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publications > paper > PP 1403-G > ground-water movement > movement based on natural isotopes
Hydrogeology, Ground-Water Movement, and Subsurface Storage in the Floridan Aquifer System in Southern Florida
By Frederick W. Meyer
Professional Paper 1403-G
Ground-Water Movement in the Floridan Aquifer System in Southern Florida: Ground-Water Movement Based on Natural Isotopes as Tracers
Naturally occurring isotopes of carbon and uranium in samples of ground water from the Floridan aquifer system at nine sites in southeastern Florida were compared with those in modern seawater (table 4) to assess their potential as tracers of ground-water movement. Carbon isotopes were determined in 20 samples and uranium isotopes in 9 samples. Included are data on chloride and dissolved solids concentrations, which also were compared with concentrations in present-day seawater. Tritium was determined in selected samples to evaluate possible contamination of the sample by modern water. Oxygen isotopes were determined in 12 samples to assess their usefulness as climate indicators.
Table 4. Summary of isotope analyses of selected water samples from the Floridan aquifer system, southeastern Florida, 1971-83
[Site locations shown in fig. 2. Dashes indicate no data]
County: B, Broward; D, Dade; M, Martin; PB, Palm Beach; STL, St. Lucie.
3H tritium: Values in picocuries per liter.
 13C: 13C/12C stable isotope ratio of sample with respect to that of the standard (Pee Dee Belemnita).
R: Relative activity of sample with respect to standard x 100.
d14C: Millesimal difference with respect to standard.
D14C: Millesimal difference normalized for isotopic fractionation.
PMC: Percent of modern carbon (normalized).
Apparent age: Years before present (1950), in Libby years.
AR: 234U/238U alpha-activity ratio.
18O: 18O/16O stable isotope ratio of sample with respect to that of standard mean ocean water.
Laboratory: GS , U.S. Geological Survey; UM, University of Miami ; FS, Florida State University Geology Department. |
| |
in milligrams
per liter |
|
Site
No. |
County |
Local
well
No. |
Depth
(feet) |
Date
of
sample |
Chloride |
Dissolved
solids |
3H
tritium |
13C
(per mil) |
R
(percent) |
| 3 |
PB |
PB-1141 |
2,914 - 3,163 |
6/29/76 |
19,000 |
36,100 |
-- |
-- |
-- |
| 5 |
STL |
STL-255 |
898 - 1,268 |
2/4/83 |
1,700 |
3,240 |
-- |
-3.3 |
<0.19 |
| |
|
|
1,610 - 1,663 |
2/23/83 |
530 |
1,280 |
-- |
+4.3 |
<.04 |
| |
|
STL-254 |
2,715 - 3,418 |
11/2/82 |
20,000 |
35,300 |
-- |
-1.3 |
19.7 |
| 6 |
M |
M-1034 |
1,990 - 2,980 |
6/6/74 |
20,000 |
36,500 |
-- |
-- |
-- |
| 7 |
PB |
PB-965 |
3,025 - 3,680 |
5/30/77 |
21,000 |
37,400 |
-- |
-- |
-- |
| 8 |
B |
G-2292 |
2,046 - 3,278 |
3/29/74 |
20,000 |
35,900 |
-- |
-- |
-- |
| 9 |
B |
G-2331 |
2,532 - 2,705 |
10/21/81 |
21,00 |
37,200 |
0 |
-4.2 |
1 <.72 |
| |
|
|
1,008 - 1,072 |
10/21/81 |
3,400 |
6,490 |
-- |
-2.4 |
3.1 |
| |
|
|
2,532 - 2,705 |
12/16/82 |
20,000 |
37,500 |
-- |
-1.7 |
1 1.17 |
| |
|
G-2333 |
2,800 - 3,525 |
4/28/83 |
21,000 |
37,500 |
-- |
-2.4 |
65.9 |
| 10 |
B |
G-2296 |
895 - 934 |
10/18/80 |
1,200 |
2,670 |
-- |
-- |
1 17.5 |
| |
|
|
2,463 - 2,811 |
3/3/81 |
19,500 |
38,800 |
0 |
-3.8 |
1 30.3 |
| |
|
|
1,433 - 1,618 |
3/7/81 |
1,800 |
3,640 |
0 |
-1.6 |
4.7 |
| |
|
|
895 - 1,249 |
3/8/81 |
760 |
1,930 |
3 |
-2.6 |
5.8 |
| |
|
|
895 - 1,124 |
3/9/81 |
850 |
2,000 |
0 |
-2.4 |
4.7 |
| |
|
|
2 895 - 2,811 |
10/19/81 |
1,100 |
2,400 |
-- |
-1.2 |
11.9 |
| |
|
|
811 - 816 |
10/19/81 |
1,600 |
3,500 |
-- |
-1.8 |
7.3 |
| |
|
|
2,500 - 2,811 |
10/19/81 |
22,700 |
36,700 |
0 |
-3.7 |
1 7.6 |
| |
|
|
2,520 - 2,811 |
7/7/83 |
19,000 |
37,800 |
-- |
-2.1 |
38.9 |
| 12 |
D |
I-2 |
1,280 - 1,300 |
7/7/71 |
1,960 |
-- |
-- |
-- |
5.6 |
| |
|
|
1,902 - 1,922 |
7/9/71 |
4,740 |
-- |
-- |
-- |
4.3 |
| 14 |
D |
MDWSI - 5 |
2,746 - 3,200 |
12/19/79 |
19,400 |
38,300 |
-- |
-- |
-- |
| |
|
MDWSBZ-1 |
1,005 - 1,037 |
10/22/81 |
1,400 |
2,890 |
-- |
-3.9 |
6.8 |
| |
|
|
2,689 - 2,960 |
10/22/81 |
19,000 |
37,900 |
0 |
-5.3 |
41.2 |
| |
| Gulfstream seawater3 |
19,300 |
35,800 |
12 |
+0.5e |
|
Site
No. |
Local
well
No. |
d14C
(per mil) |
D14C
(per mil) |
PMC
(percent) |
Apparent
age |
AR |
U (uranium)
(micrograms
per liter) |
18O
(per mil) |
Laboratory |
| 3 |
PB-1141 |
-- |
-- |
-- |
-- |
1.24 |
2.0 |
-- |
FS |
| 5 |
STL-255 |
-998.1 |
-998.2 |
<0.18 |
>49,900 |
-- |
-- |
-- |
UM |
| |
|
-999.6 |
-999.6 |
<.04 |
>55,000 |
-- |
-- |
-- |
UM |
| |
STL-254 |
-803 |
-812.3 |
18.8 |
13,400 |
1.26 |
7.97 |
-- |
UM,FS |
| 6 |
M-1034 |
-- |
-- |
-- |
-- |
1.50 |
.45 |
-- |
FS |
| 7 |
PB-965 |
-- |
-- |
-- |
-- |
1.21 |
1.42 |
-- |
FS |
| 8 |
G-2292 |
-- |
-- |
-- |
-- |
1.15 |
3.42 |
-- |
FS |
| 9 |
G-2331 |
-992.8 |
-993.1 |
<.69 |
40,000 |
-- |
-- |
+0.2 |
GS |
| |
|
-969 |
-970.4 |
3.0 |
28,200 |
-- |
-- |
-1.7 |
GS |
| |
|
-998.3 |
-998.8 |
1.12 |
36,100 |
2.08 |
.244 |
-- |
UM,FS |
| |
G-2333 |
-341 |
-370.8 |
62.9 |
3,700 |
1.14 |
3.04 |
-- |
UM,FS |
| 10 |
G-2296 |
-825 |
-833e |
1 16.7e |
14,400 |
-- |
-- |
-2.2 |
GS |
| |
|
-697 |
-709.8 |
29 |
9,900 |
-- |
-- |
-.3 |
GS |
| |
|
-953 |
-955.2 |
4.5 |
24,900 |
-- |
-- |
-2.3 |
GS |
| |
|
-942 |
-944.6 |
5.5 |
23,300 |
-- |
-- |
-2.6 |
GS |
| |
|
-953 |
-955.1 |
4.5 |
24,900 |
-- |
-- |
-2.6 |
GS |
| |
|
-881 |
-886.7 |
11.3 |
17,500 |
-- |
-- |
-2.2 |
GS |
| |
|
-927 |
-930.4 |
7.1 |
21,200 |
-- |
-- |
-1.8 |
GS |
| |
|
-924 |
-927.2 |
<7.3 |
>21,000 |
-- |
-- |
-.2 |
GS |
| |
|
-611 |
-628.8 |
37.1 |
8,000 |
1.20 |
2.44 |
-- |
UM,FS |
| 12 |
I-2 |
-944 |
-946.6e |
5.4 |
23,400 |
-- |
-- |
-- |
GS |
| |
|
-957 |
-959e |
4.1e |
25,700 |
-- |
-- |
-- |
GS |
| 14 |
MDWSI-5 |
-- |
-- |
-- |
--- |
1.22 |
2.50 |
-- |
FS |
| |
MDWSBZ-1 |
-932 |
-934.9 |
6.5 |
22,000 |
-- |
-- |
-2.3 |
GS |
| |
|
-588 |
-604.2 |
39.6 |
7,400 |
-- |
-- |
+1.2 |
GS |
| |
| Gulfstream seawater3 |
-60e |
94e |
500 |
1.14 |
3.30 |
+0.8e |
|
1 Probably contaminated.
2 Probably represents zone 895 to 1,160 feet.
3 Estimated from Stuiver and Ostlund, 1980.
e = estimated. |
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