Jül - 514 - LW
KERNFORSCHUNGSANLAGE JOLICH GESELLSCHAFT MIT BESCHRÄNKTER
Institut für Landwirtschaft
Studies on tagged clay migration
due to water movement
H. W Scharpenseel and W. Kerpen -
Als Manuskript gedruckt
Berichte der Kern forsch u n g so n 1 o g e J ü 1 ich - Nr. 514
Institut für Landwirtschaft Jül - 514 - LW
Dok.: Soils - Clay Migration Clays - Tracer T echniques
DK: 631.41 :552.52:574.91 552.52: 621.039.85
Zu beziehen durch: ZENTRALBIBLIOTHEK der Kernforschungsanlage
Jülich, Jülich, Bundesrepublik Deutschland
Reprint f rom
''ISOTOPE AND RADIATION TECHNIQUES
IN SOIL PHYSICS AND IRRIGATION STUDIES"
INTERNATIONAL ATOMIC ENERGY AGENCY
STUDIES ON TAGGED CLAY MIGRATION DUE TO WATER MOVEMENT
H. W. r§._CHARPENSEEL INSTITUT FÜR BODENKUNDE DER UNIVERSITÄT
BONN, AND W. KERPEN ARBEITSGRUPPE, INSTITUT FÜR LANDWIRTSCHAFT DER
KFA JÜLICH, FEDERAL REPUBLIC OF GERMANY
STUDIES ON TAGGED CLAY MIGRATION DUE TO WATER MOVEMENT. 55
Fe-tagged clay minerals, produced by hydrothermal synthesis, serve
to clarify the question whether clay migration or clay formation in
situ is the predominating mechanism in the Bcdevelopment of
Parabraunerde (sol brun lessive, grey brown podsolic, hapludalf,
demopodsol). They further indicate the possibilities of clay
transportation caused by water percolation. Suitable experimental
approaches, such as thin-layer chromatography and autoradiography.
translocation tests in columns filled with monotypical textural
fractions or with undisturbed soil profiles, and synchronous
hydrothermal treatment of 5iöpe-containing material from different
horizons of Parabraunerde, to reveal the specific readiness of the
different _profile zones for 55Fe-clay production, are described.
The possibilities of clay percolation are discussed.
Although clay migration is traditionally considered to be the
valid explanation for the phenomenon of horizons of clay
accumulation, such as that in argids, alfisols and ultisols, this
assumption is based on indirect evidence arising from the textural
comparison of the horizons and micro-morphological thin- slide
demonstration of plasmatic flow structures.
While the movement is certainly too slow to be detected by
direct observation, one could expect to confirm or refute the clay
migration concept from: ( 1) Model experiments with columns of
undisturbed soil profiles, or of
different textural composition; (2) Thin- layer chromatographic
tests with layers of different grain- sizes; (3) Trials to detect
in- situ clay formation in the accumulation horizon as
proof of an alternative mechanism; (4) Chemical and physical
comparison of the clay minerals in the A 1- and
A1 -horizon with those along the plasmatic flow structures. The
methods connected with (1) - (3) require the use of tagged
which is distinguished by its radiation from the resident clay
and mineral substance.
In earlier reports [1, 2) the production of 55Fe-labelled
kaolinite and montmorillonite by hydrothermal synthesis in
high-pressure autoclaves were explained.
A comparison of the constituents taking part in the synthesis of
the clay minerals montmorillonite and kaolinite, with the partial
substitution of 55Fe in isomorphic exchange for aluminium, is given
in Table 1.
1. COLUMN EXPERIMENTS
In studying tagged clay migration, the approach that is closest
to natural field conditions is to administer 55Fe-tagged clay,
280 SCHARPENSEEL and KERPEN
T ABLE I. CONSTITUENTS IN THE SYNTHESIS OF MONTMORILLONITE AND
672. 7 mg
Alp 3 214. 9 mg
Mg-acetate 396 mg
KCl 68. 9 mg
55 Fe (OH)3
HP 71 ml
Treatment 14 d, 300°C, 80 atm, or 42 d, 225°C, 50 atm.
Autoclave 205 ml.
1= ... l=o=
' „. ' ~· . „ ' . - . ~
'u'« ~ 'v'* ~ „~ - - ~ - ~ I / = =~ ~
/ / ........ -- ~ ..:~ ,/' - - -~=' I~ 1 1 t •I V//ll/!1
(///l/il 1YXIX K.'1!//l!(h '/////;'u //~
v ~- ---FIG. l. Columns with well-defined soil
texture-fractions; conternporary percolation by rneans of a dosis
1.50-m-long glass columns, in the upper zone of undisturbed soil
profiles. By perfusion with known, sufficiently large amounts of
water, and by activity scanning, the potential clay movement can be
observed (3, 4]. Results so far obtained show little evidence of a
clay migration, but rather an immobile storage of the tagged clay
in a layer near the surface.
Since such experiments have not yet confirmed a measurable clay
migration, a second perfusion method, in 50-cm columns filled with
well-defined textural soil fractions, was carried out (Fig. 1).
The following fractions were singled out with the aid of
0 .002 - 0.02 mm diam. 0.02 - 0.06 mm diam. 0.06 - 0.2 mm diam.
0.2 - 1 mm diam.
- 2 mm diam.
Incorporated in the upper 1- cm layer of the five columns were
150 mg of 55Fe - labelled montmorillonite with 6000 dpm/mg,
suspended by ultrasonic treatment in 0.4_!'i sodium pyrophosphate .
Each percolation amounted to 1000 ml, equivalent to about 10000-mm
precipitations. A thin inner coating of the columns with silicon
oil prevents the water from forming preferential flow tracks along
the glass walls. After the percolation the collected water was
agitated and aliquots were tested for their activity. The activity
rate in the liquid- scintillation spectrometer, minus the
back-ground (slightly increased), would express quantitatively the
extent of eluted tagged clay.
FIG. 2. Thin-layer chromatographs with 55Fe-montmorillonite, ehe
tagged compound remainin g at the starting line.
Table II show s clay migration resulting from percolation with
water only in the textural fractions, down to 0.06 mm diam. This
occurs to a m e asurable extent only with coarse sand (2 - 0.2 mm
diam.). In the c olumns with particle si zes of less than 0.06 mm
diam. the whole tagged c lay remained immobile in the top l ayer
where it was administered.
TABLE II. MIGRATION OF TAGGED MONTMORILLONITE IN FIVE SOIL
COLUMNS WITH DIFFERENT TEXTURAL FRACTIONS
(mm diam.) lst percola ti on 2nd percola tion 3rd percolation
4th percola tion 5th percolation Total
(cpm/litre) ( cpm/litre) ( cpm/li tre) ( cpm/li tre) (cpm/litre)
1 - 2 516 210 387 230 386 - - 903 826
0.2 - 1 204 118 318 050 821 - - 522 989 0.06-0.2 - 217 557 - -
774 0.02 - 0.06 - - - - - -0.02 - 0.002 - - - - - -
"' CX> "'
~ ~ ~ ~ cn trl
~ II> ::i c..
2. THIN-LAYER CHROMATOGRAPHY
Thin- layer chrom atography of plated soil / or clay / silic a -
gel / starch mixtures (13:15:2) is used to test migration and
fixation processes of ions, humic matter or clay minerals in the
FIG.3. Set-up of high-pressure autoclaves in a tube-oven.
It can also be applied exclusively to a certain fraction of the
soil-plus-starch binder either in conventional discontinuous
partition chromat-ography or in continuous flow chromatography.
Again, 55Fe-clay, well dispersed by ultrasonic treatment, is
administered at a sequence of points on the starting line. Only
with the coarse sand fraction was there observed a scanty clay
translocation within the lower Rf-region (see Fig.2).
3. HYDROTHERMAL TREATMENT
The general belief that the textural differences, i. e. higher
concen-trations of the clay fraction in the B1 -horizon (clay
284 SCHARPENSEEL and KERPEN
lessive-profiles, exist as a result of clay migration , is
disputed. Model experiments in colurnns with undisturbed soil
profiles indicate leaching and percolation of considerable
quantities of colloidal Si02 , alurninium an~ other required
solvent associates, that might equally well form the excessive
clay, wholly or in part, on the site of the Bc-horizon.
The potentialities of this alternative mechanism can be
estimated by the comparative testing of newly formed clay-yields in
the various profile horizons owing to mutual hydrothermal treatment
in a high-pressure autoclave. As described in Figs. 3 and 4
truncated cylinders with repre-sentative soil samples of the
genetic horizons, previously rnixed with finely ground 55Fe(OH)a
(20 g soil + 6 rnl ~0+20 rng 55Fe(OH)3 ), were piled up in the
autoclave (Fig. 4) and treated hydrotherrnally for 42 d at 225°C
and 50-atrn steam pressure.
FIG.4. High-pressure autoclave filled with truncated cylinders
containing soil of the different horizons.
The hydrothermally newly formed clay minerals, from the
components available in the various horizons, were labelled with
55Fe, i. e. incorpo-rated in the clay minerals by isomorphic
exchange for aluminium (see the basic constituents of clay
synthesis, Table I).
After hydrothermal treatrnent the soil samples were transferred
into sedirnentation cylinders. Only the clay fraction of less than
2 µm diarn. is recovered and extracted with a dithionite-solution
(40 ml 0.3 M Na-citrate- solution + 5 rnl 1 M Na2(HC03ksolution+l g
Na-dithionite) so as to rernove all the remaining free unbound
55Fe. Finally the clay fractions were tested for their specific
activity by suspension counting in.a liquid-scintillation
spectrometer. The specific activities rneasured were directly
related to the clay-forming ability of the various genetic profile
Results so far available (Table III) consistently show that
newly synthesized clay occurs more frequently in the A1- and
B/C-horizons. While, in the A1-horizon, part of the 55Fe might be
tied up in stable clay-
humic acid-complexes with Fe-cation-bridge (7], the pronounced
clay-forming predisposition in the B/C-horizon is genuine, and
points to tendencies for clay to form in the transition zone
between calcareous loess (Cc-horizon) and the decalcified,
weathered loess-material of the Br-horizon. This, however, confirms
the supposition that the higher clay content in the Br -horizon
might at least partly stem from the development in loco because of
the particularly favourable supply conditions with the required
percolated structural components.
4, CHEMICAL AND PHYSICAL COMPARISON OF THE CLAY MINERALS IN THE
Ab- AND A1-HORIZON WITH THOSE ALONG THE PLASMATIC FLOW
Studies are under way to compare the general clay fractions of
the Ab-and A1 -horizons with the silicous-clayey substance, scraped
off the plasmatic flow structures. Only if it is identical can the
material from the plasmatic flow structures be considered to be
translocated because of the clay-migration--mechanism. Appropriate
X- ray diffraction analysis (control of background level due to
amorphous matter); Differential-thermo-analysis;
Electron-microscopy; Infra- red spectroscopy; and
28Si/29Si/30Si-isotope ratio measurement.
The problem of whether or not in terrestrial soils, such as
Parabraun-erde, grey brown podsolic, sol brun lessive, dernopodsol
and hapludalf, clay particles can be transported downwards with the
flow of percolating water, is still open to question. So far the
clay-migration concept is based on indirect evidence. Five
different methods, mainly involving the use of tagged material, are
( 1) Tagged clay was found to remain concentrated in the upper
layer when administered to large undisturbed soil-profile columns.
Even after several years of repeated percolation this did not
(2) 55Fe-labelled clay, administered to the upper layer of
columns filled with varying soil fractions, showed a marked clay
migration in the coarse- sand range of 2 - 0.2 mm diam., and a
slight migration in the range down to 0.06 mm diam.
(3) Thin-layer chromatography with different soil fractions
reveals only a very slight clay migration and only in the coarse
sandy soil fraction.
(4) Hydrothermal treatment of material from all genetic horizons
of Parabraunerde, mixed with 55Fe(OH)3, consistently yields the
highest specific activity of the clay fractions in Ab- and
BC-horizon. The highest ability to produce clay seems to be
associated with the transition zone of decalcification,
superimposed on to the calcareous loess, in direct contact with the
clay-accumulation zone (Br) above.
This at least points to a certain degree of new clay formation
in or adjacent to the clay- accumulation horizon, apart from the
clay migration alone claimed up to now.
TABLE III. SPECIFIC CLAY-PRODUCING ABILITY OF DIFFERENT HORIZONS
IN PARABRAUNERDE PROFILES BELOW FOREST AND FIELD
Parabraunerde below forest Parabraunerde below field (Roesberg)
Genetic Depth Sample First Second
Depth Sample First Second
horizon run run depth run run
(cm) (cm) (dpm/g) (dpm/g) horizon (cm) (cm) (dpm/g) (dpm/g)
Ab 0 - 18 12- 18 73000 106 000 Ab o- 20 10- 18 34000 62000
A1 18- 30 20- 25 18000 44000 Al 20- 42 25- 38 36000 58000
A1Bt 30- 40 30- 40 25000 44000 Bu 42- 75
Bt 39- 72 50- 72 23000 45000 8t2 75-107 75- 93 26000 34000
Bcfi:c 72- 80 BtCc 126-145 130-142 127 000 32000
(5) Comparative tests of the clay in the Ab- and A1-horizons
with the clayey material of the plasmatic flow-structures in the
Bt-horizon must show identical characteristics, if the
clay-migration concept is tobe maintained. Experiments such as
those done by X-ray diffraction tests, DTA, electron-microscopy,
infra-red spectroscopy and 28Si/29Si/30Si-isotope ratio measurement
are being carried out.
[l] SCHARPENSEEL, H. W., GEWEHR, H. , BECKMANN, H., Die
Herstellung radioaktiven Montmorillonits und seine Verwendung zu
bodenchemischen wie -morphologischen Studien, Z. PflErnähr. Düng.
Bodenk. 101 2 (1963) 122.
 BECKMANN, H., GEWEHR, H., SCHARPENSEEL, H. W. , Über eine
Synthese radioaktiver Tonminerale, Landw. Forsch. 17. Sonderheft
 SCHARPENSEEL, H. w., KERPEN, W •• Modellversuche an
ungestörten Bodensäulen zum Studium bodengenetischer
Bildungsmechanismen unter Benutzung radioaktiver
Bodenkonstituenten, z. PflErnähr. Düng. Bodenk. 101 1 (1963) 1.
 KERPEN, W., SCHARPENSEEL, H. W., SCHOEMBS, !. ,
Untersuchungen der Perkola,te ungestörter Bodensäulen, MitL dL
Bodenkund. Gesellschaft i (1965) 151.
 SCHARPENSEEL, H. W ., Zur Darstellung der
Wanderungsfähigkeit und Festlegung von Ionen und Kolloiden in
dispersen Systemen, MitL dt. Bodenkund. Gesellschaft i (1966)
 SELKE, M., Die Böden Süd-Niedersachsens,
Wirtschaftswissenschaftliche Gesellschaft zum Studium
Niedersachsens 12 (1935).
 SCHARPENSEEL-;-H. W ., Aufbau und Bindungsform der
Ton-Huminsäure-Komplexe, Teil 1 und 2., z. PflErnähr. Düng. Bodenk.
114 3 (1966) 175.
P. A. C. RAATS: Did you attempt in your column experiments to
saturate the clays with any particular ion? The mobility of the
clay would appear to depend strongly on the type of exchangeable
H. W. SCHARPENSEEL: Following synthesis the labelled
.montmoril-lonite is mainly calcium -saturated, but after washing
with a solution of sodium citrate + sodium bicarbonate + sodium
dithionite it is preferentially sodium:-saturated. After it has
been fed to the columns and percolated, the superficial cations are
quickly equilibrated with the medium, in which ca++ constitute
70-80% of the exchange cations coating the clay minerals.
P. A. C. RAATS: The predominance of plasmatic flow structures on
the walls of large pores, cracks and so on strongly suggests that
these structures cannot be explained in terms of in-situ clay
H. W. SCHARPENSEEL: The pores with plasmatic flow are not very
large - some25-60µmindiameter -
andclayformationfromthedownward-moving soil solution is quite
M.DE BOODT: Have you allowedfordryingofthe soilinyourcolumn
experiments? One would expect the mechanical movement of the clays
to occur through the fissures, which in Parabraunerde are
sufficiently large (200 µm in diameter) when the water tension
rises to 30 atm or more.
H. W. SCHARPENSEEL: For two days each month water is percolated
through the soil columns. In the intervening period the soil dries
until it reaches a condition somewhere between field capacity and
288 SCHARPENSEEL and KERPEN
point. In view of the good water-holding capacity of loess, this
procedure corresponds fairly well to field conditions.
M. DE BOODT: I should have thought it would be more logical to
expect clay to form in the B 1 rather than the Bc/C horizon, the
higher 55F'e activity in the latter being caused by the formation
of iron phosphate or some other chemical with the ions present.
H. W. SCHARPENSEEL: The tendency for clay to form mainly in the
Be/Ce horizon accords well with our experience of hydrothermal clay
synthesis, from which we have come to expect maximum formation of
montmorillonitic /illitic clay minerals in the region of maximum
Si°'2 and ca++ availability. Iron phosphate formation does sound
chemically feasible, but it is not substantiated by iron and
phosphate values obtained by analysing the soil in different
W. KERPEN: I should like to amplify Mr. Scharpenseel 1 s reply.
Clay formation depends on the ratio of Si02 to bivalent cations.
Since the availability of silicic acid is about the same in all
horizons, the bivalent cations (particularly calcium) determine the
extent of clay formation. The greatest availability of bivalent
cations, together with a suitable amount of water, is in the B 1 /C
D. J. BROWN: Did you determine the mineral distribution
throughout the soil columns before carrying out your tests? If so,
was there any correlation between mineral content and clay
W. KERPEN: The reasons for the concentration of clay enrichment
in the Bt horizon can be extremely varied. For example, they can be
genetic, that is to say, associated with clay migration or
formation. Alternatively, they can be geological - associated with
the stratification of substrata with different clay contents. We
were interested in the former processes and accordingly used
Parabraunerde (which is similar to the grey brown podsolics) for
the column experiments. The initial material, Würmian loess, was
mineralogically uniform from the surface down to the subsoil, so
that the formation of horizons with reduced and enhanced clay
contents could be due only to clay migration and/or synthesis.
Nevertheless, we performed a wide range of soil analyses,
including mineralogical, structural, radiographic,
electron-optical, micro-morphological and other physical
Data on the correlation between mineral content and clay
formation, obtained from hydrothermal synthesis studies, have been
published in the following papers: Landw. Forsch. _!1 Supplement
(1963) 61, and z. PflErnähr. Düng. Bodenk. 101 (1963) 122.
M.J. FRISSEL (Chairman): Many substances, such as DDT, are
insoluble in water. Nevertheless these compounds are transported
down-wards. Some authors assume that they are adsorbed on and
transported together with clay particles. Does your model allow for
such a phenomenon?
H. W. SCHARPENSEEL: No, we did not attempt to study chelating
processes. While podsols would favour such processes the
Parabraunerde would probably not, since the organic matter is
inherently stable mull and the clay migration rate is too slow to
allow direct observation.
O. TEODORU: In the literature opinions differ as to the role of
different fractions in the microstructure of soils. In the light of
your results, what influence do you think clay has on the formation
H. W. SCHARPENSEEL: This question relates rather to paper
SM-94/8, 1 in which micromorphological and thin-section
autoradiographic evaluation is the final aim of the protracted
column percolation tests.
Unfortunately, it is impossible to answer the question at
present, since the first series of Parabraunerde columns has only
just reached (after four years of percolation and chemical
measurements) the stage where thin sections are being prepared. The
tagged clay that has been added will become visible within its
M. DE BOODT: The formation of microaggregates is completely
dependent on the kind of cations absorbed on the clay minerals, on
the concentration of the ions and on the speed and number of the
1 KERPEN. W .• SCHARPENSEEL, H. W., "Movement of ions and
colloids in undisturbed soil and parent rock material columns",
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