1960 1995 ground water age and chemistry data along flow paths: implications for trends and...
TRANSCRIPT
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]