Rev. roum. GÉOPHYSIQUE Rom. GEOPHYS. J., tome 54, p. 8395, 2010, București GEOPHYSICAL MAPPING OF SOILS. [616327]

Rev. roum. GÉOPHYSIQUE / Rom. GEOPHYS. J., tome 54, p. 83–95, 2010, București GEOPHYSICAL MAPPING OF SOILS.
NEW DATA ON ROMANIAN S OILS BASED ON MAGNETIC
SUSCEPTIBILITY
GEORGE FLORIN GÂRBACEA, DUMITRU IOANE
University of Bucharest, Facu lty of Geology and Geophysics,
Department of Geophysics, 6 Trai an Vuia St., 020956 Bucharest, Romania, e-mail: [anonimizat]
The geophysical investigation of soils is based on a number of physical parameters, the magnetic susceptibility being
usually employed for studying pa st climate changes on loess and paleosols or topsoil po llution with heavy metals.
The magnetic susceptibility of non-polluted soils is mostly inf luenced by the mineralogical composition of parental
rocks and the pedogenetic processe s. The recent advent of a new domain of Geophysics, Agricultural Geophysics,
opened new ways of research and offered new scientific and prof essional objectives. Studies of in situ soil magnetic
susceptibility, supported by the analysis of other magnetic and /or chemical properties, are used in the soil type
determination and in-depth loca tion of soil horizons. The study of soils situated in several regions located in the
south-eastern part of Romania ( Prahova county, Tulcea county, D anube river and Danube Delta) revealed good
possibilities of this method to dis criminate between soil types and precisely illustrate in-depth horizon boundaries.
Key words : geophysical mapping, soil types, magnetic susceptibility, hor izon boundary, SE Romania.
1. INTRODUCTION
Magnetic properties in soils are usually a
consequence of the presence of mineral compounds that include iron. Specific types of
iron oxides, iron and titanium oxides and iron
sulfides are the main causes of magnetic soil properties. The soil iron oxides are magnetic minerals, primary or secondary ones, inherited from the rocks or geological formations, formed during pedogenesis or from products of anthropogenic activities.
Soil magnetic properties are generally
controlled by the presence of magnetite and maghemite. The occurrence of maghemite is due to the conversion of iron oxides from antiferromagnetic form like hematite (α Fe
2O3)
or goethite (α FeOOH ), into the ferromagnetic form, maghemite (γ Fe
2O3). The formation of
maghemite in topsoils is attributed to the dehydration of goethite a nd lepidocrocite, in the
presence of organic matter. Aeolian deposition of mineral grains may significantly enhance soil magnetic properties.
The concentration of iron oxides in soils is
influenced by the parental material, biological activity, age of soil, pedogenetic processes, soil temperature, physico-chemical properties and
anthropic activities. The magnetic susceptibility
c a n v a r y o n t h e s o i l p r o f i l e d u e t o a
considerable number of factors, but the most important is the mineralogical composition. The magnetic susceptibility depends also on the direction and the form of magnetic particles spatially distributed in soil.
The magnetic susceptibility of soils is many
times based on the mineralogical composition of
parental rocks, but most of soil samples display higher magnetic properties than the geological
background. Studies of in situ soil magnetic
susceptibility, supported by the analysis of other
magnetic and/or chemical properties, may be
used in the soil diagnosis for determination of
its genesis and identification of soil forming
processes. Chemical and magnetic data on soils horizons are closely studied in order to better
understand the relationships between soil chemistry
and magnetic propertie s during pedogenetic
processes (Spassov et al. , 2004).
Magnetic susceptibility mapping of soils
represents nowadays one of the most important
tools for estimating the anthropogenic pollution
on industrial areas when probing the topsoil or

George Florin Gârbacea, Dumitru Ioane 2
84
road dust (Hoffman et al. , 2004; Lu et al. , 2007;
Sangode et al. , 2010). An interesting approach,
able to rapidly illustrate the degree of pollution
with heavy minerals in industrial urban areas, is represented by the simultaneous study of mean
magnetic susceptibility of neighboring agricultural
and urban land areas (Hu et al. , 2010).
Important advances in the study of magnetic
susceptibility of soils are presently observed in
regions affected by military conflicts, due to the
need of locating buried explosive objects such
as mines or aviation bombs, since the natural variation of the soil magnetic properties is able
to generate similar magnetic anomalies (Preetz
et al. , 2009).
An actual research direction in geophysical
soil mapping is the investigation of magnetic properties of both topsoil and subsoil in areas
with different geological and environmental
conditions, for a better understanding of soil
spatial variability and regional dependence on
particular lithogenic and/or anthropogenic processes (Fialova et al. , 2004).
A recent application of m agnetic susceptibility
measurements on soils is included in a new
domain of Geophysics, Agricultural Geophysics. In this field, the spatial variability of magnetic
properties may be related to the soil type based
on its mineralogical content (Petrovsky et al. ,
2004), and hence, the possibility of precisely
locating in-depth soil horizons boundaries
(Ioane et al. , 2010). Future development of
magnetic investigations for precision farming is
envisaged within the Agricultural Geophysics
techniques (Allred, 2010).
The magnetic susceptibility studies on soils
in Romania were mainly devoted so far to climate
and environmental changes during Quaternary
and to soil pollution with heavy metals due to
anthropogenic activities.
Significant information on climate and
paleoenvironmental changes in the south-eastern
part of Romania were obtained in the Mostiștea
lake area (Panaiotu et al. , 2001; Necula et al. ,
2005) on a sequence of four loess and three paleosol layers, illustrating by variations of
magnetic properties the alternations of dry and wet time intervals in Quaternary. The magnetic
properties of loess layers are lower as compared
to those measured on paleosols, the latter
preserving during time a part of their magnetic
signature.
Evaluation of soil pollution using magnetic
susceptibility data was carri ed out within large
cities in Romania, such as Bucharest, or smaller
towns as Baia Mare, long time affected by industrial pollution with heavy metals (Panaiotu
et al. , 2006). In Baia Mare, the soil content in
heavy minerals was found to be statistically
linked with variations in magnetic susceptibility.
2. SOIL MAGNETIC SUSCEPTIBILITY
MEASUREMENTS AND SAMPLING
2.1. Location of studied areas
A soil magnetic susceptibility study was
recently carried out in several areas located in
the south-eastern part of Romania in view of better
understanding the magnetic spatial variability of
soils under different pe do-climatic conditions.
The soil magnetic and chemical sampling
was performed in areas situated in the Moesian
Platform and the North Dobrogean Orogen (Fig. 1),
the soil geologic background offering sufficient
rock variability. A large part of the analyzed
soil profile locations follows the Danube river towards the Danube Delta, zones with obvious
particular pedologic and climatic features.
The location of investigated soil profiles is
the following (Fig. 1):
a) soil profiles in the Prahova county
represented by red dots;
b) soil profiles in the Tulcea county (North
Dobrogea) marked by blue dots;
c) soil profiles along Danube river represented
by yellow dots.
On the soil profiles situated within the three
studied areas magnetic susceptibility measurements were carried out and soil samples were collected
for chemical analyses, the latter corresponding
to the main soil horizons.

3 Geophysical ma pping of soils 85
2.2. Magnetic susceptibility measurements
The horizontal or vertical mapping of
magnetic susceptibility of soils offers important information about soil properties, as result of pedogenetic or anthropogenic processes.
The magnetic susceptibility measurements
on the soil profiles were performed with a SM 30 (Gf Instruments) digital portable susceptibility meter. This technique was applied in view of a
fast mapping of the vertical and horizontal soil
magnetic properties variability. The accuracy of magnetic susceptibility field measurements compared with similar observations made in laboratory on soil samples was previously found satisfactory (Kapick et al. , 1997).
The soil profiles were prepared with a spade
at variable depths in order to observe the in-depth soil horizon structure.
The magnetic susceptibility profile mapping
was carried out on grids with measurement
points situated at 10 or 20 cm interval on the
vertical profile of each studied soil profile. Prior
of taking measurements the soil profile vertical
surface was smoothed with the spade for a
proper contact with the geophysical instrument.
In each measurement point the magnetic susceptibility was observed four to five times,
being recorded only its highest value.
The magnetic susceptibility data, measured
in 10
-3SI units, were mostly represented as
contoured maps of the soil profile vertical walls.
In view of a rapid comparison and data interpre-
tation a common color code was employed.
In a single case the magnetic susceptibility
measurements on a soil profile are presented as
contoured data in a sequence of three horizontal
soil layers.
2.3. Soil chemical analyses
Chemical analyses of soils are important for
determining the soil type and assessing the nutrient status of soils for agricultural production
and in determining the environmental hazards
imposed on soils by industrial, municipal, and
agricultural wastes.
The investigated soil profiles were sampled
in view of enabling laboratory chemical analyses, each sample being taken from the middle part of
soil horizons.
The chemical analyses included important
soil chemical properties such as PH, carbonate concentration, Ht (total humus), Nt (total nitrogen), Sh (exchangeable hydrogen), Sb (the capacity for base exchange), Fe, K, Na, Mg, Ca, T (total exchange capacity), V (base saturation).
The soils PH was established electrochemically,
the readings being taken with a PH–meter Thermo Orion 3. The carbonates concentration from soils probes were determined using gas volumetric method with Scheibler calcimeter. The total nitrogen (Nt) was determined using the wet oxidation method and titrimetric graduation – Kjeldahl method, with Gerhardt mineralizator and distiller. The determination of exchangeable hydrogen was made through percolation after the Cernescu method.
3. VERTICAL VARIABILITY OF
MAGNETIC SUSCEPTIBILITY
ON SOIL PROFILES
Magnetic susceptibility measurements on the
soil profiles offer significant advantages as
compared to measurements taken at the
topographic surface.
Many times boundaries of the horizon
structure of a particular soil type are illustrated
by a fast increase or decrease of magnetic susceptibility allowing rapid and correct
decisions for in-depth soil mapping.
Knowledge on the presence of soil layers
bearing high magnetic properties, situated at different depths at the scale of a few meters may be useful for geophysicists when performing detailed magnetic surveys for near-surface geological structures (civil engineering, hydro-geology, environment), for archaeology or agriculture (Ioane et al. , 2010).
3.1. Prahova county
In the Prahova county the magnetic
susceptibility measurements were carried out on
three soil profiles situated at distances of 4 and
16 km. All three soil profiles exhibit different types of luvisols, a specific soil for this region.

George Florin Gârbacea, Dumitru Ioane 4
86
For this soil type the pedogenetic processes of
eluviation and illuviation are characteristic,
leading in time to the for mation of clay minerals
in the B horizon.
The in situ observations of the Prahova
county soil profiles are presented as follows:
– P1, Stagnic preluvisol with thickness of Ao
horizon 0–10 cm, a loamy-sandy texture,
glomerular structure and Bt (argic) horizon with
thickness 10–70 cm and situated on a hilly relief
at 300 m altitude;
– P2, Epicalcari-gleyic luvisol with thickness
of Ao horizon 0–12 cm, a loamy-sandy texture
and blocky structure; Elka horizon with thickness
of 12–40 cm with sandy texture and glomerular
structure; Bt horizon with thickness of 40–90 cm,
loamy clay texture and prismatic structure. The
profile is situated at 100 m altitude.
– P3, Stagnic luvisol with thickness of A
horizon 0–10 cm, brown dark color, sandy-
loamy texture, glomerular structure; El horizon
with thickness of 10–30 cm, brown–yellow color,
loamy texture and blocky structure; Bt horizon
with thickness of 30–90 cm, brown with rusty
spots, clay texture and prismatic structure. The
soil profile is situated at 100 m altitude.
The magnetic susceptibility data for all three
sites, presented as contoured maps of a vertical
wall in the soil profile, are displayed in Fig. 2.
The magnetic soil properties illustrate a clear vertical variability (Fig. 2a, 2b and 2c) and at
higher depths, a horizontal variability (Fig. 2c).
The vertical variability of magnetic
susceptibility in all three cases follows in good
conditions the soil horizons structure.
The Stagnic luvisol and Epicalcari-gleyic
luvisol (Fig. 2a and 2b) are characterized by the
lowest values in magnetic susceptibility in the E
horizon, showing that the horizon is depleted of iron oxides, as well as of colloids like organic matter. They were mostly accumulated in the B
horizon, where higher values of magnetic
susceptibility were obtained. The rise of magnetic susceptibility in B luvisol horizons can
also be determined by pedogenetic processes of gleying (Gr) and pseudogleying (w); the
difference is that the BtkaGr horizon (Fig. 2b)
has lower values in magnetic properties due to a high concentration in carbonates (diamagnetic)
that fill in places the soil pores.
The S tagnic preluvisol h a s h i g h e r m a g n e t i c
susceptibility in the A horizon as compared to
the B horizon and does not have an E eluviation
horizon.
On the Stagnic preluvisol p r o f i l e t h e
horizontal distribution of magnetic susceptibility
was measured in order to compare it with its
vertical distribution. The measuring horizontal area was 80 cm long and 60 cm wide.
The horizontal distribution of magnetic
susceptibility (Ka) for the Stagnic preluvisol
profile presented in Fig. 3 depicts a similar
variation alike its vertical distribution presented in Fig. 2c. However, a good picture of the horizontal variability is observed at the lowest measured level (50 cm depth), a feature that
may be useful when analyzing soil cracks and
water permeability.
3.2. Tulcea county
The studied soil profiles are situated in North
Dobrogea, in contrasting areas as concerned the geological background. Four soil type profiles were investigated here on the magnetic susceptibility vertical variability.
The in situ observations of the Tulcea county
soil profiles are presented as follows:
D1 – Mollic preluvisol with thickness of Am
horizon of 0–40 cm, dark color, loamy texture and prismatic texture. Bt horizon between 40–
70 cm, brown color, loamy clay structure and prismatic structure. C horizon from 70 cm
depth. The soil profile is situated in a hilly area at 170 m altitude.
D2 – Rendzic leptosol with thickness of
Amka (A mollic carbonatic) horizon between 0–
40 cm, black color, sandy-loamy texture and glomerular structure. AR/ka horizon between
40–75 cm, dark brown color, loamy-sandy texture and glomerular structure. The soil profile is situated at 240 m altitude.
D 3 – T i p i c p r e l u v i s o l with thickness of Ao
horizon 0–40 cm, dark brown color, loamy-
sandy texture, glomerular structure. Bt between

5 Geophysical ma pping of soils 87
40–120 cm, brown red color, loamy texture and
prismatic structure. The soil profile is situated at 150 m altitude in hilly area.
D4 – Eutri-calcaric cambisol w i t h t h i c k n e s s
of Amka horizon 0–25 cm, dark brown color, sandy-loamy texture and glomerular structure. Bvka between 25–110 cm, brown yellow color,
loamy-sandy texture and glomerular texture. The soil profile is situated at 80 m altitude.
The soil profile, determined as a E u t r i –
calcaric cambisol , is situated in the northern
part of the Dobrogea county on Quaternary loess deposits (Fig. 4a). The major pedogenetic process that affected this soil profile is the in
situ formation of clay. The highest values of
magnetic susceptibility were recorded in the A
horizon; the values decrease in the B horizon
and even more in the loess parental deposit ( C),
which displays here the lowest magnetic susceptibility.
In the Mollic preluvisol and the Renzic
leptosol (Figs. 4b and 4c), an important decrease
with depth in magnetic susceptibility was observed, the highest values being recorded in
the upper Am horizon.
On the contrary, the Typical preluvisol
profile presented in Fig. 4d presents a significant
increase in magnetic susce ptibility with depth.
The decrease of magnetic susceptibility with
depth within the first three soil profiles (Fig. 4a,
4b and 4c) is due to weathering soil processes,
while the increase with depth in magnetic
properties for the Typical preluvisol (Fig. 4d) is
determined by the high magnetic properties of
its parental material (magmatic rock).
It may be also interesting and useful to
consider the parental material and the vertical
distribution of magnetic susceptibility for both the Rendzic leptosol (limestone) and the Typical
preluvisol (magmatic rock) (Fig. 4c and 4d).
The Renzic leptosol displays a “normal” in-
depth distribution of magnetic properties, with
highest values in A and lowest in C, while the
Typical preluvisol illustrates an “anomalous” in-
depth distribution of magnetic susceptibility, the
highly magnetic C horizon being responsible for
this reversed vertical distribution. 3.3. Danube river
and Danube Delta soil profiles
The studies areas are located in the Brăila
and Tulcea counties, along the Danube river and within the Danube Delta, the analyzed soil
profiles being developed on alluvial deposits.
The specific type of soil formed in seasonal
flooded areas, where water is present long time intervals during the year. These soils are
developed on the same pa rental material, so the
major factor in spatial variability of magnetic susceptibility may be attributed to weathering conditions.
The soil profiles display generally the same
horizon structure. There may be separated two
soil types due to the vertical extension of an
aerobic oxidation horizon ( Go): a) soils which
have a Go horizon at depths higher than 50 cm
are Fluvisol soils type; b) soils which have Go
horizon above 50 cm depth are Gleysol t y p e
soils.
The magnetic susceptibility varies with
depth and display specific values associated with soil horizons. All these soil profiles are rich in carbonates and have a thin horizon rich
in organic matter ( A) because it is usually
depleted during flooding episodes.
In the majority of the presented soil profiles
(Figs. 5a, 5b, 5c, 5e and 5f) higher magnetic susceptibility values ar e recorded in the Go
horizon, being noticed a substantial decrease in
magnetic susceptibility in the Gr horizon.
4. CORRELATION OF CHEMICAL SOIL
PROPERTIES AND MAGNETIC
SUSCEPTIBILITY
Correlating results of magnetic susceptibility
measurements and significant chemical soil
proprieties in the soil profiles of the studied areas may lead to a better understanding of soil magnetism and the causes of its spatial variability. Soil pH, organic matter content (Ht) and cation exchange capacity (T) provide a
general description for the chemical
characteristics of soil, while the Fe content may be related to magnetic properties (Table 1).

George Florin Gârbacea, Dumitru Ioane 6
88

Table 1
Chemical analyses and magnetic susceptibility data on soil samp les

Soil type
Soil sub
type
Soil
horizon
Horizon
depth Ka (magnetic
susceptibility)
x 10 -3 SI
Fe
mg/kg

PH
Ht
(%)
Total
humus
T
(me/100g)

Prahova county
Ao 0–10 cm 0.234 5.57 5.71 26.31 Preluvisol stagnic
Btw 10–70 cm 0.116 5.17 0.51 19.54
Aoka 0–12 cm 0.134 7.73 5.95
Elka 12–40 cm 0.1 8.22 1.55 Luvisol gleic,
epicalcaric
BtkaGr 40–90 cm 0.14 8.07 2.51
Ao 0–10 cm 0.127 5.69 9.26 37.16
El 10–30 cm 0.096 4.89 2.19 35.97 Luvisol stagnic
Btw 30–90 cm 0.161 4.85 0.57 37.2
North Dobrogea area
Am 0–40 cm 0.986 15090 6.88 2.64 Preluvisol mollic
Bt 40–70 cm 0.792 13940 7.61 1.15
Amka 0–40 cm 0.797 20390 8.07 5.64 Leptosol rendzic
A/Rka 40–75 cm 0.261 11140 8.30 2.82
Ao 0–20 cm 0.469 24520 6.83 7.19 Preluvisol tipic
Bt 20–130 cm 0.840 15450 5.92 0.90 77.90
Amka 0–25 cm 0.360 11560 7.89 3.59 Eutri –
cambisol mollic,
calcaric Bvka 25–110 cm 0.194 10546 8.40 1.10
Brăila and Tulcea counties
Aoalka 0–5 cm 0.173 7.64 6.63
Goalka 5–30 cm 0.246 8.14 2.72 Gleysol Fluvic,
proxicalcaric
Gralka 30–80 cm 0.212 8.34 0.39
Aoalka 0–10 cm 0.408 15632 7.47 8.95
Goalka 10–30 cm 0.365 15321 8.06 2.27 Gleysol Fluvic,
proxicalcaric
Gralka 30–90 cm 0.274 15001 8.32 0.75
Aoalka 0–10 cm 0.405 15542 7.38 7.04
Goalka 10–30 cm 0.516 15112 8.12 2.22 Gleysol Fluvic,
proxicalcaric
Gralka 30–80 cm 0.214 14996 8.20 2.15
Aoka 0–10 cm 0.326 11230 7.51 5.88
Goka 10–60 cm 0.392 11321 8.22 1.50 Fluvisol gleic,
proxicalcaric
Grka 60–100 cm 0.242 11169 8.49 1.18
Aoka 0–5 cm 0.254 11289 7.44 7.65
Goka 5–55 cm 0.375 11351 8.02 2.67 Fluvisol gleic,
proxicalcaric
Grka 55–80 cm 0.184 11301 8.08 2.64
Aoalka 0–10 cm 0.288 7.39 8.69
Goalka 10–30 cm 0.329 7.44 5.13 Gleysol Fluvic,
epicalcaric
Gralka 30–80 cm 0.208 8.27 1.52

The magnetic susceptibility vertical variation
has the same trend as the total organic matter
content and the cation exchange capacity in the studies soils, excepting the Stagnic luvisol i n
Btw horizon, were magnetic susceptibility is
increasing from El horizon while the total
organic matter is decreasing. The increase in magnetic susceptibility in
Btw horizon can be attributed to oxidation
processes during lower water table intervals, being created conditions f or converting hematite
to maghemite. The Stagnic luvisol and Preluvisol
have an acid reaction; while the Epicalcari-
gleyic luvisol have an alkaline reaction because

7 Geophysical ma pping of soils 89
of high carbonates concentration (12.7% in
Aoka horizon, 16% in Elka horizon and 17% in
BtkaGr horizon) (Fig. 6). The carbonates soil
content does not have in the case of these soil
types an important effect in the distribution of magnetic susceptibility, because other pedogenetic processes play a major role in the magnetic susceptibility increase (bioaccumulation, eluviation, illuviation and gleying).
The vertical variability in magnetic
susceptibility for the North Dobrogea and Danube
river and Danube Delta studied areas illustrates a good correlation with soil chemical properties. There is a strong correlation between magnetic susceptibility and total iron content (Fe) on the
studied soil profiles, with some exceptions in
Gleysols a n d Fluvisols i n t h e Go horizon
(Gleyic-oxidation horizon), where an increase in
magnetic susceptibility was noticed. The increase in magnetic susceptibility in Go
horizon is due to iron oxides that result from the
pedogenetic process of gleying (Fig. 7).
Even the majority of the soil profiles have
the same trend of vertical variation in magnetic
susceptibility and iron content, when we compare
the analyzed soils we may notice that the soil
profile with highest values in magnetic
susceptibility does not have greatest iron content.
This aspect is due to different mineralogical
composition and mainly, to different types of iron oxides with specific magnetic properties.
The vertical variability in organic matter
content displays the same trend as the magnetic
susceptibility, with the exception of Gleysols
and Fluvisols, w h e r e t h e A horizon presents
higher values. These types of soil have a higher
concentration of organic matter but are not characterized by high values of magnetic
susceptibility. This lack of correlation is due to
a different type of organic matter that is formed
normally in flooding areas and does not have
enough time to decompose because of flood
cycles and does not form organic-mineral
complexes that accumulate iron oxides.
Soil PH is mainly influenced by the soil
carbonates content. All studied soil profiles
have an alkaline reaction with the exception of
the Mollic preluvisol . 5. CONCLUSIONS
This paper presents results obtained in a first
stage of researches dedicated to soil geophysical
investigation using the magnetic susceptibility
spatial variability, being probably the first study
of this kind carried out on Romanian soils.
The vertical magnetic susceptibility distribution,
observed in soil profiles situated in analyzed geological, climate and vegetation conditions
indicated a structured in-depth distribution of
magnetic susceptibility that generally corresponds
with the soil horizons.
The comparison of vertical variability of
magnetic susceptibility with those of selected chemical compounds and properties showed correlations that were considered as natural
(enhanced magnetic susceptibility with
increased organic matter), or non-correlations which may arise presently interpretation problems (decreasing magnetic susceptibility and increasing
PH).
Considering the correlation between magnetic
susceptibility and organic matter content, high values were especially noticed at the upper part of the soil profiles, especially on the mollic type
of organic matter.
Acknowledgements. The scientific researches were performed
with financial support fro m the CNCSIS-UEFISCU
998/2009 scientific project. Th e authors acknowledge the
support of “Forest Research and Management Institute”, Bucharest, Romania soil scientists in determining the studied soil types and their chemical characteristics.
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Received: November 19, 2010
Accepted for publicat ion: January 12, 2011

Fig. 1 – Location of studied soil profiles in the south-eastern part of Romania.

9 Geophysical ma pping of soils 91

Fig. 2 – Vertical variability o f magnetic susceptibility in Pra hova county soil profiles:
a) Stagnic luvisol ; b) Epicalcari-gleyc luvisol; c) Stagnic preluvisol .

Fig. 3 – Horizontal variabilit y of magnetic susceptibility at v arious depths
in the Stagnic preluvisol profile.

George Florin Gârbacea, Dumitru Ioane 10
92

Fig. 4 – Spatial variability in magnetic susceptibility (Ka) on
soil profiles in North Dobrogea.

11 Geophysical ma pping of soils 93

Fig. 5 – Vertical variability in magnetic susceptibility (Ka) o n soil profiles
along Danube river and within Danube Delta.

George Florin Gârbacea, Dumitru Ioane 12
94

Fig. 6 – Vertical variability in magnetic susceptibility (Ka), total organic matter (Ht)
and total cation exchange capacity (T) in studied soil profiles .

13 Geophysical ma pping of soils 95

Fig. 7 – Vertical variability in magnetic susceptibility (Ka), total organic matter (Ht),
Fe content and PH in st udied soil profiles.