Groundwater Nitrate Distributions and Denitrification in...

Groundwater Nitrate Distributions and Denitrification in a Portion of the Abbotsford-Sumas Aquifer, Northwest Washington

Robert Mitchell, Leslie McKee & Scott Babcock

Abbotsford-Sumas Aquifer

The aquifer covers approximately 200 km2 and serves as a water supply for approximately 110,000 people in BC and WA.

∆ N S

BC WA

15 - 25 m

1 - 10 m

Sumas Outwash

Glacial Marine Drift

Abbotsford-Sumas Aquifer

The aquifer is unconfined and comprised of glacial outwash sands and gravels (Sumas Outwash) deposited about 10,000 years ago.

The groundwater flows from north to south in the aquifer at an rate of about 1 to 5 meters per day (Cox and Kahle, 1999).

Frasier and Nooksack Lowlands

Land use on the aquifer is dominated by agriculture because the surface soils are productive

The lowlands over the aquifer are agriculturally productive

Abbotsford

Sumas

Lynden

BC, Canada

Whatcom County, WA

Study area



Whatcom County’s Raspberry Industry is # 1 in the Nation

Abbotsford

Sumas

Lynden

BC, Canada

Whatcom County, WA

Whatcom County’s Dairy Industry is # 2 in the State (~60,000 cows)

Study area



Southern British Columbia is dominated by Raspberry and Poultry Industries

Abbotsford

Sumas

Lynden

BC, Canada

Whatcom County, WA

Study area

N S

∆

BC, Canada Whatcom County, WA

Problem

Elevated nitrate concentrations (> 10 mg N/L) occur in the aquifer due to

shallow water table

heavy rain

agricultural land use

permeable soils

BC WA

Our Objectives at

• Quantify nitrate concentrations and distributions in a study site adjacent to the International border.

• Attempt to distinguish BC nitrate sources from sources in Washington.

Monitor groundwater quality using shallow and deep domestic wells.

Measure nitrogen isotope values as a means to identify nitrogen sources.

Monitor surface-water quality in perennial streams.

Funding provided by the Washington State Department of Ecology (Centennial Clean Water Fund).

Study Area

~ 6 sq miles

PANGBORN RD

HALVERSTIC RD

VAN

BU

REN

RD

HALVERSTIC RD

Judson Lake

Pangbor Lake

JN5

JN4JN3JN2

JN1

PB5

PB4PB3

PB2PB1

V9

T1P3

V6V5

V4

V1

H8H6H5H2

H1

V10

K1

V8

V7

V3

V2T2

P2

H7H4H3

V12

BC3BC6

BC5BC4

±0 0.5 1 1.50.25

Miles

0 0.7 1.4 2.10.35Kilometers

Legend

Deep Wells

Shallow Wells

Stream Sampling Sites

Streams

CANADA

UNITE STATES

Study Area

26 wells

10 surface-water sites

Domestic wells were sampled monthly for 2 years

Surface Water was Sampled Bi-Monthly for 2 years

Nitrogen Isotopes were measured quarterly for 2 years

Water Quality Parameters were measured at the Institute for Watershed Studies Water-Quality Lab

Nitrogen Isotopes were measured at the Colorado Plateau Stable Isotope Laboratory, Northern Arizona University

Numerous factors may influence a nitrate concentration measured at well, including:

nitrate originating in BC

vadose zone thickness and residence time

well depth below the water table

up-gradient nutrient loading (timings and types)

seasonal precipitation and irrigation

vertical and lateral mixing due to intermingling plumes

mixing due to excessive well pumping

nitrate recirculation due to irrigation, and

denitrification (especially due to peat deposits in the area).

Judson Lake

Pangbor Lake

V9

T1

P3

V6V5

V4

V1

H8H6H5H2

H1

V10

K1

V8

V7

V3

V2T2

P2

H7H4H3

V12

V11

BC3BC6

BC5BC4

PANGBORN RD

HALVERSTIC RD

VAN

BU

RE

N R

D

HALVERSTIC RD

±0 0.5 1 1.50.25

Miles

0 0.7 1.4 2.10.35Kilometers

Legend

3

3 - 10

10 - 15

15 - 20

20

Shallo Wells

Deep Wells

Rasp

blueberry

corn

grass

nuts

pasture

Crop Typ (2003)Nitrate m N/L

CANADA

UNITE STATES

Nitrate Results (7/02 to 6/04)

21 out of 26 wells had median nitrate values > 3 mg-N/L

14 out of 26 wells had median nitrate values > 10 mg-N/L (> EPA MCL)

Shallow wells had higher values then deeper wells, highest value was 43 mg-N/L

H1

H2

H3

H4

H5

H6

H7

H8 K1 P1 P2 P3 T1 T2 V1 V

10V

11V

12 V2 V3 V4 V5 V6 V7 V8 V9

0

10

20

30

40N

itrat

e+N

itrite

(mgN

/L)

EPA MCL (10 mgN/L)

shallow wellsdeep wells (> 25 ft)

(< 25 ft)

0 10 20 30 40

010

2030

40

Total Nitrogen (mgN/L)

Nitr

ate+

Nitr

ite (m

gN/L

)

tau = 0.95pvalue <2.2e16

Judson Lake

Pangbor Lake

V9

T1

P3

V6V5

V4

V1

H8H6H5H2

H1

V10

K1

V8

V7

V3

V2T2

P2

H7H4H3

V12

V11

BC3BC6

BC5BC4

PANGBORN RD

HALVERSTIC RD

VAN

BU

RE

N R

D

HALVERSTIC RD

±0 0.5 1 1.50.25

Miles

0 0.7 1.4 2.10.35Kilometers

Legend

3

3 - 10

10 - 15

15 - 20

20

Shallo Wells

Deep Wells

Rasp

blueberry

corn

grass

nuts

pasture

Crop Typ (2003)Nitrate m N/L

CANADA

UNITE STATES

Nitrate Results (7/02 to 6/04)

Nitrate concentrationswere higher in wells north of PangbornLake and Creek

12 out of 15 wells had median nitrate values > 10 mg-N/L

Lower values at V7, V10 and V12 are likely due to denitrification.

•Judson Lake

Study Area

Pangborn Bog

BCWA

H-3

V-9

H-4

V-8

Wells near the border are likely receivinggroundwater and (nitrate) from BC

Deep Wells Near the Border

0

5

10

15

20

25

30

35

Mar-02 May-02 Aug-02 Nov-02 Jan-03 Apr-03 Jul-03 Sep-03 Dec-03 Mar-04 May-04 Aug-04

Time (months)

Nitr

ate

Con

cent

ratio

n (m

g-N

/L)

H3 H4 V8 V9

MCL

•Judson Lake

Study Area

Pangborn Bog

BC

WA

H-3

V-9

H-4

V-8

BC3BC4

BC5

BC6

The nitrate concentrations measured in BC wells are similar in magnitude to bordering WA wells

BC Wells Near the Border

0

5

10

15

20

25

30

35


Time (months)

Nitr

ate

Con

cent

ratio

n (m

g-N

/L)

BC3 BC4 BC5 BC6

MCL

Judson Lake

Study Area

Pangborn Bog

BCWA

T-1

V-5V-6

H-7

Shallow wells in the study area had the highest nitrate concentrations due to a combination of BC and Whatcom County sources

Shallow Wells in the Study Area

0

5

10

15

20

25

30

35

40

45


Time (months)

Nitr

ate

Con

cent

ratio

n (m

g-N

/L)

H7 T1 V5 V6

MCL

Shallow Wells in the Study Area

0

5

10

15

20

25

30

35

40

45


Time (months)

Nitr

ate

Con

cent

ratio

n (m

g-N

/L)

H7 T1 V5 V6

MCL

Judson Lake

Study Area

Pangborn Bog

BCWA

K-1

P-1

P-2

P-3

Wells south of Pangborn Bog and the creek had low nitrate concentrations due to denitrification in the organic-rich peat

Wells South of Pangborn Bog

0

5

10

15

20

25

30

35

31-May-02 19-Aug-02 8-Nov-02 27-Jan-03 17-Apr-03 6-Jul-03 24-Sep-03 13-Dec-03 2-Mar-04 21-May-04

Time (months)

Nitr

ate

Con

cent

ratio

n (m

g-N

/L)

K1 P1 P2 P3

MCL

PANGBORN RD

HALVERSTIC RD

VAN

BU

REN

RD

HALVERSTIC RD

Judson Lake

Pangbor Lake

±0 0.5 1 1.50.25

Miles

0 0.5 1 1.50.25Kilometers

CANADA

UNITE STATES

LegendSoil Type

PUGET

SKIPOPA

SUMA S

TERRI MEDISAPR ISTS

TR OMP

WATER

WH ATCO M

PANGBORN

PANGBORN VARIANT

BRISCOT

CAGEY

EVER ETT

HALE

HISTOSOLS

KICKER VILLE

LABO UNTY

LAXT ON

ORIDIA

Soils Map(peat is blue)

Peat has excellent denitrification potential

N S∆

denitrification

peat


N S∆

denitrification

• high organic content

peat


N S∆

denitrification


• reducing conditions

peat


N S∆

denitrification



• iron and manganese

peat


N S∆

denitrification



• iron and manganese

• nitrate input

peat

Denitrification Evidence

N S∆

denitrification

• low nitrate concentrations

• low DO (< 1 mg N/L)

• enriched δ15N values (> 12 0/00)

• high ammonia (> 100 µg/L)

• excess N2 gas (2 to 10 mg/L)

nitrate 10 – 30 mg N/L

nitrate 0 – 10 mg N/L

peat

∆ N S

It is likely that peat occurs at various depths due to multiple glacial phases during the Sumas Stade

BC WA

Denitrification

Indicators such as low DO, high metals, and/or enriched δ15N values suggest denitrification at a variety of wells.

0 10 20 30 40

02

46

810

12

Nitrate+Nitrite (mgN/L)

YS

I Dis

solv

ed O

xyge

n (m

g/L,

fiel

d m

eter

)

tau = 0.36pvalue <2.2e16

N S

∆

Nitrate Concentration Stratification

The nitrate concentrations are higher near the water table because it’s closer to the surface sources (median of 15.7 mg N/L).

BC WA

Lower concentrations occur deeper in the aquifer because of mixing and dilution (median of 11.3 mg N/L).

PANGBORN RD

HALVERSTIC RD

VAN

BU

REN

RD

HALVERSTIC RD

Judson Lake

Pangbor Lake

JN5

JN4JN3JN2

JN1

PB5

PB4PB3

PB2PB1

V9

T1P3

V6V5

V4

V1

H8H6H5H2

H1

V10

K1

V8

V7

V3

V2T2

P2

H7H4H3

V12

BC3BC6

BC5BC4

±0 0.5 1 1.50.25

Miles

0 0.7 1.4 2.10.35Kilometers

Legend

Deep Wells

Shallow Wells


Streams

CANADA

UNITE STATES

Study Area

05

1015

Site T2

Nitr

ate+

Nitr

ite (m

gN/L

)

2Jul2002 1Jan2003 2Jul2003 1Jan2004 1Jul2004

Nitrate+NitriteDepth


2025

3035

40

Dep

th to

Wat

er (f

t)

irrigation well50 feet below the water table

05

1015

Site T2

Nitr

ate+

Nitr

ite (m

gN/L

)


Nitrate+NitriteDepth


2025

3035

40

Dep

th to

Wat

er (f

t)

irrigation well50 feet below the water table

static water level

drawdown

Judson Lake

Pangbor Lake

V9

T1

P3

V6V5

V4

V1

H8H6H5H2H1

V10

PANGBORN RD

HALVERSTIC RD

VAN

BU

RE

N R

D

HALVERSTIC RD

K1

V8V7

V3

V2T2

P2P1

H7H4H3

V12

±0 0.5 1 1.50.25

Miles

0 0.7 1.4 2.10.35Kilometers

Legend

Shallo Wells

Deep Wells

Rasp

blueberry

corn

grass

nuts

pasture

Crop Type (2003)

2

2 - 8

8 - 12

12

d 15 N 0/00

CANADA

UNITE STATES

Nitrogen Isotope values (δ15N) indicate animal N sources and mixed animal and commercial N sources.

Nitrogen Isotope Results (7/02 to 6/04)

H1

H2

H3

H4

H5

H6

H7

H8 K1 P1

P2

P3 T1 T2 V1

V10

V11

V12 V3

V4

V5

V6

V7

V8

V9

0

5

10

15

20

25

30N

itrog

en Is

otop

e R

atio(

δ15N

,‰)

shallow wellsdeep wells

inorganic N source

organic N source

mixed N sources

Judson Lake

Pangbor Lake

JN5

JN4JN3

JN2

JN1

PB5

PB4PB3

PB2PB1PANGBORN RD

HALVERSTIC RD

VAN

BU

REN

RD

HALVERSTIC RD

±0 0.4 0.8 1.20.2

Miles

0 0.7 1.4 2.10.35Kilometers


Legend

CANADA

UNITE STATES

3

3 - 10

10 - 15

15 - 20

20

Nitrate m N/LRasp

blueberry

corn

grass

nuts

pasture

Crop Typ (2003)

Study Area – Surface Water

JN1 JN2 JN3 JN4 JN5 PB1 PB2 PB3 PB4 PB5

510

15

Nitr

ate+

Nitr

ite (m

gN/L

)

5 10 15

510

15

Total Nitrogen (mgN/L)

Nitr

ate+

Nitr

ite (m

gN/L

)

tau = 0.86pvalue < 2.2e16


050

100

150

200

250

300

Am

mon

ia(µ

gN/L

)

Study Area – Surface Water

Judson Lake

Pangbor Lake

JN5

JN4JN3

JN2

JN1

PB5

PB4PB3

PB2PB1PANGBORN RD

HALVERSTIC RD

VAN

BU

REN

RD

HALVERSTIC RD

±0 0.4 0.8 1.20.2

Miles

0 0.7 1.4 2.10.35Kilometers


Legend

CANADA

UNITE STATES

3

3 - 10

10 - 15

15 - 20

20

Nitrate m N/LRasp

blueberry

corn

grass

nuts

pasture

Crop Typ (2003)

V4

02

46

810

YS

I Dis

solv

ed O

xyge

n (m

g/L,

fiel

d m

eter)

2Jul2002 2Jul2003 1Jul2004

V4PB4

05

1015

Nitr

ate+

Nitr

ite (m

gN/L

)

2Jul2002 2Jul2003 1Jul2004

V4PB4

050

100

Am

mon

ia (u

gN/L

)

2Jul2002 2Jul2003 1Jul2004

V4PB4

02

46

810

12

Chl

orid

e (m

g/L)

2Jul2002 2Jul2003 1Jul2004

V4PB4


89

1011

12

Nitr

ogen

Isot

ope

Rat

io(δ15

N,‰

)

organic N source


510

5010

050

050

00

Feca

l Col

iform

s (c

fu/1

00m

l)

Conclusions

• Nitrate concentrations remain high in both surface water and groundwater in the study area.

• Nitrate concentrations transported across the border from BC range from about 10 to 25 mg-N/L and reflect a mix of manure and inorganic N sources.

• Nitrate concentrations in shallow wells in Washington range fromabout 15 to 35 mg-N/L and correlate to a combination of BC and local N sources.

• Denitrification is occurring in the peat in Pangborn Bog resulting in lower nitrate concentrations south of the bog.

• Denitrification is also occurring at other isolated locations.

Resulting Works

Mitchell, R. and others, Abbotsford-Sumas Water Quality: Draft Final Report (http://kula.geol.wwu.edu/rjmitch/absum.html).

McKee, L. Denitrification along Pangborn Creek in the Abbotsford-Sumas Aquifer, Washington. M.S. Thesis, Western Washington University, Bellingham, WA, 2004.

Burton, M. Correlations between surface processes and groundwater nitrate concentrations in Northwestern Whatcom County, Washington. M.S. Thesis, Western Washington University, Bellingham, WA (expected 2006).

1113

15

Site H1

Nitr

ate+

Nitr

ite (m

gN/L

)


1113

15

Site H2

Nitr

ate+

Nitr

ite (m

gN/L

)


1011

12

Site H3

Nitr

ate+

Nitr

ite (m

gN/L

)


1011

1213

14

Site H4

Nitr

ate+

Nitr

ite (m

gN/L

)


910

1112

13

Site H5

Nitr

ate+

Nitr

ite (m

gN/L

)


1520

2530

35

Site H6N

itrat

e+N

itrite

(mgN

/L)


1020

3040

Site H7

Nitr

ate+

Nitr

ite (m

gN/L

)


1315

1719

Site H8

Nitr

ate+

Nitr

ite (m

gN/L

)


68

10

Site K1

Nitr

ate+

Nitr

ite (m

gN/L

)


67

89

Site P1

Nitr

ate+

Nitr

ite (m

gN/L

)


3.0

4.0

5.0

Site P2

Nitr

ate+

Nitr

ite (m

gN/L

)


510

1520

Site P3N

itrat

e+N

itrite

(mgN

/L)


1618

2022

Site T1

Nitr

ate+

Nitr

ite (m

gN/L

)


68

1014

Site T2

Nitr

ate+

Nitr

ite (m

gN/L

)


2.0

3.0

4.0

Site V1

Nitr

ate+

Nitr

ite (m

gN/L

)


0.00

0.04

0.08

Site V2

Nitr

ate+

Nitr

ite (m

gN/L

)


2.0

2.5

3.0

Site V3

Nitr

ate+

Nitr

ite (m

gN/L

)


510

15Site V4

Nitr

ate+

Nitr

ite (m

gN/L

)


05

1525

Site V5

Nitr

ate+

Nitr

ite (m

gN/L

)


1418

2226

Site V6

Nitr

ate+

Nitr

ite (m

gN/L

)


12

34

56

Site V7

Nitr

ate+

Nitr

ite (m

gN/L

)


1416

1820

Site V8

Nitr

ate+

Nitr

ite (m

gN/L

)


1618

2022

Site V9

Nitr

ate+

Nitr

ite (m

gN/L

)


78

910

Site V10N

itrat

e+N

itrite

(mgN

/L)


23

45

6

Site V11

Nitr

ate+

Nitr

ite (m

gN/L

)


0.2

0.4

0.6

Site V12

Nitr

ate+

Nitr

ite (m

gN/L

)


1416

1820

2224

26

Site BC3

Nitr

ate+

Nitr

ite (m

gN/L

)

2Jul2002 2Jul2003 1Jul2004

46

810

1214

Site BC4

Nitr

ate+

Nitr

ite (m

gN/L

)

2Jul2002 2Jul2003 1Jul2004

810

1418

22

Site BC5

Nitr

ate+

Nitr

ite (m

gN/L

)

2Jul2002 2Jul2003 1Jul2004

2022

2426

Site BC6

Nitr

ate+

Nitr

ite (m

gN/L

)

2Jul2002 2Jul2003 1Jul2004

D1 D2 D3 H5 K1 P1 P2 P3 S1 S2 S3 V4

0.0

e+00

5.0

e+06

1.0

e+07

1.5

e+07

2.0

e+07

Site

Sul

fate

Pea

k

Date post:	18-May-2018
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Groundwater Nitrate Distributions and Denitrification in...

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