Journal of Environmental Protection, 2011, 2, 923-931
doi:10.4236/jep.2011.27105 Published Online September2011 (
Copyright © 2011 SciRes. JEP
Properties of a Lateritic Red Soil for Pollutant
Maria Eugenia Gimenez Boscov1, Waldemar Coelho Hachich1, Claudio Fernando Mahler2,
Elisabeth de Oliveira1
1University of São Paulo, São Paulo, Brazil; 2Federal University of Rio de Jane iro, Rio de Janeiro, Braz il.
Received May 22nd, 2011; revised July 6th, 2011; accepted August 16th, 2011.
In many regions of Brazil, lateritic clays are the natural candidates for the construction of compacted clay liners of
waste disposal sites because of their a vailability and appro priate geotechnica l characteristics. Lateritic soils have been
extensively used in recent decades in dam and road construction, but little is known about the migration of pollutants
through compacted la yers of such soils. This paper describes the characteristics of a lateritic clay, representing a group
of soils of significant occurrence in the State of São Paulo, to be employed in a clay liner of a waste disposal site.
Laboratory tests to assess permeability, adsorption and diffusion of six metals through the compacted soil showed that
permeability criterion may be met in the field, that the soil presents a modest capa city to retain cadmium and that con-
stituent metal oxides may be dissolved from the soil grains by acidic solutions.
Keywords: Compacted Clay Liner, Lateritic Soil, Permeability, Cadmium, Adsorption
1. Introduction
There is growing concern in Brazil regarding the prob-
lem of disposal of domestic and industrial wastes. Sani-
tary landfills have been built in most cities in the last
decade, but 34% of the total collected mass of municipal
solid wastes (MSW) are still disposed of inadequate
landfills or dumped [10]. Industrial conglomerates and
large industrial plants are controlled by environmental
authorities, but wastes from smaller industries are still
co-disposed with solid municipal waste in small munici-
International regulations for the design of waste dis-
posal sites adopted in Brazil provide general guidelines,
but understanding the peculiarities of Brazilian soils and
climate is essential to check the applicability of such
regulations to specific sites. Large areas of the country
are covered with tropical soils [14], among which the
lateritic red clays are natural candidates for the construc-
tion of compacted clay liners [5]. Lateritic soils have
been extensively u sed in th e last decades in dam and road
construction; nevertheless, very little is known about the
migration of pollutants through compacted layers of such
The main mechanisms of solute transport through a
porous medium are: advection, mechanical dispersion,
diffusion, chemical reaction s of th e solute in the solution,
such as radioactivity, and chemical reactions among sol-
ute and solids, such as adsorption [9]. Advectio n, i.e. the
movement of solute as it is carried by the water seeping
through the so il, and mechanical dispersion, i.e. the mix-
ing that occurs together with advection, are dependent on
the hydraulic conductivity of the soil. Diffusion, i.e. the
movement of ionic and molecular constituents by their
thermal-kinetic energy in the opposite direction of the
concentration gradient, is controlled by the diffusion co-
efficient in the chemical species of the soil. Adsorption,
which is a physical-chemical process by which a solute is
accumulated in a solid-liquid interface, is essentially due
to clay minerals, which are negatively charged because
of isomorphic substitution of cations in the silicate or
aluminate layers of the crystalline reticule. Other reten-
tion mechanisms may occur, such as precipitation, ion
complexation and specific adsorption. The capacity of
soils for attenuating pollution has been intensively stud-
ied in the last thirty years; an important application is the
utilization of compacted clay liners in waste disposal
sites or waste treatment plants to control subsoil con-
tamination [15].
This paper describes the characteristics of a lateritic
clay, representing a group of soils of significant occur-
rence in the State of São Paulo, to be employed in a clay
Properties of a Lateritic Red Soil for Pollutant Containment
liner of a waste disposal site. Procedures for the geotech-
nical characterization of a lateritic soil for the perform-
ance-oriented design of compacted clay liners are also
discussed. A case study is used as an example for the
suggested procedures.
2. Lateritic Soils
Lateritic clays are natural candidates for the construction
of compacted layers of low permeability in Brazil, be-
cause of their availability in large areas of the country
and current and past use in dam and embankment con-
As shown in Figure 1, lateritic soils occur all over the
country in surface layers of the pedological horizon, from
tens of centimeters to 10 meters thick. Important dams,
such as Itaparica, Três Irmãos, Juquiá, Poços de Caldas
and Itaipu, among others, have been built with lateritic
clays [6]. The more granular groups have also been ex-
tensively employed in the last decades as material for
road bases and subbases in the Southeast, particularly in
the State of São Paulo [3].
Lateritic soils were formed by the intensive p edo logical
process called laterization, which comprises leaching of
alkali and alkaline-earth metals and decreasing silica con-
tent, with concurrent maintenance of stable minerals, such
as quartz; presence of clay minerals in advanced degrees
of transformation; and accumulation and adhesion of hy-
drated iron and aluminum oxides to the surfaces of the
clay particles [11]. Thus, the clay fraction of lateritic soils
is essentially constituted of clay minerals of the kaolinite
group and iron and/or aluminum oxides and hydroxides.
These components are combined in the form of wa-
ter-stable popcorn-shaped micro-aggregates. Iron and
aluminum, besides covering the surfaces of the clay min-
erals with consequent reduction of the capacity of water
absorption, act as natural cementing agents amongst clay
A peculiar characteristic of lateritic soils is the shape
of the compaction curve, which presents a well defined
peak at the maximum dry unit weight and a steep slope-
Quartz sands
Podz ol ics
Latosoils, structured red soils,
Lateritic so ils with concretions
Soils with lateritic geotechn ical behaviour:
(a) + part of [(b)+(c)]
Figure 1. Distribution of lateritic soils in Brazil [14].
Copyright © 2011 SciRes. JEP
Properties of a Lateritic Red Soil for Pollutant Containment 925
on the dry side, even for the clayey soils [3,14]. A slight
deviation in the dry unit weight causes significant
changes in resistance, deformability and permeability
[4,14]. Lateritic clays do not swell nor lose resistance
when wet, but shrink significantly by loss of water. Road
and dam construction engineers have learned to cope
with the development of shrinkage cracks, for example,
by means of scarification and recompaction of several
centimeters of the embankment surface before placement
of a new layer.
3. Case Study
Tietê River flows across the metropolitan region of São
Paulo and collects wastes from its 18 million inhabitants
and 39,000 industrial plants. Every year up to 2 million
cubic metres of sediments are dragged from the bottom
of the river and disposed of at natural or artificial depres-
sions around the city to minimize the disastrous floods
that frequently overwhelm São Paulo. Past studies
showed high concentration levels of heavy metals in the
sediment pore water [7], originated from non treated do-
mestic sewage and industrial (automotive, metallurgy,
chemical, pharmaceutical, textile, among others) efflu-
ents discarded in the river [13]; this situation has re-
versed in the past years by means of environmental con-
trol of emissions. A prospective final disposal area was
chosen for the research: a former sand borrow pit located
in the outskirts of the City, near Guarulhos International
Airport, sided by a water course, and exhibiting a shal-
low water table.
The material dragged from the bottom of Tietê is a
black sludge emitting an unpleasant smell, with high
concentrations of organic compounds and large amounts
of rubbish. After pre-treatment consisting of drainage,
open air exposure to enhance organic matter deterioration,
sieving, and temporary storage in intermediate disposal
areas, the sediments can be classified as uniform fine
sand (SP) by the Unified System of Soil Classification,
and exhibit a clean appearance, normal colour, and no
particular smell.
Biochemical analyses were carried out to determine
the concentration of metals, volatile organic compounds,
mononuclear and polynuclear aromatics in the pre-
treated sediments. Solubility and leaching tests con-
ducted according to Brazilian regulations indicated the
presence of aluminum, cadmium, iron, manganese, mer-
cury and zinc in concentrations higher than the maximum
allowable limits.
For an environmentally safe design a clay liner is con-
sidered mandatory to protect the subsoil, as the water
level in the prospective disposal area is practically at the
surface. Therefore, the study was focused on the behav-
iour of a compacted clayey Brazilian red soil, a natural
candidate for a liner, in relation to the transport of the
metal ions detected in excessive concentrations. Perme-
ability, adsorption, and diffusion tests were carried out. It
is acceptable to consider pollutant transport through cover,
liner and subsoil layers in the aforementioned disposal
site as one-dimensional, sin ce the area is large, the subsoil
layers fairly ho ri zont al and t he water table high.
The soil is a red lateritic clay from the outskirts of the
City of São Paulo. 77% of the total mass of dry soil has
diameters smaller than 0.075 mm, and 62% smaller than
0.002 mm (ASTM D422). Liquid and plastic limits
(ASTM D4318) are 51% and 34%, respectively. Soil
classification is CH, inorganic clay of high plasticity
(ASTM 2487)). A standard Proctor compaction test
(ASTM D698) yielded 14.65 kN/m3 and 26.5% as, re-
spectively, the maximum dry unit weight
dmax and the
optimum water content wopt (Figure 2). Primary minerals
are quartz, nacrite, kaolinite, gibbsite and hematite.
The soil is naturally flocculated. A sedimentation test
performed without the addition of a deffloculant agent
indicated that, even after 24 hours immersed in water and
dispersed by a mixer, soil particles behave like silt-sized
flocks of around 0.01 mm diametre.
4. Experimental Procedure
4.1. Permeabilty Tests
The influence of compaction on the permeability coeffi-
cient, k, was evaluated, to verify under what conditions k
values lower than 10–9 m/s could be obtained. Twenty-
seven specimens were compacted statically at varying
20 22 24 26 28 30 32 34
Water content (%)
Dry unit weight (kN/m)
Figure 2. Compaction curve of the red lateritic clay from
Sao Paulo (ASTM D).
Copyright © 2011 SciRes. JEP
Properties of a Lateritic Red Soil for Pollutant Containment
Copyright © 2011 SciRes. JEP
Tests were carried out until a constant flow rate and
permeability coefficient was achieved, which corre-
sponds to saturation equilibrium, i.e. the maximum
saturation degree that can be reached by seepage. The
permeability coefficient deter mined in specimens satu-
rated by backpressure represent a maximum limit
unlikely to occur in the field. For optimum compaction
conditions, the final degree of saturation, between
90% and 97%, was reached after two pore volumes of
flow through the specimen, as shown in Figure 4. In
other compaction conditions, corresponding to higher
or lower permeabilities, greater or smaller volumes of
water, respectively, were needed to reach equilibrium.
moulding water contents, from wopt–2.5% to wopt+2.5%,
and at relative compactions (RC =
dmax) from 95% to
103% (wopt and
dmax at st andard Pr oct or ene rg y ).
Flexible wall permeability tests were performed in tri-
axial cells using distilled water in a temperature- con-
trolled room at (20 2)˚C. Preliminary tests indicated a
negligible influence of the applied confining pressure and
hydraulic gradients in the measured permeability coeffi-
cient, as shown in Figure 3; test duration could therefore
be reduced. Meriggi & Zagollin [12] observed double or
triple variations in the permeability coefficient when the
confining pressure increased from 100 to 300 kPa, and
practically gradient-independent permeability coeffcients
for hydraulic gradients varying from 10 to 40.
00.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Seeped volume (void volumes)
Permeability coefficient (m/s)
Probe no. 27
d = 1,003 dmax
ot = -0,1%
Figure 3. Permeability test with varying confining pressure (c) and hydraulic coefficient (i).
Seeped volume (void volumes)
Permeability coefficient (m/s)
Probe no. 9
d = 0,986 dmax
ot = 0%
Figure 4. Variation of the measured permeability coefficient during a permeability test.
Properties of a Lateritic Red Soil for Pollutant Containment 927
4.2. Compatibility Tests
In order to check the compatibility of the soil to the
leachate, liquid and plastic limits were determined with
addition of 1000 mg/kg (maximum allowable value of
pollutant mass per dry mass of soil according to Brazilian
regulations) of each metal separately.
4.3. Diffusion Tests
Diffusion tests followed the procedure described by
Barone, et al. [1]. The specimens were compacted di-
rectly in the moulds, and saturated by capillarity and
seepage. Saturation was calculated by measuring the
specimen weight and volume during the processes of
water absorption and seepage. Specimens were then
submitted to approximately ten days of diffusion. The
diffusion mould had a reservoir for the pollutant solution
topping the so il speci men with no po ssibility for seep age,
so that ions were expected to migrate from the solution
through the soil, driven only by a concentration gradient.
At constant time intervals, samples were taken from the
fluid reservoir to monitor the solution composition.
Tested solutions were synthetic mixtures of the metals
detected in excess in the pore water of Tietê River´s
sediments with 18 different compositions (different con-
centrations of each metal and relative proportions of the
six metals).
4.4. Batch Equilibrium Tests
Batch equilibrium adsorption tests were performed in
accordance with USEPA guidelines (1992) [16] with
cadmium and mercury solutions. Initially, method A was
tested twice for each metal separately, i.e. by varying
quantities of soil with equal volumes of the same solu tion,
resulting in different soil/solution ratios but in equal ini-
tial concentrations. However, results were poor since the
mass of adsorved solute was practically independent of
the mass of dry soil. Simultaneously, the mass of man-
ganese liberated in the solution increased with the mass
of dry soil, clearly indicating a process of solubilization
and/or desorption of manganese from the clay particles,
since this metal was not present in the initial solution.
The same behaviour was observed for aluminum, iron,
and zinc. Tests were again carried out with method B, i.e.
equal quantities of soil and equal volumes of solutions
with varying concentration, resulting in equal soil/solu-
tion ratios but different initial concentrations.
4.5. Spectrometry of Atomic Emission
Concentrations of metal ions in the liquid samples of
diffusion, dispersion and batch equilibrium tests were
determined by spectrometry of atomic emission with
induced argonium plasma.
5. Results
5.1. Permeability tests
The results of permeability tests are shown in Figure 5.
Figure 6 illustrates trends of the variation of the perme-
ability coefficient as a function of moulding water con-
tent and dry unit weight based on the test results. The
permeability coefficient of the red soil is about 10–9 m/s
-3 -11 3
ot (%)
ot (%)
94 95 96 97 98 99100 101
d/dmax (%)
k (m/s)
k (m/s)
Figure 5. Permeability tests results.
Copyright © 2011 SciRes. JEP
Properties of a Lateritic Red Soil for Pollutant Containment
Figure 6. Permeability coefficient as a function of water
content and dry unit weight.
under optimum compaction conditions. Such a high
value when compared to clays with similar Atterberg
limits and grain size distribution curves may be ex-
plained by the porous microstructure of lateritic soils.
Furthermore, it must be remembered that laboratory tests
underestimate the permeability of in situ compacted lay-
ers [8]. The soil can be compacted at a higher energy to a
higher dry unit weight and lower k-value, as already ob-
served in field compaction. However, the consequent
rigidity of the liner must be evaluated since it will in-
crease cracking by differential settlement.
Permeability of this soil depends drastically on
moulding water content and compaction degree, being
more influenced by compaction degree than by water
content, and showing variations of three orders of mag-
nitude for the ran ge of tested compaction cond itions. The
relevance of this conclusion is enhanced by the experi-
mental evidence that deviations from the specifications
usually occur in the field, even when compaction is well
controlled, and that significant spacial variation of per-
meability is the rule fo r compacted soil layers [2].
5.2. Compatibility Tests
The results in Figure 7 show a rise in wL and a slight
decrease in wP for all the studied metals except mercury,
for which wP also rose. With exception of mercury, PI
increased significantly for all metals, due mainly to wL,
probably because of the dispersion caused by the poly-
valent ions. For mercury, PI remained constant, because
wL and wP increased by the same amount.
5.3. Diffusion Tests
Lateritic soils are highly enriched with iron and alumi-
num oxides and hydroxides throughout the intense
weathering, which is a characteristic of the process of
soil formation known as laterization. These oxi-hydrox-
ides occur as “concretions”, assembling clay particles in
arrangements usually regarded as physically and chemi-
cally stable. Pure diffusion through the soil of the metal
ions utilized in the tested solutions seem to be accompa-
nied by more complex phenomena derived from the con-
tact of the concretions with an acidic environment. This
speculation arises, for example, by Figure 8, which
shows the measured concentration of aluminum in the
fluid reservoir for five specimens compacted statically at
standard Proctor optimum conditions, each topped by a
different synthetic solution. The initial solutions had pH
values ranging from 1 to 2. It should be pointed out that
aluminum was present in just one of these solutions, and
that its initial concentration in the specimen pore water
was below 1 g /g. Repeatabilit y of the results of Figure
8 was verified in 32 different tests.
Mass balance indicated that the amount of aluminum
that entered the reservoir from the soil could not be ex-
plained in terms of desorption alone, suggesting the oc-
currence of dissolution phenomena due to the acidic pH.
Peak values varied for each tested solution, but no corre-
lation was found between peak value and initial alumi-
num concentration, initial ionic concentration or pH
The same behavior was observed for iron, manganese
and zinc, which are soil constituents. Cadmium and
mercury, which do not exist originally in the soil parti-
cles according to X-ray fluorescence test, showed the
expected behaviour for diffusion tests, as shown in Fig-
ure 9.
Compaction variations showed no sensible influence
on diffusion. Figure 10, for example, shows the variation
of cadmium concentration in the reservoir with time for
four specimens at different relative compactions topped
with the same solution.
010 20 30 40 50 60 70 80 90100
wL (%)
PI (%)
Cd Fe
Figure 7. Atterberg limits with addition of metals.
Copyright © 2011 SciRes. JEP
Properties of a Lateritic Red Soil for Pollutant Containment 929
050100 150 200
Time (hours)
Aluminum concentration (mg/L)
0.5 ppm Cd
1.2 ppm Cd
2.3 ppm Cd
1.2 ppm Cd, 4 p pm Hg
2 ppm Al, 1 ppm Mn, 1 ppm Zn
Figure 8. Aluminum concentration in the fluid reservoir.
010 20 30 40 50 60 70 80 90100
Time (hour)
Cadmium concentration (mg/L)
0.5 ppm Cd
1.2 ppm Cd
2.3 ppm Cd
2.4 ppm Cd, 12 ppm Mn, 10 ppm Zn
Figure 9. Cadmium concentration in the fluid reservoir.
050100 150 200 250
Time (hours)
Cadmium concentration (mg/L)
Initial solution:
1.1 ppm Al, 0.8 ppm Cd,
1.5 ppm Fe, 3 ppm Mn, 0.4 ppm Zn
Figure 10. Influence of compaction degree on the diffusion behaviour.
Copyright © 2011 SciRes. JEP
Properties of a Lateritic Red Soil for Pollutant Containment
Batch tests indicate a low adsorption capacity for cad-
mium, as might be expected from the soil mineralogy:
kaolinite is the p redominant clay mineral. Fitting the lin-
ear model to experimental results yielded Kd values of 13
mL/g for low concentrations, and 0.2 mL/g for concen-
trations higher than 6 mg/L. Mass balance from diffusion
tests, on the other hand, suggests Kd values of about 1 to
2 mL/g when adsorption in the whole probe is considered,
whereas the assumption of adsorption equilibrium with
the upper layer of the probe leads to Kd values of 4 to 10
mL/g. Freundlich equation fitting for cadmium may be
expressed by:
S 19.2C(mL/g)
where S is the adsorption degree (mass of adsorved sol-
ute/dry mass of soil) and C is the equilibrium concen-
tration (mass o f d issolv ed so lut e/so lut ion volume)
5.4. Mineralogical Tests
Mineralogical tests were carried out in orde r to verify the
occurrence of solubilization of aluminum from soil parti-
cles, i.e. from aluminum oxides and hydroxides, as indi-
cated by the results of diffusion and batch tests. Samples
from the natural soil and from prob es prev iously tested to
diffusion were submitted to X-ray diffraction tests, X-ray
fluorescence tests and scan electron microscopy tests.
Figure 11 shows conglomerates of kao linite particles
bonded by iron/aluminum oxides in the natural soil and
after days of contact with a metal solution with pH 2.
Leaching of the conglomerate is visible: contours of kao
linite particles are clearer after part of the cementing ox-
ides was removed from the soil.
6. Conclusions
The consideration of the pollution transport through the
soils is very important for the improvement of the design
of waste disposal sites. More research is necessary to use
all potentialities of lateritic soils, one of the most fre-
quently and extensively used type of soil for compacted
fills in Brazil, for clay liners. Advection can be the
dominant phenomenon, since drastic variations in per-
meability can result from small deviations from the
specified compacted conditions. More investigations are
needed to account for the chemical reactions that may
take place when such soils are exposed to acidic solu-
tions, and that migh t turn out to be as significative as the
diffusion and adsorption mechanisms.
7. Acknowledgments
The authors would like to FAPESP (Foundation for Re-
search Support of the State of São Paulo) for the finantial
support. Physical-chemical analyses of the Tietê River
Figure 11. Kaolinite-oxides conglomerates: a. natural soil; b.
after a diffusion test in acidic environment.
sediments were kindly bestowed by Dr. Dione Morita.
Access to data related to managament and disposal sites
of the Tietê River sediments was granted by DAEE
(Water Resources and Energy Department of the State of
São Paulo). The mineralogical tests were performed at
the Technological Characterization Laboratory of the
Mining Engineering Department of the Polytechnic
School of São Paulo.
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