Specific
components
of
dissolved
organic
matter
(DOM)
may
serve
as
indicators
the
nitrate
accumulation
process
in
groundwater.
However,
precise
mechanisms
underlying
enrichment
based
on
DOM
characterization
groundwater
systems
remain
unclear.
This
study
aims
to
reveal
sources
and
pathways
through
application
three-dimensional
Excitation
Emission
Matrices
(EEM)
Fourier
Transform
Ion
Cyclotron
Resonance
Mass
Spectrometry
(FT-ICR-MS).
The
presence
fresh
which
show
high
biological
activity,
resulting
from
leaching
subsoil
excessive
input
manure
sewage,
contributes
elevated
levels
porous
aquifer.
main
contributors
inorganic
are
formulas
containing
a
higher
number
nitrogen
atoms.
three
atoms,
characterized
by
larger
mass
weights
lower
H/C
ratios,
closely
associated
with
readily
bioavailable
fraction.
Consequently,
observed
rate
samples
can
be
attributed
bioavailability
nitrogen-containing
molecules.
provides
molecular
perspective
its
relationship
systems,
offering
valuable
insights
for
more
accurate
assessment
potential
stocks
The
sandy
subterranean
estuary
(STE)
connecting
fresh
groundwater
to
saline
sea
water
is
characterized
by
strong
geochemical
(salinity,
redox,
and
pH)
gradients,
with
evidence
emerging
for
its
role
as
a
hot
spot
consumption
of
labile
substrates.
This
inspired
us
conduct
study
evaluate
whether
this
holds
true
dissolved
organic
matter
(DOM),
especially
given
the
still
mysterious
origin
marine
recalcitrant
DOM.
Here,
characterization
DOM
21
samples
(depth
1-13
m,
salinity
3.9‰
32.4‰)
across
65
m
transect
an
STE
located
in
coastal
Guangdong,
China,
has
found
systematic
biotransformation
toward
"recalcitrant"
carboxyl-rich
alicyclic
molecules
(CRAM).
fraction
CRAM
(%CRAM)
increases
from
33.1%
76.7%
increasing
degree
degradation
salinity.
Further,
processing
DOM,
including
more
"biolabile"
lower
%CRAM
released
aquitard,
active
under
oxic
conditions
than
reducing
conditions.
Given
large
quantities
that
recirculates
through
STEs
globally,
amount
(RDOM)
entering
ocean
after
likely
be
considerable.
While
studies
are
needed,
can
gain
CRAM-like
compounds
way.
The
property
of
groundwater
dissolved
organic
matter
(DOM)
subjected
to
anthropogenic
recharge
(AGR)
might
be
affected
by
the
water
quality
disparity
between
surface
and
natural
groundwater.
However,
diverse
molecular
scenarios
DOM
under
uneven
recharging
levels
remain
largely
unexplored.
We
combined
characteristics,
carbon
isotopic
signatures
molecules,
end-member
mixing
analysis
explore
sensitivity
potential
tracking
capabilities
AGR
along
with
gradients.
Our
findings
suggested
that
enriched
diverse,
saturated,
labile,
sulfur-rich
amplifying
abundance
intensity,
which
intensified
Additionally,
S-containing
molecules
their
indicators
like
CHOS%
(with
threshold
values
7.82%)
exhibited
high
predictive
power
for
recognition.
major
(diversity,
saturated
degree,
stability)
indicated
13C-containing
were
similar
whole
pool.
Notably,
specific
(C12H10O5S
C15H16O12),
although
not
detected
in
all
samples,
exhibit
robust
stability
or
favorable
solubility,
rendering
them
candidates
as
AGR-sensitive
molecules.
R13C/12C
ratio
C19H24O5
emerged
most
tracer,
exhibiting
a
strong
correlation
smallest
deviation
from
theoretical
line,
signifying
its
optimal
suitability
precise
source
apportionment.
This
study
offers
novel
insights
into
impacts
contributes
fostering
harmonious
balance
human
activities
resource
sustainability.
Little
is
known
about
the
electron
shuttle
ability
of
dissolved
organic
matter
(DOM)
and
its
effects
on
arsenic
(As)
mobilization,
which
makes
underlying
mechanism
groundwater
As
enrichment
elusive.
In
this
study,
both
electrochemical
properties
molecular
compositions
DOM
in
high
were
quantified
Hetao
Basin,
China.
We
found
that,
along
flow
path,
average
electron-transferring
capacity
(ETC)
DOM,
including
capacities
electron-accepting
electron-donating,
continuously
increased
from
2.85
to
3.59
mmole-/gC
with
concentrations.
The
increasing
ETC
reflected
an
increase
DOM.
Furthermore,
was
mainly
attributed
recalcitrant
compounds
especially
CHOS
CHONS
formulas
highly
unsaturated
structures
oxygen
(HUSHO)
CHO
CHON
aromatic
(AS).
significantly
positive
correlation
between
concentration
indicated
that
promoted
through
shuttling
for
inducing
reductive
dissolution
As-containing
Fe(III)
oxide
minerals,
further
supported
by
our
culture
experiments
showing
goethite
more
reduced
[133
μM
Fe(II)]
presence
a
higher
(3.35
mmole-/gC)
as
than
[65.2
relatively
lower
(2.41
mmole-/gC).
Our
study
highlights
AS
have
ability,
promoting
groundwater.
