Translocation Of Heavy Metals Research Articles

Effect of microbial inoculation and EDTA on the uptake and translocation of heavy metal by corn and sunflower

A greenhouse experiment was carried out to study the effect of microbial inoculation and EDTA as synthetic chelator on heavy metals (Zn, Cu, Pb and Cd) uptake into and translocation within corn ( Zea mays) and sunflower ( Helianthus annuus) grown on contaminated soil. Four treatments were included: the control, EDTA as synthetic chelator, inoculation with arbuscular mycorrhizal fungi (AMF), and the inoculation with yeast. Microbial inoculation increased biomass of both species of agricultural crop plants, but EDTA addition decreased only biomass of sunflower. The results also showed that EDTA was more effective than microbial inoculation at increasing the concentrations of all metals in plants. Generally, there were significant differences among the treatments in the most metals taken up, especially by corn plants, with an order: AM fungi > yeast > EDTA > control except for Pb. It was found that the efficiency of EDTA in increasing Pb uptake was significantly higher than that of microbial inoculation treatments. The most effective treatments to stimulate the translocation of the studied metals from roots to shoots were EDTA and/or AM fungi. Overall, the maximum metal uptake and phytoextraction efficiencies were pronounced for corn either with AM fungi treatment for Zn, Cu and Cd or after EDTA addition for Pb. However, heavy metals uptake was not high enough to achieve extraction rates which would be necessary for practical use.

Translocation and toxicity assessment of heavy metals from circulated fluidized-bed combustion of oil shale in Huadian, China

Oil shale and fly ash collected from two thermal power plants located in Huadian, the northeast city of China were subjected to fraction distribution, translocation regularity and toxicity assessment to provide preliminary assessment of suitability for land application. By Tessier sequential extraction, the results showed that Ni, Cr, Pb and Zn were mostly bounded with iron-manganese and organic bound in oil shale, but Cu and Cd were mostly associated with iron-manganese bound and residue fraction. Through circulated fluidized-bed combustion, high concentration of heavy metals (Cu, Cd, Ni, Cr, Pb, and Zn) was found in iron-manganese bound and residue fraction in fly ash. There was accumulation of all studied metals except Ni and Cr in fly ash and translocation mass of metals were as follows: Pb>Zn>Cu>Cd during circulated fluidized-bed combustion. Fly ash was contaminated with Cd higher than the pollution concentration limits listed in GB15168-1995, China. This work demonstrated that it was unadvisable way to carry out landfill without any treatment. By means of STI model, toxicity assessment of heavy metals was carried out to show that there was notable increase in toxicity from oil shale to fly ash.

Application of fly ash on the growth performance and translocation of toxic heavy metals within Cajanus cajan L.: Implication for safe utilization of fly ash for agricultural production

The present study was undertaken to examine the influence of the application of fly ash (FA) into garden soil for Cajanus cajan L. cultivation and on accumulation and translocation of hazardous metals from FA to edible part. Numerous studies have been reported on the growth and yield of agricultural crops under FA stress; however, there is a dearth of studies recommending the safe utilization of fly ash for crop production. Pot experiments were conducted on C. cajan L., a widely cultivating legume in India for its highly nutritious seeds. C. cajan L. were grown in garden soil and amended with varying concentrations of FA in a weight/weight ratio (0%, 25%, 50% and 100%; w/w). Incorporation of fly ash from 25% to 100% in garden soil increases the levels of pH, particle density, porosity and water holding capacity from 3.47% to 26.39%, 3.98% to 26.14%, 37.50% to 147.92% and 163.16% to 318.42%, respectively, than the control while bulk density decrease respectively from 8.94% to 48.89%. Pot experiment found that accumulation and translocation of heavy metals in tested plant depends on the concentration of FA. Addition of FA at lower concentration (25%) had shown positive results in most of the studied parameters of growth and yield (14.23% than control). The experimental results confirmed that lower concentration of FA (25%) is safe for C. cajan cultivation, which not only enhanced the yield of C. cajan L. significantly but also ensured the translocation of heavy metals to edible parts within the critical limits.

Accumulation and Translocation of Toxic Heavy Metals in Winter Wheat (Triticum aestivum L.) Growing in Agricultural Soil of Zhengzhou, China

A field experiment was conducted to study the accumulation of toxic heavy metals by winter wheat (Triticum aestivum L.) grown in the agricultural soil in the suburb of Zhengzhou City, China. The quantities of heavy metals (Cd, Cr, Pb, As, Hg) were determined in different parts of wheat plant. The content of five toxic metals was found significantly higher in roots than in the aerial parts of wheat (stems and leaves, and grains). Additionally, wheat roots were enriched in Cd, Pb, and Hg from the soil, while Cr and As were hardly taken up by the roots. On the other hand, the winter wheat transported five toxic heavy metals very weakly from root to grain in the various irrigation regions.

Phytoremediation of soils polluted by heavy metals and metalloids using crops: (i) the state of the art

Phytoremediation has a strong potential as a natural, solar-energy driven remediation approach for the treatment of soils and sediments polluted. Research has focused several aspects of the process of uptake, translocation and storage of heavy metals in plants. However we can not predict when the technique could find practical application on large scale. Beyond the evaluation of the best suited species, little has been inquired on the multiple aspects of the agronomic management of phytoextraction. This review provides a synthesis of current knowledge on phytoextraction of metals from soils and their accumulation in plants.

Chemical fractionation and translocation of heavy metals in Canna indica L. grown on industrial waste amended soil

A pot experiment was carried out to assess the effect of different amendments of industrial sludge on the growth of Canna indica L. as well as the translocation potential of heavy metals of this plant. The accumulation of metals (Cr, Fe, Cd, Cu, Ni, Zn, Mn and Pb) in different parts of C. indica L. grown on industrial sludge-amended soil increased with time and increasing doses of sludge amendments. Sequential extraction method was followed to estimate the different fractions of heavy metals in sludge-amended soils collected from different periods of this study. The results showed that Mn, Zn, Cd, Cr and Pb were mostly associated with Fe–Mn oxide fraction in all amendments, whereas, Ni was mostly found in residual (RES) fraction. Cu and Fe were found to be higher in organically bounded form (OM) and RES fraction. The metal concentration in C. indica L. after 90 days of experiment started, was in the order of Fe > Cr > Mn > Zn > Ni > Cu > Cd > Pb and the metal translocation was found lesser in shoot. With the increasing percentage of sludge amendments in soil the metal concentrations increased in different parts of plants. Overall, the plant C. indica L. was found to be well adapted in industrial sludge amendments and it may be recommended that this plant was found suitable for phytoremediation of most of the studied metals.

Seasonal variation of metal accumulation and translocation in yellow pond-lily (Nuphar lutea)

Heavy metal bioaccumulation and translocation properties of aquatic plants are interesting because of their potential use in phytoextraction. However, there is not enough knowledge about the seasonal changes of the metal distribution properties of aquatic plants. Our study focused on seasonal variation of some heavy metals in relation to their bioaccumulation and translocation in Nuphar lutea, a floating leaved, widespread plant that is important to wildlife. In this study, N. lutea, corresponding sediment and water samples were collected at different seasons from Lake Abant (Turkey) and analysed for their heavy metal content (Pb, Cr, Cu, Mn, Ni, Zn and Cd). Accumulation and translocation of heavy metal ratios were calculated seasonally. It was found that Cr and Zn were actively transported from sediment to the root, where they accumulated especially in summer; it was also shown that Cu, Mn and Zn were not only taken up from the sediment but also from the surrounding water. The investigations suggested that translocation ratios for leaf/root of Pb, Cr, Mn and Zn reached their highest levels in spring. It was found that the bioaccumulation and translocation of heavy metals at different parts of N. lutea changes with respect to season and the type of heavy metal.

Phytoremediation of mine tailings in temperate and arid environments

Phytoremediation is an emerging technology for the remediation of mine tailings, a global problem for which conventional remediation technologies are costly. There are two approaches to phytoremediation of mine tailings, phytoextraction and phytostabilization. Phytoextraction involves translocation of heavy metals from mine tailings to the plant shoot biomass followed by plant harvest, while phytostabilization focuses on establishing a vegetative cap that does not shoot accumulate metals but rather immobilizes metals within the tailings. Phytoextraction is currently limited by low rates of metal removal which is a combination of low biomass production and insufficiently high metal uptake into plant tissue. Phytostabilization is currently limited by a lack of knowledge of the minimum amendments required (e.g., compost, irrigation) to support long-term plant establishment. This review addresses both strategies within the context of two specific climate types: temperate and arid. In temperate environments, mine tailings are a source of metal leachates and acid mine drainage that contaminate nearby waterways. Mine tailings in arid regions are subject to eolian dispersion and water erosion. Examples of phytoremediation within each of these environments are discussed. Current research suggests that phytoextraction, due to high implementation costs and long time frames, will be limited to sites that have high land values and for which metal removal is required. Phytostabilization, due to lower costs and easier implementation, will be a more commonly used approach. Complete restoration of mining sites is an unlikely outcome for either approach.

Translocation of heavy metals to tomato ( Solanum lycopersicom L.) fruit irrigated with treated wastewater

A field experiment was conducted to investigate the extent of translocation of heavy metals to tomato ( Solanum lycopersicom L. cvs. “GS 12” and “RS 589956”) fruit produced in an open field near to Abu-Nusiar Wastewater Treatment Plant, Amman-Jordan. Seedlings were planted during the seasons of 1999 and 2000 and furrow irrigated with different mixtures of potable water to treated wastewater {100%:0% (1:0, control); 25%:75% (1:3); 50%:50% (1:1); 0%:100% (0:1)}. Tomato fruit, soil and water were examine for heavy metals concentrations, and changes in the pH and electrical conductivity (EC) of the soil were tested. The obtained results revealed an increase in the concentrations of Cu, Mn and Fe, in the soil correlated with high concentrations found in the wastewater. Additionally, an increase in the pH and EC in the soil was observed with increasing the proportions of wastewater. Results of tomato fruit analysis showed an increased concentration of Fe, Cu, Ni, Mn and Zn in the cultivar “RS 589956”, whereas, an increased concentration of Mn and Zn were detected in the cultivar “GS 12”, but no accumulation of Cd and Pb in both cultivars. The accumulation of heavy metals in fruit was below the Jordanian standard limits, thus, the use of treated wastewater in irrigation might be feasible.

Uptake and Translocation of Heavy Metals in Salt Marsh Sediments by Spartina patens

The Hackensack Meadowlands is a coastal marsh system in northeastern New Jersey, located approximately 10 km west of New York City. Within the Meadowlands, twelve destructed or degraded estuarine wetland sites are currently part of ecological restoration projects that are in various phases of development from planning to completion (http:// www.meadowlands.state.nj.us/naturalresources/wetlands/ Wetlands.cfm). A completed restoration site is Harrier Meadow (North Arlington, NJ) where mitigation work included the creation of channels, impoundments, low marsh habitat and upland habitat islands. Important salt marsh plant species such as salt-meadow grass (Spartina patens), and spike grass (Distichlis spicata) dominate portions of the marsh. The sediments of Harrier Meadow contain heavy metals at concentrations that are below regulatory action limits (e.g., cadmium (Cd) 0–1 ppm; chromium (Cr) 10–18 ppm; copper (Cu) 13–60 ppm; nickel (Ni) 7–15 ppm; lead (Pb) 0–87 ppm; zinc (Zn) 28–94 ppm) (http:// www.meri.njmeadowlands.gov/ecorisk/), but above those typically found in uncontaminated environments (van Driel et al. 1995; Swaileh et al. 2004). Since Spartina species have been shown to take up heavy metals into roots and translocate them into aboveground parts (see Weis and Weis (2004) for review), we had investigated the fate and the effects of selected heavy metals (i.e., Cd, Cr, Cu, Ni, Pb, and Zn) in sediment cores that were densely covered with Spartina patens in a recent short-term study (Suntornvongsagul et al. 2007). Since levels of metals taken up and translocated had been shown to vary depending on the metal concentration in the substrate (Vogel-Mikus et al. 2005), and to be affected by the presence of other metals (McKenna et al. 1993; Podar et al. 2004), half of these cores were artificially amended with Ni in order to increase its availability, and to assess potential effects on uptake of other metals. Ni was chosen since it was the most accumulated metal in shoots from a mixture containing Cd(II), Cu(II), Ni(II) and Zn(II) in identical concentrations (Peralta-Videa et al. 2002), and was assumed to persist in hydrated form in pore water. We demonstrated that Ni-amendment had no significant effect on the fate of other metals in sediments, however, observed increased root-uptake of certain metals. Although translocation of Ni into shoots reflected the 10-fold higher concentrations in sediments and roots in Ni-amended cores, metal translocation into shoots was generally small for all metals (Suntornvongsagul et al. 2007). The goal of the current study was to extend the observations beyond the first growing season, and to assess whether Ni-amendment had effects on metal uptake and translocation after three growing seasons.

Concentração de metais pesados em grãos de plantas cultivadas em solo com diferentes níveis de contaminação

O objetivo deste trabalho foi avaliar a absorção e a capacidade de translocação de metais pesados do solo para os grãos de soja e arroz. O experimento foi realizado em casa de vegetação, em Latossolo Vermelho distroférrico, proveniente de Município de Paulínia, SP. As amostras de solo foram coletadas em sete pontos e organizadas em função da distância de uma fábrica emissora de poluente. O delineamento utilizado foi o inteiramente casualizado, com quatro repetições. Raízes, parte aérea e grãos foram submetidos à digestão por via úmida. A concentração dos metais pesados foi determinada por ICP-OES. Os teores de cádmio e cobre no grão estiveram em níveis adequados para ambas as culturas, enquanto os teores de manganês e zinco apresentaram-se em excesso, tendo acompanhado os níveis de contaminação do solo, com possibilidade de atingir níveis mais altos da cadeia trófica. As raízes limitaram a translocação de cádmio, cobre, ferro e chumbo para a parte aérea de ambas as culturas. Mesmo com a translocação limitada pelas raízes, o chumbo apresentou-se em altos teores nos grãos de soja, e pode, também, como o manganês e o zinco, atingir a cadeia alimentar.

Heavy metal tolerance in common fern species

The effects of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) on the growth and uptake of 10 fern species was investigated under a controlled environment in order to evaluate their suitability for phytoremediation. Fern species included Adiantum aethiopicum, Blechnum cartilagineum, Blechnum nudum, Calochlaena dubia, Dennstaedtia davallioides, Doodia aspera, Hypolepis muelleri, Nephrolepis cordifolia, Pellaea falcata and the arsenic (As) hyperaccumulating Pteris vittata. Ferns were exposed to four levels of metals at concentrations of 0, 50, 100 and 500 mg kg–1 for a period of 20 weeks. The response of ferns significantly varied among species and metals. In general, heavy-metal translocation was limited, with metals being absorbed and held in roots, suggesting an exclusion mechanism as part of the ferns’ tolerance to the applied metals. Similar metal-accumulation patterns were observed for all species in that accumulation generally increased with increasing metal treatments; in most cases a sharp increase in metal accumulation was observed between 100 and 500 mg kg–1 treatments, suggesting a breakdown in tolerance mechanisms and unrestricted metal transport. This was corroborated by enhanced visual toxicity symptoms and a reduction in survival rates among ferns when exposed to 500 mg kg–1 metal treatments; and to a lesser extent 100 mg kg–1 metal treatments. Of the species investigated, N. cordifolia and H. muelleri were identified as possible candidates in phytostabilisation of Cu, Pb, Ni or Zn contaminated soils. Similarly, D. davallioides appeared favourable for use in phytostabilisation of Cu and Zn contaminated soils. These species had high survival rates and accumulated high levels of the aforementioned metals relative to other ferns investigated. Ferns belonging to the family Blechnaceae (B. nudum, B. cartilagineum and D. aspera) and C. dubia (Family Dicksoniaceae) were least tolerant to most metals, had a low survival rate and were classified as being unsuitable for phytoremediation purposes. Metal tolerance was also observed in P. vittata when exposed to Cd, Cr and Cu; however, no hyperaccumulation was observed.

Seasonal variations of cadmium and zinc in Arrhenatherum elatius, a perennial grass species from highly contaminated soils

There is interest in studying bioaccumulation in plants because they form the base of the food chain as well as their potential use in phytoextraction. From this viewpoint, our study deals with the seasonal variation, from January to July, of Cd and Zn bioaccumulation in three metallicolous populations of Arrhenatherum elatius, a perennial grass with a high biomass production. In heavily polluted soils, while Zn bioaccumulation is weak, A. elatius accumulates more Cd than reported gramineous plants, with concentration of up to 100 μg g −1. Our results also showed seasonal variations of bioaccumulation, underlying the necessity for in situ studies to specify the date of sampling and also the phenology of the collected plant sample. In our experimental conditions, accumulation is lower in June, leading us to the hypothesis of restriction in heavy metals translocation from roots to aerial parts during seed production.

Enhanced Phytoextraction: II. Effect of EDTA and Citric Acid on Heavy Metal Uptake by Helianthus annuus from a Calcareous Soil

High biomass producing plant species, such as Helianthus annuus, have potential for removing large amounts of trace metals by harvesting the aboveground biomass if sufficient metal concentrations in their biomass can be achieved. However, the low bioavailability of heavy metals in soils and the limited translocation of heavy metals to the shoots by most high biomass producing plant species limit the efficiency of the phytoextraction process. Amendment of a contaminated soil with ethylene diamine tetraacetic acid (EDTA) or citric acid increases soluble heavy metal concentrations, potentially rendering them more available for plant uptake. This article discusses the effects of EDTA and citric acid on the uptake of heavy metals and translocation to aboveground harvestable plant parts in Helianthus annuus. EDTA was included in the research for comparison purposes in our quest for less persistent alternatives, suitable for enhanced phytoextraction. Plants were grown in a calcareous soil moderately contaminated with Cu, Pb, Zn, and Cd and treated with increasing concentrations of EDTA (0.1, 1, 3, 5, 7, and 10 mmol kg−1 soil) or citric acid (0.01, 0.05, 0.25, 0.442, and 0.5 mol kg−1 soil). Heavy metal concentrations in harvested shoots increased with EDTA concentration but the actual amount of phytoextracted heavy metals decreased at high EDTA concentrations, due to severe growth depression. Helianthus annuus suffered heavy metal stress due to the significantly increased bioavailable metal fraction in the soil. The rapid mineralization of citric acid and the high buffering capacity of the soil made citric acid inefficient in increasing the phytoextracted amounts of heavy metals. Treatments that did not exceed the buffering capacity of the soil (<0.442 mol kg−1 soil) did not result in any significant increase in shoot heavy metal concentrations. Treatments with high concentrations resulted in a dissolution of the carbonates and compaction of the soil. These physicochemical changes caused growth depression of Helianthus annuus. EDTA and citric acid added before sowing of Helianthus annuus did not appear to be efficient amendments when phytoextraction of heavy metals from calcareous soils is considered.

The effect of EDTA on Helianthus annuus uptake, selectivity, and translocation of heavy metals when grown in Ohio, New Mexico and Colombia soils

The use of two EDTA concentrations for enhancing the bioavailability of cadmium, chromium, and nickel in three natural soils (Ohio, New Mexico and Colombia) was investigated. The resulting uptake, translocation and selectivity with Helianthus annuus after mobilization were also examined. In general, plants grown in the sandy-loam Ohio soil had a higher uptake that resulted in a selectivity and total metal content of Cd > Cr ≫ Ni and 0.73 mg and Cr > Cd ≫ Ni and 0.32 mg for 0.1 and 0.3 g kg −1 EDTA, respectively. With the silty-loam New Mexico soil, although the total metal uptake was not statistically different the EDTA level did alter the selectivity; Cd > Cr ≫ Ni (0.1 g kg −1 EDTA) and Cd ≫ Cr > Ni (0.3 g kg −1 EDTA). Conversely, with the Colombian (sandy clay loam) soil increasing the EDTA level resulted in a higher total metal uptake (0.62 mg) than the 0.1 g kg −1 (0.59 mg) treatment. For all three soils, the translocation of Cd was limited. Evaluating the mobile metal fraction with and without EDTA determined that the chelator was capable of overcoming mass transfer limitations associated with the expandable clay fraction in the soils. Root wash results and root biomass concentrations indicated that Cd sorption was occurring. Therefore limited Cd translocation was attributed to insufficient phytochelatin levels.

Concurrent plant uptake of heavy metals and persistent organic pollutants from soil

The extent of anthropogenic environmental pollution—in the United States (Black, 1999; Glass, 1999), in the European Union (Chaudhry et al., 2002), and in the third world is well documented. For example, the Food and Agriculture Organization of the United Nations has estimated that at a minimum 10 t of unwanted pesticides are in ‘‘storage’’ in undeveloped countries, with at least 2 10 t in African countries (Chaudhry et al., 2002). The potential for negative impacts of these stocks on humans and the environment is of major concern. In situ remediation techniques, such as phytoremediation— the attenuation of pollution through the use of plants—which impose minimal environmental disturbance, offer economic, agronomic, and societal benefits to all countries. Up to the present time phytoremediation of soilborne heavy metals and of organic contaminants has been pursued as two distinct disciplines. This compartmentalized approach applies to fundamental studies of the mechanisms of action, as well as to the development of remediation technologies. Based on data from the authors’ laboratories over the preceding several years we propose that far more convergence as opposed to divergence in the underlying plant physiology and soil science impacts the soil/vegetation microcosm to attenuate both soil-borne heavy metals and organic pollutants. For example, our published research has established that zucchini (Cucurbita pepo L.) and spinach (Spinacia oleracea) bioaccumulate soil-bound persistent organic pollutants (POPs) (Mattina et al., 2002). Other published reports have shown that spinach bioaccumulates heavy metals from soil (Romer and Keller, 2001). The data which are presented here demonstrate that these two plants simultaneously bioconcentrate and translocate both categories of weathered, soil-bound pollutant. Such simultaneous uptake and translocation of heavy metal and organic pollutants, if confirmed and optimized, could have enormous implications for plant/soil interaction mechanisms, and impact on practical remediation approaches, and ultimately on risk to human health.

미나리 재배에 의한 중금속 오염수의 식물정화

중금속 오염원을 제거하는 기술을 개발하고자 미나리를 도입하여 중금속 종류에 따른 적정 농도별로 중금속 흡수, 정화효율성 및 식물체내에서 중금속 축적과 이행과정을 조사하였다. 미나리를 이용한 중금속 정화효율성은 Cd의 경우 미나리 정식 6일 후 Artificial solution 처리구와 문막 공업폐수 처리구는 각각 53%, 73%의 정화효율성을 보였으며, Cu의 경우에는 각각 28%, 100%의 정화효율성을 보였다. 환경부에서 규정한 Cd의 청정지역 배출허용기준인 0.02 mg/L은 모든 처리구에서 10일 이후에 나타났으며, Cu의 기준농도인 0.5 mg/L은 Artificial solution 처리구의 경우 10일 이후, 문막 공업폐수 처리구는 3시간 이후에 나타났다. 또한 시간이 경과함에 따라 미나리내 중금속의 축적농도는 높아지는 경향을 보였으며, 처리구의 오염수 중금속 농도보다도 5<TEX>$\sim$</TEX>10배 이상 축적되었다. 미나리 식물체에 흡수된 중금속의 뿌리에서 지상부로의 이행율은 Artificial solution 처리구에서 Cd은 25%, 문막 공업폐수 처리구에서 Cu는 25% 이행하였다. 중금속에 대한 미나리의 생육반응은 문막 공업폐수 처리를 제외한 모든 처리구에서 미나리 생장이 억제되는 결과를 보였다. 따라서 본 연구결과 미나리는 중금속 오염수의 중금속 정화를 위한 식물정화기술에 유용하게 활용할 수 있을 것으로 판단된다. The removal rate of heavy metals from the wastewater, the accumulation and translocation of heavy metals in plants after transplanting, and the responses of water celery growth with different wastewater treatments were investigated to determine the potential ability of green-remediation with hydroponic culture of water celery. The removal rate and translocation of Cd, Cu, Ni and Pb from different wastewater to plants were compared with cultivation periods after transplanting. The removal rate of heavy metals from wastewater was different with each treatment but increased with growing periods of water celery plants. The removal rate of Cd, Cu, Ni and Pb in Artificial solution, Artificial solution+EDTA, Munmark industrical wastewater, Jungsun minewater is ranged from 22 to 73%, from 28 to 100%, from 13 to 92% and from 41 to 100% at 6 days after transplanting, respectively. The translocations of Cd, Cu, Ni and Pb from roots to shoots in Artificial solution, Artificial solution+EDTA, Munmark industrical wastewater, Jungsun minewater are ranged from 14 to 28%. 8 to 30%. from 28 to 45% and from 2 to 15% at 12 days after transplanting, respectively. In plant growth responses, it appears to be inhibited the plant growth over all treatments excepts for Munmark industrial wastewater in these glowing periods. Therefore the water celery might play a useful role in phytoremediation to clean up wastewater contaminated with Cd, Cu, Ni or Pb.

Medicinal herbs: a potential source of toxic metal exposure for man and animals in India.

To explore the possibility of translocation of heavy metals into humans and animals, the authors studied 28 commonly used medicinal plants and estimated their heavy metal content. The plant materials were collected from the same sources used by traditional healers and commercial drug manufacturers. The plants were identified, authenticated, and processed for the analysis of toxic metals. Lead and cadmium levels were estimated in leaf, stem bark, root, or seeds, depending on the medicinal value of the plant portion. The authors used an atomic absorption spectrophotometer to determine levels of metals. The mean lead concentration in medical herbs ranged between 2.624 ppm (standard deviation = 0.426) and 32.757 (standard deviation = 0.124 ppm), and the cadmium concentration ranged between 0.056 ppm (standard deviation = 0.002) and 0.419 ppm (standard deviation = 0.006). Interestingly, the heavy metal concentrations (i.e., lead and cadmium) were higher in leaf than in stem bark or roots, and the lowest values were recorded in seeds. No published reports on the permissible level of toxic metals in commonly used medicinal plants of India have come to the authors' attention; therefore, it was difficult for the authors to determine the role of toxic metals in drug-induced health hazards. However, the presence of toxic metals in different plants led to the conclusion that prolonged consumption of such medicinal plants may be detrimental to health.

Crescimento e nutrição mineral de Eucalyptus maculata e Eucalyptus urophylla em solução nutritiva com concentração crescente de cobre

Avaliou-se o efeito de concentrações crescentes de Cu no crescimento, teores e translocação de metais pesados e nutrientes no eucalipto em solução nutritiva. Mudas de Eucalyptus maculata e Eucalyptus urophylla foram crescidas em vasos de 2L contendo solução nutritiva de Clark, adicionando-se 0, 32, 64, 128 e 192 m M de Cu fornecido como CuSO4. Após cinco semanas de exposição aos tratamentos, as plantas exibiram sintomas típicos de toxidez de Cu como manchas aquosas foliares, clorose e necrose internerval, além do escurecimento das raízes e inibição do crescimento mesmo nas menores concentrações do elemento. A concentração crítica de Cu na solução para reduzir em 10% a matéria seca da parte aérea foi de 8,3 miM e 3,3 miM para E. urophylla e E. maculata, respectivamente. O nível crítico de toxidez na matéria seca da parte aérea foi muito baixo, entre 12 e 13 mg Kg-1 para ambas espécies. E. urophylla mostrou-se menos sensível do que E. maculata, sendo isso relacionado à capacidade dessa em restringir a translocação do Cu das raízes para a parte aérea. Além disso, E. urophylla absorveu mais Fe na presença do excesso de Cu. A translocação de Fe das raízes para a parte aérea foi reduzida, independentemente da espécie, de 27% no controle para apenas 12% na concentração de 192 m M Cu, evidenciando a alta interferência do Cu na translocação do Fe, podendo ser uma das causas da fitotoxidez do Cu para o eucalipto. Altas concentrações de Cu não causaram redução na absorção e translocação de P, K, S, Ca e Mg, não representando, portanto, mecanismo de fitotoxidez desse metal pesado para essas espécies.

Intra-ring variability of Cr, As, Cd, and Pb in red oak revealed by secondary ion mass spectrometry: implications for environmental biomonitoring.

Reconstructing the history of ambient levels of metals by using tree-ring chemistry is controversial. This controversy can be resolved in part through the use of selective microanalysis of individual wood cells. Using a combination of instrumental neutron activation analysis and secondary ion mass spectrometry, we have observed systematic inhomogeneity in the abundance of toxic metals (Cr, As, Cd, and Pb) within annual growth rings of Quercus rubra (red oak) and have characterized individual xylem members responsible for introducing micrometer-scale gradients in toxic metal abundances. These gradients are useful for placing constraints on both the magnitude and the mechanism of heavy metal translocation within growing wood. It should now be possible to test, on a metal-by-metal basis, the suitability of using tree-ring chemistries for deciphering long-term records of many environmental metals.