Art08 Journal of Applied Botany and Food Quality 81, 145 - 150 (2007) 1Department of Biology, University of Isfahan, Isfahan, Iran 2School of Botany, The University of Melbourne, Parkville, Australia Accumulation of lead and zinc by plants colonizing a metal mining area in Central Iran S.M. Ghaderian1, G.R. Hemmat1, R.D. Reeves2, A.J.M. Baker2 (Received February 1, 2007) Summary The Irankouh area, located in Central Iran, is a vast mountainous region with mineralized soils and several active zinc and lead mining and smelting sites. In this study plants and soils from 5 different sites in this area were collected and analyzed for Zn and Pb. Analy- sis of soils from different sites showed the expected high concentra- tions of Zn and Pb - up to 23,000 and 18,000 µg g-1 for total, 30 and 20 µg g-1 for exchangeable, 1 and 0.6 µg g-1 for water-soluble frac- tions, respectively. Plants collected from these sites total 67 species from 66 genera and 29 families. Most of these are annual herbs found also on non-metalliferous soils in this region. The concentrations of Zn and Pb in the leaf dry matter of plants were variable, with up to 4800 µg g-1 for Zn and 740 µg g-1 Pb in Matthiola chenopodiifolia and Pinus elderica, respectively. A significant positive correlation was detected between the concentrations of Zn and Pb in plant dry matter and those in soils. The concentrations of Zn and Pb in the leaves of most species collected were significantly higher than for other plants from non-metalliferous soils. Some accumulator plants found in this area could have potential for soil clean-up by phyto- extraction. Introduction Heavy metal contamination is a most serious form of environmental pollution and has received widespread attention owing to toxicity to a wide variety of organisms. High concentrations of heavy metals in the soils are due to both natural processes as a result of weathering of rock minerals, and human industrial activities such as mining and smelting. On metal contaminated soils, a range of plants which have evolved physiological mechanisms to tolerate heavy metal toxicity can survive and reproduce (BAKER, 1987). Some tolerant plants are restricted to these metalliferous soils, either absolutely or regionally, and are recognized as absolute or local metallophytes. Others, oc- curring on both contaminated and uncontaminated soils as tolerant and non-tolerant races in the same region, are recognized as pseudo- metallophytes (BAKER, 1987). The latter group can be divided into selective, indifferent and accidentals (BAKER and PROCTOR, 1990). Some endemic forms of tolerant plants have been described on metal- liferous soils, as with the zinc floras in Western Europe (BROOKS, 1998). The tolerance of plants to heavy metals is achieved either by metal exclusion or metal accumulation. Some plants on heavy metal-contaminated soils accumulate extra- ordinary concentrations of heavy metals into their above ground parts. According to BAKER and BROOKS (1989) ‘hyperaccumulators’ of Co, Cu, Cr, Ni or Pb are those containing more than 1000 µg g-1 metal on a dry weight basis; for Mn and Zn the critical concentration was set at 10000 µg g-1. To date more than 450 metal hyperaccumulator species belonging to 45 families have been identified, of which about 18 and 5 species are zinc and lead hyperaccumulators, respectively, mostly from contaminated sites of Europe (SHIMWELL and LAURIE, 1972; REEVES and BROOKS, 1983; REEVES and BAKER, 2000). Many hyperaccumulators are endemic to metalliferous or metal conta- minated soils and thus are absolute metallophytes. While Zn is an essential element for plants and is normally present at concentrations of 10-200 µg g-1, Pb is neither essential nor beneficial in plant nutrition and is generally present at about 1-10 µg g-1 in plant tissues. Hyper- accumulation of Pb by plants is exceedingly rare, owing to the readiness with which it can be precipitated as the insoluble sulfate in the rhizosphere, hence minimizing potential uptake and transport to the aerial parts of the plants (BAKER and BROOKS, 1989). There are about 8000 plant species in Iran, belonging to 150 families; about 1727 of these species are endemic to the country (JALILI and JAMZAD, 1999). Due to the shortage of rainfall in central Iran, most plant species in these areas are herbaceous. While there are numerous natural metalliferous and metal-contaminated soils in different parts of Iran, little information is available regarding their flora, con- centration of metals in plants and any relationship between the concentrations of metals in plants and soils. The aims of this study were to identify the plant species growing on mineralized and contaminated soils in the Irankouh Zn and Pb mining area and to determine the concentrations of Zn and Pb in its soils and plants. Materials and methods Site description The Irankouh mining area is located 20 km southwest of Isfahan in central Iran in a mountain area at 1670-2750 m above sea level, between 32° 28´ and 32° 37´ N, and 51° 31´ and 51° 37´ E, in an area about 25 km by 3 km. The climate is semi-dry and the average annual rainfall is about 130 mm, mostly in winter and to some extent in autumn and spring. The maximum and minimum temperatures in summer and winter in this area are about 45°C and -10°C, respec- tively. There are several Zn and Pb mining sites, mostly exploited as open mines; some have been active during the last 60 years. In some parts the surface soils naturally contain high concentrations of Zn and Pb. Owing to the mining activity, and the distribution of dust and spoil, surrounding soils in a vast area have been affected by Zn and Pb. Ore concentration using flotation methods, and smelting, are carried out close to the mining sites, where dust and contaminated water cover the surroundings. In the present study, for collection of soils and plants, three different sites near three open-air mines (site1, Colahdarvazeh; site 2, Gooshfile; and site 3, Tapehsorkh), one small spoil heap (site 4) and an area around the smelting operation (site 5) were selected. Soil and plant sampling and analysis During June 2003-July 2004, plants growing on the above sites were collected for identification, analysis and preservation of reference specimens. Soil samples were taken from 0-15 cm depth from the same areas as the plants. The soils were air-dried and sieved to < 2 mm. For the analysis of total Zn and Pb, subsamples of 4 g were ground to pass a -80 mesh sieve (< 190 µm) and oven-dried at 70°C to constant 146 S.M. Ghaderian, G.R. Hemmat, R.D. Reeves, A.J.M. Baker weight. A further subsample of 0.5 g was transferred to a Kjeldahl digestion tube for extraction with 10 ml of a 3:1 HCl/HNO3 mixture. Tubes were left at room temperature overnight and were then trans- ferred to a heating block. Each was covered with an air condenser and the heating control adjusted so that the mixture refluxed gently at 80°C for 2 hours. After cooling, the digests were filtered through a moistened filter paper into 50 ml volumetric flasks. Flasks were made up to volume with distilled water. Analysis for Zn and Pb was performed by atomic absorption spectrophotometry (AAS, Phillips model PU 9100). For the analysis of exchangeable elements, 20 g of air-dry soil which had been sieved to < 2 mm was placed in a 100 ml screw-cap poly- thene bottle, 50 ml of 1M NH4NO3 solution added, and the suspen- sion was shaken for 2 hours at 20°C in an end-over-end shaker. After shaking, the soil suspension was left to stand for 5 min, and then filtered into a clean bottle. The filtrate was then acidified to 0.2% HNO3 for analysis of the above elements by AAS. For the analysis of water-soluble elements, a 3-inch pot was filled with soil which had been sieved to < 2 mm and watered with distilled water via its saucer. The saucer was refilled as required over 4 days to allow the sample to approach filled capacity. A conical flask with side-arm extension and a Büchner funnel with a 9 cm filter paper were placed on a top pan balance. The flask was connected to a vacuum line and wet soil from the pot was added gradually until the funnel was full. After 10 min, sufficient H2O-extractable had been drawn into the flask and the apparatus was disconnected. The ap- paratus including the collected solution and the Büchner funnel was reweighed. The H2O-extractable was decanted into an AAS tube and acidified with concentrated HCl to produce a final concentration of 4% HCl. The above elements were measured by AAS. The soil in the Büchner funnel was spread out and air-dried for a week and then reweighed. The concentration of Zn and Pb in H2O-extractable could then be related to the soil in terms of w/w (dry weight) by calculating and compensating for water content. The pH of the soil was deter- mined using a glass electrode after 10 g of soil had been stirred well in 30 ml distilled water in a beaker and allowed to stand for about 30 min. For the analysis of plants for Zn and Pb, leaf materials were washed well with double distilled water and dried at 70°C for 48 h. Then about 0.5 g dry leaf sample was weighed into 25 ml beakers and ashed in a muffle furnace for 14 h at 480°C. The ash was taken up in 5 ml 10% HNO3 and the digest finally made up to 10 ml in 10% HNO3. The solutions were analyzed for Zn and Pb by AAS. Results The soils of the Irankouh mining area are of near neutral pH, except site 5 (pH 6), and are highly enriched with Zn and Pb (Tab. 1). The total concentrations are as high as 23500 µg g-1 Zn in site 1 and 18000 µg g-1 Pb in site 5 (Tab. 1). For exchangeable metals, the highest concentrations of Zn are 25-30 µg g-1 (sites 5 and 1), and the highest Pb concentrations are 17-21 µg g-1 (sites 1 and 5). For H2O-extractable metals, the concentrations are low, only up to 1 µg g-1 Zn and 0.6 µg g-1 Pb (both at site 5) (Tab. 1). In our study, 67 species of vascular plants were collected from dif- ferent sites of the Irankouh mining areas (Tab. 2). They belong to 66 genera and 29 families. Major families represented are: Asteraceae (10), Brassicaceae (9), Poaceae (6), Apiaceae (5), Lamiaceae (5) and Chenopodiaceae (4). Most plants are herbaceous annuals, biennials or perennials. There are only 6 shrubs and 3 man-planted tree species: Pinus eldarica, Platanus orientalis and Elaeagnus angustifolia. These trees have been planted around sites 5 and 2. The concentrations of Zn and Pb in the leaves of collected plants are shown in Tab. 2. The Zn concentrations ranged from 35 µg g-1 in Peganum harmala (site 2) to 4800 µg g-1 in Matthiola chenopodiifolia (site 1). In addition Ebenus stellata (site 1), Heliotropium lasiocarpum (site 5), Diptychocarpus strictus (site 1), Phragmites australis (site 5), Kochis sp. (site 4), Descurainia sophia (site 5), Scorzonera tor- tuosissima (1), Tamarix ramosissima (site 5) and Capparis spinosa (site 5) contained Zn at 2000-3000 µg g-1. Concentrations of Zn in 23 species were more than 1000 µg g-1, belonging to site 1 (10 species), site 5 (9 species), site 3 (2), site 2 (1 species) and site 4 (1 species). The range of Pb concentrations was between 8 µg g-1 in Acantholimon aspadanum (site 2) and 740 in Pinus eldarica (site 5). Elaeagnus angustifolia (site 5), Scorzonera tortuosissima (site 5) and Stachys inflata (site 3) contained up to 600-700 µg g-1 Pb. Concentrations of Pb in 15 species were more than 300 µg g-1, belonging to sites 1, 5 and 3 with 9, 5 and 1 species, respectively. There were 9 species with both >1000 µg g-1 Zn and 300 µg g-1 Pb in their leaves; among these, Scorzonera tortuosissima and Ebenus stellata contained 2400 and 2900 µg g-1 Zn and 650 and 500 µg g-1 Pb, respectively. There was no significant positive correlation between the concentrations of Zn and Pb in these 9 species (r = 0.05, p>0.05). There was a significant positive correlation between the concen- trations of Zn in 20 species with more than 1000 µg g-1 Zn and the Tab. 1: Means (n=5) and ranges (below) of total (T), exchangeable (E) and H2O-extractable (H2O-E) Zn and Pb concentrations, and soil pH for the study sites. Site No. Zn (µg g-1) Pb (µg g-1) pH T E H2O-E T E H2O-E 1 16350 18.3 0.32 3700 13.5 0.35 7.0 10000-23500 10-30 0.30-0.35 1200-6400 10-17 0.30-0.40 6.9-7.1 2 5850 2.0 0.29 2150 1.35 0.25 6.9 4400-7700 1.5-2.5 0.27-0.31 1900-2400 1.2-1.5 0.20-0.30 6.8-7.0 3 5150 11.0 0.35 4200 2.25 0.36 7.2 3000-8500 10-12 0.30-0.40 3000-5700 2.0-2.35 0.30-0.40 7.1-7.3 4 11000 19.5 0.41 2900 3.4 0.31 7.4 6500-18500 18-21 0.40-0.42 1400-4400 3.0-4.0 0.25-0.35 7.35-7.46 5 5700 23.5 0.90 14800 20 0.57 6.0 5200-6250 22-25 0.80-1.00 12000-18000 18-21 0.55-0.60 5.9-6.2 Accumulation of lead and zinc by plants colonizing a metal mining area in Central Iran 147 Tab. 2: Concentrations of Zn and Pb in leaf dry matter (µg g-1) of plants from sites in the Irankouh mining area. Key: AH: annual herb; BH: biennial herb; PH: perennial herb; S: shrub; T: tree †Single specimens, or range of values where 2-4 specimens were analyzed. Species Plant form Site Zn† Pb† Apiaceae Eryngium billardieri F. Delaroche AH 2 80 150 Ferula sp. AH 1 135 45 Psammogeton canescens (DC.) Vatke AH 1 420 65 Pycnocycla spinosa Decne. ex Boiss. AH 1,2 330-515 175-205 Zosima radians Boiss. & Hohen. AH 1 800 115 Asclepiadaceae Cynanchum acutum L. PH 1 1135 70 Asteraceae Acroptilon repens (L.) DC. AH 5 920 240 Anthemis gayana Boiss. AH 3 365 80 Artemisia sieberi Besser AH 3 220 60 Centaurea gaubae (Bornm.) Wagenitz AH 3 180 58 Centaurea ispahanica Boiss. AH 1 730 380 Koelpinia tenuissima Pavl. & Lipsch. AH 1 1360 360 Pulicaria gnaphaloides (Vent.) Boiss. PH 2 260-305 40-105 Scorzonera tortuosissima Boiss. AH 1,5 750-2400 270-650 Senecio glaucus L. AH 1 1030 370 Zoegea purpurea Fresen. AH 2 120 45 Boraginaceae Heliotropium lasiocarpum Fisch. & C. A. Mey. AH 5 1120-2800 220-250 Lappula sp. AH 3 355 70 Brassicaceae Cardaria draba (L.) Desv. PH 1,4 600-675 50-90 Descurainia sophia (L.) Webb ex Prantl AH 5 2125 450 Diptychocarpus strictus (Fisch.) Trautv. AH 1 455-2670 185-335 Erysimum crassicaule (Boiss.) Boiss. BH 5 1800 150 Isatis cappadocica Desv. PH 1 465 65 Malcolmia africana (L.) R. Br. PH 1,4 490-1050 20-115 Matthiola chenopodiifolia Fisch. & C.A. Mey. PH 1 500-4800 160-340 Pseudocamelina sp. BH 1 520-1280 100-180 Sisymbrium septulatum DC. AH 5 1725 310 Capparaceae Capparis spinosa L. PH 1,5 860-2460 45-230 Cleome foliolosa DC. AH 2,3 340-535 50 Chenopodiaceae Anabasis setifera Moq. PH 4 570 160 Girgensohnia oppositiflora (Pall.) Fenzl AH 1 665 25 Kochis sp. AH 4 2780 225 Salsola kali L. PH 3,4 430-1390 25-86 Dipsacaceae Scabiosa olivieri Coult. AH 1 580 350 Elaeagnaceae Elaeagnus angustifolia L. T 5 520 660 Ephedraceae Ephedra strobilacea Bunge ex A. Lehm. S 1,2 45-85 10-30 Euphorbiaceae Euphorbia striatella L. PH 1 800 100 Fabaceae Astragalus sp. PH 1 690 315 Alhagi persarum Boiss. & Buhse PH 1 1800 180 Ebenus stellata Boiss. S 1 2910 500 Geraniaceae Erodium oxyrrhynchum M. Bieb. AH 1 400 300 148 S.M. Ghaderian, G.R. Hemmat, R.D. Reeves, A.J.M. Baker Lamiaceae Hymenocrater incanus Bunge PH 2 350 52 Lallemantia royleana Fisch. & C.A. Mey. AH 3 430 60 Salvia sp. AH 3 140 40 Stachys inflata Benth. AH 1,2,3 295-1635 154-640 Ziziphora tenuior L. AH 3,4 265-430 115-155 Malvaceae Alcea aucheri (Boiss.) Alef. PH 2 160 30 Moraceae Ficus johannis Boiss. S 1 1175 190 Papaveraceae Roemeria hybrida (L.) DC. AH 3 430 40 Pinaceae Pinus eldarica Medw. T 5 600 740 Platanaceae Platanus orientalis L. T 2 125 50 Plumbaginaceae Acantholimon aspadanum Bunge AH 2 50 8 Poaceae Bromus tectorum L. AH 3 430 60 Eremopyrum orientale (L.) Jaub. & Spach AH 3 1000 25 Pennisetum orientalis L. C. Rich. PH 1 435 85 Phragmites australis (Cav.) Trin. ex Steud. PH 1,5 950-2120 70-120 Poa sinaica Steud. PH 1,3 105-350 30-50 Stipa barbata Desf. PH 1 210 50 Polygonaceae Pteropyrum aucheri Jaub. & Spach S 1 235 130 Resedaceae Reseda lutea L. AH 4,5 725-1050 60-215 Rosaceae Amygdalus lycioides Spach S 3 100 20 Scrophulariaceae Linaria michauxii Chav. AH 1 400 50 Scrophularia striata Boiss. PH 3 285 40 Solanaceae Solanum nigrum L. AH 2 160 50 Tamaricaceae Tamarix ramosissima Ledeb. S 5 2600 97 Urticaceae Parietaria judaica L. PH 3 100 50 Zygophyllaceae Peganum harmala L. PH 2 35 20 concentrations of total (r = 0.45, p<0.05), exchangeable (r = 0.48, p<0.05) and H2O-extractable (r = 0.45, p<0.05) Zn in the soil. Also, a significant positive correlation exists between the concentrations of Pb in 14 species with more than 300 µg g-1 Pb and the concen- trations of total (r = 0.72, p<0.05), exchangeable (r = 0.58, p<0.02) and H2O-extractable (r = 0.56, p<0.05) Pb in the soil. Discussion The soils of all sites studied contain predictably high concentrations of Pb and Zn. This is due to natural mineralization in the parent rocks and to contamination by mining and smelting during the last 60 years. The concentrations of Zn and Pb in sites 1-3, shown in Tab. 1, are generally typical of mineralized soils in this area, although contaminated dusts arising from mining activity to some extent may have added to these elevated concentrations. High concentrations of these metals in site 4 are due to the spoil heap which has been leveled and left unchanged for nearly 20 years, whereas the high concen- trations in site 5 are mainly from the smelting operation. There is considerable variation in concentration both within and between sites pointing to the heterogeneous nature of mineral and mine wastes (GHADERIAN, 1998; WENZEL and JOCKWER, 1999; DAHMANI-MÜLLER Accumulation of lead and zinc by plants colonizing a metal mining area in Central Iran 149 et al., 2000). Concentrations of Zn in sites 1-4 are higher than those of Pb, mainly because the Irankouh mining area is more enriched with Zn minerals, and Pb is the secondary metal. Much of the metal is insoluble and not immediately available for plants and is therefore not directly toxic. However, heavy metals in the H2O-extractable and exchangeable forms may be directly accessible to organisms in the soil (LORENZ et al., 1997; POLLARD et al., 2002). Thus, the high con- centrations of Zn and Pb in the H2O-extractable and exchangeable fractions at some sites suggest extreme toxicity of the soil. According to PRÜESS (1994) the limits of NH4NO3-exchangeable Zn and Pb in soil are 5 and 0.3 µg g-1, respectively; above these concentrations, the assessment of risk and remediation needs is required. These concentrations are exceeded in all the soils in this study, except for exchangeable Zn in site 2. The highest concentrations of mean Zn and Pb (exchangeable and H2O-extractable) were in site 5, where minerals were processed and smelted. The pH here is 6 and due to the operations here the soils have more moisture. Generally, solubility and availability of metals in soils depend on many factors, including total metal content, pH and moisture regime (ALLOWAY, 1995). Most plants collected in this area were annual or perennial herbs; this dominant vegetation form is due to the climate of the area, with low annual rainfall typical of Central Iran. Among the plants collec- ted, 15 species are endemic to Iran (RECHINGER, 1963-1997), but not exclusively endemic to these metalliferous areas. As these plants naturally grow on these metal substrata, they can be categorized as pseudometallophytes (BAKER, 1987; POLLARD et al., 2002). Whether these plants are physiological races of metal tolerant species should be clear in further investigations. According to the definition of BAKER and BROOKS (1989), the criteria for hyperaccumulation for Zn and Pb are >10000 and 1000 µg g-1, respectively. On this basis, none of the collected species in the Irankouh mining area was a hyperaccumulator of either metal. The highest concentration of Zn (4800 µg g-1) was recorded in leaves of Matthiola chenopodiifolia (Brassicaceae), collected from different parts of site 1. The highest Pb concentrations (above 500 µg g-1) were found in planted trees of Pinus eldarica (740 µg g-1) and Elaeagnus angustifolia (660 µg g-1), as well as in naturally growing plants of Scorzonera tortuosissima (650 µg g-1), Stachys inflata (640 µg g-1) and Ebenus stellata (500 µg g-1). To date 18 and 5 hyper- accumulators of Zn and Pb, respectively, have been reported (REEVES and BAKER, 2000), mostly from Europe, but Zn and Pb hyper- accumulation does not occur in most plants from Pb and Zn conta- minated soils (SHIMWELL and LAURIE, 1972; REEVES, 1988; WENZEL and JOCKWER, 1999; REEVES et al., 2001). In contrast, Ni hyper- accumulators are rather more abundant in temperate and tropical ultramafic areas (REEVES, 1992; REEVES et al., 1999). YANG et al. (2002) believed that the criterion of 10000 µg g-1 Zn is too high for defining a Zn hyperaccumulator plant, and suggested 3000 µg g-1 leaf dry wt instead. Thus, the Zn accumulation in M. chenopodiifolia is notable and this plant seems to have potential for phytoremediation in some metal contaminated areas. Although there was no Pb hyper- accumulator at Irankouh, the existence here of 3 naturally occurring plants with > 500 µg g-1 Pb is notable. The significant positive correlations between the mean concentrations of Zn and Pb in the soil (as total, exchangeable or H2O-extractable) and the mean concentrations of these metals in dry leaves of plants which accumulate >1000 and 300 µg g-1, respectively, could indicate a cause-and-effect relationship. Such correlations can indicate a metal-accumulation tolerance strategy. BAKER et al. (1994), how- ever, did not find such a correlation between indices of metal tolerance in different populations of Thlaspi caerulescens and concentrations of the metals in the soils. As some soils of the Irankouh area naturally contain high concentrations of Zn and Pb, most plants growing on these substrata should be adapted to these metal stress conditions. More work should be done to determine the correlations of the Zn and Pb concentrations of each accumulator plant with its own sub- stratum. However, it is possible in areas adjacent to mines and smelters, in particular, that part of the measured heavy metals may be from external deposition not removed in sample washing. It is almost impossible to know how much might have been externally deposited on leaf surfaces. One consequence, unfortunately, is that because the contaminant is essentially soil material, it will generate strong positive correlation between soil metal and that apparently present in the plant. This is not a great problem when plant analysis is used as a biogeochemical prospecting method, but can introduce un- certainties into discussions of the physiology of heavy metal uptake into plants from the soil via the soil solution and the root system. Conclusion Plants on Zn and Pb enriched soils of the Irankouh area were collected and identified, and the concentrations of these metals in the soils and plants were determined. None of the 67 collected species were recognized as true endemics on these substrata: all were pseudo- metallophytes. Total Zn and Pb concentrations in the soils were high, in the range 3000-23500 µg g-1 Zn and 1200-18000 µg g-1 Pb. The bioavailable concentrations of these metals as NH4NO3-exchangeable and H2O-extractable were high enough to produce toxicity to non- tolerant plants. The concentrations of Zn and Pb in the plant leaves indicated that most contain elevated amounts of these metals. The concentrations of Zn were up to 4800 and 2800 µg g-1 in Matthiola chenopodiifolia and Heliotropium lasiocarpum, respectively. The highest Pb concentrations were in planted trees of Pinus eldarica (740 µg g-1) and Elaeagnus angustifolia (660 µg g-1) and in the naturally growing species Scorzonera tortuosissima (650 µg g-1) and Stachys inflata (640 µg g-1). Despite high concentrations of bio- available metals in the rhizosphere, no species showed hyper- accumulation of Zn or Pb. There were significant positive correlations between the concentra- tions of Zn or Pb in the soils and in the leaves of accumulator plants. This suggests the adaptation of some metal tolerant plants to the toxic concentrations of heavy metals in the soils by the uptake me- chanism. These accumulator plants may be valuable in phytoextrac- tion of metal-contaminated soils in some parts of Central Iran. Acknowledgements We thank M. R. Rahiminejad for his help in identification of plants, M. Nogherian for his geological advice and BAMA Co. for their help in analysis of the samples. This research was carried out using an MSc grant to GRH, offered by the Graduate School, University of Isfahan. References ALLOWAY, B.J. (ed.), 1995: Heavy metals in soils. 2nd edn. Blackie Academic and Professional, London. BAKER, A.J.M., 1987: Metal tolerance. New Phytol. 106, 93-111. BAKER, A.J.M., BROOKS, R.R., 1989: Terrestrial higher plants which hyper- accumulate metallic elements – a review of their distribution, ecology and phytochemistry. Biorecovery 1, 81-126. BAKER, A.J.M., PROCTOR, J., 1990: The influence of cadmium, copper, lead, and zinc on the distribution and evolution of metallophytes in the British Isles. Pl. Syst. Evol. 173, 91-108. 150 S.M. Ghaderian, G.R. Hemmat, R.D. Reeves, A.J.M. Baker BAKER, A.J.M., REEVES, R.D., HAJAR, A.S.M., 1994: Heavy metal ac- cumulation and tolerance in British populations of the metallophyte Thlaspi caerulescens J. & C. Presl (Brassicaceae). New Phytol. 127, 61- 68. BROOKS, R.R., 1998: Plants that hyperaccumulate heavy metals. CAB International, Cambridge. DAHMANI-MÜLLER, H., VAN OORT, F., GÉLIE, B., BALABANE, M., 2000: Strategies of heavy metal uptake by three plant species growing near a metal smelter. Environ. Pollut. 109, 231-238. GHADERIAN, S.M., 1998: The effect of toxic heavy metals upon fungi of the genus Pythium isolated from soil. Ph.D thesis, University of Sheffield, UK. JALILI, A., JAMZAD, Z., 1999: Red data book of Iran. RIFR, Tehran. LORENZ, S.E., HAMON, R.E., HOLM, P.E., DOMINGUES, H.C., SEQUEIRA, E.M., CHRISTENSEN, T.H., MCGRATH, S.P., 1997: Cadmium and zinc in plants and soil solutions from contaminated soils. Plant Soil 189, 21-31. POLLARD, A.J., POWELL, K.D., HARPER, F.A., SMITH, J.A.C., 2002: The genetic basis of metal hyperaccumulation in plants. Crit. Rev. Plant Sci. 21, 539-566. PRÜESS, A., 1994: Einstufung mobiler Spurenelemente in Böden. In: Rosen- kranz, D., Einsele, G., Harress, M. (eds.), Ergänzbares Handbuch der Maßnahmen und Empfehlungen für Schutz, Pflege und Sanierung von Böden, Landschaft und Grundwasser, 15. Lieferung, I/94. Erich Schmidt Verlag, Berlin. RECHINGER, K.H. (ed.), 1963-1997: Flora Iranica, 1-172. Akademische Druck- u. Verlagsanstalt, Graz, Austria. REEVES, R.D., 1988: Nickel and zinc accumulation by species of Thlaspi L., Cochlearia L., and other genera of the Brassicaceae. Taxon 32, 309-318. REEVES, R.D., 1992: The hyperaccumulation of nickel by serpentine plants. In: Baker, A.J.M, Proctor, J., Reeves, R.D. (eds.), The vegetation of ultra- mafic (serpentine) soils, 253-278. Intercept Ltd, Andover, U.K. REEVES, R.D., BAKER, A.J.M., 2000: Metal accumulating plants. In: Raskin, I., Ensley, B.D. (eds.), Phytoremediation of toxic metals: using plants to clean up the environment, 193-229. John Wiley & Sons Inc., NY, USA. REEVES, R.D., BAKER, A.J.M, BORHIDI, A., BERAZAÍN, R., 1999: Nickel hyperaccumulation in the serpentine flora of Cuba. Ann. Bot. 83, 29-38. REEVES, R.D., BROOKS, R.R., 1983: Hyperaccumulation of lead and zinc by two metallophytes from mining areas of Central Europe. Environ. Pol- lut. 31, 277-285. REEVES, R.D., KRUCKEBERG, A.R., ADIGÜZEL, N., KRÄMER, U., 2001: Studies on the flora of serpentine and other metalliferous areas of western Turkey. S. Afr. J. Sci. 97, 513-517. SHIMWELL, D.W., LAURIE, A.E., 1972: Lead and zinc concentration of vege- tation in the Southern Pennines. Environ. Pollut. 3, 291-301. WENZEL, W.W., JOCKWER, F., 1999: Accumulation of heavy metals in plants grown on mineralized soils of the Austrian Alps. Environ. Pollut. 104, 145-155. YANG, X., XINXIAN, L., WUZHONG, N., CHENXIN, F.U., 2002: Sedum alfredii H: a new Zn hyperaccumulating plant first found in China. Chinese Sci. Bull. 19, 1634-1637. Address of the authors: Dr. S.M. Ghaderian (corresponding author) (email: ghaderian@sci.ui.ac.ir) and G.R. Hemmat, Department of Biology, Faculty of Sciences, University of Isfahan, Isfahan, 81746-73441, Iran. Professor A.J.M. Baker and Professor R.D. Reeves, School of Botany, The University of Melbourne, Parkville, VIC 3010, Australia. << /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /All /Binding /Left /CalGrayProfile (Dot Gain 20%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (U.S. Web Coated \050SWOP\051 v2) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Warning /CompatibilityLevel 1.4 /CompressObjects /Tags /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages true /CreateJDFFile false /CreateJobTicket false /DefaultRenderingIntent /Default /DetectBlends true /ColorConversionStrategy /LeaveColorUnchanged /DoThumbnails false /EmbedAllFonts true /EmbedJobOptions true /DSCReportingLevel 0 /EmitDSCWarnings false /EndPage -1 /ImageMemory 1048576 /LockDistillerParams false /MaxSubsetPct 100 /Optimize true /OPM 1 /ParseDSCComments true /ParseDSCCommentsForDocInfo true /PreserveCopyPage true /PreserveEPSInfo true /PreserveHalftoneInfo false /PreserveOPIComments false /PreserveOverprintSettings true /StartPage 1 /SubsetFonts true /TransferFunctionInfo /Apply /UCRandBGInfo /Preserve /UsePrologue false /ColorSettingsFile () /AlwaysEmbed [ true ] /NeverEmbed [ true ] /AntiAliasColorImages false /DownsampleColorImages true /ColorImageDownsampleType /Bicubic /ColorImageResolution 300 /ColorImageDepth -1 /ColorImageDownsampleThreshold 1.50000 /EncodeColorImages true /ColorImageFilter /DCTEncode /AutoFilterColorImages true /ColorImageAutoFilterStrategy /JPEG /ColorACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /ColorImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000ColorACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000ColorImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasGrayImages false /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /GrayImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000GrayACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000GrayImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasMonoImages false /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict << /K -1 >> /AllowPSXObjects false /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputCondition () /PDFXRegistryName (http://www.color.org) /PDFXTrapped /Unknown /Description << /FRA /ENU (Use these settings to create PDF documents with higher image resolution for improved printing quality. The PDF documents can be opened with Acrobat and Reader 5.0 and later.) /JPN /PTB /DAN /NLD /ESP /SUO /ITA /NOR /SVE /DEU >> >> setdistillerparams << /HWResolution [2400 2400] /PageSize [907.087 680.315] >> setpagedevice