Distribution and mobility of toxic metals in Thymus alsarensis Ronniger in the Allchar As–Sb–Tl mine,Republic of Macedonia

Abstract

The Allchar district is an abandoned antimony–arsenic–thallium deposit located in the north-western region of Ko?uf mountain in the Republic of Macedonia. The locality of Allchar has a complex and unique mineral composition. The current study sought to investigate the levels of uptake and distribution of different heavy metals, such as As, Sb and Tl, in the different organs of Thymus alsarensis Ronniger, an endemic plant species of the area. Root, stem, leaf and flower samples, as well as corresponding soils, were processed, digested and then analysed by inductively coupled plasma atomic emission spectrometry. Significant accumulation of As, Sb and Tl in this endemic species was observed. Total As content in the soil ranged from 34.7 to 5288 mg kg^–1, and the content of As in plants ranged from 0.25 to 140 mg kg^–1. The content of Sb in soil and plants ranged from 6.3 to 130 mg kg^–1 and 0.25 to 1.51 mg kg^–1, respectively. Lastly, the content of Tl in soil and plants ranged from 2.0 to 330 mg kg^–1 and 0.10 to 496 mg kg^–1, respectively. Similar results were obtained from extraction tests of soil samples using various solvents.     

Interactive effects of chromate and arsenate on their uptake and speciation in Pteris ensiformis

Background and aims

Arsenate (AsV) and chromate (CrVI) inhibit each other’s uptake and translocation in As-hyperaccumulator Pteris vittata. In the present study, we extended the research to As-sensitive plant Pteris ensiformis to better understand the mechanism of their interactions.

Methods

Plants were exposed to 0, 0.75 or 7.5 mg L^?1 AsV and 0, 0.52, or 5.2 mg L^?1 CrVI for 7 d in hydroponics. Arsenic and Cr speciation were determined in nutrient solutions and plant biomass.

Results

P. ensiformis accumulated high levels of As and Cr in the rhizomes and roots with low levels in the fronds. However, P. ensiformis was much more effective in taking up Cr than As, as much more Cr was accumulated in the roots (306–6015 vs. 87–642 mg kg^?1). AsV and CrVI increased each other’s uptake in the rhizomes and roots when co-present. The AsV and CrVI taken up by P. ensiformis were reduced to arsenite (AsIII) and chromite (CrIII), possibly serving as detoxification mechanism.

Conclusions

Uptake of As and Cr induced oxidative stress as indicated by increased lipid peroxidation and electrical conductivity. Arsenic and Cr increased each other’s uptake by P. ensiformis.

     

An Abandoned Copper Mining Site in Cyprus and Assessment of Metal Concentrations in Plants and Soil

Mining is an important source of metal pollution in the environment and abandoned mines are extremely restricted habitats for plants. Some plant species growing on metalliferous soils around mine tailings and spoil-heaps are metal-tolerant and accumulate high concentrations of metals. In this investigation, we aimed to perform a research in the CMC-abandoned copper mining area in Lefke-North Cyprus to assess the recent metal pollution in soil and plant systems. We collected 16 soil samples and 25 plant species from 8 localities around the vicinity of tailing ponds. Some concentrations of metals in soil samples varied from 185 to 1023 mg kg^?1 Cu, 15.2 to 59.2 mg kg^?1 Ni, 2.3 to 73.6 mg kg^?1 Cd and metals for plants ranged from 0.135 to 283 mg kg^?1 Cu, 0.26 to 31.2 mg kg^?1 Ni, 0.143 to 277 mg kg^?1 Cd. Atriplex semibaccata, Acacia cyanophylla, Erodium spp., Inula viscosa, Juncus sp., Oxalis pes-caprea, Pistacia lentiscus, Senecio vulgaris and Tragopogon sinuatus accumulated higher concentrations. BCF for Atriplex semibaccata was found very high, for this reason this plant can tentatively be considered as a hyperaccumulator of Cu and Cd, but it needs further investigation for its potential in phytoremediation.     

Phytoextraction of Risk Elements by Willow and Poplar Trees

To characterize the phytoextraction efficiency of two clones of willow trees (Salix x smithiana Willd., Salix rubens) and two clones of poplar trees (Populus nigra x maximowiczii, Populus nigra Wolterson) were planted in contaminated soil (0.4–2.0 mg Cd.kg^?1, 78–313 mg Zn.kg^?1, 21.3–118 mg Cu.kg^?1). Field experiment was carried out in Czech Republic. The study investigated their ability to accumulate heavy metals (Cd, Zn, and Cu) in harvestable plant parts. The poplars produced higher amount of biomass than willows. Both Salix clones accumulated higher amount of Cd, Zn and Cu in their biomass (maximum 6.8 mg Cd.kg^?1, 909 mg Zn.kg^?1, and 17.7 mg Cu.kg^?1) compared to Populus clones (maximum 2.06 mg Cd.kg^?1, 463 mg Zn.kg^?1, and 11.8 mg Cu.kg^?1). There were no significant differences between clones of individual species. BCs for Cd and Zn were greater than 1 (the highest in willow leaves). BCs values of Cu were very low. These results indicate that Salix is more suitable plant for phytoextraction of Cd and Zn than Populus. The Cu phytoextraction potential of Salix and Populus trees was not confirmed in this experiment due to low soil availability of this element.     

LEAD TOLERANCE AND ACCUMULATION IN PTERIS VITTATA AND PITYROGRAMMA CALOMELANOS,AND THEIR POTENTIAL FOR PHYTOREMEDIATION OF LEAD-CONTAMINATED SOIL

A field survey was conducted to search for Pb accumulation in fern species at Bo Ngam Pb mine, Thailand. Eleven fern species including Pteris vittata accumulated Pb in the range of 23.3–295.6 mg kg^?1 in the aboveground parts. Hydroponic, pot, and field trial experiments were carried out to investigate Pb-accumulation ability in ferns; including P. vittata and the ornamental species, Pityrogramma calomelanos, Nephrolepis exaltata cv. Gracillimum, and N. exaltata cv. Smirha. In hydroponic experiment, Pi. calomelanos accumulated the highest concentration of Pb (root 14161.1 mg kg^?1, frond 402.7 mg kg^?1). The pot study showed that P. vittata, Pi. calomelanos, and N. exaltata cv. Gracillimum grew well when grown in soil Pb at 92900 mg kg^?1. N. exaltata cv. Gracillimum accumulated the highest Pb concentration in the frond (5074 mg kg^?1) and P. vittata accumulated the highest Pb concentration in the root (16257.5 mg kg^?1). All fern species exhibited TF values less than 1 in both hydroponic and pot experiments. When P. vittata and Pi. calomelanos were grown at mine soils for 6 months, P. vittata tolerated higher soil Pb (94584–101405 mg kg^?1) and accumulated more Pb in frond (4829.6 mg kg^?1) and showed TF > 1 after 2 months of growth. These results indicated that P. vittata can be potentially useful for phytoremediation of Pb-contaminated soil.     

Soil fertility and fine root dynamics in response to 4 years of nutrient (N,P, K) fertilization in a lowland tropical moist forest,Panama

The question of how tropical trees cope with infertile soils has been challenging to address, in part, because fine root dynamics must be studied in situ. We used annual fertilization with nitrogen (N as urea, 12.5 g N m^?2 year^?1), phosphorus (P as superphosphate, 5 g P m^?2 year^?1) and potassium (K as KCl, 5 g K m^?2 year^?1) within 38 ha of old‐growth lowland tropical moist forest in Panama and examined fine root dynamics with minirhizotron images. We expected that added P, above all, would (i) decrease fine root biomass but, (ii) have no impact on fine root turnover. Soil in the study area was moderately acidic (pH = 5.28), had moderate concentrations of exchangeable base cations (13.4 cmol kg^?1), low concentrations of Bray‐extractable phosphate (PO₄ = 2.2 mg kg^?1), and modest concentrations of KCl‐extractable nitrate (NO₃ = 5.0 mg kg^?1) and KCl‐extractable ammonium (NH₄ = 15.5 mg kg^?1). Added N increased concentrations of KCl‐extractable NO₃ and acidified the soil by one pH unit. Added P increased concentrations of Bray‐extractable PO₄ and P in the labile fraction. Concentrations of exchangeable K were elevated in K addition plots but reduced by N additions. Fine root dynamics responded to added K rather than added P. After 2 years, added K decreased fine root biomass from 330 to 275 g m^?2. The turnover coefficient of fine roots <1 mm diameter ranged from 2.6 to 4.4 per year, and the largest values occurred in plots with added K. This study supported the view that biomass and dynamics of fine roots respond to soil nutrient availability in species‐rich, lowland tropical moist forest. However, K rather than P elicited root responses. Fine roots smaller than 1 mm have a short lifetime (<140 days), and control of fine root production by nutrient availability in tropical forests deserves more study.     

Soil Nitrogen Fertilization Effects on Phytoextraction of Cadmium and Lead by Tobacco (Nicotiana tabacum L.)

A greenhouse experiment using 24 plastic pots filled with 6 kg of Pb- and Cd-contaminated soil was carried out. In all 24 pots, soils were heavy metal–contaminated with 10 mg Cd kg^?1 soil and 500 mg of Pb kg^?1 soil by using CdCl and PbNO₃. Two-month-old tobacco (Nicotiana tabacum L.) plants were used to extract these heavy metals. Results showed that tobacco is able to remove Cd and Pb from contaminated soils and concentrate them in its harvestable part, that is, it could be very useful in phytoextraction of these heavy metals. Increasing additions of ammonium nitrate to soil (50, 100, and 150 mg N kg^?1 soil) significantly (p ≤ .05) increased aboveground Cd and Pb accumulation during a 50-day experimental period, whereas increasing additions of urea to soil (50 and 100 mg N kg^?1 soil) did not show these effects at the same significance levels. Increasing additions of ammonium nitrate to soil shows as dry matter increases, both accumulated Cd and accumulated Pb also increase when tobacco plants are growing under Pb- and Cd-contaminated soil conditions. Higher Pb concentrations depress Cd/Pb ratios for concentrations and accumulations, suggesting that Pb negatively affects Cd concentration and/or accumulation.     

Uptake of arsenic by mushrooms from soil

ABSTRACT

Graphite furnace atomic absorption spectrometry (standard addition method) was used to determine the total arsenic in wild-growing mushrooms after digestion with nitric acid, then with perchloric acid and in associated soils after digestion with mixtures of nitric and hydrofluoric acids in a microwave system. Among 83 species of mushrooms the highest concentrations of arsenic on a dry mass basis were found in Laccaria amethystea (26–125 mg kg^?1), Laccaria laccata (11–33 mg kg^?1), Thelephora terrestris (38 mg kg^?1), Boletus cavipes (11.6 mg kg^?1) and Ramaria botrytis (10 mg kg^?1). Mushroom caps of L. laccata, L. amethystea, and B. cavipes had approximately double the arsenic concentrations found in stems. The arsenic concentrations in caps of L. amethystea and L. laccata were directly proportional to the concentrations in the soils. The concentrations of arsenic in the soils were in the range 6.5–65 mg kg^?1. Among the 19 mushroom caps with arsenic concentrations above the method detection limit of 0.2 mg As/kg dry mass, only L. amethystea and L. laccata had arsenic concentration ratios ‘cap/soil’ higher than 1 (between 1.1 and 1.9). Thelephora terrestris had a ratio of 2.37.     

Cd AND Zn TOLERANCE AND ACCUMULATION BY SEDUM JINIANUM IN EAST CHINA

Field survey, hydroponic culture, and pot experiments were carried out to examine and characterize cadmium (Cd) and zinc (Zn) uptake and accumulation by Sedum jinianum, a plant species native to China. Shoot Cd and Zn concentrations in S. jinianum growing on a lead/Zn mine area reached 103–478 and 4165–8349 mg kg^?1 (DM), respectively. The shoot Cd concentration increased with the increasing Cd supply, peaking at 5083 mg kg^?1 (DM) when grown in nutrient at a concentration of 100 μmol L^?1 for 32 d, and decreased as the solution concentration increased from 200 to 400 μmol L^?1. The shoot-to-root ratio of plant Cd concentrations was > 1 when grown in solution Cd concentrations ≤ 200 μmol L^?1. Foliar, stem, and root Zn concentrations increased linearly with the increasing Zn level from 1 to 9600 μmol L^?1. The Zn concentrations in various plant parts decreased in the order roots > stem > leaves, with maximum concentrations of 19.3, 33.8, and 46.1 g kg^?1 (DM), respectively, when plants were grown at 9600 μmol Zn L^?1 for 32 d. Shoot Cd concentrations reached 16.4 and 79.8 mg kg^?1 (DM) when plants were grown in the pots of soil with Cd levels of 2.4 mg kg^?1 and 9.2 mg kg^?1, respectively. At soil Zn levels of 619 and 4082 mg kg^?1, shoot Zn concentrations reached 1560 and 15,558 mg kg^?1 (DM), respectively. The results indicate that S. jinianum is a Cd hyperaccumulator with a high capacity to accumulate Zn in the shoots.     

Effect of soil cadmium application and pH on growth and cadmium accumulation in roots, leaves and fruit of strawberry plants (Fragaria × ananassa Duch.)

Three strawberry (Fragaria × ananassa Duch.) cultivars Rainier, Totem and Selva were grown under greenhouse conditions in a Parkhill sandy loam soil with a background DTPA-extractable Cd concentration of 0.18 mg kg^-1 and a pH of 5.1. Experimental treatments included combinations of 4 Cd applications (0, 15, 30 and 60 mg Cd kg^-1 soil) applied as CdSO₄ and 2 soil pH values 5.1 and 6.8. Both the application of Cd and pH of the soil significantly affected plant growth, yield and Cd accumulation in plant tissue anf fruit. Although roots accumulated the highest concentrations of Cd of all plant parts investigated, increased soil Cd application reduced leaf weight more than root weight. In general, yield of strawberries was decreased by an increase in amount of soil-applied Cd, however the yield response varied among cultivars. At 60 mg Cd kg^-1 soil, yield of Rainier cultivar was reduced to 17.6% of control plants. Over 90% of total Cd taken up by plants grown in Cd-treated soil accumulated in roots, regardless of the Cd level in the soil. Root Cd concentrations ranged from 2.6 mg kg^-1 (control plants) to 505.7 mg kg^-1 (Totem plants grown in soil at highest Cd and a soil pH 5.1) and were directly related to soil Cd concentrations. Cd translocation from roots to leaves and fruit was very limited, resulting in a maximum Cd concentration in root leaf tissue of 10.2 mg kg^-1. Accumulation of Cd in fruit was found to correlate well with leaf Cd, although even at the highest amount of applied Cd, fruit Cd concentration did not exceed 700 g kg^-1 of fresh weight.Contribution no. 951     

Selenium Accumulation by Brassica Napus Grown in Se-Laden Soil From Different Depths of Kesterson Reservoir

Selenium (Se) may be present in soils and sediments in high concentrations and yet not be mobile or available for plant uptake. Phytoremediation of Se by canola (Brassica napus) was evaluated in sediment from Kesterson Reservoir at three different depths (0 to 30, 30 to 60, 60 to 90?cm) under greenhouse and field conditions. In the greenhouse study, total soil Se concentrations at preplant ranged from 10 to 112?mg kg^?1. Shoot Se concentrations of canola were 182, 53, and 19?mg kg^?1 DM in the 0 to 30, 30 to 60, and 60 to 90?cm depths, respectively. Percentages of Se accumulated by canola relative to total Se loss in the soil at postharvest were as high as 24%. In the field study, total soil Se concentrations were as high as 26?mg kg^?1 soil. Field-grown canola accumulated approximately 50?mg kg^?1 DM, which accounted for less than 10% of total Se lost in the soil at postharvest. Phytoremediation of Se-laden soils under field conditions was about 50% of that observed under controlled greenhouse conditions. This relationship may be useful for prediction of field remediation operation using greenhouse generated data.     

Determination of the water-extractable fraction of iron in selected medicinal plant raw materials: Folium Menthae,Folium Urticae and Folium Salviae

Abstract

The aim of the investigation was to study the water-extractable iron species at different pH values from selected medicinal plant materials, therefore total and water-extractable iron species were determined in 30 samples of the medicinal plants Folium Menthae, Folium Urticae and Folium Salviae. The extractions were infusions popularly used by patients. Microwave digestion of the plant samples, and flame atomic absorption spectrometry (FAAS) was used for the determination of iron. Total iron ranged from 132.93 to 149.26 mg kg^?1 of dry plant weight (d.w.) in Folium Menthae, from 47.62 to 58.09 mg kg^?1(d.w.) in Folium Urticae, and from 189.81 to 233.58 mg kg^?1 (d.w.) in Folium Salviae. The ranges of concentrations of water-extractable iron species were found to be lower than those of the total iron concentrations, viz. 9.45, 5.38 and 9.04 mg kg^?1 of d.w. in Folium Menthae, Folium Urticae and Folium Salviae, respectively. Taking into consideration the potential bioavailability of iron species in solutions of different pH values representing the acidity of particular segments of the digestive system of humans, these fractions of iron are very low in comparison with the total iron contents, especially the species detected at pH = 1.2. Based on the comparison with the values of Recommended Daily Allowances (RDA) for women and men, the water-extractable fractions of iron found in the studied plant materials, cannot be significant sources of that microelement for patients.     

Bioaccumulation of Heavy Metals by Endemic Viola Species from the Soil in the Vicinity of the As-Sb-Tl Mine “Allchar”, Republic of Macedonia

Allchar mine is an abandoned arsenic-antimony-thallium deposit located on the north-western part of Ko?uf Mt., Republic of Macedonia. Allchar is a unique deposit within the world, due to the variety of its mineral composition especially and in the high content of thallium. The aim of this work was to assess the level of contamination at this post-mining area as well as to determine the intensity of accumulation of various elements (Ag, Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sb, Sr, Tl, V, and Zn) with focus on As, Sb and Tl, in two endemic Viola species from this locality (Viola allcharensis G. Beck, Viola arsenica G. Beck) and one Balkan endemic species (Viola macedonica Boiss. &; Heldr.). Samples of different plant parts and soil were digested and then analysed by ICP-AES. It was found that the accumulation of As, Sb, and Tl in these endemic species is significantly high. In this study a systematic investigation of the As-Sb-Tl contamination of soils and their bioavailability was carried out using the extraction procedure in order to explore the mobility and potential bioavailability of the As, Sb, and Tl.     

A comparison of arsenic mobility in Phaseolus vulgaris, Mentha aquatica, and Pteris cretica rhizosphere

The ability of Phaseolus vulgaris, Mentha aquatica, and Pteris cretica to release arsenic (As) species from contaminated soil was tested in rhizobox experiments in three soils differing in their physicochemical parameters and total and mobile As concentration. Relatively low uptake of arsenic by P. vulgaris and M. aquatica resulted in very low and ambiguous changes in rhizosphere soil compared to bulk soil. However, there were observed differences in the distribution of the mobile As portion in soil to individual As species as affected by plant species and/or plantation conditions of these plants. Higher percentage of mobile arsenite in mint rhizosphere seems to be related to more reducing conditions during cultivation of these wetland plants. P. cretica planted in the soils containing between 36 and 1436 mg As kg⁻¹ was able to accumulate between 80 and 500 mg As kg⁻¹ in aboveground biomass. The extractable concentrations of As compounds in rhizosphere soil of P. cretica showed a clear depletion of arsenate (representing more than 90% of extractable arsenic) with the distance from plant roots. However, the As uptake mechanisms, as well as As transformation within hyperaccumulating fern plants, differ substantially from those in higher plants. Therefore the finding of suitable higher plant tolerant to the As soil contamination with good ability to accumulate As in aboveground biomass remains for the further research.     

Potential of Sonchus Arvensis for the Phytoremediation of Lead-Contaminated Soil

Sonchus arvensis is one of the pioneer plant species that were found in the abandoned Bo Ngam Pb mine in Thailand. S. arvensis was collected from three sites. The highest Pb shoot concentration was 9317 mg kg^?1 and the highest translocation factor (TF) and bioaccumulation factor (BF) values were 2.5 and 6.0, respectively. To investigate Pb uptake capacity of S. arvensis, a hydroponic experiment was performed for 15 d. S. arvensis exposed to 5 mg L^?1 Pb solution had the highest Pb shoot accumulation (849 mg kg^?1). In a pot study, S. arvensis was grown in Pb mine soils amended with organic and inorganic fertilizers for 2 mo. The addition of organic fertilizer to the soil increased plant dry biomass sharply. All treatments with ethylene-diamine-tetra-acetic acid (EDTA) had Pb accumulation in shoots greater than 1000 mg kg^?1 and the highest Pb shoot accumulation was found in S. arvensis grown in soil amended with organic fertilizer and EDTA (1397 mg kg^?1). In a field trial study, S. arvensis was grown at three sites in the mine area for 6 mo. S. arvensis could tolerate a total Pb of 100,000 mg kg^?1 in the soil and accumulated Pb in the shoots up to 3664 mg kg^?1 with high TF (2.19) and BF (2.38) values. These results suggest that S. arvensis is a good candidate for Pb phytoremediation.     

Bioavailability and speciation of arsenic in urban street dusts from Baoding city,China

Twenty-one street dust samples were collected from the urban sites in Baoding, China, to investigate the species and bioavailabilty of arsenic in them. The ecological risk and bioavailability of arsenic were evaluated using three models including Bioavailability Factor (BF), Contamination Factors (C_f)and Geoaccumulation Index model (I_geo). The species of arsenic in the dust samples were analyzed using an optimized BCR sequential extraction method. The total concentrations of As in the street dust samples ranged from 13.16 mg kg^?1 to 67.26 mg kg^?1. Geoaccumulation index (I_geo) of As ranged from 0.28 to 1.99. The speciation analysis indicated that As in the street dust samples were mainly in the residual fraction (F4), and the proportion ranged from 84.35% to 87.07%. Moreover, the ranges of the BF and C_f were 0.650–0.129 and 0.119–0.186, respectively. The results indicated that arsenic contained in the street dust samples was with low bioavailability.     

Polycyclic Aromatic Hydrocarbon (PAH) Contamination in the Urban Topsoils of Shenyang,China

Polycyclic aromatic hydrocarbons (PAHs) in the surface urban soils of Shenyang in Northeastern China were investigated. The total concentration of the PAHs ranged from 0.09 to 8.35 mg kg^?1, with an average value of 1.51 ± 1.64 mg kg^?1. 3–5-ring PAHs accounted for 90% of total PAHs. The functional areas, such as the industrial regions (4.95 mg kg^?1) and main roads (1.56 mg kg^?1), as well as the administrative divisions, including the districts of Shenhe (1.49 mg kg^?1), Heping (2.08 mg kg^?1), and Tiexi (2.14 mg kg^?1), were heavily polluted by PAHs. The diagnostic ratios and principal component analysis (PCA) for PAHs indicate that the pollutants probably originated primarily from coal combustion and petroleum sources. The Nemerow composite index, used to assess environmental quality, shows that the soil samples were heavily polluted with PAHs, and although 52.8% of the soil sampling sites were safe, 47.2% of the soil sampling sites registered different grades of PAH pollution. The PAH contamination in Shenyang emphasizes the need for controlling fossil fuel combustion and traffic exhaust.     

The Accumulation of Risk and Essential Elements in Edible Mushrooms Chlorophyllum rhacodes,Suillus grevillei,Imleria badia,and Xerocomellus chrysenteron Growing in the Czech Republic

Risk and essential elements were determined in fruiting bodies of wild growing edible mushrooms Chlorophyllum rhacodes, Suillus grevillei, Imleria badia, and Xerocomellus chrysenteron collected in an unpolluted site in South Bohemia, the Czech Republic. The elements were also determined in underlying soils and the bioconcentration factors were calculated. The analyses revealed that C. rhacodes accumulated Ag, Cu, Rb, Se, Zn, As, Cd, and Tl. On the other hand, S. grevillei accumulated Cd, Rb, Ag, Se, and Cs. I. badia and X. chrysenteron strongly accumulated Rb, Cs, and Ag; these species showed the ability to accumulate Cu and Zn as well. Contents of detrimental Cr^VI were in all cases below the quantification limit (0.003 mg kg^?1 dry matter). Studied mushroom species (mainly C. rhacodes) accumulated some toxic elements. However, no considerable effect on human health is expected since they are usually consumed as a delicacy and do not represent a major component of diet.     

Effects of Indole-3-Acetic Acid (IAA), a Plant Hormone,on the Ryegrass Yield and the Removal of Fluoranthene from Soil

A soil culture experiment was conducted to determine whether a plant hormone, indole-3-acetic acid (IAA), could influence fluoranthene (Flu) removal from soil. Four treatments were utilized: (i) unplanted soil (CK), (ii) soil planted with ryegrass (P), (iii) soil planted with ryegrass and treated with 0.24 mg kg^?1 IAA (P+0.24), (iv) soil planted with ryegrass and treated with 2.4 mg kg^?1 IAA (P+2.4). The Flu initial concentration was 200 mg kg^?1. After 3 months, the percentage of Flu removal and plant root biomass were significantly increased under the P+2.4 and the removal rate was 35.68%. The total Flu content in plants was higher than that in the other treatments. The Flu concentration was significantly increased in the shoots, but not significantly altered in the roots. The highest translocation factor was observed in the P+2.4. Increase in number of bacteria, actinomycetes and fungi were observed in the planted treatments, and the amount of fungi was significantly increased in P+2.4. Flu removal was related to the Flu in ryegrass, and was insignificantly correlated with the stimulation of soil microflora, which suggesting that IAA may work mainly on improving plant growth, the Flu uptake, and eventually leading to enhanced remediation of Flu polluted soil.     

METAL UPTAKE AND ALLOCATION IN TREES GROWN ON CONTAMINATED LAND: IMPLICATIONS FOR BIOMASS PRODUCTION

Phytostabilization aims to reduce environmental and health risks arising from contaminated soil. To be economically attractive, plants used for phytostabilization should produce valuable biomass. This study investigated the biomass production and metal allocation to foliage and wood of willow (Salix viminalis L.), poplar (Populus monviso), birch (Betula pendula), and oak (Quercus robur) on five different soils contaminated with trace elements (TE), with varying high concentrations of Cu, Zn, Cd, and Pb as well as an uncontaminated control soil. In the treatment soils, the biomass was reduced in all species except oak. There was a significant negative correlation between biomass and foliar Cd and Zn concentrations, reaching up to 15 mg Cd kg^?1 and 2000 mg Zn kg ^?1 in willow leaves. Lead was the only TE with higher wood than foliage concentrations. The highest Pb accumulation occurred in birch with up to 135 mg kg ^?1 in wood and 78 mg kg ^?1 in foliage. Birch could be suitable for phytostabilization of soils with high Cd and Zn but low Pb concentrations, while poplars and willows could be used to stabilise soils with high Cu and Pb and low Zn and Cd concentrations.