1960 1995 Ground Water Age and Chemistry Data along Flow Paths: Implications for Trends and Transformations of Nutrients and Pesticides Jim Tesoriero,

19601995

Ground Water Age and Chemistry Data along Flow Paths: Implications for Trends

and Transformations of Nutrients and PesticidesJim Tesoriero, Karen Burow, Betsy Frick, David Saad, Larry Puckett

U.S. Geological Survey

Increased influx of nutrients and pesticides Five-fold increase in nitrogen fertilizer applied since 1960

Commonly used herbicides introduced

What are the implications for ground water quality?

0

2

4

6

8

10

12

1940 1950 1960 1970 1980 1990 2000

Mil

lion

s of

Met

ric

Ton

s P

er Y

ear N Fertilizer

Atrazine Alachlor

Pesticides Introduced:

Metolachlor

NO3-→N2

Study Objectives: 1) Determine and explain trends in concentrations.

2) Determine where transformations occur.

19901990

1985 1980

19801975

1970

1950

2000

1960

1970

1. Determine recharge dates of ground water along flow pathsDesign:

2. Characterize water chemistry and natural attenuation 3. Compare constituent concentrations to loading history

Nutrient and Pesticide Application

Reactions

Redox Zone DO

NO3- or N2

IronAerobic Respiration:

O2 H2OOxic High NO3

- Low

Denitrification:

NO3- N2

Nitrate-reducing

Low NO3

- N2Low

Ferric Iron Reduction:

Fe3+ Fe2+

Iron-reducing

Low N2 High

Natural Attenuation: Redox Reactions Important in Determining Fate of Constituents

Water Chemistry

Western Lake Michigan Drainages

Wisconsin

Albemarle-Pamlico Basin

North Carolina

Apalachicola-Chattahoochee-

Flint River Basin

Georgia

Investigate the Influence of Hydrogeologic Setting on Contaminant Fate

Eastern San Joaquin Valley

California

Unsaturated Zone

Thin Thick

Oxic Zone

In

Ground Water

ThinNorth

Carolina------

Thick GeorgiaWisconsin California

•Nitrate concentrations are high but limited to upper few meters.

•Downstream impacts are limited by denitrification.

North Carolina: Nitrate Concentrations and Fate

OxicNitrate ReducingIron Reducing

10 mg/L

<1 mg/L

0

2

4

6

8

10

12

14

0 10 20 30 40 50

Ground Water Age (years)

Nit

rate

(as

N),

N2

fro

m

den

itri

f., D

isso

lved

Oxy

gen

(m

g/L

)

0.01

0.10

1.00

10.00

Iro

n (

mg

/L) Iron

N2 from denitrification

Nitrate

Diss.Oxygen

Use of Residence Times to Understand Chemical Evolution of Ground Water

Low Nitrate, High Denitrification

High Nitrate, No Denitrification

Low Nitrate, Low Denitrification

Wisconsin: Nitrate Concentrations and Fate

•High nitrate concentrations in top 10 m of saturated thickness.•Oxic conditions suggest significant downstream impacts on ground water and streams likely.

Oxic 8 mg/L8 mg/L

Larger Oxic Zone at Wisconsin Site is Due to Slower O2 Consumption Rates than at NC Site

0

2

4

6

8

10

0 10 20 30 40 50

Ground Water Age (years)

Dis

solv

ed O

xyge

n (m

g/L)

Wisconsin

North Carolina

0

2

4

6

8

0 10 20 30 40 50

Ground Water Age (years)

Dis

solv

ed O

2

Co

nsu

mp

tio

n (

mg

/L) NC: 0.36 mg O2/L per yr

WI: 0.18 mg O2/L

per yr

0

2

4

6

8

10

12

14

10 20 30 40 50 60

Recharge Nitrate Concentrations Increase From 1960 to 2000

1

10

100

10 20 30 40 50 60

Rec

har

ge

[NO

3- ] (m

g/L

as

N)

1950 1960 1970 1980 1990 2000

North Carolina

Note: 1) Independent variable in regression equations is years since 1940.

1950 1960 1970 1980 1990 2000

Wisconsin

R2=0.88 R2=0.33

Recharge Nitrate Concentrations =[NO3-]+[N2 from denitrification]

Rec

har

ge

[NO

3- ] (m

g/L

as

N)

Recharge Year Recharge Year

0

2

4

6

8

10

12

14

1950 1960 1970 1980 1990 2000

0

5

10

15

20

Nitrate Concentration Increases AreConsistent with Fertilizer and/or Manure Usage

1

10

100

1950 1960 1970 1980 1990 2000

0

5

10

15

20

25

30Wisconsin North Carolina

Nit

rog

en U

se (

kg

/acr

e)

Nit

rog

en U

se (

kg

/acr

e)

Fertilizer

Manure

[NO3-]

Rec

har

ge

[NO

3- ]

(mg

/L a

s N

)

Rec

har

ge

[NO

3- ]

(mg

/L a

s N

)

02468

101214

1950 1970 1990 2010

Nitrate Concentrations in Ground Water Explained by 30% of Fertilizer Applied

Wisconsin

30 % of applied N

Applied N dissolved in 21 cm of recharge applied to cropped area of county.

[NO3-]

in ground water

Rec

har

ge

[NO

3- ]

(mg

/L a

s N

)

Trends From This Study Agreewith Larger Spatial Study

1950 1960 1970 1980 1990 2000

Nit

rate

(m

g/L

as

N)

0

5

10

15

20

25

30

Land Use Study

Flow System Study

Pesticide Trends and Transformations

Relate atrazine concentrations to:

- crops planted in the county

- atrazine use rate Examine parent and degradate concentrations of

atrazine. Similar findings for metolachlor and alachlor and

their degradates.

Georgia: Land Use Changes Related to Increase and then Decrease in Atrazine + DEA?

1960 1970 1980 1990 2000

% o

f C

ou

nty

in C

orn

an

d S

oyb

ean

0

10

20

30

40

50

Atr

azin

e p

lus

Dee

thyl

atra

zin

e (

g/L

)

0.001

0.01

0.1

Atrazine+DEA

% Corn &Soybean

0.00

0.02

0.04

0.06

0.08

0.10

0.12

1950 1960 1970 1980 1990 2000

Atr

azin

e pl

us d

eeth

ylat

razi

ne

(g/

L)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Atr

azin

e U

se R

ate

(lbs

ai/a

cre)

AtrazineUse Rate

Atrazine + DEA

LocalLocalAtrazineAtrazineBanBan

Wisconsin:

-Atrazine or Deethylatrazine Found in All Samples

-Effects of Atrazine Ban Not Observed Yet

0 10 20 30 40 500.0

0.2

0.4

0.6

0.8

1.0

ACFB ALBE SANJ WMIC ALBE-AL

Ground Water Age (years)

Dee

thyl

atra

zin

e (D

EA

)M

ole

Fra

ctio

nDeethylatrazine Dominant at Sites with Thick Unsaturated

Zones but Not at Sites with Thin Unsaturated Zones-Suggests Degradation Occurs Primarily in the Unsaturated Zone

All Deethylatrazine

All Atrazine

DEA=Atrazine

Thick unsaturated zones

Thin unsaturated zones

Wisconsin California

North Carolina

Georgia

Summary

Coupling age dating with water chemistry data improves our understanding of:

•The Linkage Between Land Use Practices

and Water Quality

•Trends in Constituent Concentrations

•Transformation Rates of Constituents

Contact Information

Jim Tesoriero: [email protected] Karen Burow: [email protected] David Saad: [email protected] Elizabeth Frick: [email protected] Larry Puckett: [email protected]