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Republiek van Suid-Afrika Republic of South Aftica
DEPARTEMENT VAN MYNWESE DEPARTMENT OF MINES
Annale van die Geologiese OpnalDe Annals of the Geologieal Su.evey
Jaargang Volulne 1~ 1962
,17 FE B 1965
Kopiereg . voorbehou Copyright reserved
Gedruk deur en verkrygbaar van die Staatsdrukker, Bosmanstraat, Pretoria. Printed by and obtainable from the Government Printer, Bosman Street, Pretoria.
INHOUD - CONTENTS
BLADSY PAGE
VOORWOORD-PREFACE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Deel I-Part I I. KORT GESKIEDENIS.................................................. 1
n. HUIDIGE ORGANISASIE............................................... 10
Ill. VERSLAG OOR DIE WERK GEDURENDE 1962 VERRIG.............. 17 A. INLElDING............................................................ 17 B. BYWONING VAN KONFERENSIES.......................................... 19 C. VERTEENWOORDIGING IN EN SAMEWERKING MET ANDER WETENSKAPLIKE
ORGANISASIES.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 D. ALGEMENE GEOLOGIE.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 E. NON-ORGANIC MINERALS....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 F. BRANDSTOWWE....................................................... 34 G. UNDERGROUND WATER.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 H. GEOFISIKA............................................................ 42 1. INGENIEURSGEOLOGIE................................................... 43 J. PALAEONTOLOGy...................................................... 45 K. NUCLEAR RAw MATERIALS........................ .... ................ 46 L. LABORATORIUM....................................................... 48 M. WORKSHOP.. . . . .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 N. MUSEUM............................................................. 50 O. DRAWING-OFFICE...................................................... 51 P. INLIGTlNG EN PUBLIKASIES.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Q. BIBLIOTEEKAANGELEENTHEDE............................................ 55 R. HUISHOUDELIKE KOMlTEES..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Deel 2-Part 2
"The Geology along the Lower Reaches of the Molopo River and a Note on the Riemvasmaak Thermal Spring, Gordonia District, Cape Province ", by J. W. von Backstrom. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
"The Relationship between the Pretoria Series and the Bushveld Igneous Complex Northeast of Pretoria ", by F. J. Coertze.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
" Markers in the Lower Griquatown Stage near Kuruman, Cape Province ", by L. N. J. Engelbrecht. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
" A Cryptovolcanic Structure on Hatzium Il 28, South West Africa ", by D. C. Heath and D. K. Toerien. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
" Plaaslike Plooiing in die Serie Dwyka naby Lichtenburg, Wes-Transvaal ", deur J. W. von Backstrom... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
"A Petrographic Description of the Ecca Sediments in the Southeru Karroo and Eastern Orange Free State ", by H. J. Nel.. ......................... ',' . . . . . . . . 91
" The Relationship between Solid Geology and Oesophageal Cancer Distribution in the Transkei ", by J. A. H. Marais and E. F. R. Drewcs,........................ 105
v
BLADSY PAGE
"Fluor-spar Deposits on Pyp Klip West and Wit Vlei, Kenhardt District, Cape Province ", by P. J. Hugo.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
" Wollastonite near Garies, Namaqualand ", by D. H. de Jagerand W. Simpson... . . 127
" Zircon, Ilmenite and Monazite Occurrences on Bulls Run Estate, North-northwest of Eshowe, Natal ", by J. W. von Backstrom.......................... .. ...... 137
" Voorkomste van Kalsiet in die Omgewing van Mopane en Waterpoort, Distrik Soutpansberg, Transvaal ", deur D. P. Wilke.. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . 147
" Notes on an Algal Problem Encountered at Certain Salt-pans in the Dealesville Area, Orange Free State ", by C. B. Coetzee... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
" Metallogenic Provinces and Maps-A First Approach ", by D. W. Bishopp... . . . . . 163
"Die Warmbron Klein-Tshipise in Noord-Transvaal ", deur L. E. Kent............. 169
"Warm and Cold Springs on Richmond, Pilgrim's Rest District, Transvaal ", by L. E. Kent and D. Groeneveld... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
"Thermal Springs on Driefontein 317 KR, North of Naboomspruit, Potgietersrus District, Transvaal ", by J. W. von Backstrom... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
" Warmbronne in die Omgewing van Venterstad, Kaapprovinsie ", deur D. J. L. Visser 189
" The Chemical Composition of the Water of the Orange River at Vioolsdrif, Cape Province ", by P. R. de Villiers.... .................................... ...... 197
" Waarnemings op Soutpanne met die Elektriese Weerstandapparaat in die Omgewing van Prieska, Kaapprovinsie ", deur F. W. Schumann. . . . . . . . . . . . . . . . . . . . . . . . . . . 209
"Locating Zones of Weathering and Fracturing by the Electromagnetic Techniqne Using a Long Earthed Cable ", by J. R. Vegter................. ... .. .. ........ 219
" Die Korrelasie van Sones in die Btage Onder-Griekwastad met Behulp van Elektriese Boorgatmetings ", deur S. B. de Villiers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
" A Contact Electrode System for Electrical Bore-hole Logging ", by G. Krol and J. F. Gordon-Welsh............ .......................... .. ...... .......... 235
" Hammer-electrode Unit for Electrical Resistivity Surveys ", by M. J. Steyn. . . . . . . . 239
"The Response of a Torsion-type Magnetometer during Regional Magnetometric Surveys ", by R. J. Kleywegt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
" Reasons for Repeated Breaks in an Irrigation Canal, Olifants River Irrigation Scheme, Cape Province ", by J. W. von Backstrom.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
" An Albian Astacurid from Zululand ", by E. C. N. van Hoepen.. . . . . . . . . . . . . . . . . 253
" Two Problematic Fossils from the Transvaal System ", by S. H. Haughton... . . . . . . 257
" The Occurrence of Fish Remains in the Witteberg-Dwyka Transition Zone", by J. N. Theron. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
INDEX............................. ................. ....................... 269
VI
The the
Chemical Composition of the Water· of Cape Province Orange River at Vioolsdrif,
by
P. R. DE VllLlERS, M.Se.
ABSTRACT South Africa was invited to participate in a world-wide program to obtain quantitative
data on the dissolved chemical substances the major river-systems of the world carry to the oceans.
Samples of water from the Orange River were taken at Vioolsdrif, approximately 60 miles from the mouth of the river, by the Department of Water Affairs at fortnightly intervals from September 1958 to November 1959.
The Soils Research Institute, Department of Agricultural Technical Services, analysed the samples for the major constituents. Residues obtained by evaporation in a platinum dish were submitted to the Geological Survey for spectrographic de terminations of the trace elements. As far as is known, no trace elements in river water have previously been determined in this country.
The results indicated that a daily average of approximately 3200 short tons of dissolved solids passed the sampling point and that the dissolved solids were at their maximum when the flow was at its minimum. For comparative purposes figures for the Vaal River, taken over the same period, are given.
The dissolved solids of the Orange River consist mainly of bicarbonates of calcium and magnesium, and sodium chloride.
The macroconstituents are SiO" Ca, Mg, Na, CO" SO, and Cl and the microconstituents are Ba, Sr, Rb, Li, Fe, Mn, AI, Cu, Pb, Ag, Bi, V, Ni, Cr, F, NO, and K. The results of the determinations are given in tables and graphs.
INTRODUCTION
South Africa was invited to participate in a world-wide program to obtain quantitative data on the dissolved chemical. substances the major river-systems of the world carry to the oceans. As a result of a request from Professor Tison, General Secretary of the International Association of Hydrology of the International Union of Geodesy and Geophysics, samples of water from the Orange River were taken at Vioolsdrif, approximately 60 miles from the mouth of the river, by the Department of Water Affairs at fortnightly intervals from September 1958 to November 1959. The flow data are given in table 2.
The Soils Research Institute, Department of Agricultural Technical Services. analysed the samples for the major constituents and the methods used are indicated in the table. Residues obtained by evaporation in a platinum dish were submitted to the Geological Survey for spectrographic determinations of the trace elements. As far as is known. no trace elements in river water have previously been determined in this country.
198
The Orange River, with its main tributaries the Vaal and the Caledon, traverses virtually the whole South African succession from the Archaeozoic to Recent. The catchment covers about 313,200 square miles, i.e. 60 per cent of the Republic. The rainfall over the catchment varies from 80 inches per year in the east to only a few inches in the west, where near-desert conditions prevail.
In the Vaal River basin, mines, industries and sewage disposal contribute towards the chemical constituents of the water. In the Northern Cape, drainage from the various irrigation schemes is responsible for further mineral contamination. The quality of the water at Vioolsdrif must of necessity have been affected by these factors.
SPECTROCHEMICAL DETERMINATIONS
It is well known that different elements behave differently in the D.e. arc used for spectrographic determinations. Different methods have to be applied for determining volatile and involatile elements and alkali metals (Ahrens, 1954). Of the 69 elements listed by Professor Tison, only those shown in table 1 were detected.
The individual samples in powder form, brownish of colour, as received from the Soils Research Institute, weighed only from O· 2 to O· 5 grm. A composite sample was prepared from the 24 samples and the following trace elements were found:-
TABLE 1.-TRACE ELEMENTS FOUND IN COMPOSITE SAMPLE OF EVAPORATES
Elements
Volatile Ag, Cu, Bi, Pb ............................... . Involatile V, Al, Ni, Cr, Sr, Ba ....................... . Alkali metals Rb, Li.. ................................ . Other elements B ..................................... .
Internal standard used
In Pd Cs
During the individual determinations aluminium had to be grouped with the involatiles as the samples were too small for separate determinations. For the same reason boron could not be determined, although it was detected in the composite sample (say O· 005 p.p.m. water). Its sensitive lines fall outside the general wave-length range covering the other elements. Artificial standard samples, prepared from pure chemicals, were arced and working curves were drawn by means of which the final determinations were computed.
DISCUSSION OF RESULTS
To facilitate the interpretation of the results and to demonstrate the characteristics of the water from the Orange River, the results given in tables 2 and 3 are presented diagrammatically in folder 1. The values obtained at Vereeniging by the Rand Water Board on the corresponding days to those at Vioolsdrif are represented by the dotted curves in folder 1 for T.DS., pH, Ca and Mg. The various elements are grouped as suggested by Hem (1959, p. 153).
TABLE 2.-ANALYSES OF SAMPLES FROM THE ORANGE RIVER AT VlOOLSDRIF
, \ t ! ~ ~ 1\ I I I ' :~ ~ 1 ~ ~ I I . I "0 ! El El I I 2... 1 ,,,,,S< 18 I] 8 'I
"0 o .c '0 ~
i c: \ . 0 0 I i ~ 4) 1 c .~ () d ..c: .... 'I i ~ I 2 I 3 ...c: ...c: c: I c: .s .~ 't .9 t> ~ U IV t
. i .... Q I ro p.. 0.. 0 0 cIj c: E .....::l 25 . c: C c: (l) = ; Cl I ._._ c: ._ col "0
l,s ,s ,S-a"II':'A I':'A 8 8 7" \' ~ :'A 1:) i3 I § oC'B"'I~ go" u 1 I r/1 (/) CJ:l H ..... ro ro .... .... .... > - L (/) 8 iO 0
\
:::; ::3 ::I I Q) Q) ...-1 - .;:: .~ <U :- 0 .- () ..c: r/1__ i.DU 0 .,.. .,..,.,.. :> I:> .,.. .,.. f-< f-< :> ,;; U r:I <.>uol~P. @lj N
1 I I '-0 OD, C a <.> ~ . i ' =0 <U 'E IV 6 f/.l
f'l " '" " <.>
.S ~
£ Date 1 Si02 I Fe I Mn 'I Ca I Mg " ~a I K HCO, CO, SO. I Cl F NO, ~N al~,;;:, Z'" ::r: 1 I i ' Parts per ml!lhon parts water 1 >-<! 0-
19/9/58 1 17 ' 0 \' 0 I 34 12 20 I 2 174 0 1 22 21 ,25 1 0 I' 310 135 0 7·6 448 30/9/58 16 0 0 29 13 20 1 153 0 22 23 '25 I 0 310 125 3 7·2 127
17/10/58 11 0' 0 14 28 29 1 189 0 22 32'4 0 \ 380 150 0 7·0 606 31/10/58 9 0 0 10 32 37 1 195 0 26, 34'4 0 420 155 0 7·1 448 13/11/58 8 0 0 23 24 45' 1 207 0 34 I 39'4 0 460 155 0 7·8 74 1/12/58 19 ·65 ,5 16 \ 9 12 I 2 104, 0 i 0 1 7 ·35 0 1165 75 0 7·3 6,095
11/12/58 12 ·12 0 34 4 11' 3 116 0 26 I 14 ,3 ' 0 240 95 5 7,3 4,890 31/12/58 23 ·69 0 32 5 9 11 3 110' 0 11 19 12,'3 1 12 'I 215 90 10 7·9 I 9,414 15/1/59 19 I ·55 0 19 I 7 i 9 3 92 0 2 7 1'5 ' 0 165 75 0 7·2 4,890 2/2/59 18 I ·46 0, 20 7 i 7 2 92 0 5 7 I' 5 0 170 75 2 7, 6 1,682
15/4/59 30/4/59 12/5/59 19/5/59 25/5/59 8/6/59
20/7/59 1/8/59
15/8/59 ,31/8/59 14/9/59 30/9/59 '
20/10/59 9/11/59
'I I I I Four samplies lost I'in tran,sit 9 ·30 0 21 8 15 3 104 0 5 12' ,65 0 200 85 0 7·3
I 12 ·35 0 23 8 15 3 110 I 0 5 I 11 '65 0 190 90 0 7·2
, 19 I' ·23 0 16 9 8 2 I 98 0 10 1 5'6 9 145 75 0 7·7 I 24 ·23 0 20 6 8 2 1107 'I 0 5 I 7'8 3 160 75 0 6'4
17 '38 0 18 4 7 4 76 0 0 7·7 3 140 60 0 6·7 23 I ·30 ·70 16 6 8 2, 79 I o! 5 I 7 '8 12 11135 i 65 0 6·2
I Twol sampl es lost \in tran sit I 14 ·35 0 24 6 14 2 1'110 0 2 11 1'3 9' 175 ,85 0 7·9 12 ,45 0 22 8 13 2, 116 1 0 0 I 11'2 6 155 88 0 7·4 16·8 0 17 7 9 2 92 i 0 7 I 7 ·25 0 150 73 0 7·9 18·5 0 18 7 11 2 101 I 0 5 9 ·25 0 170 75 0 8'1 12·3 0 21 9 I 14 2 122 I 0 I 10 9'2 0, 200 90 0 7·6 12 ·75 0 22 9 I 16 2 131 0 I 5 12'2 0 \225 I 90 0 8·1 14·4 0' 25 13 17 1 113 0 14 14 ·15 3 210 92 22 7·8 10·2 0 I 25 12 I 19 1 113 1 0 ,12 18 ,15, 0 220 92 18 7·8
Analysts: P. T. Viljoen and N. A. van der Wait, Soils Research Institute, Pretoria.
1,682 996
41,493 7,330
101,420 22,360
3,122 11,001 4,890 3,428 1,682
606 3,122 9,414
-\0 \0
TABLE 3.-RESULTS OF SPECTROCHEMICAL DETERMINATIONS ON SAMPLES FROM THE ORANGE RIVER AT VIOOLSDRIF
Date
19/9/58 ............. . 30/9/58 ............. .
17/10/58 ............. . 31/10/58 ............. . 13/11/58 ............. . 1/12/58 ............. .
11/12/58 ............. . 31/12/58 ............. . 15/1/59 ............. . 2/2/59 ............. .
15/4/59 ............. . 30/4/59 ............. . 12/5/59 ............. . 19/5/59 ............. . 25/5/59 ............. . 8/6/59 ............. .
20/7/59 ............. . 1/8/59 ............. .
15/8/59 ............. . 31/8/59 ............. . 14/9/59 ............. . 30/9/59 ............. .
20/10/59 ............. . 9/11/59 ............. .
Ba
·056 ·028 '062 ·051 ·06 ·017 ·031 ·027 ·024 ·04
·03 ·014 ·018 ·026 ·015 ·01
·012 ·016 ·023 ·02 ·013 ·027 ·017 n.d.
Sr
'54 '26 ·36 '73 ·18 '15 ·14 '163 ·088 '14
·107 ·16 ·08 ·09 ·09 ·01
·01 ·12 ·07 ·09 '09 ·18 ·16 n.d.
Rb
·09 ·05 ·03 ·15 .]3 ·01 ·03 ·013 ·03 ·025
·07 ·04 ·04 ·06 n.d. ·008
·01 ·009 ·04 ·008 ·01 ·01 ·009 '01
Li
·2 ·04 '054 ·027 ·29 '016 ·015 ·014 ·026 '02
n.d. '01 ·03 ·10 n.d. ·002
·01 ·001 ·1 ·001 ·016 ·017 ·009 ·017
Determined by P. R. de Villiers, Geological Survey.
Al Cu Pb Ag Bi
Parts per million parts water
·11 ·26 ·42 ·16
3·6 ·04 ·14 ·34
1·06 1·08
·5 ·67
1·03 1·06
·036 ·35
·11 ·18 ·15
1·1 ·12 n.d. ·189 n.d.
·005 ·012 ·015 ·005 ·005 ·004 ·006 ·003 ·007 ·007
·2 ·01 '015
1'36 ·015 ·008 ·001 b.d.I. ·001 ·002
·003 ·0009 '0002 ·0007 ·0003 '0003 '0004 b.d.!. ·0003 ·0003
Four sa mples los t in transiit
'002 ·002 ·004 b.d.I. ·0003 '0006 '0007 '001 ·0001 ·0006
·004 b.d.I. '0002 ·001 b.d.1. b.d.1. b.d.!. b.d.1. ·004 ·002 ·0006 ·0001 ·004 ·001 ·0003 ·0001 ·007 ·003 ·0003 b.d.I. ·0007 ·006 ·0001 '0001
Two sam pIes lost i n transit ·008 ·34 ·0002 ·004 . 007 b.d.!. ·004 ·002 ·0002 ·008 ·006 ·0005
. ·004 ·003 ·0004 ·004 b.d.1. b.d.1. ·004 ·001 ·0002 . 004 n.d. b.d.!.
·0001 ·001 ·0006 ·0004 ·001
b.d.I. ·001 n.d.
v
·002 '0002
b.d.1. b.d.I. ·004 '0001
b.d.1. ·006 ·0007 '0001
·0009 ,000, '0003 b.d.I. ·0001 b.d.!.
·0001 ·003 ·001
b.d.1. ·0007 '001 ·0001 n.d. I
Ni I Cr
b.d.!. b.d.!. b.d.I. ·001 b.d.1. ·0007
b.d.I. I b.d.!. ·0006 ·0003
'0006 b.d.1. ·0005 ·0001 b.d.!. b.d.!.
b.d.I. b.d.I. '0001
b.d.I. b.d.!. b.d.!. ·0007 n.d.
b.d.I. '0006 ·002 ·0006 ·004 ·0006 '0008 '001 ·0008 ·001
·0004 ·001 ·0009 ·001 ·0007 ·0004
b.d.1. '001 ·0009 .0006 ·0006 '001 ·001 n.d.
n.d. = Not determined-too little material b.d.!. = below detection limit. * Calculated from dionic conductivity (table 2).
!T.D.S.*
200 200 245 271 297 106 155 139 106 110
129 123 94
103 90 87
113 100 97
110 129 145 135 141
8
201
DISSOLVED SOLIDS
It is significant to note that during the dry season, when the flow was below 1000 cusecs, the concentration of dissolved solids was at its highest. The maximum concentrations were recorded from 19/9/58 to 13/11/58. From the generally inverse relationship which exists between the flow and dissolved solid concentration it may be assumed that the salts leached from the soil and rocks by run-off water were masked by dilution during the flood period. Note particularly the period from 30/4/59 to 8/6/59 when the concentration was less than 100 p.p.m. A noteworthy feature is that the concentration did not increase considerably after the floods had subsided, even when the flow dropped to less than 1000 cusecs on 30/9/59. This would indicate that the water of the Orange River passing the sampling point at Vioolsdrif does not carry appreciable dissolved mineral loads. Stander et al. (1962, p. 5) reported to the contrary in the case of the Vaal River at BothavilJe. Note the fluctuations of the dissolved solids of the Vaal River as in folder 1.
pH VALUE
It is significant that the pH dropped to less than 7 during the flood period 30/4/59 to 8/6/59 (see fold. 1). This is probably due to the diluting-effect of rainwater with a low pH.
From folder 1 it is noticeable that in the case of the Vaal the pH was not affected during the periods of flood.
SILICA
Next to oxygen, silicon is the most abundant element. The greater part of . the dissolved silica in water originates in the chemical breakdown of silicates during the processes of weathering and metamorphism. The process of serpentinisation, for example, yields silica and magnesium carbonate which may be dissolved in water. Although silica is an important constituent of most natural waters, it does not occur in the dissociated form, but probably in particles of sub colloidal size.
Goldschmidt (1954, p. 370) states that the presence of calcium bicarbonate reduces the solubility of silica in water. This inverse correlation between silica and calcium as well as T .D.S. is evident from folder 1.
THE ALKALINE-EARTH METALS (Ca, "Mg", Sr, Ba)
Calcium and magnesium are major constituents of all rock-types, whereas strontium and barium are common in rocks, although only as minor constituents.
The chemical properties of the individual members of the group are similar, and of these metal ions calcium is by far the most abundant constituent of natural water. Magnesium is the only other member of the group that is important in natural water and, with calcium, contributes to the hardness of water. This does not imply that they behave similarly towards water in all respects. Magnesium has a stronger tendency to remain in solution than does calcium; this is indicated by the higher concentration of magnesium in sea-water. Some calcium may, however, be removed from sea-water as the result of extraction by organisms (Hem, 1959, p. 79). In general, calcium seems to be more abundant in rocks and soil than magnesium and this accounts for the predominance of calcium in natural water (not sea-water). Note the inverse relationship of the calcium and magnesium concentrations on 31/10/58 (fold. 1).
202
Strontium and barium were detected in trace quantities and from folder 1 it is interesting to note that strontium is by far the more abundant, particularly when the flow was less than 1000 cusecs; also note the sympathetic behaviour of the plotted values for the two elements. Barium is more common than strontium in igneous rocks (Rankama and Sahama, 1949, p. 458), but the low solubility of barium sulphate accounts for the small quantities of barium in solution. Skougstad and Horr (1963, p. 55) state-analyses of samples from 75 major rivers of the United States of America show that the strontium concentration ranges from 0'007 to 13'7 p.p.m. The greatest strontium concentration in surface water occurs in the highsalinity streams of the southwest. In this area, characterised by relatively low annual rainfall. high evaporation rate. and low physical relief, the concentration of strontium in the streams is generally 2 to 3 times as great as in most other streams of the United States of America.
THE ALKALI METALS (Na, K, Rb, Li)
Sodium and potassium are among the main constituents of the lithosphere. Rubidium is one of the more abundant trace elements (Rankama and Sahama, 1949, p. 422), about the same as strontium. whereas lithium is relatively rare.
Of the alkali-metal group, sodium and potassium are the more abundant members in natural water with sodium predominating. Sodium tends to remain in solution when leached from rocks and soils. whereas potassium is easily absorbed by other products of weathering such as the clay minerals. Also, sodium feldspar decomposes more readily than potassium feldspar. All this may explain why sodium is by far the more abundant in natural water. Folder 1 demonstrates this predominance of sodium over potassium.
Discharge of sewage and industrial wastes may add sodium in large quantities to water.
Rubidium in trace quantities is a fairly common constituent of natural water. In the process of weathering rubidium resembles potassium in its behaviour and has an even greater tendency to be absorbed.
As already mentioned, lithium is comparatively rare. It is concentrated in lithium minerals in granite, syenite and pegmatite. In the Orange River water the concentration of lithium was less than O' 3 p.p.m., although in other areas concentrations of 1 to 5 p.p.m. were reported.
CHLORIDE, FLUORIDE AND NITRATE
Of these anions. chloride is the most common member and is present in all natural water. In surface streams it is usually present in lesser quantities than SO, or HCO,. Domestic sewage waste may add appreciable quantities of chlorine to water.
Unlike the chlorides. most fluorides are relatively low in solubility. Fluorine in appreciable quantities is found in phosphatic fertiliser and water draining from fertilised lands may contain relatively larger quantities of fluorine. Swaine (1962, p. 102) reports that phosphatic fertilisers commonly contain more than 1 per cent fluorine. This is evident from folder 1, where the higher values for fluorine coincide with the period of flood 15/4/59 to 8/6/59.
Nitrogen is present in relatively small quantities in igneous rocks, rainwater and the ocean. Riffenburg (1925. p. 31-56) reports the average content of nitrate in rain-water to be 0'2 p.p.m. Rankama and Sahama (1949. p. 313) reports
203
values of 0 to 6 p.p.m. in rain-water. Stander et al. (1962, p. 10) in table 5 reported 12 p.p.m. nitrates in mine effluent from the Reef, whereas in natural underground water of that area the nitrate content is nil. It is an essential part of organic matter and excessive growth of algae may be associated with increased nitrate concentrations. As the anomalous values of nitrate of the Orange River water coincide with the flood periods, it is concluded that the major source of this nitrate is from rain-water, fertilisers, sewage disposal and from explosives in mining areas. Nitrogen fertilisers that are commonly used are ammonium sulphate and ammonium nitrate.
THE HEAVY METALS
(Fe, Mn, AI, Cu, Pb, Bi, V, Ni, Cr)
These elements are mainly present in natural water as minor constituents. As iron may be present in the colloidal form and because of the possibility of contamination, it generally is not a good constituent on which to base geochemical interpretations of water analyses.
Manganese is much less abundant in rocks than iron and the concentration in natural water is generally much less than that of iron (normally less than o· 2 p.p.m.). The anomalous high values from the Orange River water on 1/12/58 and 8/6/59 coincide with flood periods and may therefore be from various sources. Swaine (1962, p. 150) reports values for manganese, from a trace to a few per cent in fertilisers.
AlLlmini!lm occurs in important quantities in rocks, but is highly resistant to removal by solution during weathering and is left behind in the insoluble residue. Consequently concentrations of more than 1 p.p.m. in natural water are not common. High concentrations of aluminium may be from industrial or mine wastes. The anomalous high value on 13 / 11 /58 is possibly erroneous. As already stated aluminium had to be grouped with the involatiles during the spectrochemical determinations owing to lack of sufficient material. Furthermore, aluminium in the blank graphite electrodes gave line density corresponding to values of O· 01 to 0·02 per cent when read off on the standard curves-also the distillation of aluminium was possibly affected because the samples were not burnt to completion for the purpose of suppressing the appearance of cyanogen bands.
In rocks copper occurs mainly as sulphides; during weathering they are oxidised and the copper may go into solution as a sulphate. It is thus a common trace constituent in natural water; large concentrations may be added by the discharge of mine water.
Lead is found in rocks mainly as the sulphide, galena, and as oxides, and by weathering and alteration it is extracted in more soluble compounds. Concentrations of 0·4 to O' 8 p.p.m. in natural water have been reported. This is important as 0·1 p.p.m. is the upper limit for drinking water in the standards adopted by the U.S. Public Health Service (1946). The high values (up to l' 3 p.p.m.) at Vioolsdrif coincide with the drier periods when the flow was less than 1000 cusecs.
Industrial and mine wastes may be responsible for the high values, but contamination may be from petrol fumes in the atmosphere, where the samples were analysed and also from fume cupboards, coated with paint containing lead.
204
According to Rankama and Sahama (1949, p. 738) bismuth is a very rare constituent in the upper lithosphere. Only minor traces were detected in the water from Vioolsdrif (see fold. 1).
The concentration of vanadium was very low at Vioolsdrif. The fluctuation may possibly be explained by pollution from industrial waste or from fertiliservanadium in small quantities has been reported in phosphatic fertiliser. Swaine (1962, p. 253) reports values for vanadium in fertilisers, ranging from a trace to a few thousand p.p.m.
Nickel is present in most igneous rocks in minor quantities being more common in basic types. During the process of weathering, it goes into insoluble minerals and any nickel in natural water is likely to be in minor quantities and possibly in the colloidal state. Folder 1 indicates only trace quantities in the Orange River water.
Chromium is amphoteric, and can thus exist in water in different states. In igneous rocks it is generally present only as a minor constituent but in basic and ultra basic types it is much more common. During the process of weathering chromium behaves like iron. Little chromium goes into solution and it can be expected in natural water as a trace constituent only (see fold. 1). The discharge of industrial waste may add chromium to the water in the oxidised form (chromate).
CONCLUSIONS
The dissolved solids in the Orange River water are generally at a maximum when the flow is at its minimum, since percolating ground-water which, as effluent seepage, is an important proportion of the low flow, will take up more mineral matter into solution than rapidly flowing run-off. The concentration of the dissolved solids is also increased by the higher rate of evaporation during periods of low flow when the river is shallow. (See fold. 1 for Ca, Mg, Na, Sr, Pb, CI and SO,.)
Taken over a period of 12 months approximately 1,200,000 short tons (weighted) of dissolved solids passed the sampling point at Vioolsdrif. Calculated to a daily figure this comes to approximately 3200 short tons. Over the same period of 12 months approximately 260,000 short tons (weighted) of dissolved solids passed the Barrage on the Vaal River near Vereeniging--<iaily this is approximately 700 short tons-this is 21 per cent of the dissolved solids at Vioolsdrif, whereas the flow at the Barrage is only 14 per cent of the flow at Vioolsdrif. According to Stander et al. (1962, p. 11), the average composition of the Vaal River water changes very little between the Barrage and Kimberley. Analyses of samples collected on the Orange River near Upington (kindly made available by the Department of Water Affairs) over the same period showed that there was little variation in the concentration of dissolved solids between Upington and Vioolsdrif.
However, it is beyond the scope of this paper to assess the exact mineral load of the water of the Orange River, or the specific origin of the various salts. The probable source of the mineral salts in the Vaal River is discussed by Stander et aI. (1962). According to them, drainage from the Witwatersrand and West Rand mining areas constitutes important sources of mineral salts. This additional load is derived mainly from the decomposition of the iron pyrites in the mine slimes dams and mine-dumps and the water is eventually acidified. It thus leaches mineral matter from formations and soils that contain for example carbonate.
205
TABLE 4.-AVERAGE PERCENTAGE COMPOSITION (BY WEIGHT) OF THE TOTAL DISSOLVED SOLIDS IN ORANGE RIVER WATER AT VIOOLSDRIF, ON THE AVERAGE MONTHLY FLOW OVER THE PERIOD 19/9/58 TO 9/11/59
Si02 ••••••••••••••••••••••••••••••••••••••••••••••••••
Ca .................................................... . Mg .................................................. . Na .................................................. . K ................................................... . CO •..................................................
. SO •................................................... CL .................................................. . F ........................................ ~ ........... . NO •.................................................. Ba ................................................... . Sr ................................................... . Rb .................................................. . Li ................................................... . Fe ................................................... . Mn .................................................. . Al. .................................................. . Cu ................................................... . Pb ................................................... . Ag .................... : .............................. . Bi. .................................................. . V .................................................... . Ni.. ................................................. . Cr ................................................... .
Per cent
12·68 13·60 5·90
10·08 1·68
38·82 (from HCO,) 5·38 7·96 0·39 2·42 0·018 0·106 0·027 0·027 0·270 0.052 0·485 0·0045 0·0587 0·0002 0·0002 0·0004 0·0003 0·0007
100·0000
The method by which the average percentage composition of the total dissolved solids in the Orange River water (table 4) was calculated is as follows:
(1) The mean p.p.m. for each ion were calculated for each month-in most cases 3 analyses were available save for the two periods, when samples were lost, when only 1 analysis was available.
(2) The mean p.p.m. per ion thus obtained were multiplied by the total flow for the month in question.
(3) The products (p.p.m. x flow) for each ion were summed and then divided by the sum of the total monthly flows over the whole sampling period. A weighted value for each ion was thus obtained.
(4) The percentages were calculated on the sum of all the items determined and not on the values for the total dissolved solids as calculated from the dionic conductivity. This was done as it was found that the weighted averages of the ions over the whole sampling period totalled 132·9 p.p.m., whereas the weighted T.D.S. calculated from the dionic conductivity were only 120·5 p.p.m. The discrepancy of 12·4 p.p.m. may be accounted for by colloidal silica (weighted average 16·3 p.p.m.).
It is evident from table 4 that the dissolved solids consist mainly of bicarbonates of calcium and magnesium, and sodium chloride, and that the hardness is essentially carbonate, i.e. temporary hardness. According to the classification of irrigation water based on the sodium percentage/dionic conductivity relationship (Wilcox, 1948, p. 6) the water of the Orange River may be described as "excellent to good".
206
As the samples for analysis were taken only at fortnightly intervals over a comparatively short period of 15 months, and as only one dip sample was taken in each case, a high order of accuracy cannot be claimed for the average percentages in table 4-nevertheless, it may serve as a general guide.
ACKNOWLEDGEMENTS
The writer wishes to express his appreciation and sincere thanks to the Secretary for Water Affairs, who was originally approached by Professor Tison, for kindly furnishing the flow measurements for the Orange and Vaal Rivers and also the results of the chemical analyses of the samples of the Orange River water and allowing them to be published; the Director of the Soils Research Institute for his permission to publish the analyses of the samples for the major constituents as determined by Messrs. N. A. van der Walt and P. T. Viljoen; the Rand Water Board for the chemical data on the Vaal River and Dr. Kent for his constructive criticism.
BIBLIOGRAPHY
AHRENS, L. H., 1954. Quantitative spectrochemical analysis of silicates: Pergamon Press, London.
GOLDSCHMIDT, V. M., 1954. Geochemistry: Oxford at the Clarendon Press. HEM, J. D., 1959. Study and interpretation of the chemical characteristics of natural water:
Wat.-Supp. Pap., geo!. Surv. U.S., 1473. MALAN, W. c., 1960. Survey of the Vaal bam catchment area Part 1: C.S.l.R. Res. Rep., 166. RANKAMA, K. and SAHAMA, T. H., 1949. Geochemistry: Univ. of Chicago Press. RIFFENBURG, H. B., 1925. Chemical character of ground waters of the northern Great Plains;
Wat.-Supp. Pap., geo!. Surv. U.S., 560-B. SKOUGSTAD, M. W. and HORR, C. A., 1963. Occurrence and distribution of strontium in
natural water: Wat.-Supp. Pap., geo!. Surv. U.S., 1496-D. STANDER, G. J., MALAN, W. C. and HENZEN, M. R., 1962. The chemical quality of the water
of the lower Vaal River between the Barrage and Kimberley; C.S.I.R. Spec. Rep., W.14 . . SWAINE, D. J., 1962. The trace-element content of fertilizers; Tech. Commun., Commonw.
Bur. Soils, Harpenden, 52. WILCOX, L. V., 1948. Circ. Dep. Agric. U.S., 784, May.
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