The Critical Zone: Environmental research at the intersection of atmosphere, hydrosphere, geosphere and biosphere
Presenter
Dr.
Fereidoun
Rezanezhad
Earth
and
Environmental
Sciences
University
of
Waterloo
Abstract
The
Critical
Zone
is
the
Earth's
permeable
layer
that
extends
from
the
top
of
the
vegetation
to
the
bottom
of
the
fresh
groundwater
zone.
The
biogeochemical
functioning
of
the
Critical
Zone
results
from
intricately
linked
physical,
chemical
and
biological
processes.
These
processes
respond
dynamically
to
variations
in
hydrological
and
climatic
conditions,
such
as
wet-dry
cycles,
flooding
events,
groundwater
extraction,
and
freezing
and
thawing,
as
well
as
to
changes
in
land
use.
The
ensuing
spatial
and
temporal
variations
in
chemical
properties,
texture,
temperature
and
water
content
modulate
the
turnover
of
carbon,
nutrients
and
redox-active
elements,
in
some
cases
resulting
in
highly
variable
emissions
of
greenhouse
gases
produced
by
microbial
respiration
and
fermentation
processes.
My
research
focuses
on
the
vadose
zone
and
the
underlying
shallow
groundwater
that,
together,
form
the
most
reactive
portion
of
the
Critical
Zone.
I
aim
to
unravel
the
mechanisms
that
control
soil
microbial
respiration,
water
flow
regime,
and
the
biogeochemical
transformations
of
nutrients
and
pollutants,
in
order
to
develop
a
predictive
understanding
of
how
Critical
Zone
processes
modulate
gas
exchanges
with
the
atmosphere
and
groundwater
quality.
I
will
present
novel
experimental
approaches
I
use
to
acquire
integrated
physical,
chemical
and
microbial
data
series,
coupled
to
model
simulations.
In
addition
to
providing
examples
of
past
and
current
research
projects,
I
will
highlight
emerging
and
future
directions
in
Critical
Zone
research,
with
an
emphasis
on
the
response
of
soil
biogeochemistry
to
human-driven
environmental
changes.