Abstract
Clay
formations
are
currently
considered
as
a
possible
host
rock
for
the
storage
of
radioactive
waste
(RW).
The
low
permeability
and
large
sorption
capacity
make
clay
formations
suitable
sediments
for
RW
deposition.
The
Boom
clay
member
in
Belgium
and
the
Netherlands
is
currently
studied
as
a
reference
rock
for
methodological
studies
on
the
disposal
and
storage
of
RW
(De
Craen
et
al.
2004a).
Iron-‐containing
constituents
are
assumed
to
dominate
the
redox
properties
of
the
Boom
clay,
and
have
been
researched
by
De
Craen
(2004a)
and
De
Craen
et
al.
(2004b).
Here,
the
composition
of
the
Boom
clay
in
the
Netherlands
has
been
geochemically
characterized.
Sediment
samples
originating
from
Limburg
and
Zeeland
have
been
analysed,
to
identify
the
mineralogy,
geochemical
composition
and
redox
status
The
objectives
for
this
research
are
to
determine
of
the
in
situ
porewater
composition,
to
identify
processes
that
take
place
in
the
porewater
after
perturbation.
In
addition,
the
possibility
of
redox
potential
determination
based
on
the
activities
of
reactants
and
products
of
the
Fe2+/Fe3+
couple
is
assessed.
The
porewater
composition
was
determined
by
squeezed
porewater
from
a
sediment
core,
and
a
leaching
method.
The
composition
of
the
porewater
during
the
leaching
method
was
measured
at
4
different
points
in
time,
which
gives
insight
in
the
processes
that
take
place
in
the
porewater
after
perturbation.
The
iron
speciation
was
determined
by
sequential
extraction
(Claff
et
al.
2010).
This
research
provided
insight
on
the
geochemical
porewater
composition
and
the
solid
fraction
content
of
the
Boom
clay
in
the
Netherlands.
The
results
from
both
the
leaching
and
the
squeezing
method
show
that
the
porewater
composition
has
a
strong
marine
influence.
The
selective
enrichment
in
SO42-‐
and
Ca2+
that
was
found
is
probably
due
to
oxidation
of
pyrite
during
the
storage
of
the
sediment
cores.
However,
only
part
of
the
pyrite
was
oxidized
since
there
is
still
pyrite
present
in
the
sediment.
Additionally
to
pyrite
oxidation,
sulphate
reduction
was
observed.
Sulphate
was
used
as
a
terminal
electron
donor
during
the
degradation
of
organic
matter
by
SRB.
Assigning
a
redox
potential
to
system
in
our
research
was
found
to
be
very
difficult.
Pyrite
oxidation
in
the
sediment
samples
made
it
impossible
to
constrain
a
substantiated
redox
potential
for
the
in
situ
conditions.