The Uptake of Lead and the Effects of EDTA on Lead-Tissue Concentration in Mesquite (Prosopis spp.)

Mary V. Aldrich, University of Texas at El Paso, Department of Environmental Science and Engineering, El Paso, TX 79922
J.L. Gardea-Torresdey, University of Texas at El Paso, Department of Chemistry, El Paso, TX 79922, Tel: 915-747-5359, Fax: 915-747-4758, Email: jgardea@utep.edu
J.R. Peralta-Videa, University of Texas at El Paso, Department of Environmental Science and Engineering, El Paso, TX 79922
J. H. Gonzalez, University of Texas at El Paso, Department of Environmental Science and Engineering, El Paso, TX 79922

By screening the desert plant species mesquite (Prosopis spp.) for its ability to uptake heavy metals, we found that this species is capable of accumulating high levels of lead in the roots and translocating the lead to the stems and leaves. One-week old mesquite seedlings were treated for seven days in a hydroponic culture that contained a modified Hogaland’s solution.  Six treatments were used; three treatments contained only Pb(II) as (Pb(NO₃)₂) at the 25, 50, 75 mg L^-1 level and three treatments contained the same levels of Pb(II), but with equimolar concentrations of disodium EDTA.  While our results showed that the addition of EDTA reduced the amount of lead taken up by mesquite in the stems and roots, EDTA increased lead movement to the leaves.  This paper describes the ability of this plant to survive in a lead-contaminated environment and the effects of EDTA on lead tissue concentrations.

Phytoremediation of Mercury and TNT in our Oceans

Donald Cheney, Paula Bernasconi, Brian Curtis, Northeastern University, Biology Department, Boston, MA  02115, Tel: 617, 373-2489, Fax: 617, 373-3724
Gregory Rorrer, Oregon State University, Dept. Chemical Engineering, Corvalis, OR  97331
Neil Bruce, University of York, UK 

Compared to its status on land, phytoremediation of toxic compounds from marine and estuarine habitats is a brand new field. Our work is aimed at developing seaweeds for the removal and detoxification of toxic heavy metals and man-made compounds from seawater, in particular mercury and TNT. Because mercury is “biomaginified” in marine food chains, its concentration in commercially-valuable, top predator fish like swordfish and tuna is of great concern today. The explosive compound TNT poses less of a broad scale threat, but is extremely toxic to marine organisms and has accumulated in sites where there is unexploaded ordinance.  Our approach is to screen native seaweeds for their natural ability to metabolize mercury and TNT, as well as to develop new strains with enhanced removal abilities through metabolic engineering. In preliminary work, we have found a tropical red alga, Portieria hornemannii, that removes dissolved TNT from seawater, and a temperate red alga, Porphyra yezoensis, that can be transformed to do so. Strains of  Porphyra yezoensis transformed with the bacterial nitroreductase gene nfsI are tolerant to toxic concentrations of TNT and are being tested for TNT detoxification. Porphyra yezoensis is also being investigated as a possible remediator of mercury. It has an EST that shares considerable similarity with part of a bacterial mercuric reductase gene and is being tested for its ability to break down ionic mercury to elemental mercury. Once a mercury or TNT-remediating seaweed strain has been identified or metabolically engineered, we envision it being deployed in the ocean in an environmentally safe “seaweed remediation / containment system” that could be deployed in or above contaminated sediments and be easily harvested after the toxin was removed. Current methods of remediating marine sediments require their removal, which is both very expensive and detrimental to the environment. This research is supported by a grant from the Office of Naval Research.

Polycyclic Aromatic Hydrocarbon Stress Responses In Arabidopsis thaliana

Tomoko Tabuchi, Annika Marschall, Shirley Micallef and Adán Colón-Carmona, Department of Biology, University of Massachusetts Boston, 100 Morrissey Blvd., Boston, MA 02125, Tel: 617-287-6680, Fax: 617-287-6650
Xuchen Wang and Robert Chen, Department of Environmental Coastal and Ocean Sciences, University of Massachusetts Boston, 100 Morrissey Blvd., Boston, MA 02125, Tel: 617-287-7491, Fax: 617-287-7474

Polycyclic aromatic hydrocarbons (PAHs) are toxic organic compounds that originate from fossil fuel burning, power plants, wood-treating facilities, and petroleum based manufacturing.  For example, acute exposure to the PAH naphthalene can lead to liver damage, hemolytic anemia and neurological damage in infants.  In an effort to develop PAH phytoremediation strategies, we studied the mustard model system Arabidopsis thaliana for its ability to respond to PAHs.  We will present physiological responses of plants grown on phenanthrene, a 3-ring aromatic.  Responses include reduction in growth, decreased chlorophyll content and development of brown lesions on aerial tissue, similar to the spots developed during a plant’s immune response.  Because phenanthrene is fluorescent upon UV light exposure, fluorescence microscopy was used to detect PAHs in situ in phenanthrene grown plants.  Interestingly, the lesion patterns on aerial tissues matched that of the fluorescence pattern.  Spectroscopic analysis on PAH-treated plants yielded a phenanthrene specific “fingerprint”.  Additional evidence for PAH internalization was obtained by gas chromatography/mass spectrometry which revealed that approximately 3% of the phenanthrene in the media was incorporated into plant tissue.  Phenanthrene also appeared to inhibit the production of hormones and secondary metabolites, which may explain why phenanthrene-treated plants are stunted in growth. For phytoremediation to be practical, the use of bigger and more “up-take efficient” plants, or even trees, would be ideal.  As a first step towards these ends, four different plants from the mustard family (radish, turnip, white mustard, and Alyssum) were grown on phenanthrene.  Preliminary results on stress physiological responses suggested that other mustards internalize phenanthrene similar to Arabidopsis.  Strategies to identify Arabidopsis genes that can be engineered into plants for PAH remediation and biomonitoring will also presented. Overall, data to be presented suggest that plants can efficiently take-up PAHs, and could potentially serve as efficient tools for cleaning up PAH-contaminated sites.

Chlorophenol Phytoremediation with L. minor:  Glycosidation and Storage of Nucleophilic Contaminants

James A. Day*, School of Civil and Environmental Engineering, Georgia Institute of Technology, 899 Powers Ferry Road, Apartment A-18, Marietta, Georgia 30067
F. Michael Saunders, School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Mail Code 0512, Atlanta, Georgia 30332

Acceptance of phytoremediation applications requires increased understanding of fundamental mechanisms governing uptake and transformation of contaminants.  To this end, experiments were performed to determine the fate of chlorophenols, i.e. 2,4-dichlorophenol (DCP) and 2,4,5-trichlorophenol (TCP) in a simulated wetland environment dominated by the aquatic plant, L. minor.  Removal of contaminants from simulated natural waters was rapid and complete in the presence of active plants.  In contrast, removal in absence of plants was negligible and non-existent in the absence of light.  Removal in the presence of inactivated tissues reached a rapid equilibration with no significant photolysis.  Removed contaminants were isolated from plant tissues as parent and three glycosides, e.g. 2,4-dichlorophenyl-b-D-glucopyranoside (DCPG), 2,4-dichlorophenyl-(6-O-malonyl)-b-D-glucopyranoside (DCPMG) and 2,4-dichlorophenyl-b-D-glucopyranosyl-b-D-apiofuranoside (DCPAG).  Metabolite identifications were based on chromatographic, spectral (ESI-MS. ESI-MS-MS, ¹H-NMR, COSY-NMR) comparisons to synthesized reference compounds.  Metabolite identifications suggested contaminants were stored through two mechanisms, vacuolization (malonyl glycosides) and incorporation into undetected polysaccharide cell-wall fragments (apiosyl glycosides). Quantitative methods were developed for metabolites.  Like many phytoremediation studies, uptakes and assimilation exhibited significant temporal variation in assimilation kinetics.  However, when the fraction of assimilated contaminant was normalized to contaminant removed from media strong correlations emerged demonstrating that identified storage mechanisms were dominant.  At times corresponding to complete contaminant removal from media, ~50% of DCP and ~80% of TCP were present as one of the identified metabolites.  Metabolites of competing processes, i.e. photolysis or microbial transformation, were not detected in media or tissues.  Therefore, these values represent a conservative estimate of the contaminants actually assimilated into plant tissues.  In absence of evidence for competing processes, decreased recoveries of DCP (50% vs. 80%) relative TCP were attributed to increased process kinetics leading to terminal storage products.  The general nature of glycosidation in the plant kingdom suggests these results may be generally applicable to phytoremediation of nucleophilic contaminants.  

^*Note, Dr. Day is currently unaffiliated. Research reported here is from his doctoral studies at Georgia Tech. 

Phytoremediation of Weathered Hydrocarbon-Contaminated Soil, and Bioavailability and Toxicity of Contaminants

Marja Palmroth, Research Associate, Institute of Environmental Engineering and Biotechnology, Tampere University of Technology, Korkeakoulunkatu 4, P.O. Box 541, FIN-33101 Tampere, Finland, Tel: 358-3-365-2111, Fax: 358-3-365-2869, Email: marja.palmroth@tut.fi
|John Pichtel, Professor, Ball State University , Natural Resources and Environmental Management, Muncie, IN 47306-0495, USA, Tel: 765-285-2182, Fax: 765-285-2606, Email: jpichtel@bsu.edu
Kati Vaajasaari, Pirkanmaa Regional Environmental Centre, Research Unit, Tampere, Finland , Email: Kati.Vaajasaari@ymparisto.fi
Anneli Joutti, Senior Research Scientist, Finnish Environment Institute, Research Laboratory, Helsinki, Finland, Email: Anneli.Joutti@ymparisto.fi
Tuula Tuhkanen, Professor, Institute of Environmental Engineering and Biotechnology, Tampere University of Technology, Korkeakoulunkatu 4, P.O. Box 541, FIN-33101 Tampere, Finland, Tel: 358-3-365-2850, Fax: 358-3-365-2869, Email: tuhkanen@cc.tut.fi

Field-scale phytoremediation of weathered hydrocarbon- and lead (Pb)-contaminated soil from a bus depot was conducted in southern Finland.  Hydrocarbons detected in soil consisted of used lubricating oils and diesel fuel.  Total petroleum hydrocarbon (TPH) concentrations measured approximately 10,000 mg/kg and consisted of unresolved complex mixture (UCM).  Soil Pb concentrations ranged from 300 to 3000 mg/kg, and approximately one-third was considered plant-available.  High variations in contaminant concentrations occurred, reflecting the heterogeneity of the soil.  Soil amendments included NPK fertilizer and composted biosolids.  The site was vegetated with Scots Pine (Pinus sylvestris), poplar (Populus deltoides), a grass mixture (red fescue, Festuca rubra; tall fescue, F. arundinacea; perennial ryegrass, L. perenne) and a legume mixture (red clover, Trifolium pratense; pea, Pisum sativum).  Plants grew better (i.e., greater biomass, less phytotoxicity symptoms) in the biosolids-amended plots, and TPH levels decreased most rapidly under the vegetated biosolids treatment.  Metals did not accumulate markedly in any plant tissue.  Soil microbial activity was assessed using Biolog™ Eco plates and microbial extracellular enzymatic assays.  The pH of collected leachates was near-neutral, but metal concentrations exceeded drinking water standards.  Leachates were not, however, toxic to Vibrio fischeri (Biotox^TM, Finland). Toxicity was determined directly from soil samples with Enchytraeus albidus survival tests and with an improved Vibrio fischeri BioTox^TM test designed for sediment or solid samples.  Soil toxicity to Vibrio fischeri decreased during the first year of study, and soil samples were not toxic in E. albidus survival tests.

Accumulation of Heavy Metals by Japanese Weeds and their Seasonal Movement

Ryuji Takeda, Noriyoshi Yoshimura, Sadayoshi Matsumoto, Sadao Komemushi, Department of Agricultural Chemistry, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan, Tel: +81-742-43-1511, Fax: +81-742-43-1445
Akiyoshi Sawabe, Department of Agricultural Chemistry, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan, Tel: +81-742-43-1511 ext. 3318, Fax: +81-742-43-1445, Email: sawabe@nara.kindai.ac.jp

Phytoremediation is the technique that removed contaminants in environment by plants, and is researched in world, recently.  We focused attention on Japanese weeds having large biomass and high environmental adaptability as a metal hyperaccumulator.   Especially, we investigated seasonal metals movement of roots, stems and leaves on Artemisia princeps Pampan, one of the Japanese weeds, and examined method of heavy metal removal from soil.  Plants and surface soils were collected at watersides such as reservoir and adjustment pond around our University at Nara Prefecture, and around Kizu river of Seika town at Kyoto Prefecture in Japan.   Collected soils were air-dried.   On the other hand collected plants were washed with distilled water and then separated the roots, stems and leaves, and were dried with oven at 80C for 24hrs.   The soils and plants were ashed using H₂NO₃, HCl, and 30% H₂O₂.   Mn, Ni, Cr, Fe, Cu, Zn and Li in the ashes were measured by AAS.   Metal hyperaccumulator was not found yet from investigation places.  However, Aster leiophyllus Artemisia princeps Pampan and Stenactis annuus Cass accumulated 2 or 3 times more metals (Cr, Cu, Mn) rather than other plants in the same collection place.  As to seasonal metals movement of roots, stems and leaves on Artemisia  princeps Pampan, plants contents and accumulation ratio of Cu that compared the contents between soil and plants are high in autumn.   Except for Cu, other metals Cr and Mn were accumulated in summer.   As a result it is thought that Cu has special role different from other metals.   Accordingly, this movement is important in examination of treatment stage after having taken in heavy metal.

Potential For Cobalt and Palladium Phytoextraction

Trevor L. Woodard, B.S., University of Massachusetts, Dept. of Plant & Soil Science, Stockbridge Hall, Amherst, MA 01003-9246, Tel: 413-545-3862, Email:  twoodard@alumni.bates.edu
Dula Amarasiriwardena, Ph.D., Hampshire College, School of Natural Sciences, Amherst, MA 01002 Tel: 413-559-5561, Email: dula@hampshire.edu
Baoshan Xing, Ph.D., University of Massachusetts, Dept. of Plant & Soil Science, Stockbridge Hall, Amherst, MA 01003-9246, Tel: 413-545-5212, Email: bx@pssci.umass.edu

Metals play an important role in the environment.  However, some metals can build up to levels in soils toxic to biota.  Phytoextraction is the use of plants to accumulate contaminants (such as metals) in the plant roots and (preferably) shoots for removal and potential re-use.  This method remediates the soil and provides for possible metal recycling.  This experiment investigates four plant species (Lycopersicon esculentum, Lupinus perennis, Brassica juncea, and Panicum virgatum) in their potential for phytoextraction of cobalt and palladium.  Cobalt and palladium are present in small quantities in some soils, though levels are increasing due to anthropogenic activities.  Plants were grown in greenhouse conditions for several weeks, then harvested by plant part, weighed, ground, ashed, digested in nitric acid and analyzed with inductively coupled plasma atomic emission spectrometry (ICP-AES) for Mn, Fe, Co, Ni, Cu, Zn and Pd.  Soils used were sequentially extracted into five phases (exchangeable, carbonate, Fe/Mn oxides, organic matter, and residual) for ICP-AES analysis of Mn, Fe, Co, Ni, Cu, Zn and Pd.  Results thus far indicate that Indian mustard (Brassica juncea) and tomato (Lycopersicon esculentum) both accumulate Co in the aerial portion of the plant (300 µg/g and 100 µg/g respectively).  Preliminary results indicate that Pd does not accumulate in the flowers of tomatoes.  Overall, the plants tested thus far have the potential for phytoextraction of cobalt.

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