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Biogeochemical prospecting in the South-Eastern Desert of Egypt
Journal of Arid Environments(1994)28:257-264
Biogeochemical prospecting in the South-Eastern Desert of Egypt
M. Badri & I. S p r i n g u e l Faculty of Science in Aswan, Assiut University, Egypt (Received 4 November 1992, accepted 19 March 1993) The distribution of the nine metal elements in 20 desert plants was studied in order to detect the indicator value of these plants for mineral prospecting. The plants vary greatly in their ability to absorb and accumulate the elements and so the concentrations vary between species. Plants show a selective absorption of the elements. Selenium was only recorded in eight species, titanium in 11 species. Each species shows considerable variability in accumulation of the elements in different locations. The indicator capacity ofMaerua crassifolia,Zilla spinosa and Balanites aegyptiaca to the different elements is revealed.
Keywords: indicator geobotany; desert; Egypt; arid climates; desert plants; soil; mineral prospecting
Introduction Biogeochemical prospecting is an advanced method used in indicator geobotany which studies the relationship between plants and bedrock. Biogeochernical methods of prospecting depend on the chemical analysis of different elements in plants. Environmental variables, particularly climatic and pedogenic conditions, affect the concentration of trace elements in the plant tissue. Biogeochemical prospecting seems to be more powerful under arid climates which support sparse vegetation (Brooks, 1983) and poor development of the soil. Biogeochemical prospecting is widely used in mineral exploration in many countries. This work was reviewed by Brooks (1983), but few data were published on arid regions in Egypt, except for E1 Shazly et al. (1971), who used the twigs of Acacia trees in biogeochemical prospecting and Bogoch & Brenner (1984) who worked in similar habitats in Sinai. The South-Eastern Desert of Egypt, where the present study was conducted, is characterized by a hyper-arid climate (Ayyad & Ghabbour, 1986) and very special pedogenic conditions. Plant life is strictly confined to the wadis (dry desert river beds), a very special type of habitat where plants are in direct contact with geological features without an intermediate soil layer in which minerals usually undergo different biogeochemical changes. The present work was carried out in order to study the distribution of metal elements in 20 desert plants sampled in different parts of the desert and the inter-relationships of these elements in plant tissue and in situ. The study could help to detect the indicator value of desert plants for mineral prospecting.
0140-1963/94/030257 + 08 $08'00/0
(~) 1994AcademicPress Limited
31 °
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F i g u r e 1. Part of the Eastern Desert, lithological and location m a p (Limestone, [ ~ ; Sandstone, [ ] ; B a s e m e n t complex, Ii~; Recent, [ ] ) . T a b l e 1. The chemical concentration of 9 elements in Dysprosium Species
n
Mean
Capparisdecidua(Forssk.)Edgew AcaciaehrenbergianaHayne Balanitesaegyptiaca(L.)Del. Cassia italica Mill. Lain. ex Steud. CrotalariaaegyptiacaBenth. MaeruacrassifoliaForssk. OchradenusbaccatusDel. Panicum turgidum Forssk. Pergularia tomentosa L. Salsola baryosma (Roem. & Schult.) D a n d y Tamarixnilotica(Ehrenb.)Bunge Acacia tortilisH a y n e ZillaspinosaPrantl Acacia raddiana Savi Cleome droserifolia Del. Aervajavanica (Burro. f.) Spreng Fagonia indica B u r m . f. FarsetiaaegyptiaTurra Salvadorapersica L. Hyphaenethebaica(L.)Mart.
4 10 6 2 2 9 3 4 2 9 4 4 3 26 1 1 1 1 1 1
0"013 0'013 0"005 0'009 0"045 0"009 0"023 0"576 0-024 0"009 0"016 0"011 0"012 0"008 2"61 0"02 0"005 0"99 0"039 0"084
Analysis of variance ~' p <
0"05; ** p <
0"01; NS
S.D.
** = not significant.
0"003 0"015 0'008 0'013 0'007 0'018 0"008 0"569 0"033 0"01 0"018 0"01 0"015 0"017 -------
Scandium Mean
S.D.
0"01 0"015 0"008 0"059 0"125 0"008 0"024 0"324 0"052 0"009 0-022 0"024 0"015 0"011 1 "04 0"05 0"015 0"56 0"061 0"034 **
0"011 0"024 0"007 0"007 0'035 0"009 0"014 0"458 0"035 0"009 0"025 0"023 0"013 0"02 -------
Hafnium Mean
S.D.
0"004 0"007 0"001 0"026 0"801 0"031 0"024 0'692 0"009 0-018 0-049 0"007 0"006 0"009 24'63 0"002 0"009 0"27 0"039 0"019 **
0"005 0-009 0"001 0"034 0"055 0"058 0"015 0"667 0 0"032 0"072 0"009 0"005 0"02
--
Materials and methods Plant material Samples o f 20 a b u n d a n t desert plants b e lo n g in g to 14 families were tested for distribution of nine e l e m e n t s c o m p r i s i n g both m a j o r and trace elements. Plants were collected f r o m wadis in b a s e m e n t c o m p l e x f o r m a t i o n (Wadi Shait area) and N u b i a sandstone c o u n t r y (W ad i A g a g area), (Fig. 1). Plant material is r e p r e s e n t e d by two types: (a) frutescent, i.e. trees and shrubs with a deep root system and (b) suffrutescent, i.e. u n d e r s h r u b s rooting in the shallow wadi-fill deposits. Plant samples were carefully selected in o r d er to r e d u c e the effect of e l e m e n t a c c u m u l a t i o n in different parts of the plants. F o l l o w i n g the r e c o m m e n d a t i o n s of W a r r e n et al. (1955) and Brooks (1983) samples of twigs f r o m frutescent species and main stems f r o m suffrutescent species were subjected to chemical analyses.
Analyses of chemical elements Plant samples were carefully washed three times with d ei o n i zed water and dried for 10 h at 105°C. A b o u t 10g of each sample were c o n v e r t e d to ash in a muffle furnace for 8 h at 450°C. T h e Short T i m e N e u t r o n A c t i v a t i o n Analysis (Grass et al., 1987) was used to d e t e r m i n e the total c o n t e n t o f nine e l e m e n t s in the ash of 96 plant samples. Analyses were carried out in the A t o m i c E n e r g y I n s ti tu te o f the T e c h n i c a l U n i v e r s i t y of Vienna.
20 desert plants (concentration in p.p.m, in dry weight) Selenium Mean 0'041 0'007 0 0 0-077 0"565 0'133 0 0 0-033 0"212 0 0"04 0 0 0 0 0 0 0
S.D. 0-047 0"016 0 0 0"108 1'114 0"126 0 0 0"065 0"181 0 0"069 0 -------
Vanadium
Titanium
Magnesium
Mean S.D.
Mean S.D.
Mean S.D.
0"158 0"243 0"186 0-24 0"348 0"256 0'386 3'64 0"833 0"174 1"21 0"256 0"109 0"195 9"66 0"021 0"08 3"72 0"073 0-163
0 6-96 0 6-68 35-1 6"88 19-9 281 44"5 6"55 12"7 0 10"94 6"91 876"6 0 10"06 221"6 0 0
0-109 0"261 0"103 0"042 0"492 0"244 0"177 2"76 0"801 0"123 2"11 0"243 0"095 0-266 -------
0 15"13 0 9"44 49"7 20-65 20"2 240 63 13"02 25"5 0 10"83 17-96 -------
1130 783 1467 635 996 1344 3067 1107 1075 2329 2503 790 140 1785 4100 1600 120 1450 1050 1690
427 542 11"5 431 1278 1381 2730 668 742 1690 926 537 78"1 1352 -------
Aluminium Mean S.D. 74"5 117"1 378 135 495 281 161"3 1420 1050 66'7 97"5 111"8 68 128 9600 100 50 230 31 91
45"6 130'3 655 21"2 191 480 35"6 1387 636 37"1 93-2 101"6 3"46 229"7 -------
Manganese Mean S.D. 13"77 18"54 45'3 10"51 26"4 10"71 10"94 59"9 79"9 18"33 21"62 25"4 24"6 16"32 153"3 15"5 4"39 59"6 13"42 19"28
10"83 15"12 39"3 2"85 20 9-74 7"27 43"3 76"6 11"13 12"08 26'9 23"1 14"03 -------
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BIOGEOCHEMICAL PROSPECTING IN EGYPT
261
Statistical analysis The statistical package MINITAB was used in data analysis. The correlation coefficient (r) was calculated to estimate the relationships between the elements in the plant samples. The analysis of variance was used to evaluate the variations and difference in the absorption of the elements by different species.
Results and discussion Data on concentration of the nine elements in 20 plants are shown in Table 1. The mean value and standard deviation is given for those plants which were sampled more than once. It is clear that plants vary greatly in their ability to absorb and accumulate the elements. Selenium was recorded in eight species out of 20, whereas titanium was not recorded in four species. The concentration of elements varied in different species. Cleome droserifolia seemed to accumulate the highest amount of all elements except selenium. Second is Panicum turgidum which accumulates considerable amounts of dysprosium, scandium, vanadium, titanium and aluminium. Twigs ofMaerua crassifolia and Ochradenus baccatus are rich in selenium and magnesium respectively. It was only possible to conduct an analysis of variance (species and concentration of the elements) for the 14 species which had been sampled more than once. Figures in Table 1 show that there is a significant difference in absorption of all elements except selenium by the different species. Comparing the present results with earlier records, the average concentrations of manganese, vanadium and aluminium in most species are in the range given by Cannon (1960) and Koskinen (1981) for the same elements, but in Cleome droserifolia the concentration of aluminium is more than the average value of 8610 p.p.m, given by Cannon (1960). Concentration of magnesium in Panicum turgidum and Leptadenia pyrotechnica is slightly less than that recorded by A1-Homaid (1990) for the same species. Concentration of selenium in the ash of all plants is much less than that recorded by Miller & Byers (1937), and especially by Trelease (1945) who recorded average selenium to be 500 p.p.m, and as high as 15,000 p.p.m. On the other hand the concentration of titanium is much higher than Koskinen's (1981) record of titanium from 3 to 20 p.p.m., but less than the Bogoch & Brenner (1984) record of a maximum 10,000 p.p.m, in some desert plants. Table 2 shows a matrix of correlation coefficients for selected elements in the plants. It should be noted that all elements correlate well except magnesium, which shows a significant correlation with only manganese and selenium, which, although having a negative correlation, is not significant. The wide range in concentration of the elements in each species indicates the great variability in element absorption and accumulation in different locations. Table 3 shows the range of element accumulation in well distributed species. These plants show that the selective absorption of rare elements (dysprosium, scandium, hafnium, selenium and titanium) were not recorded in plant tissues in some locations. Magnesium was not absorbed by Maerua crassifolia, Acacia ehrenbergiana and Acacia raddiana in certain areas. The latter species shows a lack of aluminium in some locations. Association or correlation between two variables, which are (1) the concentration of an element in one species; and (2) the mean value of this element in other species collected in its close vicinity, shows the relative absorption capacity by the plant of certain elements. This biogeochemical parameter is similar (but not identical) to the Relative Absorption Coefficient (RAC) given by Brooks (1983). Only stands where more than three species were sampled have been selected for this analysis. Table 4 shows the correlation coefficients of the nine widely distributed species to the nine elements. Maerua crassifolia is significantly correlated to the trace elements dysprosium, scandium, hafnium, vanadium
262
M. BADRI & I, SPRINGUEL
Table 3. The range of accumulation of the elements in Dysprosium Species
n
Capparis decidua (Forssk.) Edgew Acacia ehrenbergiana Hayne Balanites aegyptiaca (L.) Del. Cassia italica Mill. Lam. ex Steud. Crotalaria aegyptiaca Benth. M aerua crassif olia Forssk. Ochradenus baccatus Del, Panicum turgidum Forssk. P ergularia tomentosa L. Salsola baryosma (R~em & Schult.) Dandy Tamarix nilotica (Ehrenb.) Bunge Acacia tortilis Hayne Zilla spinosa Prantl Acacia raddiana Savi
4 10 6 2 2 9 3 4 2 9 4 4 3 26
Min
Scandium
Max
0"01 0 0 0 0"04 0 0"01 0-04 0 0 0 0 0 0
Min
0"16 0"05 0"02 0"02 0"05 0"06 0"03 1"38 0"05 0-02 0'03 0-02 0"03 0"07
0 0 0 0"05 0"1 0 0"01 0"01 0"03 0 0 0 0 0
Max 0"02 0"08 0-02 0"06 0"15 0-02 0"03 0-98 0"08 0"03 0"06 0"05 0"02 0"07
Hafnium Min
Max
0 0 0 0 0"04 0 0"01 0" 11 0"01 0 0 0 0 0
0"01 0"03 0"01 0"05 0"12 0" 15 0"04 1"53 0"01 0"1 0"16 0'02 0-01 0"08
Min = minimum;Max = maximum.
Table 4. Correlation coefficients show the degree of association
in the other Dysprosium
Maerua crassifolia
Scandium
Hafnium
0"99"*
0"47
0"99"*
0"44
0"23
0"34
0"59
0"76
0"81
0"00
0"06
0"00
0"22
0'48
0"45
0"04
0"37
0"39
0"08
0"99**
0"84
0"96
0'96
0"88
0"42
0"86
0"26
Forssk.
Acacia raddiana Savi
Acaciaehrenbergiana Hayne
Balanites aegyptiaca (L.) Del.
Tamarix nilotica Bunge
Salsola baryosma (R~em & Schuh.) Dandy
Zillaspinosa Pranfl
Panicum turgidum Forssk.
Ochradenus baccatus Del. * p ~ 0"05; * * p < 0"01.
BIOGEOCHEMICAL PROSPECTING IN EGYPT
263
14 desert species (concentration in p.p.m, in dry weight) Selenium Min
Vanadium
Max
0 0 0 0 0 0 0 0 0 0 0 0 0 0
Min
0"08 0"04 0 0 0"15 3-5 0"25 0 0 0'18 0"37 0 0"12 0
0-06 0"02 0"04 0'21 0 0"06 0-27 0"73 0"27 0"04 0"06 0"02 0 0
Max 0"25 0"87 0"31 0"27 0"70 0"78 0'59 6'08 1"4 0"42 4-37 0"59 0"17 0"90
Titanium Min 0 0 0 0 0 0 0 47 0 0 0 0 0 0
Max 0 42-6 0 13"35 70"3 61"94 40"3 568 89"1 31-17 50-9 0 21"65 60"92
Magnesium
Aluminium
Manganese
Min
Min
Min
Max
760 260 600 330 92 400 1200 400 1550 360 1870 190 90 90
1500 1760 3600 940 1900 4700 6200 1980 2600 4800 3860 1350 230 6050
Max
35 5 18 120 360 20 130 300 600 20 20 8 64 0
between concentration of the elements m one species and mean value of this element speciesfrom the same location Selenium
Vanadium
Titanium
Magnesium
Aluminium
Manganese
0'03
0"98*
0"99**
0"49
0"64*
0"47
0"00
0"17
0"17
0"59
0"08
0'49
0'00
0'30
0"00
0'73
0"82*
0"80
0'00
0'67
0"00
0"52
0"99*
0"95
0"55
0"00
0"07
0"72
0'43
0"73
0'37
0"06
0"07
0"69
0"15
0"74
0"89
0'61
0'42
0'88
O"14
0-49
0"00
0"95
0"97
0-90
0"52
0'78
0"26
0"72
0'07
0-48
0-93
0"86
114 420 1700 150 630 1480 200 3260 1500 140 220 250 70 1530
4"4 0 16'2 8"49 12"3 0 2"57 12"3 25-7 1'85 8"68 4"1 6"7 0
Max 23-15 40"47 40-47 12"52 40-6 33"66 15"68 98"8 134 36"84 37"42 64"8 50"7 68'16
264
M. BADRI & I. SPRINGUEL
and titanium and Zilla spinosa is significantly correlated to scandium. On the other hand Balanites aegyptiaca shows significant correlation to the macro elements aluminium and manganese. We assume that a highly significant correlation could help to detect the indicator value of the species to a particular element. We could conclude that the present paper is the first step in a survey of the indicator value of desert plants for biogeochemical prospecting in the rocky deserts of arid lands. The results show the selective absorption of the elements by different species and great variation in absorption of the elements by the same species in different locations. The indicator capacity of three species to the different elements is revealed. Further studies are required to assess the value of the desert plants in biogeochemical prospecting. The authors thank Dr S. Ismail, Faculty of Science in Aswan, Assiut University, for making the chemical analysis of the plant samples and the Atomic Energy Institute of the Technical University of Vienna for providing facilities for these analyses.
References AI-Homaid, N., Sadiq, M. & Khan, M. H. (1990). Some desert plants of Saudi Arabia and their relation to soil characteristics. Journal of Arid Environments, 18: 43-49. Ayyad, M. A. & Ghabbour, S. I. (1986). Hot deserts of Egypt and Sudan. In: Evenari, M., NoyMeir, I. & Goodall, D. W. (Eds), Ecosystems of the World, 12B, Hot Deserts and Arid Shrublands, pp. 149-202. Amsterdam: Elsevier. x + 365 pp. Bogoch, R. & Brenner, I. B. (1984). A biogeochemical orientation survey in an arid rocky desert. Journal of Geochemical Exploration, 20:311-321. Brooks, R. R. (1983). BiologicalMethods of Prospectingfor Minerals. New York: Wiley-Interscience. 313 pp. Cannon, H. L. (1960). Botanical prospecting for ore deposits. Science, 3427: 591-598. E1 Shazly, E. M., Barakat, N., Eissa, E. A., Emara, H. H., Ali, I. S., Shaltait, S. & Sharaf, F. S. (1971). The use of Acacia trees in biogeochemical prospecting. Canadian Institute of Minerals & Metallurgy, 11: 426---434. Grass, F., Westphal, G. P. & Kassa, T. (1987). Short-time activation analysis in Geoscience. Nuclear Geophysics, 1: 253-261. Koskinen, N. S. (1981). Molybdenum, titanium and manganese in the plants of a few Karelian landscapes. In: Microelements in Karelia Biosphere and surrounding regions, pp. 31-35. Petrosavodsk. Miller, J. T. & Byers, H. G. (1937). Selenium in plants in relation to its occurrence in soils.Journal of Argicultural Research, 55: 59-68. Trelease, S. F. (1945). Selenium in soils, plants and animals. Soil Science, 60: 125-131. Warren, H. V., Delavault, R. E. & Fortescue, J. A. C. (1955). Sampling in biogeochemistry. Bulletin of the GeologicalSociety of America, 66: 229-238.
Biogeochemical prospecting in the South-Eastern Desert of Egypt
M. Badri & I. S p r i n g u e l Faculty of Science in Aswan, Assiut University, Egypt (Received 4 November 1992, accepted 19 March 1993) The distribution of the nine metal elements in 20 desert plants was studied in order to detect the indicator value of these plants for mineral prospecting. The plants vary greatly in their ability to absorb and accumulate the elements and so the concentrations vary between species. Plants show a selective absorption of the elements. Selenium was only recorded in eight species, titanium in 11 species. Each species shows considerable variability in accumulation of the elements in different locations. The indicator capacity ofMaerua crassifolia,Zilla spinosa and Balanites aegyptiaca to the different elements is revealed.
Keywords: indicator geobotany; desert; Egypt; arid climates; desert plants; soil; mineral prospecting
Introduction Biogeochemical prospecting is an advanced method used in indicator geobotany which studies the relationship between plants and bedrock. Biogeochernical methods of prospecting depend on the chemical analysis of different elements in plants. Environmental variables, particularly climatic and pedogenic conditions, affect the concentration of trace elements in the plant tissue. Biogeochemical prospecting seems to be more powerful under arid climates which support sparse vegetation (Brooks, 1983) and poor development of the soil. Biogeochemical prospecting is widely used in mineral exploration in many countries. This work was reviewed by Brooks (1983), but few data were published on arid regions in Egypt, except for E1 Shazly et al. (1971), who used the twigs of Acacia trees in biogeochemical prospecting and Bogoch & Brenner (1984) who worked in similar habitats in Sinai. The South-Eastern Desert of Egypt, where the present study was conducted, is characterized by a hyper-arid climate (Ayyad & Ghabbour, 1986) and very special pedogenic conditions. Plant life is strictly confined to the wadis (dry desert river beds), a very special type of habitat where plants are in direct contact with geological features without an intermediate soil layer in which minerals usually undergo different biogeochemical changes. The present work was carried out in order to study the distribution of metal elements in 20 desert plants sampled in different parts of the desert and the inter-relationships of these elements in plant tissue and in situ. The study could help to detect the indicator value of desert plants for mineral prospecting.
0140-1963/94/030257 + 08 $08'00/0
(~) 1994AcademicPress Limited
31 °
30 ° 28 ° --
32 °
33 °
34 °
35 °
36 °
2 7 ° __
26 ° -
W
25 ° --
24 °
23
F i g u r e 1. Part of the Eastern Desert, lithological and location m a p (Limestone, [ ~ ; Sandstone, [ ] ; B a s e m e n t complex, Ii~; Recent, [ ] ) . T a b l e 1. The chemical concentration of 9 elements in Dysprosium Species
n
Mean
Capparisdecidua(Forssk.)Edgew AcaciaehrenbergianaHayne Balanitesaegyptiaca(L.)Del. Cassia italica Mill. Lain. ex Steud. CrotalariaaegyptiacaBenth. MaeruacrassifoliaForssk. OchradenusbaccatusDel. Panicum turgidum Forssk. Pergularia tomentosa L. Salsola baryosma (Roem. & Schult.) D a n d y Tamarixnilotica(Ehrenb.)Bunge Acacia tortilisH a y n e ZillaspinosaPrantl Acacia raddiana Savi Cleome droserifolia Del. Aervajavanica (Burro. f.) Spreng Fagonia indica B u r m . f. FarsetiaaegyptiaTurra Salvadorapersica L. Hyphaenethebaica(L.)Mart.
4 10 6 2 2 9 3 4 2 9 4 4 3 26 1 1 1 1 1 1
0"013 0'013 0"005 0'009 0"045 0"009 0"023 0"576 0-024 0"009 0"016 0"011 0"012 0"008 2"61 0"02 0"005 0"99 0"039 0"084
Analysis of variance ~' p <
0"05; ** p <
0"01; NS
S.D.
** = not significant.
0"003 0"015 0'008 0'013 0'007 0'018 0"008 0"569 0"033 0"01 0"018 0"01 0"015 0"017 -------
Scandium Mean
S.D.
0"01 0"015 0"008 0"059 0"125 0"008 0"024 0"324 0"052 0"009 0-022 0"024 0"015 0"011 1 "04 0"05 0"015 0"56 0"061 0"034 **
0"011 0"024 0"007 0"007 0'035 0"009 0"014 0"458 0"035 0"009 0"025 0"023 0"013 0"02 -------
Hafnium Mean
S.D.
0"004 0"007 0"001 0"026 0"801 0"031 0"024 0'692 0"009 0-018 0-049 0"007 0"006 0"009 24'63 0"002 0"009 0"27 0"039 0"019 **
0"005 0-009 0"001 0"034 0"055 0"058 0"015 0"667 0 0"032 0"072 0"009 0"005 0"02
--
Materials and methods Plant material Samples o f 20 a b u n d a n t desert plants b e lo n g in g to 14 families were tested for distribution of nine e l e m e n t s c o m p r i s i n g both m a j o r and trace elements. Plants were collected f r o m wadis in b a s e m e n t c o m p l e x f o r m a t i o n (Wadi Shait area) and N u b i a sandstone c o u n t r y (W ad i A g a g area), (Fig. 1). Plant material is r e p r e s e n t e d by two types: (a) frutescent, i.e. trees and shrubs with a deep root system and (b) suffrutescent, i.e. u n d e r s h r u b s rooting in the shallow wadi-fill deposits. Plant samples were carefully selected in o r d er to r e d u c e the effect of e l e m e n t a c c u m u l a t i o n in different parts of the plants. F o l l o w i n g the r e c o m m e n d a t i o n s of W a r r e n et al. (1955) and Brooks (1983) samples of twigs f r o m frutescent species and main stems f r o m suffrutescent species were subjected to chemical analyses.
Analyses of chemical elements Plant samples were carefully washed three times with d ei o n i zed water and dried for 10 h at 105°C. A b o u t 10g of each sample were c o n v e r t e d to ash in a muffle furnace for 8 h at 450°C. T h e Short T i m e N e u t r o n A c t i v a t i o n Analysis (Grass et al., 1987) was used to d e t e r m i n e the total c o n t e n t o f nine e l e m e n t s in the ash of 96 plant samples. Analyses were carried out in the A t o m i c E n e r g y I n s ti tu te o f the T e c h n i c a l U n i v e r s i t y of Vienna.
20 desert plants (concentration in p.p.m, in dry weight) Selenium Mean 0'041 0'007 0 0 0-077 0"565 0'133 0 0 0-033 0"212 0 0"04 0 0 0 0 0 0 0
S.D. 0-047 0"016 0 0 0"108 1'114 0"126 0 0 0"065 0"181 0 0"069 0 -------
Vanadium
Titanium
Magnesium
Mean S.D.
Mean S.D.
Mean S.D.
0"158 0"243 0"186 0-24 0"348 0"256 0'386 3'64 0"833 0"174 1"21 0"256 0"109 0"195 9"66 0"021 0"08 3"72 0"073 0-163
0 6-96 0 6-68 35-1 6"88 19-9 281 44"5 6"55 12"7 0 10"94 6"91 876"6 0 10"06 221"6 0 0
0-109 0"261 0"103 0"042 0"492 0"244 0"177 2"76 0"801 0"123 2"11 0"243 0"095 0-266 -------
0 15"13 0 9"44 49"7 20-65 20"2 240 63 13"02 25"5 0 10"83 17-96 -------
1130 783 1467 635 996 1344 3067 1107 1075 2329 2503 790 140 1785 4100 1600 120 1450 1050 1690
427 542 11"5 431 1278 1381 2730 668 742 1690 926 537 78"1 1352 -------
Aluminium Mean S.D. 74"5 117"1 378 135 495 281 161"3 1420 1050 66'7 97"5 111"8 68 128 9600 100 50 230 31 91
45"6 130'3 655 21"2 191 480 35"6 1387 636 37"1 93-2 101"6 3"46 229"7 -------
Manganese Mean S.D. 13"77 18"54 45'3 10"51 26"4 10"71 10"94 59"9 79"9 18"33 21"62 25"4 24"6 16"32 153"3 15"5 4"39 59"6 13"42 19"28
10"83 15"12 39"3 2"85 20 9-74 7"27 43"3 76"6 11"13 12"08 26'9 23"1 14"03 -------
260
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"to 0~
,4 _o .t) t~
c~
6 ~ 6 6 ~ 6 ~
b~
6 6 ~ 6 ~ 6 ~ I
V
V
BIOGEOCHEMICAL PROSPECTING IN EGYPT
261
Statistical analysis The statistical package MINITAB was used in data analysis. The correlation coefficient (r) was calculated to estimate the relationships between the elements in the plant samples. The analysis of variance was used to evaluate the variations and difference in the absorption of the elements by different species.
Results and discussion Data on concentration of the nine elements in 20 plants are shown in Table 1. The mean value and standard deviation is given for those plants which were sampled more than once. It is clear that plants vary greatly in their ability to absorb and accumulate the elements. Selenium was recorded in eight species out of 20, whereas titanium was not recorded in four species. The concentration of elements varied in different species. Cleome droserifolia seemed to accumulate the highest amount of all elements except selenium. Second is Panicum turgidum which accumulates considerable amounts of dysprosium, scandium, vanadium, titanium and aluminium. Twigs ofMaerua crassifolia and Ochradenus baccatus are rich in selenium and magnesium respectively. It was only possible to conduct an analysis of variance (species and concentration of the elements) for the 14 species which had been sampled more than once. Figures in Table 1 show that there is a significant difference in absorption of all elements except selenium by the different species. Comparing the present results with earlier records, the average concentrations of manganese, vanadium and aluminium in most species are in the range given by Cannon (1960) and Koskinen (1981) for the same elements, but in Cleome droserifolia the concentration of aluminium is more than the average value of 8610 p.p.m, given by Cannon (1960). Concentration of magnesium in Panicum turgidum and Leptadenia pyrotechnica is slightly less than that recorded by A1-Homaid (1990) for the same species. Concentration of selenium in the ash of all plants is much less than that recorded by Miller & Byers (1937), and especially by Trelease (1945) who recorded average selenium to be 500 p.p.m, and as high as 15,000 p.p.m. On the other hand the concentration of titanium is much higher than Koskinen's (1981) record of titanium from 3 to 20 p.p.m., but less than the Bogoch & Brenner (1984) record of a maximum 10,000 p.p.m, in some desert plants. Table 2 shows a matrix of correlation coefficients for selected elements in the plants. It should be noted that all elements correlate well except magnesium, which shows a significant correlation with only manganese and selenium, which, although having a negative correlation, is not significant. The wide range in concentration of the elements in each species indicates the great variability in element absorption and accumulation in different locations. Table 3 shows the range of element accumulation in well distributed species. These plants show that the selective absorption of rare elements (dysprosium, scandium, hafnium, selenium and titanium) were not recorded in plant tissues in some locations. Magnesium was not absorbed by Maerua crassifolia, Acacia ehrenbergiana and Acacia raddiana in certain areas. The latter species shows a lack of aluminium in some locations. Association or correlation between two variables, which are (1) the concentration of an element in one species; and (2) the mean value of this element in other species collected in its close vicinity, shows the relative absorption capacity by the plant of certain elements. This biogeochemical parameter is similar (but not identical) to the Relative Absorption Coefficient (RAC) given by Brooks (1983). Only stands where more than three species were sampled have been selected for this analysis. Table 4 shows the correlation coefficients of the nine widely distributed species to the nine elements. Maerua crassifolia is significantly correlated to the trace elements dysprosium, scandium, hafnium, vanadium
262
M. BADRI & I, SPRINGUEL
Table 3. The range of accumulation of the elements in Dysprosium Species
n
Capparis decidua (Forssk.) Edgew Acacia ehrenbergiana Hayne Balanites aegyptiaca (L.) Del. Cassia italica Mill. Lam. ex Steud. Crotalaria aegyptiaca Benth. M aerua crassif olia Forssk. Ochradenus baccatus Del, Panicum turgidum Forssk. P ergularia tomentosa L. Salsola baryosma (R~em & Schult.) Dandy Tamarix nilotica (Ehrenb.) Bunge Acacia tortilis Hayne Zilla spinosa Prantl Acacia raddiana Savi
4 10 6 2 2 9 3 4 2 9 4 4 3 26
Min
Scandium
Max
0"01 0 0 0 0"04 0 0"01 0-04 0 0 0 0 0 0
Min
0"16 0"05 0"02 0"02 0"05 0"06 0"03 1"38 0"05 0-02 0'03 0-02 0"03 0"07
0 0 0 0"05 0"1 0 0"01 0"01 0"03 0 0 0 0 0
Max 0"02 0"08 0-02 0"06 0"15 0-02 0"03 0-98 0"08 0"03 0"06 0"05 0"02 0"07
Hafnium Min
Max
0 0 0 0 0"04 0 0"01 0" 11 0"01 0 0 0 0 0
0"01 0"03 0"01 0"05 0"12 0" 15 0"04 1"53 0"01 0"1 0"16 0'02 0-01 0"08
Min = minimum;Max = maximum.
Table 4. Correlation coefficients show the degree of association
in the other Dysprosium
Maerua crassifolia
Scandium
Hafnium
0"99"*
0"47
0"99"*
0"44
0"23
0"34
0"59
0"76
0"81
0"00
0"06
0"00
0"22
0'48
0"45
0"04
0"37
0"39
0"08
0"99**
0"84
0"96
0'96
0"88
0"42
0"86
0"26
Forssk.
Acacia raddiana Savi
Acaciaehrenbergiana Hayne
Balanites aegyptiaca (L.) Del.
Tamarix nilotica Bunge
Salsola baryosma (R~em & Schuh.) Dandy
Zillaspinosa Pranfl
Panicum turgidum Forssk.
Ochradenus baccatus Del. * p ~ 0"05; * * p < 0"01.
BIOGEOCHEMICAL PROSPECTING IN EGYPT
263
14 desert species (concentration in p.p.m, in dry weight) Selenium Min
Vanadium
Max
0 0 0 0 0 0 0 0 0 0 0 0 0 0
Min
0"08 0"04 0 0 0"15 3-5 0"25 0 0 0'18 0"37 0 0"12 0
0-06 0"02 0"04 0'21 0 0"06 0-27 0"73 0"27 0"04 0"06 0"02 0 0
Max 0"25 0"87 0"31 0"27 0"70 0"78 0'59 6'08 1"4 0"42 4-37 0"59 0"17 0"90
Titanium Min 0 0 0 0 0 0 0 47 0 0 0 0 0 0
Max 0 42-6 0 13"35 70"3 61"94 40"3 568 89"1 31-17 50-9 0 21"65 60"92
Magnesium
Aluminium
Manganese
Min
Min
Min
Max
760 260 600 330 92 400 1200 400 1550 360 1870 190 90 90
1500 1760 3600 940 1900 4700 6200 1980 2600 4800 3860 1350 230 6050
Max
35 5 18 120 360 20 130 300 600 20 20 8 64 0
between concentration of the elements m one species and mean value of this element speciesfrom the same location Selenium
Vanadium
Titanium
Magnesium
Aluminium
Manganese
0'03
0"98*
0"99**
0"49
0"64*
0"47
0"00
0"17
0"17
0"59
0"08
0'49
0'00
0'30
0"00
0'73
0"82*
0"80
0'00
0'67
0"00
0"52
0"99*
0"95
0"55
0"00
0"07
0"72
0'43
0"73
0'37
0"06
0"07
0"69
0"15
0"74
0"89
0'61
0'42
0'88
O"14
0-49
0"00
0"95
0"97
0-90
0"52
0'78
0"26
0"72
0'07
0-48
0-93
0"86
114 420 1700 150 630 1480 200 3260 1500 140 220 250 70 1530
4"4 0 16'2 8"49 12"3 0 2"57 12"3 25-7 1'85 8"68 4"1 6"7 0
Max 23-15 40"47 40-47 12"52 40-6 33"66 15"68 98"8 134 36"84 37"42 64"8 50"7 68'16
264
M. BADRI & I. SPRINGUEL
and titanium and Zilla spinosa is significantly correlated to scandium. On the other hand Balanites aegyptiaca shows significant correlation to the macro elements aluminium and manganese. We assume that a highly significant correlation could help to detect the indicator value of the species to a particular element. We could conclude that the present paper is the first step in a survey of the indicator value of desert plants for biogeochemical prospecting in the rocky deserts of arid lands. The results show the selective absorption of the elements by different species and great variation in absorption of the elements by the same species in different locations. The indicator capacity of three species to the different elements is revealed. Further studies are required to assess the value of the desert plants in biogeochemical prospecting. The authors thank Dr S. Ismail, Faculty of Science in Aswan, Assiut University, for making the chemical analysis of the plant samples and the Atomic Energy Institute of the Technical University of Vienna for providing facilities for these analyses.
References AI-Homaid, N., Sadiq, M. & Khan, M. H. (1990). Some desert plants of Saudi Arabia and their relation to soil characteristics. Journal of Arid Environments, 18: 43-49. Ayyad, M. A. & Ghabbour, S. I. (1986). Hot deserts of Egypt and Sudan. In: Evenari, M., NoyMeir, I. & Goodall, D. W. (Eds), Ecosystems of the World, 12B, Hot Deserts and Arid Shrublands, pp. 149-202. Amsterdam: Elsevier. x + 365 pp. Bogoch, R. & Brenner, I. B. (1984). A biogeochemical orientation survey in an arid rocky desert. Journal of Geochemical Exploration, 20:311-321. Brooks, R. R. (1983). BiologicalMethods of Prospectingfor Minerals. New York: Wiley-Interscience. 313 pp. Cannon, H. L. (1960). Botanical prospecting for ore deposits. Science, 3427: 591-598. E1 Shazly, E. M., Barakat, N., Eissa, E. A., Emara, H. H., Ali, I. S., Shaltait, S. & Sharaf, F. S. (1971). The use of Acacia trees in biogeochemical prospecting. Canadian Institute of Minerals & Metallurgy, 11: 426---434. Grass, F., Westphal, G. P. & Kassa, T. (1987). Short-time activation analysis in Geoscience. Nuclear Geophysics, 1: 253-261. Koskinen, N. S. (1981). Molybdenum, titanium and manganese in the plants of a few Karelian landscapes. In: Microelements in Karelia Biosphere and surrounding regions, pp. 31-35. Petrosavodsk. Miller, J. T. & Byers, H. G. (1937). Selenium in plants in relation to its occurrence in soils.Journal of Argicultural Research, 55: 59-68. Trelease, S. F. (1945). Selenium in soils, plants and animals. Soil Science, 60: 125-131. Warren, H. V., Delavault, R. E. & Fortescue, J. A. C. (1955). Sampling in biogeochemistry. Bulletin of the GeologicalSociety of America, 66: 229-238.