Transcript Slide 1

Nitrate Sourcing and
Ground Water Age
for the Springs of
Merritt’s Mill Pond
Kevin DeFosset
NWFWMD
HISTORICAL NITRATE CONCENTRATIONS
JACKSON BLUE SPRING
4.0
3.5
Nitrate (mg/L)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
1/1/1960
1/1/1970
1/1/1980
1/1/1990
1/1/2000
DISCHARGE MEASURMENTS
JACKSON BLUE – SPRING CREEK
200
39%
180
160
46%
Discharge (cfs)
140
28%
120
100
19%
18%
80
11%
24%
60
40
20
0
Spring Creek ds Hwy 90
Jackson Blue Spring
Merritt's Mill Pond
July 2007 Discharge Measurements
Measurement
Section
Discharge (cfs)
Spring Crk ds Hwy 90
56.0
Jackson Blue
39.1
Merritt's Mill Pond
16.9
Shangri-La
3.9
Twin Caves
1.6
Hole in the Wall
1.3
Heidi Hole
0.2
Gator Hole
0.9
Springs Total
7.9
Merritt's Mill Pond
16.9
Springs Discharge
7.9
Miscellaneous Discharge
9
RECENT NITRATE CONCENTRATIONS
MERRITT’S MILL POND SPRING
4.5
4.0
3.5
Nitrate (mg/L)
3.0
Jackson Blue
Shangri-La
2.5
Twin Caves
Hole in the Wall
2.0
Heidi Hole
1.5
Gator Hole
1.0
0.5
0.0
1/1/06
1/1/07
1/1/08
1/1/09
Magnesium, Barium, and Strontium Concentrations
Merritt’s Mill Pond
7
6
Jackson Blue
5
Shangri-La
4
Twin Caves
3
Hole in the Wall
2
Heidi Hole
1
Gator Hole
0
1/1/06
1/1/07
1/1/08
1/1/09
Ba Concentration (µg/L)
14
12
Jackson Blue
10
Shangri-La
8
Twin Caves
6
Hole in the Wall
4
Heidi Hole
2
Gator Hole
0
1/1/06
1/1/07
1/1/08
1/1/09
90
Sr Concentration (µg/L)
Mg Concentration (mg/L)
8
80
Jackson Blue
70
Shangri-La
60
Twin Caves
50
Hole in the Wall
40
Heidi Hole
30
Gator Hole
20
1/1/06
1/1/07
1/1/08
1/1/09
Range of Nitrogen Isotope Values for
Inorganic and Organic Nitrogen Sources
NO3 Concentrations vs. Delta 15N-NO3
12
Nitrate associated with manure
spreading and waste disposal
Delta N-15, 0/00
10
8
6
Nitrate associated with
artificial fertilizer use
4
Heidi Hole
Gator Hole
Twin Caves
Hole in the Wall
2
Jackson Blue
Shangri-La
0
0
1
2
3
Nitrate Concentration (mg/L)
4
5
Range of Nitrogen Isotope Values for
Inorganic and Organic Nitrogen Sources
NO3 Concentrations vs. Delta 15N-NO3
12
Nitrate associated with manure
spreading and waste disposal
Delta N-15, 0/00
10
8
Merritts Mill Pond
6
Nitrate associated with
artificial fertilizer use
1st Magnitude
Middle Suwannee River
4
Sante Fe River
2
0
0
1
2
3
4
Nitrate Concentration (mg/L)
5
6
SF6 age
Dating Ground Water with SF6
3H/3He
• Stable, atmospheric gas
• Primarily of anthropogenic origin
• Record of atmospheric input over time
Dating Ground Water with Tritium and Helium
Jackson Blue
16.5
18.8
32.8
Shangri-La
16.5
11.2
11.6
Twin Caves
17.3
Modern
44
• Tritium results from atmospheric nuclear bomb testing
• Record of atmospheric input over time
Hole in the Wall
14
Modern 46.4
Heidi Hole
18
15.5
31.5
Gator Hole
9
Modern
>55
• Helium is decay product and helps to refine age
• Atmospheric gases (N, Ar, Kr, Xe, Ne, He) needed for
age determination.
What can be said?
• Based on available data, ground water sources other than
Jackson Blue Spring contribute between 11 and 46 percent
of the discharge of Merritt’s Mill Pond.
• Elevated levels of nitrate exist at all springs in Merritt’s Mill Pond.
• Artificial fertilizer is the predominate source of nitrate
for the springs of Merritt’s Mill Pond.
• The waters feeding Merritt’s Mill Pond are of mixed age.
COMPARISON OF
HYDROLOGIC
CONDITIONS
EARLY 2008 – CURRENT
DISCHARGE, cfs
(USGS Gaging Station)
Date
Measurement
Value
2/1/2008
50
1/12/2009
114
2/1/2008
79
WATER LEVEL, ft msl
(NWFWMD Monitoring Well) 12/12/2008
84