Genotypic and environmental variation in chromium, cadmium and lead concentrations in rice

Genotypic and environmental variation in Cr, Cd and Pb concentrations of rice grains and the interaction between these metals were investigated by using 138 rice genotypes grown in three contaminated soils. There were significant genotypic differences in the three heavy metal concentrations of rice grains, with the absolute difference among 138 genotypes in grain Cr, Cd and Pb concentrations being 24.5-, 9.1- and 23.8-folds, respectively, under the slightly contaminated soil (containing 4.61mgkg(-1) Cr, 1.09mgkg(-1) Cd and Pb 28.28mgkg(-1), respectively). A highly significant interaction occurred between genotype and environment (soil type) in the heavy metal concentrations of rice grains. Cr concentration in rice grains was not correlated with Cd and Pb concentration. However, there was a significant correlation between Cd and Pb in slightly and highly contaminated soils. The results suggest the possibility to develop the rice cultivars with low Cd and Pb concentrations in grain.     

Screening the phytoremediation potential of desert broom (Baccharis sarothroides Gray) growing on mine tailings in Arizona, USA

The metal concentrations in a copper mine tailings and desert broom (Baccharis sarothroides Gray) plants were investigated. The metal concentrations in plants, soil cover, and tailings were determined using ICP-OES. The concentration of copper, lead, molybdenum, chromium, zinc, arsenic, nickel, and cobalt in tailings was 526.4, 207.4, 89.1, 84.5, 51.7, 49.6, 39.7, and 35.6mgkg(-1), respectively. The concentration of all elements in soil cover was 10-15% higher than that of the tailings, except for molybdenum. The concentration of copper, lead, molybdenum, chromium, zinc, arsenic, nickel, and cobalt in roots was 818.3, 151.9, 73.9, 57.1, 40.1, 44.6, 96.8, and 26.7mgkg(-1) and 1214.1, 107.3, 105.8, 105.5, 55.2, 36.9, 30.9, and 10.9mgkg(-1) for shoots, respectively. Considering the translocation factor, enrichment coefficient, and the accumulation factor, desert broom could be a potential hyperaccumulator of Cu, Pb, Cr, Zn, As, and Ni.     

An engineered plant that accumulates higher levels of heavy metals than Thlaspi caerulescens, with yields of 100 times more biomass in mine soils

Nicotiana glauca transformed with TaPCS1 was tested for its application in phytoremediation. When plantlets were grown in mine soils containing Cu, Zn, and Pb (42, 2600, and 1500 mg kg(-1)) the plant showed high levels of accumulation especially of Zn and Pb. Adult plants growing in mine soils containing different heavy metal concentrations showed a greater accumulation as well as an extension to a wider range of elements, including Cd, Ni and B. The overexpressed gene confers up to 9 and 36 times more Cd and Pb accumulation in the shoots under hydroponic conditions, and a 3- and 6-fold increase in mining soils. When the hyperaccumulator Thlaspi caerulescens was compared, the results were higher values of heavy metal and Boron accumulation, with a yield of 100 times more biomass. Thlaspi was unable to survive in mining soils containing either a level higher than 11000 mg kg(-1) of Pb and 4500 mg kg(-1) of Zn, while engineered plants yielded an average of 0.5 kg per plant.     

Zn, Cd and Pb accumulation and arbuscular mycorrhizal colonisation of pennycress Thlaspi praecox Wulf. (Brassicaceae) from the vicinity of a lead mine and smelter in Slovenia

Significant hyperaccumulation of Zn, Cd and Pb in field samples of Thlaspi praecox Wulf. collected from a heavy metal polluted area in Slovenia was found, with maximal shoot concentrations of 14,590 mg kg(-1) Zn, 5960 mg kg(-1) Cd and 3500 mg kg(-1) Pb. Shoot/root ratios of 9.6 for Zn and 5.6 for Cd show that the metals were preferentially transported to the shoots. Shoot bioaccumulation factors exceeded total soil Cd levels 75-fold and total soil Zn levels 20-fold, further supporting the hyperaccumulation of Cd and Zn. Eighty percent of Pb was retained in roots, thus indicating exclusion as a tolerance strategy for Pb. Low level colonisation with arbuscular mycorrhizal fungi (AMF) of a Paris type was observed at the polluted site, whereas at the non-polluted site Arum type colonisation was more common. To our knowledge this is the first report of Cd hyperaccumulation and AMF colonisation in metal hyperaccumulating T. praecox.     

Heavy metal accumulation by Nicotiana glauca Graham in a solid waste disposal site

Nicotiana glauca Graham, is the only perennial shrub growing in a solid waste contaminated site in the Negev desert of Israel. The concentration of heavy metals (Cu, Fe, Mn, Zn, Ni, Cd and Pb) in the upper soil layer was significantly higher (p<0.01) than in non-contaminated desert soil. In root and shoot of N. glauca, growing in the site, the concentration of Cu, Zn and Fe was significantly higher (p<0.05) than in plants of a non-contaminated site. In a controlled experiment, the concentrations of Zn and Cu in root of plants grown, in a mixture of contaminated and non-contaminated soil (1:1) was 9.5 and 4.7 higher than that of plants grown in non-contaminated soil, respectively. While Zn was accumulated in shoot of plants grown in contaminated soil (531 mgkg(-1)) in significantly higher concentration than in plants grown in non-contaminated soil (56 mgkg(-1)), no significant differences were found in Cu accumulation. Growth of N. glauca was inhibited on contaminated soil, but no other obvious stress symptoms were apparent. Therefore, long term experiments under controlled conditions are planned to study the mechanism of heavy metal tolerance and accumulation in N. glauca.     

Chemical methods and phytoremediation of soil contaminated with heavy metals

The effects of chemical amendments (calcium carbonate (CC), steel sludge (SS) and furnace slag (FS)) on the growth and uptake of cadmium (Cd) by wetland rice, Chinese cabbage and wheat grown in a red soil contaminated with Cd were investigated using a pot experiment. The phytoremediation of heavy metal contaminated soil with vetiver grass was also studied in a field plot experiment. Results showed that treatments with CC, SS and FS decreased Cd uptake by wetland rice, Chinese cabbage and wheat by 23-95% compared with the unamended control. Among the three amendments, FS was the most efficient at suppressing Cd uptake by the plants, probably due to its higher content of available silicon (Si). The concentrations of zinc (Zn), lead (Pb) and Cd in the shoots of vetiver grass were 42-67%, 500-1200% and 120-260% higher in contaminated plots than in control, respectively. Cadmium accumulation by vetiver shoots was 218 g Cd/ha at a soil Cd concentration of 0.33 mg Cd/kg. It is suggested that heavy metal-contaminated soil could be remediated with a combination of chemical treatments and plants.     

Effects of lead and cadmium nitrate on biomass and substrate utilization pattern of soil microbial communities

A study was conducted to evaluate the effects of different concentrations of lead (Pb) and cadmium (Cd) applied as their nitrates on soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)), and substrate utilization pattern of soil microbial communities. The C(mic) and N(mic) contents were determined at 0, 14, 28, 42 and 56 days after heavy metal application (DAA). The results showed a significant decline in the C(mic) for all Pb and Cd amended soils from the start to 28 DAA. From 28 to 56 DAA, C(mic) contents changed non-significantly for all other treatments except for 600 mgkg(-1) Pb and 100 mgkg(-1) Cd in which it declined significantly from 42 to 56 DAA. The N(mic) contents also decreased significantly from start to 28 DAA for all other Pb and Cd treatments except for 200 mgkg(-1) Pb which did not show significant difference from the control. Control and 200 mgkg(-1) Pb had significantly lower soil microbial biomass C:N ratio as compared with other Pb treatments from 14 to 42 DAA, however at 56 DAA, only 1000 mgkg(-1) Pb showed significantly higher C:N ratio compared with other treatments. No significant difference in C:N ratio for all Cd treated soils was seen from start to 28 DAA, however from 42 to 56 DAA, 100 mgkg(-1) Pb showed significantly higher C:N ratio compared with other treatments. On 56 DAA, substrate utilization pattern of soil microbial communities was determined by inoculating Biolog ECO plates. The results indicated that Pb and Cd addition inhibited the functional activity of soil microbial communities as indicated by the intensity of average well color development (AWCD) during 168 h of incubation. Multivariate analysis of sole carbon source utilization pattern demonstrated that higher levels of heavy metal application had significantly affected soil microbial community structure.     

Zinc and cadmium accumulation and tolerance in populations of Sedum alfredii

To investigate the variation of Zn and Cd accumulation and tolerance of Sedum alfredii (a newly reported Zn/Cd hyperaccumulator), field surveys and hydroponic experiments were conducted among three populations of this species: two originating from old Pb/Zn mines in Zhejiang (ZJ) and Hunan (HN) Provinces and one from a "clean" site in Guangdong (GD) Province, China. Under field conditions, up to 12,524 and 12,253 mg kg(-1) Zn, and 1400 and 97 mg kg(-1) Cd in shoots of ZJ and HN plants were recorded respectively. Under hydroponic conditions, ZJ and HN plants accumulated significantly higher Zn and Cd in their leaves and stems, and possessed significantly higher Zn and Cd tolerance than GD plants. Among the two contaminated populations, ZJ plants showed higher Cd tolerance and accumulation (in leaves) than HN plants. The present results indicate that significant differences in Zn and Cd accumulation and tolerance exist in populations of S. alfredii.     

Multi-step leaching of Pb and Zn contaminated soils with EDTA

The efficiency of multi-step leaching of heavy metal contaminated soils was evaluated in a laboratory scale study. Four different soils contaminated with Pb (1136+/-16-4424+/-313mgkg(-1)) and Zn (288+/-5-5489+/-471mgkg(-1)) were obtained from industrial sites in the Mezica Valley, Slovenia and Príbram district, Czech Republic. Different dosages (2.5-40mmolkg(-1)) of ethylenediamine tetraacetate (EDTA) were used to treat soils in 1-10 leaching steps. Higher EDTA dosages did not result in a proportional gain in Pb and Zn removal. EDTA extracted Pb more efficiently than Zn from three of four tested soils. The percentage of removed Zn did not exceed 75% regardless of the soil, EDTA dosage and leaching steps. Significantly more Pb (in three of four soils) and Zn were removed from soils when the same amount of EDTA was applied in several leaching steps. The interference of major soil cations Fe and Ca with EDTA complexation as a possible factor affecting Pb and Zn removal efficiency with multi-step heap leaching was examined and is discussed. The results of our study indicate that, for some soils, using multi-step leaching instead of the more traditionally used single dose EDTA treatment could improve heavy metal removal efficiency and thus the economics of soil remediation.     

Growth and metal accumulation in vetiver and two Sesbania species on lead/zinc mine tailings

The lead (Pb)/zinc (Zn) tailings contained high concentrations of heavy metals (total Pb, Zn, Cu and Cd concentrations 4164, 4377, 35 and 32 mg kg(-1), respectively), and low contents of major nutrient elements (N, P, and K) and organic matter. A field trial was conducted to compare growth performance, metal accumulation of Vetiver (Vetiveria zizanioides) and two legume species (Sesbania rostrata and Sesbania sesban) grown on the tailings amended with domestic refuse and/or fertilizer. It was revealed that domestic refuse alone and the combination of domestic refuse and artificial fertilizer significantly improved the survival rates and growth of V. zizanioides and two Sesbania species, especially the combination. However, artificial fertilizer alone did not improve both the survival rate and growth performance of the plants grown on tailings. Roots of these species accumulated similar levels of heavy metals, but the shoots of two Sesbania species accumulated higher (3-4 folds) concentrations of Pb, Zn, Cu and Cd than shoots of V. zizanioides. Most of the heavy metals in V. zizanioides were accumulated in roots, and the translocation of metals from roots to shoots was restricted. Intercropping of V. zizanioides and S. rostrata did not show any beneficial effect on individual plant species, in terms of height, biomass, survival rate, and metal accumulation, possibly due to the rather short experimental period of 5 months.     

Colonisation of a Zn, Cd and Pb hyperaccumulator Thlaspi praecox Wulfen with indigenous arbuscular mycorrhizal fungal mixture induces changes in heavy metal and nutrient uptake

Plants of the Zn, Cd and Pb hyperaccumulator Thlaspi praecox Wulfen (Brassicaceae) inoculated or not with indigenous arbuscular mycorrhizal (AM) fungal mixture were grown in a highly Cd, Zn and Pb contaminated substrate in order to evaluate the functionality of symbiosis and assess the possible impact of AM colonisation on heavy metal uptake and tolerance. The results suggest AM development in the metal hyperaccumulating T. praecox is favoured at elevated nutrient demands, e.g. during the reproductive period. AM colonisation parameters positively correlated with total soil Cd and Pb. Colonised plants showed significantly improved nutrient and a decreased Cd and Zn uptake as revealed by TRXRF, thus confirming the functionality of the symbiosis. Reduced heavy metal uptake, especially at higher soil metal contents, indicates a changed metal tolerance strategy in colonised T. praecox plants. This is to our knowledge the first report on AM colonisation of the Zn, Cd and Pb hyperaccumulator T. praecox in a greenhouse experiment.     

Transfer of cadmium, lead, and zinc from industrially contaminated soil to crop plants: a field study

The documeneed adverse health effects of soil Cd and Pb have led to public concern over soil contamination with metals. A 4-year field experiment was conducted to study the transfer of Cd, Pb, and Zn from soil contaminated by smelter flue-dust to crop plants grown in a rotation. The soil was amended with Pb?Zn smelter flue-dust (2-66.8 kg per 10 m(2) plot) to simulate the long-term effect that the smelting of non-ferrous metal ore has on arable soils. The treated soil became strongly contaminated with metals (Cd 3.2-106 mg/kg, Pb 146-3452 mg/kg, Zn 465-11 375 mg/kg). Concentrations of Cd, Pb, and Zn in barley grain, barley straw meadow bluegrass, red clover, and potatoes were generally low. The highest metal concentrations were found in potato tubers (intact), meadow bluegrass, and barley straw. The observed reduction in crop yield was probably the result of possible nutrient imbalances rather than of metal (Zn, Cu) phytotoxicities. Zn and Cd uptake by the plants can be described by the saturation (plateau) model (y = ax(b), b < 1). The relationship between Pb in the soil and plants was linear with an extremely low slope (0.0001-0.0003). No excessive dietary intake of Cd is expected when Cd concentrations in barley grain and potato tubers grown on the contaminated soil are not higher than 0.6 and 1.0 mg/kg, respectively. Based on the risk analysis and taking into account the saturation model of the soil-plant metal relationship, it was concluded that, under the conditions of this experiment (neutral soil pH), soil with Cd concentrations of up to 30 mg/kg is still safe for production of these crop plants.     

Total dissolved and bioavailable elements in water and sediment samples and their accumulation in Oreochromis mossambicus of polluted Manchar Lake

The concentrations of 15 elements were determined in water, sediment and tissues of fish (Oreochromis mossambicus) collected from five sampling stations of Manchar Lake in 2005 for two successive seasons, winter (WS) and summer (SS). Elements analysis was performed by atomic absorption spectrometry with flame (FAAS) and electrothermal (ETAAS) modes, using multielement standard solution. The obtained results show that, the trace and toxic elements (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and macronutrients (Al, Ca, K, Mg and Na) concentrations in lake water were above the recommended drinking water standards by WHO. Concentrations of Na detected in lake water in WS and SS, were in the range of 445.5-562.7 and 420.6-643.5 mgl(-1), respectively. While among toxic elements As concentration in both seasons, have been found in the range of 60.4-88.9 and 64.9-101.8 microgl(-1) respectively, these values are 6-10 times higher than the permissible limit of WHO. The mean concentrations of elements understudy in muscles of fish were found as 2.35, 1.39, 0.46, 2.3, 1517.9, 2.2, 2.4 and 188.9 mgkg(-1) for As, Cd, Cr, Cu, Fe, Ni, Pb and Zn, respectively. High accumulation of toxic elements in fish tissues is indicating that some of the metal contaminants are entering the food chain. Correlations among the variables were identified by multivariate analysis. The extraction of elements from sediments with EDTA, to predict the bioavailability of trace and toxic elements, has shown that among them As, Cd and Zn were the most bioavailable elements in lake sediment.     

Phytostabilization of a metal contaminated sandy soil. II: Influence of compost and/or inorganic metal immobilizing soil amendments on metal leaching

A lysimeter approach (under natural climatologic conditions) was used to evaluate the effect of four metal immobilizing soil treatments [compost (C), compost+cyclonic ashes (C+CA), compost+cyclonic ashes+steel shots (C+CA+SS)) and cyclonic ashes+steel shots (CA+SS)] on metal leaching through an industrially contaminated soil. All treatments decreased Zn and Cd leaching. Strongest reductions occurred after CA+SS and C+CA+SS treatments (Zn: -99.0% and -99.2% respectively; Cd: -97.2% and -98.3% respectively). Copper and Pb leaching increased after C (17 and >30 times for Cu and Pb respectively) and C+CA treatment (4.4 and >3.7 times for Cu and Pb respectively). C+CA+SS or CA+SS addition did not increase Cu leaching; the effect on Pb leaching was not completely clear. Our results demonstrate that attention should be paid to Cu and Pb leaching when organic matter additions are considered for phytostabilization of metal contaminated soils.     

Growth and trace metal accumulation of two Salix clones on sediment-derived soils with increasing contamination levels

The growth and metal uptake of two willow clones (Salix fragilis 'Belgisch Rood' and Salix viminalis 'Aage') was evaluated in a greenhouse pot experiment with six sediment-derived soils with increasing field Cd levels (0.9-41.4 mg kg-1). Metal concentrations of eight elements were measured in roots, stems and leaves and correlated to total and soil water metal concentrations. Dry weight root biomass, number of leaves and shoot length were measured to identify eventual negative responses of the trees. No growth inhibition was observed for both clones for any of the treatments (max. 41.4 mg kg-1 Cd, 1914 mg kg-1 Cr, 2422 mg kg-1 Zn, 655 mg kg-1 Pb), allowing their use for phytoextraction on a broad range of contaminated sediments. However, dry weight root biomass and total shoot length were significantly lower for S. viminalis compared to S. fragilis for all treatments. Willow foliar Cd concentrations were strongly correlated with soil and soil water Cd concentrations. Both clones exhibited high accumulation levels of Cd and Zn in aboveground plant parts, making them suitable subjects for phytoextraction research. Cu, Cr, Pb, Fe, Mn and Ni were found mainly in the roots. Bioconcentration factors of Cd and Zn in the leaves were highest for the treatments with the lowest soil Cd and Zn concentration.     

A survey of zinc, copper and cadmium concentrations in salt marsh plants along the Dutch coast

In autumn 1986, plants and soil were collected from the lower and the higher salt marsh zones of salt marshes along the Dutch coast. The main purpose was to get an overview of Zn, Cu and Cd concentrations in six dominant species of salt marsh plants. The roots and shoots of the plants were analysed for Zn, Cu and Cd. The highest heavy metal concentrations were found in plants collected from salt marshes near harbour areas and/or that are known to receive contaminated fluvial sediment. Dicotyledonous plant species tended to have similar heavy metal concentrations in roots and shoots, whereas in monocotyledonous species the concentrations in the roots were two to three times higher than in the shoots. Differences in accumulation in the roots between elements and between plant species were found. Cd was accumulated more than Zn or Cu. Triglochin maritima shows a low Cd uptake by roots, whereas Spartina anglica and Scirpus maritimus tend to accumulate it. The fraction of soil particles smaller than 63 microm, loss on ignition and Zn, Cu and Cd concentrations were determined in soil samples. The highest Zn, Cu and Cd concentrations in the soil were found at salt marshes in the Western Scheldt area and were nine, five and 20 times higher than background levels, respectively.     

Heavy metal immobilization by chemical amendments in a polluted soil and influence on white lupin growth

The effects of chemical amendments (zeolite, compost and calcium hydroxide) on the solubility of Pb, Cd and Zn in a contaminated soil were determined. The polluted soil was from the Southwest Sardinia, Italy. It showed very high total concentrations of Pb (19663 mgkg(-1) d.m.), Cd (196 mgkg(-1) d.m.) and Zn (14667 mgkg(-1) d.m.). The growth and uptake of heavy metals by white lupin (Lupinus albus L., cv. Multitalia) in amended soils were also studied in a pot experiment under greenhouse conditions. Results showed that the amendments increased the residual fraction of heavy metals in the soils, and decreased the heavy metals uptake by white lupin compared with the unamended control. Among the three amendments, compost and Ca(OH)2 were the most efficient at reducing Pb and Zn uptake, while zeolite was the most efficient at reducing Cd uptake by the plants. White lupin growth was better in amended soils than in unamended control. The above ground biomass increased with a factor 1.8 (soil amended with zeolite), 3.6 (soil amended with compost) and 3.1 (soil amended with Ca(OH)2) with respect to unamended soil. The roots biomass increased with a factor 1.4 (soil amended with zeolite), 5.6 (soil amended with compost) and 4.8 (soil amended with Ca(OH)2). Results obtained suggest that the soil chemical treatment improved the performance of crops by reducing bioavailability of metals in the soils. However it would be therefore interesting to find a suitable mixture of these amendments to contemporarily immobilize the three main pollutants in the polluted soils.     

Metal accumulation in wild plants surrounding mining wastes

Four sites were selected for collection of plants growing on polluted soil developed on tailings from Ag, Au, and Zn mines at the Zacatecas state in Mexico. Trace element concentrations varied between sites, the most polluted area was at El Bote mine near to Zacatecas city. The ranges of total concentration in soil were as follows: Cd 11-47, Ni 19-26, Pb 232-695, Mn 1132-2400, Cu 134-186 and Zn 116-827 mg kg(-1) air-dried soil weight. All soil samples had concentrations above typical values for non-polluted soils from the same soil types (Cd 0.6+/-0.3, Ni 52+/-4, Pb 41+/-3mg kg(-1)). However, for the majority of samples the DTPA-extractable element concentrations were less than 10% of the total. Some of the wild plants are potentially metal tolerant, because they were able to grow in highly polluted substrates. Plant metal analysis revealed that most species did not translocate metals to their aerial parts, therefore they behave as excluder plants. Polygonum aviculare accumulated Zn (9236 mg kg(-1)) at concentrations near to the criteria for hyperaccumulator plants. Jatropha dioica also accumulated high Zn (6249 mg kg(-1)) concentrations.     

Strategies of heavy metal uptake by three plant species growing near a metal smelter

Some higher plant species have developed heavy metal tolerance strategies which enable them to survive and reproduce in highly metal-contaminated soils. We have investigated such heavy metal uptake and accumulation strategies of two absolute metallophyte species (Armeria maritima ssp. halleri and Cardaminopsis halleri) and one pseudometallophyte (Agrostis tenuis) growing near a former metal smelter. Samples of plant parts and soil were analysed for Zn, Cd, Pb, and Cu. In soil, there were two dominant types of metal concentration gradients with depth. Under the absolute metallophytes, extremely high metal contents were measured in the surficial Ah horizon, followed by a strong decrease in the underlying soil horizons (L(11) and L(12)). Under the pseudometallophyte, metal concentrations in the Ah horizon were much lower and fewer differences were observed in metal concentrations among the Ah, L(11), and L(12) horizons. The concentrations of Zn, Cd, Pb, and Cu in Agrostis tenuis roots were greater than concentrations in leaves, indicating significant metal immobilisation by the roots. For C. halleri, Zn and Cd concentrations in leaves were >20,000 and >100 mg kg(-1), respectively, indicating hyperaccumulation of these elements. Armeria maritima ssp. halleri exhibited root concentrations of Pb and Cu that were 20 and 88 times greater, respectively, than those in green leaves, suggesting an exclusion strategy by metal immobilisation in roots. However, Zn, Cd, Pb, and Cu concentrations in brown leaves of Armeria maritima ssp. halleri were 3-8 times greater than in green leaves, suggesting a second strategy, i.e. detoxification mechanism by leaf fall.     

The EDTA effect on phytoextraction of single and combined metals-contaminated soils using rainbow pink (Dianthus chinensis)

Rainbow pink (Dianthus chinensis), a potential phytoextraction plant, can accumulate high concentrations of Cd from metal-contaminated soils. The soils used in this study were artificially added with different metals including (1) CK: original soil, (2) Cd-treated soil: 10 mg Cd kg(-1), (3) Zn-treated soil: 100 mg Zn kg(-1), (4) Pb-treated soil: 1000 mg Pb kg(-1), (5) Cd-Zn-treated soil: 10 mg Cd kg(-1) and 100 mg Zn kg(-1), (6) Cd-Pb-treated soil: 10 mg Cd kg(-1) and 1000 mg Pb kg(-1), (7) Zn-Pb-treated soil: 100 mg Zn kg(-1) and 1000 mg Pb kg(-1), and (8) Cd-Zn-Pb-treated soil: 10 mg Cd kg(-1), 100 mg Zn kg(-1), and 1000 mg Pb kg(-1). Three concentrations of 2Na-EDTA solutions (0 (control), 2, and 5 mmol kg(-1) soil) were added to the different metals-treated soils to study the influence of applied EDTA on single and combined metals-contaminated soils phytoextraction using rainbow pink. The results showed that the Cd, Zn, Pb, Fe, or Mn concentrations in different metals-treated soil solutions significantly increased after applying 5 mmol EDTA kg(-1) (p<0.05). The metal concentrations in different metals-treated soils extracted by deionized water also significantly increased after applying 5 mmol EDTA kg(-1) (p<0.05). Because of the high extraction capacity of both 0.005 M DTPA (pH 5.3) and 0.05 M EDTA (pH 7.0), applying EDTA did not significantly increase the Cd, Zn, or Pb concentration in both extracts for most of the treatments. Applying EDTA solutions can significantly increase the Cd and Pb concentrations in the shoots of rainbow pink (p<0.05). However, this was not statistically significant for Zn because of the low Zn concentration added into the contaminated soils. The results from this study indicate that applying 5 mmol EDTA kg(-1) can significantly increase the Cd, Zn, or Pb concentrations both in the soil solution or extracted using deionized water in single or combined metals-contaminated soils, thus increasing the accumulated metals concentrations in rainbow pink shoots. The proposed method worked especially well for Pb (p<0.05). The application of 2 mmol EDTA kg(-1) might too low to enhance the phytoextraction effect when used in silty clay soils.