordance with their content of trace
elements. However, specific studies must be considered,
depending on location, in order to eliminate other an-
thropogenic and allochthonous influences.
5. Acknowledgements
This project was partially financed by the project “Soil
Atlas of Castilla-La Mancha” elaborated by the Depart-
ment of Agriculture of the Regional Government (Re-
gional Government of Castilla-La Man c ha).
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