18 The Strontium and Barium Content of Sea Water N E I L R. A N D E R S E N Research and Development Department, Naval Oceanographic Office, Washington, D . C .
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DAVID N . H U M E Massachusetts Institute of Technology, Cambridge, Mass.
The strontium and barium analyses of sea water are reported. Concentrations of these elements in sea water were simultaneously determined by a combination of ion exchange concentration and flame photometry to ascertain more precisely strontium/chlorinity and barium/chlorinity ratios and to investigate the magnitude and nature of the strontium/chlorinity ratio variation if it was found. The results of the analyses of several ocean stations presented indicate that there is a small (ca. 3%) but statistically significant variation in the strontium/chlorinity ratio with respect to depth in sea water. An indication of a possible variation in the absolute amounts of strontium in sea water with the geographical location has also been observed. The barium/chlorinity ratio variation with respect to depth was found to be much larger (ca. 90%) than that of strontium.
T
here have been several reports on studies of the determinations of the strontium (2, 4, 5, 6, 8,10,12,14,17,19, 20, 23) and barium (7, 8, 9, 11,22) concentrations of sea water and the resulting calculated strontium/ chlorinity and barium/chlorinity ratios. The samples analyzed were from numerous geographical locations and depths, with the pretreatment and methods of analysis of the samples not always being similar. The ma jority of the reports concerning strontium distributions indicate a con stant strontium/chlorinity ratio with respect to depth and geographical location within the limits of experimental error of the methods used. The range of the values for this ratio which have been reported most recently 296
Baker; Trace Inorganics In Water Advances in Chemistry; American Chemical Society: Washington, DC, 1968.
18.
A N D E R S E N
A N D
Strontium and Barium
H U M E
297
is from 4.4 χ ΙΟ" (20) to 4.8 Χ Ι Ο (JO) in units of (mg.-at. Sr/kg.) (Clo/oo)' with the absolute amount of strontium varying from 6.2 to 8.6 p.p.m. (JO). Several other investigators on the other hand, have re ported large variations in the strontium/chlorinity ratio of sea water (4, 5,17, 19, 20). The range of the ratio in these reports is from 3.33 X 10" (4, 5) to 5.8 Χ 10" (17) i n units of (mg.-at. Sr/kg.) (CI o/oo)" with the absolute amounts of strontium varying from 5.77 (4, 5) to 10.0 p.p.m. (17). 3
3
1
Downloaded by UNIV LAVAL on May 16, 2016 | http://pubs.acs.org Publication Date: June 1, 1968 | doi: 10.1021/ba-1968-0073.ch018
3
3
1
The results of the studies on the barium concentration of sea water have conversely, clearly demonstrated the existence of a variation in the barium/chlorinity ratio. Prior to 1966 very few analyses of the barium concentration of sea water had been reported. Turekian and Johnson (22) have recently reported the results of over 250 determinations of the barium concentration of sea water. The average values reported for the barium content of 24 samples from the Atlantic Ocean, the area which is of concern in the present investigation, range from 9 to 30 p.p.b. The present authors have recently described (1,2) the development of an accurate and precise analytical method using ion-exchange concen tration and flame photometry to measure the strontium and barium con centration of sea water from the same sample. Initial analyses indicated that there is possibly a small, but significant, variation in the strontium/ chlorinity ratio with respect to depth (2, 3). The results of the analyses for barium indicated that, as expected, the variation in the barium/ chlorinity ratio is much larger. This communication reports the results of the analyses of samples from several ocean stations for strontium and barium. Experimental Methods and Results Water samples taken at sea by standard techniques were placed i n polypropylene bottles containing sufficient distilled hydrochloric acid to make the final p H 3.0. Prior to analysis, the stored samples were filtered through Millipore membrane filters type HA(0.45/A). One liter samples were then passed through a 35 X 13 cm. borosilicate glass column con taining 35 grams of Dowex 50 X 12 (200-400 mesh) cation exchange resin in the calcium form. A n extensive description of the analytical methods utilized for isolating the strontium and barium fractions and their determinations by flame photometry has been given (2) and w i l l not be dealt with in length here. T o measure the precision of the method, six replicates of 1.000 liter sea water samples were analyzed for strontium and barium following the recommended procedure (2). The mean strontium value obtained was 6.57 p.p.m. with a standard deviation of 0.03 p.p.m. and that for barium was 11.3 p.p.b. with a standard deviation of 0.5 p.p.b. The accuracy of the method with respect to strontium was measured by adding 6.50 mgms. of strontium as "Specpure" strontium carbonate
Baker; Trace Inorganics In Water Advances in Chemistry; American Chemical Society: Washington, DC, 1968.
298
T R A C E
I N O R G A N I C S
I N
W A T E R
Downloaded by UNIV LAVAL on May 16, 2016 | http://pubs.acs.org Publication Date: June 1, 1968 | doi: 10.1021/ba-1968-0073.ch018
(1 p.p.m. barium) to nine 1.000 liter samples of the same sea water used for replication. The mean recovery of the strontium was 6.51 p.p.m. with a standard deviation of 0.05 p.p.m. The accuracy of the method with respect to barium was measured b y adding 46.4/igms. of barium as "Specpure" barium carbonate (1 p.p.m. strontium) to 1.000 liter samples of sea water which showed no detectable levels of barium when analyzed by this method. The mean recovery of the barium was 46.8 p.p.b. with a standard deviation of 0.6 p.p.b. These results correspond to experi mental variations i n the strontium/chlorinity and barium/chlorinity ratios of ± 0 . 0 3 and ± 0 . 3 respectively in the units previously noted. Tables I - V I contain the data obtained from the strontium and barium of two ocean stations from the North Atlantic and four ocean stations from the Atlantic Equatorial region. Table III also has included Table I.
Depth Meters 1
a
Data Taken 7-IX-64 at 4 1 ° 3 3 ' N ; 5 0 0 3 ' W , A T L A N T I S II; Cruise 13, Station 428
Temp. °C. 16.1
0/00
Sr p.p.m.
18.407
6.11
Sr/Cl X J0" mg.-at./kg.
Chlorinity
a
Ba/Cl X J0"« Ba mg.-at./kg. p.p.b. 0/00
s
0/00
6.8
3.79
2.7
49
5.50
18.504
6.42
3.96
9.4
3.7
96
4.82
18.991
6.70
4.03
15.2
5.8
281
4.39
19.257
6.40
3.79
22.8
8.6
489
4.50
19.333
6.36
3.75
1.8
0.7
786
4.23
19.352
6.35
3.74
8.6
3.2
1006
3.91
19.344
6.47
3.82
5.3
2.0
2098
3.33
19.358
6.37
3.76
16.2
6.1
References 3, 4, 5.
Table II.
Depth Meters
Data Taken 20-IX-64 at 4 1 ° 3 3 ' N ; 2 9 4 3 ' W , A T L A N T I S II; Cruise 13; Station 430
Temp. °C.
0
0/00
Sr p.p.m.
Sr/Cl X JO" mg.-at./kg.
Chlorinity
a
0/00
3
Ba/Cl X JO"* Ba mg.-at./kg. p.p.b. 0/00 3.5
20.6
19.912
6.46
3.70
9.7
53
15.50
19.905
6.41
3.67
3.1
1.2
93
14.38
19.882
6.61
3.79
12.9
4.7
292
12.93
19.778
6.72
3.87
3.3
1.2
487
11.71
19.679
6.61
3.83
4.7
1.7
10.66 7.64
19.621
6.88
4.00
