1. Using
nitrate
δ15N
and
δ18O
values
to
iden6fy
poten6al
sources
of
nutrient
inputs
to
a
highly
impacted
inlet
in
South
Puget
Sound,
Washington
Yvonne
Wetzig1,
Jackie
Perkins2,
Liz
Roepke2,
Kena
Fox-­‐Dobbs2
1University
of
Puget
Sound,
Chemistry
Department,
Tacoma,
WA
USA
2University
of
Puget
Sound,
Geology
Department,
Tacoma,
WA
USA
Research
QuesLons
Q1:
Do
surface
and
deep
inlet
marine
water
samples
have
different
NO3
concentraLons,
δ15NNO3
values,
and
δ18ONO3
values?
Do
NO3
concentraLons
and
isotopic
values
change
with
distance
into
the
inlet?
Q2:
Can
we
detect
anthropogenic
nitrogen
sources
in
freshwater
sources
around
the
inlet?
Q3:
Do
the
δ15NNO3
and
δ18ONO3
values
of
inlet
samples
provide
insight
into
water
quality
issues?
References
CascioW
KL,
Sigman
DM,
Galanter
HasLngs
M,
Bahlke
JK,
Hilkert
A.
2002.
Measurement
of
the
oxygen
isotopic
composiLon
of
nitrate
in
seawater
and
freshwater
using
the
denitrifier
method.
Analy'cal
Chemistry
74:
4905-­‐4912.
DeGasperi
C.
2008.
EPA
Grant
ApplicaLon:
Targeted
Watershed
Grants
2008
Puget
Sound
IniLaLve
-­‐
Quartermaster
Harbor
Nitrogen
Management
Study.
HasLngs
MG,
CascioW
KL,
Elliod,
EM.
2013.
Stable
isotopes
as
tracers
of
anthropogenic
nitrogen
sources,
deposiLon,
and
impacts.
Elements
9:
339-­‐344.
Kendall
C,
Elliod
EM,
and
Wankel
SD.
2007.
Tracing
anthropogenic
inputs
of
nitrogen
to
ecosystems,
Chapter
12,
In:
R.H.
Michener
and
K.
Lajtha
(Eds.),
Stable
Isotopes
in
Ecology
and
Environmental
Science,
2nd
ediLon,
Blackwell
Publishing,
p.
375-­‐449.
King
County.
2014.
Quartermaster
Harbor
Nitrogen
Management
Study:
Final
Study
Report.
Prepared
by
C.
DeGasperi,
Water
and
Land
Resources
Division.
Seadle,
Washington.
Sigman
DM,
CascioW
KL,
Andreani
M,
Barford
C,
Galanter
M,
Bahlke
JK.
2001.
A
bacterial
method
for
the
nitrogen
isotopic
analysis
of
nitrate
in
seawater
and
freshwater.
Analy'cal
Chemistry
73:
4145-­‐4153.
1867
U.S.
Coast
Survey
Chart
or
Map
of
Puget
Sound,
Washington
-­‐
Geographicus
-­‐
PugetSound-­‐uscs-­‐1867"
by
United
States
Coast
Survey
-­‐
Report
of
the
Superintendent
of
the
United
States
Coast
Survey,
(Washington)
Licensed
under
Public
domain
via
Wikimedia
Commons.
Judd
Creek
Buoy
#52
Buoy
#53
Buoy
#54
Buoy
#55
Buoy
#56
Mileta
Creek
Backbay
Creek
Well
Acknowledgements
Our
greatest
thanks
must
be
given
to:
our
professor,
Kena
Fox-­‐Dobbs,
for
her
guidance
throughout
our
project;
Anne
Fetrow,
for
her
feedback
on
this
poster;
the
IsoLab
at
the
University
of
Washington
for
all
analyLcal
work;
Joel
Elliot
and
the
UPS
Biology
department
for
providing
a
boat
for
sample
collecLon;
the
kind
resident
who
allowed
us
to
sample
their
well
water;
and
the
kind
resident
who
allowed
us
to
sample
creek
water
on
their
property.
This
work
was
supported
by
the
UPS
Geology
Department
McMillin
Fund,
and
UPS
University
Enrichment
Commidee
Conference
Travel
Grants
to
JW
and
KFD.
*Note:
The
NO3
concentra'ons
of
the
two
samples
taken
from
Backbay
Creek
are
indis'nguishable
from
a
blank
standard,
so
their
isotopic
data
were
omiGed.
Study
Area
• Quartermaster
Harbor
(QMH)
is
a
hydrologically
restricted
inlet
on
Vashon
Island
in
Puget
Sound
surrounded
by
residenLal,
agricultural,
and
open
spaces
• The
inlet
depth
ranges
from
5
meters
(inner
QMH)
to
45
meters
(outer
QMH)
• Nutrient
loading
and
limited
circulaLon
in
the
inlet
is
related
to
environmental
issues
including
poor
water
quality
and
annual
toxic
algal
blooms,
which
contribute
to
fish
kills
and
shellfish
contaminaLon.
Sampling
and
Analysis
• 15
samples
collected
from
3
creeks,
5
buoys
in
the
inlet,
and
1
well.
• Creek
water
samples
from
outlets
of
Judd,
Mileta,
and
Backbay
Creeks.
• Two
inlet
water
samples
from
each
buoy,
one
at
depth
(just
above
Figure
4:
CollecLng
a
creek
sample.
Study
Area
0
75
150
225
300
375
450
525
600
675
750
Judd
Mileta
Backbay,
upstream
Backbay,
downstream
Well
water
(85'
deep)
[NO3]
(µM)
0.0
5.0
10.0
15.0
20.0
25.0
0
2000
4000
6000
8000
10000
[NO3]
(µM)
Distance
into
Inlet
(m)
Buoy
52
shallow
Buoy
52
deep
Buoy
53
shallow
Buoy
53
deep
Buoy
54
shallow
Buoy
54
deep
Buoy
55
shallow
Buoy
55
deep
Buoy
56
shallow
Buoy
56
deep
[Deep
sample
trend]
0.0
2.0
4.0
6.0
8.0
10.0
0
2000
4000
6000
8000
10000
δ15NNO3
‰
Distance
into
Inlet
(m)
Buoy
52
shallow
Buoy
52
deep
Buoy
53
shallow
Buoy
53
deep
Buoy
54
shallow
Buoy
54
deep
Buoy
55
shallow
Buoy
55
deep
Buoy
56
shallow
Buoy
56
deep
[Deep
sample
trend]
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
-­‐5
0
5
10
15
20
δ18ONO3
‰
(VSMOW)
δ15NNO3
‰
(air
N2)
Buoy
52
shallow
Buoy
52
deep
Buoy
53
shallow
Buoy
53
deep
Buoy
54
shallow
Buoy
54
deep
Buoy
55
shallow
Buoy
55
deep
Buoy
56
shallow
Buoy
56
deep
Well
Water
Mileta
Creek
Judd
Creek
PotenLal
sepLc
contribuLon
to
well
water
Shallow
marine
samples
from
the
the
innermost
inlet
buoys.
Streams
have
similar
NO3
-­‐
source
SepLc
Soil/Marine
Terrestrial
Marine/FerLlizer
Q2:
Mileta
Creek,
which
has
high
[NO3],
is
isotopically
very
similar
to
Judd
Creek.
Neither
creek
have
isotopic
values
that
suggest
an
anthropogenic
NO3
source.
The
well
water
has
moderate
[NO3]
and
isotopic
values
that
may
reflect
sepLc
leakage.
Q1:
The
larger
difference
in
[NO3]
and
δ15NNO3
values
of
deep
and
shallow
samples
at
inner
vs.
outer
inlet
buoys
reflects
differences
in
biological
use
and
sources
of
NO3.
The
consistent
δ15NNO3
values
of
deep
inlet
samples
may
be
due
to
relaLvely
constant
groundwater
recharge
or
marine
contribuLon.
The
correlaLon
between
between
shallow
[NO3]
and
δ15NNO3
values
and
distance
into
the
harbor
suggests
linear
change
in
nutrient
condiLons
(vs.
stepwise
or
threshold)
Q3:
All
deep
and
some
shallow
marine
samples
have
similar
NO3
source(s).
The
two
shallow
marine
samples
furthest
into
the
harbor
likely
reflect
the
influence
of
anthropogenic
source(s).
EPA
Maximum
Contaminant
Level
Background
• Manure,
ferLlizers,
sepLc
waste,
atmosphere,
and
nitrogen
fixing
plants
are
all
possible
major
sources
of
nitrate
in
this
inlet
and
surrounding
freshwater
sources.
• Nitrogen
and
oxygen
stable
isotope
analysis
of
nitrate
can
be
used
to
idenLfy
anthropogenic
and
natural
sources,
via
the
systems’
unique
isotopic
signatures.
• Nitrate
can
enter
the
inlet
through
mulLple
freshwater
sources,
Figure
8.
Nitrate
concentraLons
in
fresh
water
samples
(streams
and
well),
and
the
EPA’s
limit
of
water
considered
safe
for
drinking.
Figure
9.
Isotopic
data
ploded
relaLve
to
esLmated
values
of
possible
nitrate
sources.
Figure
6.
Nitrate
concentraLon
in
marine
samples
ploded
vs.
distance
into
inlet.
Figure
7.
δ15NNO3
values
of
marine
samples
ploded
vs.
distance
into
inlet.
Figure
2.
Sign
posted
at
Dockton
Park
on
the
waterfront
of
Quartermaster
Harbor.
some
of
which
provide
drinking
__.water
for
local
residents.
• The
unique
bathymetry
of
the
inlet
inhibits
water
circulaLon
between
the
inner
and
outer
regions,
allowing
a
greater
residency
of
pollutants.
• EPA
has
set
the
maximum
contaminant
level
for
nitrate
in
drinking
water
to
be
10mg/L
(~160µM).
Figure
3.
SchemaLc
representaLon
of
nitrate
inputs
into
Quartermaster
Harbor,
including
groundwater
seepage,
surface
stream
runoff,
sepLc
system
leakage,
and
natural
and
syntheLc
ferLlizer
runoff,
and
marine
influx.
Figure
5:
Sample
locaLons
in
the
study
area
(inset
of
fig.
1
map).
sediment
interface)
and
one
at
the
water
surface.
• Well
water
from
an
organic
farm
next
to
Backbay
Creek.
• Samples
were
frozen
and
analyzed
at
the
University
of
Washington
IsoLab
for
[NO3],
δ15NNO3
and
δ18ONO3
values
via
the
bacterial
denitrifier
method.
Findings
and
InterpretaLons
Figure
1
.
Map
of
western
Washington
and
study
area.