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Effects of fluoride emissions from industry on the fluoride concentration of soils and vegetation
Biochemical Systematics and Ecology,Vol. 21, No. 2, pp. 195-208, 1993. Printed in Great Britain.
0305-1978/93 $6.00+ 0.00 © 1993 Pergamon Press Ltd.
Effects of Fluoride Emissions from Industry on the Fluoride Concentration of Soils and Vegetation C. HAIDOUTI, A. CHRONOPOULOU and J. CHRONOPOULOS Agricultural University of Athens, lera Odos 75, Athens 118 55, Greece
Key Word Index--Fluoride emissions; contamination; soils. Abstract--The effects of fluoride emissions, from an aluminium reduction plant in Greece, on the concentration of fluoride in soils and natural vegetation and also the relation between injury and fluoride content of plants were investigated. Fluoride emissions from the factory caused toxicity to natural vegetation in the adjoining area. Some plant species accumulated high fluoride levels in the leaves and exhibited acute necrosis, chlorosis or both. Others did not show visible injury, in spite of their high fluoride accumulation. The intensity of symptoms changed a great deal from one individual plant to the other or even from leaves of the same plant. The average levels of fluoride in vegetation ranged from 621.2 to 257.2 ppm in severely damaged areas (zone I) and from 144.3 to 64.1 ppm in lightly damaged areas (zone III). The corresponding fluoride levels in the controls was 15.4-8.2 ppm. In soils total fluoride concentrations ranged from 823.5 to 297.6 respectively; the levels in controls ranged from 108.6 to 95.3 ppm.
Introduction Fluorides (F) are recognized as common gas and particulate pollutants emanating from many industrial processes. The F-emitting industrial sources are mostly aluminium smelters and phosphate fertilizer factories, but coal combustion, steel works, brick yards, and glass works may also significantly contribute to the total F pollution. The most important hazard of F contamination in soils concerns changes in soil properties due to the great chemical activity of hydrofluoric acid which is temporarily formed from both solid and gaseous F pollutants (Kabata-Pendias and Pendias, 1984). Fluroide is the most phytotoxic of the common air pollutants. Gaseous fluoride enters the leaf through the stomata and moves in the transpiration stream to the principal sites of accumulation at the tip and margins of the leaf where, should the concentration in the cell sap be sufficient, it may impel cell death (Weinstein and Alscher-Herman, 1982). A number of effects of airborne F on plants growing around major efficient sources have been reported in the literature. The most common reported have been visible effects such as necrosis and chlorosis (Scurfield, 1960; Treshow and Pack, 1970; Gilbert, 1975; Carlson et al., 1979; Sun and Su, 1985). Typically, these symptoms are associated with high F emission rates. At lower ambient concentrations, a number of physiological and biochemical changes may be initiated by F in plants without the appearance of visible injury symptoms. Some of these changes may have important consequences such as reductions in growth or yield (Treshow etaL, 1967; Pack and Sulzbach, 1976; MacLean et al., 1977; MacLean and Schneider, 1981). This paper refers to a study conducted to examine the extent of F pollution in soils and plants in the vicinity of an aluminium plant and the degree of F toxicity among native plants in the affected area. Data are presented on visible injury symptoms exhibited by different plant species. (Received 16 April 1992) 195
C. HAIDOUTIETAL
196 Materials
and
Methods
The aluminium reduction plant is situated on the gulf of Antikyra, Beotia region, Greece. The plant has been in operation since 1960. The study area is approximately 515 km 2 and is covered by Alpine sediments, which are mainly limestones. The predominant carbonates reach a thickness of 1800 m and host bauxites of economic interest (Papanikolaou, 1986). The area shows a rough relief with steep flanks and deep erosional valleys. The study area has a Mediterranean climate. The distribution of precipitation depends on the altitude, together with influence of the sea and the prevailing winds. Whatever precipitation does occur during the dry season is often unevenly distributed. There are years when very little or no rain falls at all for four months. The mean annual temperature, except in mountainous areas, varies between 17.5°C and 18.2°C (Mariolopoulos, 1982). The warmest months of the year are July and August and the coldest are January and February. Measurements of wind direction showed that winds from the south, west and east are characteristic of the region. (Fig. 1). The natural vegetation of the study area belongs to the Oleo-Ceratonion zone, which is composed of xeromorphic plants. The most characteristic species are Olea europaea var. o/easter, Cistus salvifolius, Calicotome
villosa, Pistacia lentiscus, Genista acantholada, Ceratonia siliqua, Ballota acetabulosa, Phlomis fruticosa, Verbascum undulatum, Quercus coccifera, Sarcopoterium spinosum, Corydothymus capitatus, Phagnalon rubestre, etc. (Horvat et al., 1974). The soils in the study area are calcareous with carbonates ranging from 12 to 56%. The organic matter contents were higher in the surface layer (0-5 cm) than in the lower layers, in most locations (1-11%). Clay contents ranged from 10.5 to 66%. The sampling sites were located up to a distance of 15 km from the aluminium factory. Soil samples were collected at a depth of 0-5 cm from 91 sites. Mature leaf samples, which were of similar size and age, of Phlomis fruticosa, Verbascum undulatum, Cistus salvifolius, Olea europaea var. oleaster, Pistacia lentiscus and Quercus coccifera were also collected from the same sites. The samples were then refrigerated at 0-4°C and analysed as soon as possible thereafter. Control samples of vegetation and soil were collected from similar sites located about 50 km from the factory. Samples of vegetation and soils were collected from sites during the summer of 1987. Soil samples were air-dried and passed through a 2 mm sieve. Mechanical analyses were made with a hydrometer, according to the procedure of Bouyoucos (1951). Carbonates were determined by HCI dissolution and measurement of evolved CO2. The pH was measured in a 1:1 soil:water ratio. The Walkley-Black wet digestion method, as described by Black (1965), was used for the determination of organic matter. All F determinations were made with an EA 306-F ion-specific electrode using a Microprocessor Ionanalyzer 901. The following extraction procedures were applied: for total F determination in soils 0.5 g soil dried at 105°C
N
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>6
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~ 4
, 6
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i 10
(%) S
FIG. 1. WIND FREQUENCYAND SPEED (Beaufort) DIAGRAMSIN ALUMINIUM PLANT AREA (1984-86).
FLUORIDECONCENTRATIONOF SOILSAND VEGETATION
197
was:fused in the Ni crucible for 20 min with 4.5 g of NaOH. After the sample was dissolved in distilled water the pH was adjusted to 6.0 with 1.5 M citric acid (Noemmik, 1953; H&ni, 1975). For the determination of fluoride in vegetation the sample was cut and mixed to produce a sample as nearly uniform as possible. Ten grams of the dried sample (80°C for 24 h) were transferred to a 50-ml Ni crucible. Ten millilitres (6.7 g) of NaOH were added to the crucible and the sample dried for 2 h at 150°C.At the end of the drying time, the sample was transferred to a 550°C muffle furnace and fused for 2 h. After fusion, the sample was cooled and 25 ml of H20 w e r e added to dissolve the melt that was applied. After the melt was completely dissolved, it was transferred quantitatively to a 50-ml volumetric flask. The solution was then filtered through a Whatman No. 41 paper and aliquots were taken for analysis (Baker, 1972).
Results and Discussion The aluminium reduction plant at Beotia region, Greece, has produced F emissions since it started operation in 1960. These emissions are responsible for damaging vegetation growing on areas close to the plant. It is well recognized that the concentration of airborne fluorides is a major influence on the pattern of F accumulation by vegetation (National Academy of Sciences, 1971). Gaseous and particulate fluoride compounds are emitted from the factory as a result of the electrolytic reduction of alumina (AI203) dissolved in a melt of sodium fluoride. It has been estimated by Treshow (1969) that gaseous fluorides comprise greater than 50% of the total airborne fluoride around industrial sites. Gaseous forms pass readily through the leaf stomata, while the particulate forms are deposited on the surface of the vegetation where, if soluble, they are readily removed by leaching and consequently cause less damage. The 1985 and 1986 surveys in the same area revealed severe damage to natural vegetation around the aluminium plant. Some results concerning the F concentrations in soils and plant species were published by Haidouti eta/. (1991). The severity of the damage in the study area varies from necrosis of tips of the leaves to chlorosis. These observations and the absence of parasitic agents or nutritional disorders that would account for the observed leaf injury suggest fluoride accumulation as the possible causal agent of leaf injury. Injury symptoms generally increase with leaf concentration of fluoride on a dry weight basis, but there is no distinct pattern in which symptoms appear. Craggs et aL (1985) concluded that meteorological, microclimatic and biological factors were directly or indirectly influencing grass fluoride levels. The results of the previous study (Haidouti eta/., 1991) showed a severe F accumulation at distances up to 15 km from the plant. In the present research, samples were taken in a more detailed way from a distance up to 15 km for the purpose of locating the damage zones. In the more detailed study of the area the plant species which showed the most acute and characteristic symptoms was Olea europea var. o/easter, which has been used as a criterium for locating the zones. The study area was divided into three zones. The first one was extended to the point where the Olea leaves showed a necrosis connected with F concentrations of 400-200 ppm; the second zone was extended to the point where the Olea leaves showed a chlorosis that was connected with F concentrations of 200-100 ppm and the third zone included the areas where the Olea leaves did not present any symptoms and the F concentrations were lower than 100 ppm. The area of each zone and the sampling sites are presented in Fig. 2, while the F concentrations and the symptoms for all plant species and for each damage zone are summarized in Table 1. As shown in Table 1 there are large differences in fluoride concentrations among the different plant species. All species examined contained high fluoride concentrations in their leaves and showed that there is wide variation in plant response to fluoride emissions. This may be attributed to different deposition rates, substrates and/or
iG 2 DAMAGE ZONE MAP
199
FLUORIDE CONCENTRATIONOF SOILS AND VEGETATION TABLE 1. CONCENTRATIONSOF FLUORIDE (p.g g ~) IN FOLIAGE AND SOILS FROM THREE DAMAGE ZONES AND CONTROLAREAS NEAR AN ALUMINIUM PLANT Damage zone I
Control
Plant species
Mean fluoride concentration (+S.D.)
Phlomis fruticosa Verbascum undulatum Cistus salvifolius
621.2± 151.7 454.7± 128.5 427.0±189.8
Olea europaea var oleaster Pistacia lentiscus
345.8±122.4 295.8±76.2
Quercus coccifera soil
257.2±69.3 823.5±59.9
Phlomis fruticosa Verbascum undulatum Cistus salvifolius Olea europaea var oleaster Pistacia lentiscus Quercus coccifera soil
316.4±57.3 244.9±36.9 237.0±43.3 142.9±38.2 157.8±31.7 133,5+39.9 600.2±66.5
Without symptom s Chlorosis (60-75%) Chlorosis (10-20%) Chlorosis (40-50%) Chlorosis (20-40%) Chlorosis (5-10%)
Phlomis fruticosa Verbascum undulaturn Cistus salvifolius Olea europaea var oleaster Pistacia lentiscus Quercus coccifera soil
144.3±30,8 131.5±27.5 114.8±35.5 74.4±12.3 72.5±15.0 64.1± 15,1 297.6±88.4
Without symptoms Chlorosis (20-40%) Without symptoms Without symptoms Without symptoms Without symptoms
Phlomis fruticosa Verbascum undulatum Cistus salvifolius Olea europaea var oleaster Pistacia lentiscus Quercus coccifera soil
15.4±2.8 15.8±3.1 10.8±2.3 9,5±2.1 9.3±2.4 9.2± 1.9 98.7±21.9
Observed damage Without symptoms Chlorosis (80-95%) Chlorosis (25-50%) and necrosis (5-10%) Necrosis (50-65%) Necrosis (10-20%) and chlorosis (30-60%) Necrosis (10-20%)
tolerance. The species Phlomis frutJcosahad the highest F concentration and Quercus coccifera, the lowest. In addition, Table 1 shows that there are differences in the symptoms which the plant species exhibit in the three zones as well as in the percentage of leaves with discrete symptoms. There are also plant species, (e.g. Phlomis fruticosa) which although exhibiting the highest F concentration in all three zones, does not show any symptoms. A t-test has been done in order to confirm statistically the mean differences in F concentrations between the plant species in each zone. Important differences have been observed statistically in all plant species at P 0.01 and P 0.05 significance levels except for Cistus- Verbascum and Olea-Pistacia in the three zones, as well as PhlomisVerbascum and Quercus-Pistacia for the first zone, which do not present statistically important differences. Great differences in F concentrations have been observed among the same plant species in the same damage zone. This should be attributed to different degrees of exposure to emissions as well as to the individuality of each plant. The F content in the samples of each species was extremely variable but in every group there was a sequence of increasing fluoride content from the control zone to the high exposure zones.
FIG. 3. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS lu.g gr ~) tN PHLOMIS FRUTICOSA
FIG. 4, ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (~.g gr ~) IN VERBASCUMUNDUL.a.TUM.
5
I1
2
t}
u
:IG. 5. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (~g gr ~) IN CISTUSSALV/FOLIUS.
:IG. 6 ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (pg gr ~) IN OLEA EUROPEA V. OLEASTER.
FIG. 7. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (itg gr ~) IN PISTACIALENTISCUS.
FIG, 8. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATION:5 (~-g gr '1 ir~
cLuctlt.uo
~.u~.L.ir~,
Z
m
z
b~
z
5
_7
-)
FIG. 9. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (l~g gr ~) IN SOILS.
FLUORIDE CONCENTRATIONOF SOILS AND VEGETATION
207
Control samples of leaves collected from sites located 50 km from the aluminium plant showed concentrations from 8.2 to 15.8 l~g g r-1 F dry weight. Assuming that these values characterize normal fluoride levels for the vegetation in the research area, any amount of leaf fluorides exceeding the above values should be considered as an airborne enrichment. The normal fluoride level for the soil of the region is about 100 ilg gr -1. The results of F analysis for plants and soils were used in order to prepare the isofluor maps (Figs 3-8) which show fluoride concentrations in the foliage of plants and concentrations of F in soils (Fig. 9). Phlomis fruticosa which exhibits the highest F values, also exhibits the highest density isofluors of all other plants in the area, while Quercus cocc/feFa with the lowest F values exhibits the lowest density isofluors. Consequently the isofluor distribution is connnected with the degree of pollution. In zone I, where the more severe damage was found in the plants, the isofluors are closer to each other for all the plant species as well as for the soil, compared with the other two zones. The isofluor shape shows an increasing F value in the north as well as to the east of the aluminium plant, which is connected with the prevailing wind direction in the area. In addition, to the east of the plant and at a certain distance of about 9 km from it, in zone II, an area of high F values is located. This is due to the relief combined with the prevailing winds. This study showed that the soils and all the plant species examined contained high F concentrations. The plant leaves exhibited leaf chlorosis, necrosis or both, whereas other plants with the same or higher leaf F content displayed little or no injury. Consequently, plant species differed greatly in their sensitivity to fluoride, but the intensity of symptoms varied among the individuals of the same species. A great deal of variability was observed in the F content of leaves of the same plant; the age, the position and the portion of leaves analysed influenced their fluoride status. Mature leaves and those found at the most exposed parts of the plant contained more F. These factors which affect the concentration of fluoride in the leaves should always be taken into account when leaf analysis is used for detection of air contamination with fluorides. Phytotoxic effects of airborne F, in respect to visual symptoms and F content of plant species growing in the vicinity of the aluminium factory, showed that Olea europea var. o/easter is the most sensitive plant to the toxicity, whereas Phlomis fruticosa did not exhibit leaf damage, in spite of a high accumulation of fluoride in its foliage. It would appear that Phlomis fruticosa is tolerant to F as far as visual injury is concerned. Holevas (1980) who worked in the same region, found that F toxicity symptoms in cultivated plants appeared only in the sensitive species of grapevine and apricot, while olive trees did not suffer extensive leaf damage. in summary, the aluminium plant is responsible for the high concentration of F in the soils and damage to vegetation, which is close to the plant. The short term effects of this pollution are obvious by visual inspection. In the long term the data of isofluor maps seem to indicate a spread of F pollution in both soil and vegetation as a function of the distance, the geomorphology and the direction of the prevailing winds. Acknowledgements--Theauthors would
like to thank the Ministry of Agriculture for financial support of the research project and Mrs J. Haidouti and Mr M. Pagonis for their assistance in chemical analyses,
References Baker, R. L. (1972) Determination of fluoride in vegetation using the specific ion electrode. Analyt Chem. 44(7), 1326-1327. Black, C. A. (ed.) (1965) Methods of soil analysis. Am. Soc. Agron. Madison, Wisconsin.
208
c. HAIDOUTIETAL.
Bouyoucos, G. H. (1951) A recalibration of the hydrometer method for making mechanical analysis of soils. Agron. J. 43, 434-438. Carlson, C. E., Gordon, C. C. and Giliigan, C. J. (1979) The relationship of fluoride to visible growth/health characteristics of Pinus mondcola, Pinus contorta and Pseudotsuga menziesi~ Fluoride 12, 9-17. Craggs, C. E. and Dvison, A. W. (1985) The effect of simulated rainfall on grass fluoride concentrations. Environ. Pollut., Series B. 9, 309--318. Gilbert, O. L. (1975) Effects of air pollution on landscape and land use around Norwegian aluminium smelters. Environ. Pollut, 18, 113-121. Haidouti, C., Chronopoulou, A. and Chronopoulos, J. (1991) Distribution of airborne fluoride in soils and natural vegetation around an aluminium reduction plant. Zeitschrift Geomorphologie 83, 39-45. H~ni, H. (1975) Wechselwirkung von fluorid mit eine mineralischen illithaltigen Boden und Veranderung in den darauf wachsenden Maispflanzen. Schweiz. Landwirtsch. Forsch. 14, 189-201. Holevas, C. D. (1980) Fluoride air pollution in relation to injury and fluorine content of cultivated plants. 5th International colloquium on the control of plant nutrition. 25-30 August. Instituto Professionale di stato per I'Agricoltura, Treviso, Italy. Horvat, I., Clavac, V. and Ellenberg, H. (1974) Vegetation Sudosteurepas. Fischer, Stuttgart. Kabata-Pendias, A. and Pendias, H. (1984). Trace Elements in Soils and Plants, p. 315. CRC Press, Florida. MacLean, D. C., Schneider, R. E. and McCune, C. D. (1977) Effects of chronic exposure to gaseous fluoride on yield of field-grown bean and tomato plants. J. Am. Soc. Hort. Sci. 102, 297-299. MacLean, D. C. and Schneider, R. E. (1981) Effects of gaseous hydrogen fluoride on the yield of field-grown wheat. Environ. Pollut. Series A 24, 39-44. Mariolopoulos, H. (1982) The Climate of Greece. Academy of Athens, Athens. National Academy of Sciences (1971) Biological Effects of Atmospheric Pollutants: Fluorides. Washington, DC. Noemmik, H. (1953) Fluorine in Swedish agriculutral product soils and drinking water. Acta Polytech. 127, 1-121. Pack, M. R. and Sulzbach, C. W. (1976) Response of plant fruiting to hydrogen fluoride fumigation. Atmos. Environ. 10, 73-81. Papanikolaou, D. I. (1986) Geology of Greece, p. 275. Eptalophos Press, Athens. Scurfield, G. (1960) Air pollution and tree growth. For. Abstr. 21, 339-347. Sun, E. J. and Su, H. J. (1985) Fluoride injury to rice plants caused by air pollution emitted from Ceramic and Brick factories. Environ. Pollut., SeriesA. 37, 335-342. Treshow, M., Anderson, F. K. and Harrier, F. (1967) Responses of Douglas fir to elevated atmospheric fluorides. For. Sc~ 13, 114-120. Treshow, M. (1989) Symptomology of fluoride injury on vegetation. In Handbook of Effect Assessment: Vegetation Damage, Vol. 7, pp. 1-41. Pennsylvania State Univ. Centre for air Environment studies, Univ. Park, Pennsylvania. Treshow, M. and Pack, M. R. (1970) Fluoride. In Recognition of Air-pollution Injury to Vegetation: A PictorialAtlas, (Jacobson, J. S, and Hill, A. C. eds), D1-17. Air Pollution Control Association, Pittsburgh. Weinstein, L. H. and Alscher-Herman, R. (1982) Physiological responses of plants to fluorine. In Effects of Gaseous Air Pollution in Agriculture and Horticulture (Unsworth, M. H. and Ormrod, D. P. eds), pp. 139-67. Butterworth Scientific, London.
0305-1978/93 $6.00+ 0.00 © 1993 Pergamon Press Ltd.
Effects of Fluoride Emissions from Industry on the Fluoride Concentration of Soils and Vegetation C. HAIDOUTI, A. CHRONOPOULOU and J. CHRONOPOULOS Agricultural University of Athens, lera Odos 75, Athens 118 55, Greece
Key Word Index--Fluoride emissions; contamination; soils. Abstract--The effects of fluoride emissions, from an aluminium reduction plant in Greece, on the concentration of fluoride in soils and natural vegetation and also the relation between injury and fluoride content of plants were investigated. Fluoride emissions from the factory caused toxicity to natural vegetation in the adjoining area. Some plant species accumulated high fluoride levels in the leaves and exhibited acute necrosis, chlorosis or both. Others did not show visible injury, in spite of their high fluoride accumulation. The intensity of symptoms changed a great deal from one individual plant to the other or even from leaves of the same plant. The average levels of fluoride in vegetation ranged from 621.2 to 257.2 ppm in severely damaged areas (zone I) and from 144.3 to 64.1 ppm in lightly damaged areas (zone III). The corresponding fluoride levels in the controls was 15.4-8.2 ppm. In soils total fluoride concentrations ranged from 823.5 to 297.6 respectively; the levels in controls ranged from 108.6 to 95.3 ppm.
Introduction Fluorides (F) are recognized as common gas and particulate pollutants emanating from many industrial processes. The F-emitting industrial sources are mostly aluminium smelters and phosphate fertilizer factories, but coal combustion, steel works, brick yards, and glass works may also significantly contribute to the total F pollution. The most important hazard of F contamination in soils concerns changes in soil properties due to the great chemical activity of hydrofluoric acid which is temporarily formed from both solid and gaseous F pollutants (Kabata-Pendias and Pendias, 1984). Fluroide is the most phytotoxic of the common air pollutants. Gaseous fluoride enters the leaf through the stomata and moves in the transpiration stream to the principal sites of accumulation at the tip and margins of the leaf where, should the concentration in the cell sap be sufficient, it may impel cell death (Weinstein and Alscher-Herman, 1982). A number of effects of airborne F on plants growing around major efficient sources have been reported in the literature. The most common reported have been visible effects such as necrosis and chlorosis (Scurfield, 1960; Treshow and Pack, 1970; Gilbert, 1975; Carlson et al., 1979; Sun and Su, 1985). Typically, these symptoms are associated with high F emission rates. At lower ambient concentrations, a number of physiological and biochemical changes may be initiated by F in plants without the appearance of visible injury symptoms. Some of these changes may have important consequences such as reductions in growth or yield (Treshow etaL, 1967; Pack and Sulzbach, 1976; MacLean et al., 1977; MacLean and Schneider, 1981). This paper refers to a study conducted to examine the extent of F pollution in soils and plants in the vicinity of an aluminium plant and the degree of F toxicity among native plants in the affected area. Data are presented on visible injury symptoms exhibited by different plant species. (Received 16 April 1992) 195
C. HAIDOUTIETAL
196 Materials
and
Methods
The aluminium reduction plant is situated on the gulf of Antikyra, Beotia region, Greece. The plant has been in operation since 1960. The study area is approximately 515 km 2 and is covered by Alpine sediments, which are mainly limestones. The predominant carbonates reach a thickness of 1800 m and host bauxites of economic interest (Papanikolaou, 1986). The area shows a rough relief with steep flanks and deep erosional valleys. The study area has a Mediterranean climate. The distribution of precipitation depends on the altitude, together with influence of the sea and the prevailing winds. Whatever precipitation does occur during the dry season is often unevenly distributed. There are years when very little or no rain falls at all for four months. The mean annual temperature, except in mountainous areas, varies between 17.5°C and 18.2°C (Mariolopoulos, 1982). The warmest months of the year are July and August and the coldest are January and February. Measurements of wind direction showed that winds from the south, west and east are characteristic of the region. (Fig. 1). The natural vegetation of the study area belongs to the Oleo-Ceratonion zone, which is composed of xeromorphic plants. The most characteristic species are Olea europaea var. o/easter, Cistus salvifolius, Calicotome
villosa, Pistacia lentiscus, Genista acantholada, Ceratonia siliqua, Ballota acetabulosa, Phlomis fruticosa, Verbascum undulatum, Quercus coccifera, Sarcopoterium spinosum, Corydothymus capitatus, Phagnalon rubestre, etc. (Horvat et al., 1974). The soils in the study area are calcareous with carbonates ranging from 12 to 56%. The organic matter contents were higher in the surface layer (0-5 cm) than in the lower layers, in most locations (1-11%). Clay contents ranged from 10.5 to 66%. The sampling sites were located up to a distance of 15 km from the aluminium factory. Soil samples were collected at a depth of 0-5 cm from 91 sites. Mature leaf samples, which were of similar size and age, of Phlomis fruticosa, Verbascum undulatum, Cistus salvifolius, Olea europaea var. oleaster, Pistacia lentiscus and Quercus coccifera were also collected from the same sites. The samples were then refrigerated at 0-4°C and analysed as soon as possible thereafter. Control samples of vegetation and soil were collected from similar sites located about 50 km from the factory. Samples of vegetation and soils were collected from sites during the summer of 1987. Soil samples were air-dried and passed through a 2 mm sieve. Mechanical analyses were made with a hydrometer, according to the procedure of Bouyoucos (1951). Carbonates were determined by HCI dissolution and measurement of evolved CO2. The pH was measured in a 1:1 soil:water ratio. The Walkley-Black wet digestion method, as described by Black (1965), was used for the determination of organic matter. All F determinations were made with an EA 306-F ion-specific electrode using a Microprocessor Ionanalyzer 901. The following extraction procedures were applied: for total F determination in soils 0.5 g soil dried at 105°C
N
.......
W'
iii ¸
i¸
~iLII
..
[]
, 0
>6
J 2
~ 4
, 6
, 8
i 10
(%) S
FIG. 1. WIND FREQUENCYAND SPEED (Beaufort) DIAGRAMSIN ALUMINIUM PLANT AREA (1984-86).
FLUORIDECONCENTRATIONOF SOILSAND VEGETATION
197
was:fused in the Ni crucible for 20 min with 4.5 g of NaOH. After the sample was dissolved in distilled water the pH was adjusted to 6.0 with 1.5 M citric acid (Noemmik, 1953; H&ni, 1975). For the determination of fluoride in vegetation the sample was cut and mixed to produce a sample as nearly uniform as possible. Ten grams of the dried sample (80°C for 24 h) were transferred to a 50-ml Ni crucible. Ten millilitres (6.7 g) of NaOH were added to the crucible and the sample dried for 2 h at 150°C.At the end of the drying time, the sample was transferred to a 550°C muffle furnace and fused for 2 h. After fusion, the sample was cooled and 25 ml of H20 w e r e added to dissolve the melt that was applied. After the melt was completely dissolved, it was transferred quantitatively to a 50-ml volumetric flask. The solution was then filtered through a Whatman No. 41 paper and aliquots were taken for analysis (Baker, 1972).
Results and Discussion The aluminium reduction plant at Beotia region, Greece, has produced F emissions since it started operation in 1960. These emissions are responsible for damaging vegetation growing on areas close to the plant. It is well recognized that the concentration of airborne fluorides is a major influence on the pattern of F accumulation by vegetation (National Academy of Sciences, 1971). Gaseous and particulate fluoride compounds are emitted from the factory as a result of the electrolytic reduction of alumina (AI203) dissolved in a melt of sodium fluoride. It has been estimated by Treshow (1969) that gaseous fluorides comprise greater than 50% of the total airborne fluoride around industrial sites. Gaseous forms pass readily through the leaf stomata, while the particulate forms are deposited on the surface of the vegetation where, if soluble, they are readily removed by leaching and consequently cause less damage. The 1985 and 1986 surveys in the same area revealed severe damage to natural vegetation around the aluminium plant. Some results concerning the F concentrations in soils and plant species were published by Haidouti eta/. (1991). The severity of the damage in the study area varies from necrosis of tips of the leaves to chlorosis. These observations and the absence of parasitic agents or nutritional disorders that would account for the observed leaf injury suggest fluoride accumulation as the possible causal agent of leaf injury. Injury symptoms generally increase with leaf concentration of fluoride on a dry weight basis, but there is no distinct pattern in which symptoms appear. Craggs et aL (1985) concluded that meteorological, microclimatic and biological factors were directly or indirectly influencing grass fluoride levels. The results of the previous study (Haidouti eta/., 1991) showed a severe F accumulation at distances up to 15 km from the plant. In the present research, samples were taken in a more detailed way from a distance up to 15 km for the purpose of locating the damage zones. In the more detailed study of the area the plant species which showed the most acute and characteristic symptoms was Olea europea var. o/easter, which has been used as a criterium for locating the zones. The study area was divided into three zones. The first one was extended to the point where the Olea leaves showed a necrosis connected with F concentrations of 400-200 ppm; the second zone was extended to the point where the Olea leaves showed a chlorosis that was connected with F concentrations of 200-100 ppm and the third zone included the areas where the Olea leaves did not present any symptoms and the F concentrations were lower than 100 ppm. The area of each zone and the sampling sites are presented in Fig. 2, while the F concentrations and the symptoms for all plant species and for each damage zone are summarized in Table 1. As shown in Table 1 there are large differences in fluoride concentrations among the different plant species. All species examined contained high fluoride concentrations in their leaves and showed that there is wide variation in plant response to fluoride emissions. This may be attributed to different deposition rates, substrates and/or
iG 2 DAMAGE ZONE MAP
199
FLUORIDE CONCENTRATIONOF SOILS AND VEGETATION TABLE 1. CONCENTRATIONSOF FLUORIDE (p.g g ~) IN FOLIAGE AND SOILS FROM THREE DAMAGE ZONES AND CONTROLAREAS NEAR AN ALUMINIUM PLANT Damage zone I
Control
Plant species
Mean fluoride concentration (+S.D.)
Phlomis fruticosa Verbascum undulatum Cistus salvifolius
621.2± 151.7 454.7± 128.5 427.0±189.8
Olea europaea var oleaster Pistacia lentiscus
345.8±122.4 295.8±76.2
Quercus coccifera soil
257.2±69.3 823.5±59.9
Phlomis fruticosa Verbascum undulatum Cistus salvifolius Olea europaea var oleaster Pistacia lentiscus Quercus coccifera soil
316.4±57.3 244.9±36.9 237.0±43.3 142.9±38.2 157.8±31.7 133,5+39.9 600.2±66.5
Without symptom s Chlorosis (60-75%) Chlorosis (10-20%) Chlorosis (40-50%) Chlorosis (20-40%) Chlorosis (5-10%)
Phlomis fruticosa Verbascum undulaturn Cistus salvifolius Olea europaea var oleaster Pistacia lentiscus Quercus coccifera soil
144.3±30,8 131.5±27.5 114.8±35.5 74.4±12.3 72.5±15.0 64.1± 15,1 297.6±88.4
Without symptoms Chlorosis (20-40%) Without symptoms Without symptoms Without symptoms Without symptoms
Phlomis fruticosa Verbascum undulatum Cistus salvifolius Olea europaea var oleaster Pistacia lentiscus Quercus coccifera soil
15.4±2.8 15.8±3.1 10.8±2.3 9,5±2.1 9.3±2.4 9.2± 1.9 98.7±21.9
Observed damage Without symptoms Chlorosis (80-95%) Chlorosis (25-50%) and necrosis (5-10%) Necrosis (50-65%) Necrosis (10-20%) and chlorosis (30-60%) Necrosis (10-20%)
tolerance. The species Phlomis frutJcosahad the highest F concentration and Quercus coccifera, the lowest. In addition, Table 1 shows that there are differences in the symptoms which the plant species exhibit in the three zones as well as in the percentage of leaves with discrete symptoms. There are also plant species, (e.g. Phlomis fruticosa) which although exhibiting the highest F concentration in all three zones, does not show any symptoms. A t-test has been done in order to confirm statistically the mean differences in F concentrations between the plant species in each zone. Important differences have been observed statistically in all plant species at P 0.01 and P 0.05 significance levels except for Cistus- Verbascum and Olea-Pistacia in the three zones, as well as PhlomisVerbascum and Quercus-Pistacia for the first zone, which do not present statistically important differences. Great differences in F concentrations have been observed among the same plant species in the same damage zone. This should be attributed to different degrees of exposure to emissions as well as to the individuality of each plant. The F content in the samples of each species was extremely variable but in every group there was a sequence of increasing fluoride content from the control zone to the high exposure zones.
FIG. 3. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS lu.g gr ~) tN PHLOMIS FRUTICOSA
FIG. 4, ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (~.g gr ~) IN VERBASCUMUNDUL.a.TUM.
5
I1
2
t}
u
:IG. 5. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (~g gr ~) IN CISTUSSALV/FOLIUS.
:IG. 6 ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (pg gr ~) IN OLEA EUROPEA V. OLEASTER.
FIG. 7. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (itg gr ~) IN PISTACIALENTISCUS.
FIG, 8. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATION:5 (~-g gr '1 ir~
cLuctlt.uo
~.u~.L.ir~,
Z
m
z
b~
z
5
_7
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FIG. 9. ISOFLUOR MAP SHOWING THE DISTRIBUTION OF FLUORIDE ACCUMULATIONS (l~g gr ~) IN SOILS.
FLUORIDE CONCENTRATIONOF SOILS AND VEGETATION
207
Control samples of leaves collected from sites located 50 km from the aluminium plant showed concentrations from 8.2 to 15.8 l~g g r-1 F dry weight. Assuming that these values characterize normal fluoride levels for the vegetation in the research area, any amount of leaf fluorides exceeding the above values should be considered as an airborne enrichment. The normal fluoride level for the soil of the region is about 100 ilg gr -1. The results of F analysis for plants and soils were used in order to prepare the isofluor maps (Figs 3-8) which show fluoride concentrations in the foliage of plants and concentrations of F in soils (Fig. 9). Phlomis fruticosa which exhibits the highest F values, also exhibits the highest density isofluors of all other plants in the area, while Quercus cocc/feFa with the lowest F values exhibits the lowest density isofluors. Consequently the isofluor distribution is connnected with the degree of pollution. In zone I, where the more severe damage was found in the plants, the isofluors are closer to each other for all the plant species as well as for the soil, compared with the other two zones. The isofluor shape shows an increasing F value in the north as well as to the east of the aluminium plant, which is connected with the prevailing wind direction in the area. In addition, to the east of the plant and at a certain distance of about 9 km from it, in zone II, an area of high F values is located. This is due to the relief combined with the prevailing winds. This study showed that the soils and all the plant species examined contained high F concentrations. The plant leaves exhibited leaf chlorosis, necrosis or both, whereas other plants with the same or higher leaf F content displayed little or no injury. Consequently, plant species differed greatly in their sensitivity to fluoride, but the intensity of symptoms varied among the individuals of the same species. A great deal of variability was observed in the F content of leaves of the same plant; the age, the position and the portion of leaves analysed influenced their fluoride status. Mature leaves and those found at the most exposed parts of the plant contained more F. These factors which affect the concentration of fluoride in the leaves should always be taken into account when leaf analysis is used for detection of air contamination with fluorides. Phytotoxic effects of airborne F, in respect to visual symptoms and F content of plant species growing in the vicinity of the aluminium factory, showed that Olea europea var. o/easter is the most sensitive plant to the toxicity, whereas Phlomis fruticosa did not exhibit leaf damage, in spite of a high accumulation of fluoride in its foliage. It would appear that Phlomis fruticosa is tolerant to F as far as visual injury is concerned. Holevas (1980) who worked in the same region, found that F toxicity symptoms in cultivated plants appeared only in the sensitive species of grapevine and apricot, while olive trees did not suffer extensive leaf damage. in summary, the aluminium plant is responsible for the high concentration of F in the soils and damage to vegetation, which is close to the plant. The short term effects of this pollution are obvious by visual inspection. In the long term the data of isofluor maps seem to indicate a spread of F pollution in both soil and vegetation as a function of the distance, the geomorphology and the direction of the prevailing winds. Acknowledgements--Theauthors would
like to thank the Ministry of Agriculture for financial support of the research project and Mrs J. Haidouti and Mr M. Pagonis for their assistance in chemical analyses,
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208
c. HAIDOUTIETAL.
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