103 citations from the Agricola Database
1992 - September 1998
Water Quality Information Center
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plants- bioremediation- pollutants- polluted-soils uptake-
Descriptors: contaminants- bioremediation- festuca-arundinacea medicago-sativa.
Abstract: Higher plants are being used to enhance the remediation of soils contaminated with recalcitrant organic compounds, but the mechanisms of dissipation have not been established. One possible step in the phytoremediation process is adsorpti on of the organic contaminant onto the surface of the roots and subsequent uptake and/or degradation. To determine the affinity of plant roots for naphthalene, a polycyclic aromatic hydrocarbon, adsorption was quantified for tall fescue (Festuca arundinac ea Schreber) and alfalfa (Medicago sativa L.). Equilibrium adsorption for naphthalene was determined for fresh roots of each species at three growth stages. For both fescue and alfalfa, adsorption was described by the Freundlich isotherm. Adsorption incre ased by as much as a factor of four with later growth stage of the plants. Alfalfa roots had approximately twice the affinity for naphthalene than fescue roots, despite a greater surface area per unit mass of root for fescue. Alfalfa also had a greater li pid content than fescue (10 g lipid/kg dry root vs. 4.5 g/kg), indicating that lipid content is a controlling factor in adsorption of naphthalene onto plant roots.
Descriptors: medicago-sativa rhizosphere- bioremediation- organic-compounds toluene- phenols- soil-bacteria soil-fungi respiration- groundwater-
Descriptors: aromatic-hydrocarbons biodegradation- aquatic-plants kinetics- bioremediation- trinitrotoluene-
Abstract: In addition to the often-cited advantages of using Arabidopsis thaliana as a model system in plant biological research (1), Arabidopsis has many additional characteristics that make it an attractive experimental organism for studying lea d (Pb) accumulation and tolerance in plants. These include its fortuitous familial relationship to many known metal hyperaccumulators (Brassicaceae), as well as similar Pb-accumulation patterns to most other plants. Using nutrient-agar plates, hydroponic culture, and Pb-contaminated soils as growth media, we found significant variation in Arabidopsis thaliana ecotypes in accumulation and tolerance of Pb. In addition, we have found that Pb accumulation is not obligatorily linked with Pb tolerance, suggesti ng that different genetic factors control these two processes. We also screened ethyl methanesulfonate-mutagenized M2 populations and identified several Pb-accumulating mutants. Current characterization of these mutants indicates that their phenotypes are likely due to alteration of general metal ion uptake or translocation processes since these mutants also accumulate many other metals in shoots. We expect that further characterization of the ecotypes and mutants will shed light on the basic genetic and physiological underpinnings of plant-based Pb remediation.
Abstract: Reduction of nitroaromatic compounds to their corresponding amino derivatives is one of several pathways in the degradation of nitroxenobiotics. Our studies with the nitrodiphenyl ether herbicide acifluorfen showed rapid metabolism to am inoacifluorfen followed by incorporation into unextractable soil components in both soil and rhizosphere suspensions. Aminoacifluorfen was formed more rapidly in rhizospheres compared to soil, which can be attributed to higher microbial populations, espec ially of Gram-negative bacteria. We identified several strains of Pseudomonas fluorescens that possess nitroreductase activity capable of converting acifluorfen to aminoacifluorfen. Factors affecting acifluorfen nitroreductase activity in pure cultures an d cell-free extracts, and other catabolic transformations of acifluorfen, ether bond cleavage, are discussed. Plant rhizospheres should be conducive for aromatic nitroreduction. Nitroreduction by rhizobacteria is an important catabolic pathway for the ini tial degradation of various nitroherbicides and other nitroaromatic compounds in soils under phytoremediation management.
Abstract: In laboratory exposures of wetland plants to low herbicide levels (<0.1 micrograms/mL), some plants showed increased total ascorbic acid suggesting a stimulatory effect on ascorbic acid synthesis occurred; at higher herbicide conce ntrations (greater than or equal to 0.1 micrograms/mL) a notable decline in total ascorbic acid and increase in the oxidized form, dehydroascorbic acid occurred. Vigna luteola and Sesbania vesicaria were exposed for 7 and 21 days respectively to atrazine (0.05 to 1 microgram/mL); Spartina alterniflora 28 days at 0.1 micrograms/mL trifluralin; Hibiscus moscheutos 14 days at 0.1 and 1 microgram/mL metolachlor in fresh and brackish water. The greatest increase following low dosage occurred with S. alterniflo ra, increasing from <600 micrograms/g wet wt. total ascorbic acid to >1000 micrograms/g. Ascorbic acid may be a promising biomarker of estuarine plants exposed to herbicide runoff; stimulation of ascorbic acid synthesis may enable some wetland plant s used in phytoremediation to cope with low levels of these compounds.
Descriptors: ozone- air-pollution nitrogen-dioxide nitric-oxide air-quality tolerance- bioremediation- acclimatization- nutrient-sources nutrient-uptake plants- cultivars- genetic-variation literature-reviews
Abstract: Studies were conducted in the laboratory to determine the fate of atrazine in pesticide-contaminated soils from agrochemical dealer sites. No significant differences in atrazine concentrations occurred in soils treated with atrazine i ndividually or combinations with metolachlor and trifluralin. In a screening study carried out in soils from four agrochemical dealer sites, rapid mineralization of atrazine occurred in three out of eight soils tested, with the greatest amount occurring i n Bravo rhizosphere soil (35% of the applied atrazine after 9 weeks). Suppression of atrazine mineralization in the Bravo rhizosphere soil did not occur with the addition of high concentrations of herbicide mixtures, but instead was increased. Plants had a positive impact on dissipation of aged atrazine in soil, with significantly less atrazine extractable from Kochia-vegetated soils than from nonvegetated soils.
Descriptors: polluted-soils bioremediation-
Abstract: Biological remediation of contaminated soil is an effective method of reducing risk to human and ecosystem health. Bacteria and plants might be used to enhance remediation of soil pollutants in situ. This study assessed the potential of bacteria (12 isolates), plants (16 forage grasses), and plant-bacteria associations (selected pairings) to remediate 2-chlorobenzoic acid (2CBA)-contaminated soil. Initially, grass viability was assessed in 2CBA-contaminated soil. Soil was contaminated wi th 2CBA, forage grasses were grown under growth chamber conditions for 42 or 60 d, and the 2CBA concentration in soil was determined by gas chromatography. Only five of 16 forage grasses grew in 2CBA-treated (816 mg/kg) soil. Growth of Bromus inermis had no effect on 2CBA concentration, whereas Agropyron intermedium, B. biebersteinii, A. riparum, and Elymus dauricus decreased 2CBA relative to nonplanted control soil by 32 to 42%. The 12 bacteria isolates were screened for their ability to promote the germ ination of the five grasses in 2CBA-contaminated soil. Inoculation of A. riparum with Pseudomonas aeruginosa strain R75, a proven plant growth-promoting rhizobacterium, increased seed germination by 80% and disappearance of 2CBA by 20% relative to noninoc ulated plants. Inoculation of E. dauricus with a mixture of P. savastanoi strain CB35, a 2CBA-degrading bacterium, and P. aeruginosa strain R75 increased disappearance of 2CBA by 112% relative to noninoculated plants. No clear relationship between enhance d 2CBA disappearance and increased plant biomass was found. These results suggest that specific plant-microbial systems can be developed to enhance remediation of pollutants in soil.
Descriptors: plants- bioremediation- polluted-soils soil-pollution groundwater-pollution polluted-water pollutants- biodegradation- microbial-degradation soil-flora rhizosphere- literature-reviews organic-pollutants
Abstract: Benzo(a)pyrene (B[a]P) is a carcinogenic polynuclear aromatic hydrocarbon and hexachlorobiphenyl (HCB) is a polychlorinated biphenyl (PCB) congener. Spiked, radiolabeled B[a]P and HCB mineralization, volatilization, solvent extractabilit y, soil binding and plant accumulation were measured in soil microcosms for differences between unvegetated and vegetated treatments. Aroclor 1260 and PAH contaminated loamy sand from a New Jersey plastics plant was used. Soil was planted with Tall Fescue (Festuca arundinacea Screb.) or was left unplanted. Incubation under artificial lighting for 180 days with vegetation resulted in decreased B[a]P volatilization, increased mineralization, and increased solvent extractability but had no detectable effect on soil binding. Vegetation had no effect on HCB volatilization or soil binding but enhanced its mineralization and decreased its extractability.
Descriptors: rhizosphere- aromatic-hydrocarbons polycyclic-hydrocarbons contamination- bioremediation
Abstract: Soil contaminated with petroleum sludge is often bioremediated by tillage and addition of nitrogen and phosphorus to stimulate microbial degradation of the hazardous compounds. This "landfarming" technique is effective in reduc ing concentrations of a variety of chemicals during the early stages of treatment, but degradation rates severely decline thereafter, especially for recalcitrant compounds such as polyaromatic hydrocarbons (PAHs). However, the presence of vegetation can e nhance the degradation of these compounds. In a greenhouse experiment, the degradation of PAHs was greater in the presence of plants than in their absence. Target PAHs were detectable in the plant tissue, but the total quantity of uptake was insignificant . Enhanced microbial activity was apparently responsible for increased dissipation of target PAHs. Establishment of vegetation holds promise as an inexpensive yet effective means of passive remediation of sites contaminated with petroleum hydrocarbons.
Descriptors: groundwater-pollution chromium- chemical-speciation irrigation-water bioremediation- biodegradation- medicago-sativa cattle-manure application-rates drainage-water ph- dissolved-oxygen electrical-conductivity plant-tissues pollutio
Abstract: A cost-effective method is needed for removing chromate from cooling water blowdown, wastewater effluent, and contaminated groundwater. Experiments were conducted to determine the effectiveness of treating Cr-contaminated water by using the water for irrigation, and that reduction of Cr(VI) to Cr(III) would occur in a soil amended with organic matter and irrigated to promote low oxidation/reduction status. The Cr(m) would then precipitate as oxides and hydroxides, and be immobilized and rendered plant unavailable. Samples of a field soil (mixed, thermic Typic Torripsamments) overlying a contaminated groundwater site were placed in pots and irrigated for 20 wk with water containing 1000 kg L-1 Cr(VI). Treatments included plants (alfalfa; Medicago sativa L.) vs. no plants, each at three organic matter loadings -0, 12, and 50 Mg ha-1 dried cattle manure (0, 5.5, and 21.8 g manure kg-1 soil). The drainage waters were collected weekly and analyzed for total Cr, Cr(VI), pH, dissolved O2, disso lved organic C, and electrical conductivity. The removal percentages of Cr(VI) from the enriched water ranged from 51 to 98% and increased with increasing organic matter loading. Chromium concentrations in the drainage water were consistently < 50 micr ogram L-1 in the organic-amended soil. Daily irrigation yielded lower drainage water Cr concentrations than weekly irrigation (at a constant weekly volume) due to increased residence time of the water in the bioactive zone. Chromate adsorption accounted f or < 1% of the total immobilized Cr and the amount taken up by the alfalfa shoots was < 0.5% of the total added. This method shows promise as a cost-effective treatment for Cr-contaminated groundwater.
Abstract: The ability of aquatic plants to absorb, translocate and concentrate metals has led to the development of various plant-based treatment systems. The potential to accumulate chromium by Scirpus lacustris, Phragmites karka and Bacopa mon nieri was assessed by subjecting them to different chromium concentrations under laboratory conditions. Plants showed the ability to accumulate substantial amounts of chromium during a short span of one week. When the plants were grown in tannery effluent and sludge containing 2.31 micrograms ml-1 and 214 mg kg-1 Cr, respectively; they caused significant reduction in chromium concentrations. While there was an increase in biomass, no visible phytotoxic symptoms were shown by treated plants. The plants can then be harvested easily and utilized for biogas production.
CONTENTS NOTE: Sequestration and realistic risk from toxic chemicals remaining after bioremediation -- Moving innovative biotechnologies to the field: an engineering perspective -- Roadblocks to the implementation of biotreatment strategies -- An overview
of research on the beneficial effects of vegetation in contaminated soil -- Bioavailability and biodegradation kinetics protocol for organic pollutant compounds to achieve environmentally acceptable endpoints during bioremediation -- Effect of some commo
n solubility enhancers on microbial growth -- Principle of superposition applied to adsorption experiments to differentiate strong binding mechanisms -- Treatment of trichloroethylene-contaminated water with a fluidized-bed bioreactor -- Complete reductiv
e dechlorination of trichloroethene by a groundwater microbial consortium -- Biotreatment of PAH-contaminated soils/sediments -- Microbial degradation and treatment of polycyclic aromatic hydocarbons and plasticizers -- Kinetics of BTEX degradation by a
nitrate-reducing mixed culture -- Evaluation of bioslurry ecosystems for removal of TNT from contaminated soil using a variety of process amendments -- Bioremdiation using composting or anaerobic treatment for ordnance-contaminated soils -- Screening of a
quatic and wetland plant species for phytoremediation of explosives-contaminated groundwater from the Iowa Army Ammunition Plant -- Fate of explosive contaminants in plants -- A microcosm study on remediation of explosives-contaminated groundwater using c
onstructed wetlands -- Recent developments in formulating model descriptors for subsurface transformation and sorption of trinitrotoluene.
NAL Call #: 500--N484-v.829
Descriptors: Hazardous-waste-site-remediation-Congresses Bioremediation-Congresses
Descriptors: tannery-waste effluents- chromium- nymphaea-alba bacopa-monnieri spirodela-polyrhiza aquatic-plants bioremediation-
Descriptors: myriophyllum-spicatum cadmium- metal-ions ion-uptake bioremediation- pollution-control polluted-water phytotoxicity- dry-matter-accumulation phosphorus- nutrient-content stems- roots- water-purification
Descriptors: polluted-soils trichloroethylene- microbial-degradation rhizosphere- lespedeza-cuneata pinus-taeda solidago- glycine-max paspalum-notatum uptake- leaves- pine-needles stems- roots- species-differences mineralization- soil-pollution
Abstract: A comparison of the environmental fate of [14C]trichloroethylene (14C]TCE) in vegetated and nonvegetated soils from a contaminated field site indicated increased mineralization (14CO2 production) in soils containing vegetation. Mineraliz ation in soils containing Lespedeza cuneata (Dumont), Pinus taeda (L.), Solidago sp. (all collected from a former chlorinated solvent disposal site), and Glycine max, germinated from commercially available seeds, accounted for > 26% of the total recove red radioactivity compared with approximately 15% for nonvegetated soil and < 9% for control (sterile) soil. Uptake of 14C into plant tissues ranged from 1 to 21% total for leaves (or needles), stems, and roots and appeared to be related to plant speci es and water use during the experiment. The higher mineralization rates for [14C]TCE in the vegetated soils compared with nonvegetated soils indicates that the rhizosphere provides a favorable environment for microbial degradation of organic compounds. Th erefore, vegetation may play an important role in enhancing biological remediation of contaminated surface soils in situ.
Descriptors: casuarinaceae- coriariaceae- datiscaceae- elaeagnaceae- myricaceae- rhamnaceae- rosaceae- alnus- species- frankia- nitrogen-fixing-trees symbiosis- nitrogen-fixation soil-fertility rehabilitation- nitrogen- transfer- tropical-soils
land-use land-management tropics- sustainability-
Abstract: The contribution of actinorhizal plants to soil productivity and rehabilitation depends not only on properties encountered in a number of non-N2-fixing trees but also on the input of fixed N2 that is subsequently transferred to soil and ultimately to associated crops. The nitrogen-fixing potential of a number of actinorhizal plants (e.g. Casuarina sp. and Alnus sp.) is high but the amount of N2 actually fixed in the field is often low because the expression of this potential is limited b y unfavorable environmental conditions or improper management practices. Assessing the amount of fixed N2 transferred to soil is difficult mainly because of the recycling of fixed N2 except in open ecosystems. Many examples of successful introductions of actinorhizal plants into various systems of land management are given. To increase the input of fixed N2 into ecosystems two strategies can be adopted: the first one is to use proper management practices; the second one is to improve the performances of t he N2-fixing system. Practically, in addition to optimizing actinorhizal fixation, it is recommended to develop the introduction of actinorhizal plants as soil improvers in a number of countries where they are not yet used, to domesticate hitherto neglect ed or overlooked actinorhizal plants, and to exploit their ability to contribute to the rehabilitation of wasted lands and possibly to the phytoremediation of polluted sites.
Descriptors: bioremediation- waste-water-treatment distillers'-spent-wash phanerochaete-chrysosporium coriolus-versicolor
Abstract: Modern agricultural practices make extensive use of herbicides to increase crop yields. Persistent herbicides (recalcitrant to degradation) are often preferentially used for season-long protection. The persistence of these herbicides makes them environmentally hazardous if they leach or are carried by surface runoff and erosion to pollute surface- or ground-waters. Three heavily used persistent herbicides are presented for illustration: atrazine (a triazine), fluometuron (a substitut ed urea), and trifluralin (a dinitroaniline). Vegetated border strips between agricultural fields and adjoining streams are sometimes cleared and protected from flooding to increase the amount of cultivable land. These areas, left in their natural state a s seasonally-flooded riparian wetlands, contain micro-environments conducive to immobilization and degradation of persistent herbicides. While natural riparian wetlands should not be used to treat point-source herbicide pollutants, the literature indicate s that maintenance of riparian wetlands can help to slow migration of and to enhance degradation of herbicides from non-point sources.
Descriptors: contaminants- polluted-soils biodegradation- festuca-arundinacea medicago-sativa sorghum-bicolor panicum-virgatum bioremediation- soil-pollution
Abstract: Residual contamination of soils with polycyclic aromatic hydrocarbons (PAHs) is an environmental problem for many industrial operations, including the petroleum industry. Petroleum sludges high in PAHs are often treated through landfarmi ng in which soil is mixed with sludge, kept bare of vegetation, tilled, and fertilized to encourage microbial degradation of the contaminants. However, recent research has demonstrated that plants can enhance the dissipation of organic pollutants in the i mmediate environment of the root (rhizosphere). The use of vegetation to increase the degradation of two common PAH contaminants, anthracene and pyrene, was investigated in a greenhouse experiment. Target compounds were added to a contaminated, landfarmed soil and a similar uncontaminated soil at a rate of 100 mg/kg. Four plant species were grown in each soil; after 4, 8, 16, and 24 wk of plant growth, soil and plant material were sampled and analyzed for the target PAHs. Vegetated soils had significantly lower concentrations of the PAHs than the unvegetated soils, ranging from 30 to 44% more degradation in the vegetated soils. Enhanced biological degradation in the rhizosphere appears to be a mechanism of dissipation. Leaching, plant uptake, abiotic degr adation, mineralization to CO2, and irreversible sorption were shown to be insignificant in the overall mass balance of the target compounds. The presence of plants may enhance the clean-up of PAH-contaminated soils during in situ remediation.
Descriptors: polycyclic-hydrocarbons polluted-soils soil-pollution bioremediation- toxicity- bioassays- soil-flora soil-fauna aquatic-organisms plants- polycyclic-aromatic-hydrocarbons
Descriptors: atrazine- microbial-degradation mineralization- polluted-soils metolachlor- rhizosphere- kochia-scoparia soil-pollution bioremediation-
Abstract: Mineralization of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3, 5-triazine-2,4-diamine) in soil treated with a mixture of atrazine and metolachlor (2-chloro-6'-ethyl-N-(2-methoxy-1 -methylethyl)acet-o-toluidide at concentrations typi cal of point-source contamination (50 microgram g-1 each) was significantly greater (P < 0.001) in rhizospheric soil from Kochia scoparia (L.) Roth., a herbicide-resistant plant, than in non-vegetated and control soils. Soils were collected from an agr ochemical dealership contaminated with several herbicides, including atrazine, metolachlor, trifluralin (alpha,alpha,alpha,-trifluoro-2, 6-dinitro-N,N-dipropyl-p-toluidine and pendimethalin (N-(1-ethylpropyl)-2, 6-dinitro-3,4-xylidene), at concentrations well exceeding the field application rates. Mineralization rates of ring-labeled atrazine in both rhizospheric and non-vegetated soils were quite high (> 47% of the initial 14C applied after 36 days) compared to literature values. These results suggest that plants such as Kochia might be managed at pesticide-contaminated sites to help facilitate microbial degradation of wastes such as atrazine in soil.
Descriptors: waste-treatment marine-areas water-pollution monitoring- bioremediation- oil-spills dredgings- environmental-protection marine-environment climatic-change global-change
Descriptors: bioremediation- polluted-soils plants-
Descriptors: bioremediation- brassica-napus hibiscus-cannabinus festuca-arundinacea species-differences
Abstract: Concentrations of selenium (Se) in agricultural irrigation effluent increased stored soil Se to toxic levels in the wetland sediment at Kesterson Reservoir. Vegetation management (phytoremediation) may be a strategy to reduce these soil Se concentrations to nontoxic levels. Selenium in plant shoots and depletion of soil Se removal by selected plant species were evaluated over a 1-yr period under greenhouse conditions. Two soils were used: a seleniferous Turlock soil (collected from Keste rson Reservoir) that contained high total Se (approximately 40 mg kg-1 soil), high water extractable B (approximately 10 mg B L-1), and a soil salinity of approximately 8 dS m-1, and a nonseleniferous Hanford sandy loam (collected from an agricultural fie ld site). Three plant species tested were Brassica napus cv. Westar (canola), Hibiscus cannabinus L. cv. Indian (kenaf), and Festuca arundinacea Schreb. cv. Alta (tall fescue). Only canola and kenaf grown in Turlock soil showed significant lower shoot yie ld (P < 0.01) than on the Hanford soil. Leaf Se was as high as 470 mg Se kg-1 DM in canola, 45 mg Se kg-1 DM in kenaf and 50 mg Se kg-1 DM in tall fescue. The same crops contained mean leaf B concentrations as high as 415 mg B kg-1 DM in kenaf, 180 mg B kg-1 DM in canola, and 111 mg B kg-1 DM in first clipping of tall fescue. The cultivation of all species led to a significant reduction (P < 0.01) of total soil Se between preplant and the final harvest by the following percentages: canola (47%), ken af (23%), and tall fescue (21%). Successively planting of canola and to a lesser extent kenaf and tall fescue, in Se-laden soil has the potential to reduce total soil Se.
Descriptors: polluted-soils soil-types poa-compressa biological-indicators bioremediation-
Abstract: The purpose of this study was to assess the potential of prairie grasses as bioindicators of toxicants in soil and to investigate the effect different soil types and organisms have upon the germination of plant bioindicators. As a mo del compound, we used 2-chlorobenzoic acid (2CBA), a hydrophilic, polar compound present in the degradation pathways of halogenated aromatics. The germination response of prairie grasses to Aroclor 1260-contaminated soil, with concentrations ranging from 13 to 133 micrograms kg-1 total polychlorinated biphenyls, was also investigated. The grasses responded to a wide range of contamination levels, with a 12- and 10-fold difference in the sensitivity of grass species to 2CBA and Aroclor, respectively. Canad a blue grass (Poa compressa) and slender wheatgrass (Agropyron trachycaulum) were selected for further study of the effects of soil type and biological treatments on bioindicator response to 2CBA. Canada blue grass response in three of four soils was char acterized by Y = 110 - 26 x ln(X), while in the fourth soil it was Y = 94 - 1.6 x X, where Y equals percent germination and X the 2CBA concentration. Slender wheatgrass response was Y = 140 - 23 x ln(X), with no significant difference between soil types. Previous biological treatments of soil significantly affected the response of slender wheatgrass as a bioindicator. Growing plants or plants inoculated with bacteria in noncontaminated soil before slender wheatgrass was planted inhibited emergence, changi ng the logarithmic relationship between germination and 2CBA concentrations to Y = 100 - 0.28 x X. Prairie grasses are potentially useful bioindicators of chlorinated aromatics in soil, but biological interactions may alter the. bioindicator response.
Abstract: This research project was conducted to evaluate the use of plants for reducing the environmental impact of aircraft deicers. Significant quantities of ethylene glycol-based deicing fluids spill to the ground and inadvertently cont aminate soil and surface water environments. Comparisons of the biodegradation of 14C-ethylene glycol ([14C]EG) in rhizosphere soils from five different plant species, nonvegetated soils, and autoclaved control soils at various temperatures (-10 degrees C , 0 degrees C, 20 degrees C) indicate enhanced mineralization (14CO2 production) in the rhizosphere soils. After 28 days at 0 degrees C, 60.4%, 49.6%, and 24.4% of applied [14C]EG degraded to 14CO2 in the alfalfa (Medicago sativa), Kentucky bluegrass (Poa pratensis) and nonvegetated soils, respectively. Ethylene glycol mineralization was also enhanced with increased soil temperatures. Our results provide evidence that plants can enhance the degradation of ethylene glycol in soil. Vegetation may be a metho d for reducing the volume of aircraft deicers in the environment and minimizing offsite movement to surface waters.
Abstract: The fate of benzene in planted and unplanted soils was investigated using high-flow sealed test systems specifically designed for the recovery of volatile organic compounds (VOCs). Test systems, containing established alfalfa plan ts or unplanted controls, were subirrigated with aqueous solutions of [14C]benzene to produce soil concentrations of 40 (low dose) or 620 micrograms/kg soil (high dose). The test systems allowed us to determine separately root uptake and foliar uptake of the radiolabel and to establish a mass balance for the 14C-label. During the 7 to 10 days experiment, the efflux of 14C-labeled VOCs and 14CO2 resulting from mineralization were measured at 12h intervals. At the end of each experiment, soils and plant tis sues were analyzed for 14C and, in some experiments, benzene was analyzed using gas chromatography. Less than 2% of the recovered 14C was associated with the plant shoots and between 2% to 8% in the root fraction (root tissue plus rhizosphere soil). No be nzene was detected in the soils or plant tissue by gas chromatography, even in the high dose experiments. The average total recovery of added radiolabel in all experiments was greater than 90%. Comparisons of planted and unplanted soils indicated that alf alfa did not enhance the degradation of benzene in this experimental system. The amount of benzene that was volatilized directly from soil was far greater than any that might have evolved from the plants themselves.
Descriptors: bioremediation- industrial-sites coal- gasification- town-gas microbial-degradation polycyclic-hydrocarbons polluted-soils hydrogen-peroxide ferrous-ions chemical-degradation iowa- manufactured-gas-plants polynuclear-aromatic-hydro
Abstract: A three-year field-pilot study has demonstrated that Prairie Buffalograss (Buchloe dactyloides var. 'Prairie') has accelerated naphthalene concentration reduction in clay soil. Extensive soil sampling and analyses have been perfor med to evaluate statistically significant differences between soil PAH concentrations with and without grasses. Comparative performance evaluation for other PAH compounds was restricted by analytical variability. A parallel experiment to assess the perfor mances of twelve warm season grass species from different genetic origins has shown that Kleingrass (Panicum coloratum var. 'Verde') has a greater potential to remove PAHs from rhizosphere soil than other tested grasses at the site soil. Preliminary data indicated that Kleingrass root zone soil concentrations of both low and high molecular weight PAHs were approximately one order of magnitude lower than those with Prairie Buffalograss. Grass tissue analysis found no evidence of PAH bioconcentration. Food chain effects should not be a concern for phytoremediation of aged PAH-contaminated soils. Additional soil sampling is planned in the future to confirm the findings.
Descriptors: alyssum- nickel- uptake- metal-tolerance chelation- histidine- biological-production bioremediation- polluted-soils hyperaccumulation-
Abstract: A number of terrestrial plant accumulate-large quantities of metals such as zinc, manganese, nickel, cobalt and copper in their shoots. The largest group of these so-called 'metal hyperaccumulators' is found in the genus Alyssum, in which nickel concentrations can reach 3% of leaf dry biomass. Apart from their intrinsic interest, plants exhibiting this trait could be of value in the decontamination of metal-polluted soil. However, the biochemical basis of the capacity for metal-accum ulation has not been elucidated. Here we report that exposing hyperaccumulator species of Alyssum to nickel elicits a large and proportional increase in the levels of free histidine, which is shown to be coordinated with nickel in vivo. Moreover, supplyin g histidine to a non accumulating species greatly increases both its nickel tolerance and capacity for nickel transport to the shoot, indicating that enhanced production of histidine is responsible for the nickel hyperaccumulation phenotype in Alyssum.
forest-trees tree-breeding bioremediation- pollutants- uptake-
metabolic-detoxification metal-tolerance genetic-engineering
genetic-transformation agrobacterium-rhizogenes soil-pollution
Descriptors: bioremediation- trees- forest-trees
contaminants- polluted-soils metabolic-detoxification genetic-engineering
Descriptors: plants- contaminants- pollutants-
concentration- bioremediation- pollution-control bioconcentration-
Descriptors: polluted-soils heavy-metals contamination-
bioremediation- plants- uptake- removal- plant-breeding
agricultural-research hyperaccumulators- phytoremediation-
Descriptors: medicago-sativa genotypes-
Abstract: Phytoremediation is an effective, non-intrusive, and inexpensive means of remediating soils contaminated with organic chemicals. Different plant species have different remediation capabilities, so intraspecies variation may also exis t. If intraspecific variation exists and is heritable, population improvement for performance in and phytoremediation of contaminated soils should be possible. The objectives of this study were to determine if variability exists among alfalfa (Medicago sa tiva L.) genotypes for agronomic performance in and phytoremediation of crude oil-contaminated soil and to determine the effect of contaminated soil on the agronomic performance of alfalfa. In one greenhouse experiment, 20 genotypic clones were transplant ed into 20 g kg-1 crude oil-contaminated sod. After 1 yr, differences existed among genotypes for total forage yield (P < 0.05), maturity at harvest (P < 0.001), plant height (P < 0.01), and phytoremediation potential (P < 0.001). Degradation ruses ranged from 33 to 56% among genotypes with 46% for the unvegetated control. Two genotypes had significantly greater degradation rates than that of the unvegetated control. In a second greenhouse experiment, eight genotypes from the previous experime nt were compared with their clones in uncontaminated soil. After 1 yr, men total forage yield in contaminated soil was 32% of the yield of the same clones in uncontaminated soil. Plants in contaminated soil also matured later and were shorter. Genotype va riability was present for all traits but not on all evaluation dates. The results indicate that overall agronomic performance is reduced in contaminated soil, but variability exists among genotypes for growth in. and phytoremediation of contaminated soil s.
Descriptors: alcaligenes- pseudomonas-putida corynebacterium- metabolism- organic-compounds aromatic-compounds plants- relationships- microbial-degradation polychlorinated-biphenyls bioremediation- alcaligenes-eutrophus
Descriptors: bioremediation- phytoremediation-
Descriptors: pentachlorophenol- biodegradation- agropyron-desertorum mineralization- volatilization- soil- leachates- plant-tissues shoots- uptake- polluted-soils bioremediation.
Abstract: We investigated the effects of vegetation on the fate of pentachlorophenol (PCP) in soil using a novel high-flow sealed test system. Pentachlorophenol has been widely used as a wood preservative, and this highly toxic biocide contaminat es soil and ground water at many sites. Although plants are known to accelerate the rates of degradation of certain soil contaminants, this approach has not been thoroughly investigated for PCP. The fate of [14C]PCP, added to soil at a concentration of 1 00 mg/kg, was compared in three unplanted and three planted systems. The plant used was Hycrest, a perennial, drought-tolerant cultivar of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes]. The flow-through test system allowed us to m aintain a budget for 14C-label as well as monitor mineralization (breakdown to CO2) and volatilization of the test compound in a 155-d trial. In the implanted systems, an average of 88% of the total radiolabel remained in the soil and leachate and only 6 % was mineralized. In the planted systems, 33% of the radiolabel remained in the soil plus leachate, 22% was mineralized, and 36% was associated with plant tissue (21% with the root fraction and 15% with shoots). Mineralization rates were 23.1 mg PCP mi neralized kg-1 soil in 20 wk in the planted system, and for the unplanted system 6.6 mg PCP kg-1 soil for the same time period. Similar amounts of volatile organic material were generated in the two systems (1.5%). Results indicated that establishing cre sted wheatgrass on PCP-contaminated surface soils may accelerate the removal of the contaminant.
Impact of surface modification on binding affinity distributions of Datura innoxia biomass to metal ions.
Descriptors: bioremediation- phytoremediation-
Descriptors: morus-rubra developmental-stages leaves- senescence- roots- root-exudates phenolic-compounds phenols- rhizosphere- seasonal-variation relationships- biological-activity-in-soil soil-flora bioremediation- polluted-soils
Abstract: We have tested an integrated system for phytoremediation using corn (Zea mays L.), a safener specific for chloroacetamides (benoxacor), and an inoculum of a rhizosphere-competent Pseudomonas fluorescens strain UA5-40rif capable of cat abolizing these herbicides. Initial growth chamber studies with a Bosket sandy loam soil (organic matter content < 1%), benoxacor (0.75 kg ha-1) and inocula of this bacterium provided protection to corn seedlings at herbicide application rates of up to 45 and 54 kg ha-1 of alachlor and metolachlor, respectively. Satisfactory root colonization, i.e. log (10) 6.2 to 7.4 cfu g-1 root by UA5-40rif, was observed at concentrations up to 12x of these herbicide rates. Following 12 days of plant growth, alachlo r concentrations in soil from safened and inoculated corn seedlings were about 25% and 35% of those observed in unplanted soil at the 12x alachlor and metolachlor rate, respectively. Additional experiments studied applications of up to 36x of formulated m etolachlor. At this higher metolachlor rate, normal physiological development was observed in benoxacor-safened seedlings, although there were slight reductions in root and shoot biomass. Metolachlor residues in soil treated with the 36x rate were 89%, 80 %, 75%, respectively, for the unplanted soil, corn, and corn + benoxacor treatments, while only 54% remained in corn + benoxacor + UA5-40 treatment. Results indicate that use of a combination of chemical and biological safeners (competent herbicide-detoxi fying rhizobacteria) is a novel and useful approach for increasing herbicide tolerance in an agronomic crop plant for enhanced phytoremediation.
Descriptors: bioremediation- phytoremediation-
Descriptors: brassica-juncea thlaspi- cadmium- localization- plant-composition shoots- roots- manganese- copper- leaves- chlorophyll- phytochelatins- xylem- sap- trichomes- abscisic-acid transpiration- dry-matter-accumulation ligands- transloca
tion- biomass-production species-differences bioremediation- thlaspi-caerulescens phytoremediation-
Abstract: Indian mustard (Brassica juncea L.), a high biomass crop plant, accumulated substantial amounts of cadmium, with bioaccumulation coefficients (concentration of Cd in dry plant tissue/concentration in solution) of up to 1100 in shoots and 6700 in roots at nonphytotoxic concentrations of Cd (0.1 micrograms/mL) in solution. This was associated with a rapid accumulation of phytochelatins in the root, where the majority of the Cd was coordinated with sulfur ligands, probably as a Cd-54 co mplex, as demonstrated by x-ray absorption spectroscopy. In contrast, Cd moving in the xylem sap was coordinated predominantly with oxygen or nitrogen ligands. Cd concentrations in the xylem sap and the rate of Cd accumulation in the leaves displayed simi lar saturation kinetics, suggesting that the process of Cd transport from solution through the root and into the xylem is mediated by a saturable transport system(s). However, Cd translocation to the shoot appeared to be driven by transpiration, since ABA dramatically reduced Cd accumulation in leaves. Within leaves, Cd was preferentially accumulated in trichomes on the leaf surface, and this may be a possible detoxification mechanism.
Descriptors: polluted-soils plants- bioremediation- interactions- plant-bacteria-interactions
Descriptors: arabidopsis-thaliana transgenic-plants gene-transfer structural-genes oxidoreductases- mutagenesis- induced-mutations recombinant-dna escherichia-coli gene-expression metal-tolerance mercury- metal-ions reduction- vapor- release- -
messenger-rna gold- applications- bioremediation- polluted-soils elemental-mercury mercury-vapor phytoremediation- mercuric-ion-reductase
Abstract: With global heavy metal contamination increasing, plants that can process heavy metals might provide efficient and ecologically sound approaches to sequestration and removal. Mercuric ion reductase, MerA, converts toxic Hg2+ to the less toxic, relatively inert metallic mercury (Hg0). The bacterial merA sequence is rich in CpG dinucleotides and has a highly skewed codon usage, both of which are particularly unfavorable to efficient expression in plants. We constructed a mutagenized merA s equence, merApe9, modifying the flanking region and 9% of the coding region and placing this sequence under control of plant regulatory elements. Transgenic Arabidopsis thaliana seeds expressing merApe9 germinated, and these seedlings grew, flowered, and set seed on medium containing HgCl2 concentrations of 25-100 micromolar (5-20 ppm), levels toxic to several controls. Transgenic merApe9 seedlings evolved considerable amounts of Hg0 relative to control plants. The rate of mercury evolution and the level of resistance were proportional to the steady-state mRNA level, confirming that resistance was due to expression of the MerApe9 enzyme. Plants and bacteria expressing merApe9 were also resistant to toxic levels of Au3+. These and other data suggest that t here are potentially viable molecular genetic approaches to the phytoremediation of metal ion pollution.
Abstract: The toxicity and metabolism of phenol and a series of chlorinated phenols, 4-chlorophenol to pentachlorophenol, in axenically grown Lemna gibba were studied. It was found that the toxicities of the phenols tended to increase with increas ing number of chlorine substituents on the phenol ring. Over relatively short incubation periods (< 7 days), the plants metabolized each of the phenols in the same manner, producing compounds that were more polar than the corresponding phenol from whic h they were derived. The plant-produced metabolites of phenol, 2,4-dichlorophenol and 2,4,5-trichlorophenol were isolated, purified and their structures were identified by high field NMR and chemical ionization MS to be beta-glucoside conjugates. It was f urther shown, by GC/MS, that over longer incubation periods (ca 20 days), the plants were able to progressively dechlorinate the phenols. While conversion of the chlorinated phenols to their corresponding phenyl glucosides results in compounds that are mo re water-soluble and less toxic to the plants than were the parent phenols, the potential for regeneration of the original phenols, as a result of low pH or enzymatic cleavage of the glucoside, remains. In contrast, reductive dechlorination represents a r eal detoxification since the toxicity of the chlorinated phenols decreases with decreasing number of chlorine substituents. It is possible therefore, that the ability of duckweed to perform reductive dechlorination can be exploited as part of a remediatio n technology.
Abstract: The mineralization of atrazine by mycorrhizal fungi was examined. The percent mineralization was determined by comparing the amount of 14CO2 evolved from the plant and plant-fungus systems when measured amounts of 14C-labeled atrazine were provided under axenic conditions in specially designed exposure chambers. The percent mineralization was 0.1 and 0.3. respectively, for the plant and plant-fungus systems. The study demonstrated that an ectomycorrhizal fungus in association with its host plant increased the metabolism of exogenously provided atrazine above that of the plant by itself, thereby supporting the proposed use of plant-fungal systems in bioremediation of contaminated soils.
Abstract: The present studies were undertaken to explore the possibility of using synthetically designed genes encoding phytochelatin analog (Glu-Cys)nGly peptides in transgenic plants for phytoremediation. We studied the metal-chelating charac teristics of a synthetically prepared phytochelatin analog peptide (Glu-Cys)2Gly to determine if a gene encoding such a peptide might be useful in phytoremediation, as a first step. Studies with Cd(II), Hg(II), and Pb(II) show that the synthetic (Glu-CYS) 2Gly peptide exhibits metal-chelating properties similar to the phytochelatin (gamma Glu-Cys),2Gly. GSH-bound metals were also shown to be quantitatively transferred to (Glu-Cys)2Gly. The Cd(II)-form of the synthetic (Glu-Cys)2Gly peptide-like PCs was abl e to form stable complexes with sulfide. The spectroscopic properties of (Glu-Cys)2Gly-coated complexes of CdS were comparable to those exhibited by (gamma Glu-Cys)2Gly-coated CdS particles. Both (gamma Glu-Cys)2Gly and (Glu-Cys)2Gly exhibited a Cd-bindin g stoichiometry of 0.5 Cd per peptide molecule. UV-visible, HPLC, and mass-spectral analyses indicated that one Hg(II) ion was chelated by each molecule of (gamma Glu-Cys)2Gly or (Glu-Cys)2Gly. Each molecule of (gamma Glu-Cys)2Gly or (Glu-Cys)2Gly bound t o one atom of Pb(II).
Descriptors: soil-pollution heavy-metals contamination- bioremediation- plants- metal-ions ion-uptake agricultural-research green-remediation hyperaccumulator-plants
Descriptors: medicago-sativa polluted-soils petroleum- bioremediation- genotypes- cultivars- growth- vigor- phytoremediation- total-petroleum-hydrocarbons
Descriptors: polluted-soils heavy-metals concentration- plants- metal-tolerance bioaccumulation.
Abstract: To identify populations with the ability to accumulate heavy metals, approximately 300 accessions pertaining to 30 plant species were grown for 4 wk in a hydroponic media that approximated the nutrient and heavy metal composition of a so il contaminated with moderate levels of cadmium (Cd), copper (Cur, and zinc (Zn). The results indicated that several Brassica spp. exhibited moderately enhanced Zn and Cd accumulation. Selected accessions of Brassica juncea (L.) Czern, B. napus L., and B . rapa L. were then grown in pots with heavy metal-contaminated soil to compare the Zn and Cd phytoextraction by these species to that of Thlaspi caerulescens J. & C. Presl, a known Zn and Cd hyperaccumulator, and two grass species, Agrostis capillari s L. and Festuca rubra L. The three Brassica spp. were the most effective in removing Zn from the contaminated soil, primarily because they produced more than 10 times the shoot biomass produced by T. caerulescens. When the soil was amended with Gro-Powe r, a commercial soil amendment that improves soil structure and fertility, removal of Zn by plant shoots doubled to more than 30 000 mg Zn pot-1 (4.5 kg). The results suggest that for phytoremediation of metal-polluted soils to be successful, a strategy s hould be considered that combines rapid screening of plant species possessing the ability to tolerate and accumulate heavy metals with agronomic practices that enhance shoot biomass production and/or increase metal bioavailability in the rhizosphere.
Abstract: Lead phytoextraction, the use of plants to extract Pb from contaminated soils, is an emerging technology. To develop this technology, we have conducted extensive research to study physiological and cellular mechanisms of Pb uptake, tr anslocation; and accumulation in crops, weeds, and known metal hyperaccumulators. This paper will review current progress from our laboratories and several other laboratories in the development of Pb phytoextraction technology. We will focus on the follow ing subjects: (1) physiological and cellular aspects of Pb transport in plants, (2) plant species/cultivars variation in Pb uptake and translocation, (3) role of plant genetic engineering in Pb phytoextraction, and (4) role of synthetic chelates in enchan cing Pb phytoextraction from contaminated soils. With the addition of selected chelates to soils collected from Pb-contaminated sites, we are now able to increase shoot Pb concentration from less than 500 mg kg-1 to more than 10000 mg kg-1, which is the v alue targeted for commercial Pb phytoextraction. Field testing of Pb phytoextraction technology is currently underway in a dozen sites in the United States. Current results indicate that this technology may provide an environmentally sound and cost-effect ive strategy for the clean-up of Pb-contaminated soils.
Descriptors: plants- bioremediation- soil-pollution groundwater-pollution contaminants- costs-
Descriptors: polluted-soils plants- bioremediation-
Descriptors: bioremediation- heavy-metals uptake- plants- polluted-soils
Descriptors: plants- aquatic-plants heavy-metals pollutants- uptake- polluted-soils bioremediation- polluted-water literature-reviews
Abstract: As a result of nuclear testing and nuclear reactor accidents, large areas of land have become contaminated with low concentrations of radionuclides. Removal, transport and treatment of large volumes of soil may be logistically difficu lt and prohibitively costly. Using plants to remove low concentrations of radionuclides from soil in situ is expected to be less expensive than mechanical, physical or chemical methods, particularly for treatment of large areas. Phytoremediation is applic able to a wide range of terrestrial environments and plants can be selected for given soil and climatic conditions. Phytoremediation of contaminated sites should also leave treated sites amenable to subsequent reclamation efforts. The points to consider f or initial phytoremediation and subsequent reclamation of contaminated soils include:enhancement of plant accumulation of radionuclides by addition of mycorrhizal or bacterial inocula, chelating agents or organic amendments, periodic harvests to recover o r dispose of radionuclides in the ashed plant materials minimization of potential environmental effects on non-target organisms and replacement or augmentation of the initial remediating species with a complex plant community.
Descriptors: polluted-soils bioremediation- amaranthus-retroflexus brassica-juncea phaseolus-acutifolius
Abstract: A field study was conducted to investigate the potential of three plant species for phytoremediation of a 137Cs-contaminated site. Approximately 40-fold more 137Cs was removed from the contaminated soil in shoots of red root pigweed (Ama ranthus retroflexus L.) than in those of Indian mustard [Brassica juncea (L.) Czern] and tepary bean (Phaseolus acutifolius A. Gray). The greater potential for 137Cs removal from the soil by A. retroflexus was associated with both high concentration of 13 7Cs in shoots and high shoot biomass production. Approximately 3% of the total 137Cs was removed from the top 15 cm of the soil (which contained most of the soil radiocesium) in shoots of 3-mo-old A. retroflexus plants. Soil leaching tests conducted with 0.1 and 0.5 M NH4NO3 solutions eluted as much as 15 and 19%, respectively, of the soil 137Cs. Addition of NH4NO3 to the soil, however, had no positive effect on 137Cs accumulation in shoots in any of the species investigated. It is proposed that either NH 4NO3 solution quickly percolated through the soil before interacting at specific 137Cs binding sites or radiocesium mobilized by NH4NO3 application moved below the rhizosphere, becoming unavailable for root uptake. Further research is required to optimize the phytotransfer of the NH4NO3(-) mobilized 137Cs. With two croppings of A. retroflexus per year and a sustained rate of extraction, phytoremediation of this 137Cs-contaminated soil appears feasible in < 15 yr.
Descriptors: plants- bioremediation- polluted-soils pollutants- uptake- literature-reviews biodegradation
Abstract: Plant-based remediation techniques are showing increasing promise for use in soils contaminated with organic and inorganic pollutants. Two contrasting approaches to remediation are being pursued: pollutant-stabilization and containment, w here soil conditions and vegetative cover are manipulated to reduce the environmental hazard; and decontamination, where plants and their associated microflora are used to eliminate the contaminant from the soil.
Abstract: Phytoremediation is the use of green plant-based systems to remediate contaminated soils, sediments, and water. Relative to many traditional remediation engineering techniques, phytoremediation is a fledgling technology intended to ad dress a wide variety of surficial contaminants. Phytoremediation targets currently include contaminating metals, metalloids, petroleum hydrocarbons, pesticides, explosives, chlorinated solvents, and industrial by-products. The primary market driver for co ntinued research in this area is the significant cost reduction these systems appear to afford. Phytoremediation, however has inherent limitations in that plants are living organisms with specific oxygen, water, nutrient and pH limits that must be maintai ned. In addition, significant depth, concentration, and time frame limitations also apply. Despite these limitations, many forms of phytoremediation have emerged from the laboratories and are currently in practice. Commercial phytoremediation systems for clean up of shallow aquifers and water born contaminants are now in place. Field tests for the phytoextraction of metals from contaminated soils are underway as well as advanced stabilization trials. For the most part, the current practices are technicall y sound, but far from optimized. Field tests have generally been met by good regulatory and public acceptance, yet improvements and extensions can and will be made on many of them. The biological resource for phytoremediation remains largely untapped. Bri nging multi-disciplinary teams consisting of biologists, chemists, engineers, as well as lawyers, accountants, and public advocates should continue to yield additional solutions and. possibilities for continued application of phytoremediation.
Abstract: There is current interest in the use of artificial wetlands and macrophyte-cultured ponds for the treatment of agricultural drainage water, sewage, and industrial effluents. Aquatic plant-based water treatment systems have proved effecti ve and economical in improving the quality of wastewaters containing excess nutrients, organic pollutants, and heavy metals. This investigation was conducted to test the hypothesis that herbicide-tolerant aquatic plants can remediate herbicide-contaminate d waters. The addition of Ceratophyllum demersum (coontail, hornwort), Elodea canadensis (American elodea, Canadian pondweed), or Lemna minor (common duckweed) significantly (p less than or equal to <0.01) reduced the concentration of [14C]metolachlor (MET) remaining in the treated water. After a 16-day incubation period, only 1.44%, 4.06%, and 22.7% of the applied [14C]MET remained in the water of the surface water systems containing C. demersum, E. canadensis, or L. minor whereas 61% of the applied [ 14C]MET persisted in the surface water systems without plants. C. demersum and E. canadensis significantly (p less than or equal to < 0.01) reduced the concentration of [14C] atrazine (ATR) in the surface water. Only 41.3% and 63.2% of the applied [14C ]ATR remained in the water of the vegetated systems containing C. demersum and E. canadensis, respectively. Eighty-five percent of the applied [14C]ATR was detected in the water of the L. minor and nonvegetated systems. Our results support the hypothesis and provide evidence that the presence of herbicide-tolerant aquatic vegetation can accelerate the removal and biotransformation of metolachlor and atrazine from herbicide-contaminated waters.
Phytoremediation of selenium.
Terry, N. and Zayed, A.
Environmental chemistry of selenium. New York : Marcel Dekker, c1998. p. 633-655.
NAL Call #: QH545.S45E58-1998
Descriptors: soil-pollution water-pollution
Descriptors: Phytoremediation-Congresses Soil-remediation-Congresses Water-Purification-Congresses
Phytoremediation of soil contaminated with low concentration of radionuclides.
Entry, J. A., Vance, N. C., Hamilton, M. A., Zabowski, D., Watrud, L. S., and Adriano, D. C.
Water air soil pollut. 88: 1/2 pp. 167-176. (Mar 1996).
NAL Call #: TD172.W36
Descriptors: polluted-soils soil-pollution radionuclides- cesium- strontium- ion-uptake plants- roots- bioremediation- fallout- topsoil- vesicular-arbuscular-mycorrhizas organic-amendments ashing- plant-residues harvesting- literature-reviews
Descriptors: polluted-soils organic-compounds contamination- bioremediation- plants- uptake- plant-physiology rhizosphere- biological-activity-in-soil soil-flora research-projects literature-reviews
Abstract: We tested the ability of hybrid poplar to absorb trichloroethylene (TCE) from groundwater. Initial studies used axenic tumor cultures of H11-11 grown in the presence of 14C-TCE. These cells metabolized the TCE to produce trichloroetha nol, di- and trichloroacetic acid. Some of the TCE was incorporated into insoluble, non-extractable cell residue, and small amounts were mineralized to 14C-CO2. Rooted poplar cuttings grown in PVC pipes produced the same metabolites when exposed to TCE. M ass balance studies indicate that the poplars also transpire TCE. In addition we are conducting one of the first controlled field trials for this technology. Trees were planted in cells lined with high density polyethylene and dosed with TCE via an underg round water stream during the growing season. Cells containing trees had significantly reduced TCE levels in the effluent water stream compared to control cells containing only soil. These results show that significant TCE uptake and degradation occur in poplars, which bodes well for the future use of poplars for in situ remediation of TCE.
Descriptors: polluted-soils bioremediation-
Descriptors: soil-pollution sediment- contamination- pollution-control bioremediation- plants- intake- contaminants- technical-progress trends- contamination-containment contaminant-reduction
Descriptors: thlaspi- silene-vulgaris lycopersicon-esculentum polluted-soils cadmium- zinc- soil-ph metal-tolerance
Abstract: Metal-tolerant hyperaccumulator plants may be useful to phytoremediate contaminated soils. To evaluate agronomic management practices to maximize phytoremediation, two metallophytes, Thlaspi caerulescens J. and C. Presl (Zn hyperaccumula tor) and bladder campion [Silene vulgaris (Moench) Garcke L.] (an indicator) were compared to 'Rutgers' tomato (Lycopersicon esculentum L.) in a pot study to assess Zn and Cd uptake patterns in relation to soil pH. Soils used for the study were gathered a t three different sites in the vicinity of an old Zn smelter in Palmerton, PA, and contained 48 000, 4100, and 2100 mg kg-1 Zn and 1020, 37.4, and 35.2 mg kg-1 Cd, respectively. Each soil was adjusted to three pH levels ranging from 5.06 to 7.04. Thlaspi caerulescens showed much greater tolerance to the metals than the other plants (up to 18 455 mg kg-1 Zn and 1020 mg kg-1 Cd dry shoots without yield reduction) with metal stress apparent only in the low pH treatments of the two most contaminated soils. In all treatments except for the farm soil (least contaminated) at pH 5.06, T. caerulescens had higher concentrations of both Zn and Cd than bladder campion and tomato. Thlaspi caerulescens was also more effective at translocating both Zn and Cd from soil t o plant shoots. A variety of soil extractions were used to evaluate the correlation of shoot metal concentrations with quantitative measures of "available" soil metals. Concentrations of Cd measured in several common extractants (DTPA, water, 0. 01 M Ca(NO3)2, and 1.0 M NH4NO3) were significantly correlated with Cd concentrations in tissue of each plant. Shoot Zn concentrations of bladder campion and tomato were significantly. correlated with Zn extracted by the neutral salt extractants for all soils. For T. caerulescens, the neutral salt extractable Zn was significantly correlated with shoot Zn only in the two more contaminated soils. No extractant predicted shoot Zn concentration for T. caerulescens in the least contaminated soil.
Descriptors: transgenic-plants genetic-engineering bioremediation- polluted-soils ion-uptake metal-ions mercury- metals- pollutants- toxic-substances plant-proteins binding-proteins phytoremediation- toxic-metals phytochelatins-
Descriptors: Plants,-Effect-of-heavy-metals-on Hyperaccumulator-plants
Abstract: One limitation to the rate of pesticide residue degradation in contaminated soil is the age of the residue. Research has suggested that "aged" residues may be less bioavailable and thus more persistent. Other research has sh own that simply diluting aged, herbicide-contaminated soil with uncontaminated soil can stimulate degradation. In addition to dilution, addition of a carbon source, like dried, ground plant material, stimulated degradation. These studies suggested that la ndfarming as a disposal method for pesticide-contaminated soil could be made more efficient by amendments with different organic nutrients. Landfarming of aged herbicide-contaminated soils were simulated in the laboratory by diluting contaminated soil wit h uncontaminated soil. We present results to show that the dissipation of several herbicides was stimulated by dilution of aged, contaminated soil and amendment with different forms of corn (i.e., plant residues, ground seed, or commercial meal).
Descriptors: paulownia-elongata pig-manure waste-water fertilizers- foliage- plant-composition growth-rate bioremediation- water-pollution
Abstract: A greenhouse experiment was done with vegetatively propagated trees to examine the influence of swine lagoon effluent on the growth and foliar nutrient content of the fast-growing hardwood species Paulownia elongata. Application of swine lagoon effluent promoted plant growth and was as beneficial as a complete chemical fertilizer applied at a similar nitrogen loading rate. Foliar concentrations of nitrogen were high, typically between 3.5% and 4.5%, when swine lagoon effluent was applied at a nitrogen loading rate equivalent to 205 or 409 kg/ha. Zinc and copper concentrations were also relatively high when plants received these swine lagoon effluent treatments (45 to 55 ppm and 17 to 23 ppm, respectively). Sufficient variation among P. e longata clones was revealed for growth parameters and foliar nutrient concentrations to anticipate a benefit from the selection of genotypes that are the most efficient for remediation of animal waste, i.e., high biomass production and foliar nutrient acc umulation. The data show that P. elongata has potential for use as a swine waste utilization species.
Descriptors: populus- riparian-vegetation pollution- biodegradation- nitrates- tolerance- immobilization- absorption- heavy-metals soil-flora soil-chemistry literature-reviews bioremediation-
Descriptors: plant-physiology organic-compounds contaminants- pollutants- detoxification- light- chemical-reactions literature-reviews
Descriptors: contaminants- polluted-soils biodegradation- aquatic-plants bioremediation- trinitrotoluene-
Descriptors: drainage-water water-pollution bioremediation-
Descriptors: plants- bioremediation- pollutants- uptake- metabolic-detoxification soil-pollution polluted-soils phytoremediation-
Descriptors: polluted-soils sediment- polluted-water pollution-control bioremediation- soil-pollution pollutants- extraction- degradation- biodegradation- phytoremediation- pollution-clean-up
Abstract: The rhizosphere fortuitously enhances the population numbers and activity of certain microorganisms that degrade xenobiotic soil contaminants. This review examines the ecology of degrader microorganisms in the rhizosphere, and summari zes prior research that has examined the influence of plants on biodegradation of chlorobenzoates, chlordane, polychlorinated biphenyls (PCBs), and the herbicide atrazine. Degradation rates of most xenobiotics examined to date are not significantly influe nced by the presence of a rhizosphere. However, a major benefit of the rhizosphere may be to harbor certain degrader organisms at higher cell numbers, thereby shortening the acclimation period. Another benefit may be enhanced transfer of degradative plasm ids, or in some instances, enhanced cometabolism of compounds which can not be directly utilized as substrates for microbial growth.
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are among the more resistant compounds found in petroleum contaminated soils and persist even after extensive bioremediation. Phytoremediation has been demonstrated to enhance the degradation o f PAHs, but the mechanisms of dissipation have not been identified. The degradation of pyrene and anthracene was investigated in a laboratory study in which soil was removed from the rhizosphere of a long-term stand of alfalfa and compared to degradation in non-rhizosphere and sterile soil. Low molecular weight organic acids typically found in the rhizosphere were added to the soils to determine if exudation of simple organic compounds may be part of the rhizosphere effect. Dissipation in non-sterile soil s was found to be much greater than in sterile soil, but there was no rhizosphere effect and the addition of organic acids did not enhance degradation. The effect of the rhizosphere on PAH degradation seems to be short-lived and requires the continued pre sence of roots.
Descriptors: polluted-soils alkanes- aromatic-hydrocarbons benzoic-acid polycyclic-hydrocarbons phenanthrene- rhizosphere- poa-alpina medicago-sativa bioremediation- enumeration- bacterial-count plate-count soil-bacteria soil-fungi organic-chem
ical-degraders most-probable-number cis-decahydronaphthalene- phytoremediation- hexadecane- 2,2,-dimethylpropyl-benzene pyrene-
Descriptors: thlaspi- thlaspi-arvense nickel- phytotoxicity- tolerance- ion-uptake roots- shoots- ion-transport biomass-production evapotranspiration- protoplasts- viability- soil-pollution detoxification- metal-hyperaccumulators phytoremediati
Abstract: Metal hyperaccumulators are plants that are capable of extracting metals from the soil and accumulating them to extraordinary concentrations in aboveground tissues (greater than 0.1% dry biomass Ni or Co or greater than 1% dry biomass Zn or Mn). Approximately 400 hyperaccumulator species have been identified, according to the analysis of field-collected specimens. Metal hyperaccumulators are interesting model organisms to study for the development of a phytoremediation technology, the us e of plants to remove pollutant metals from soils. However, little is known about the molecular, biochemical, and physiological processes that result in the hyperaccumulator phenotype. We investigated the role of Ni tolerance and transport in Ni hyperaccu mulation by Thlaspi goesingense, using plant biomass production, evapotranspiration, and protoplast viability assays, and by following short- and long-term uptake of Ni into roots and shoots. As long as both species (T. goesingense and Thlaspi arvense) we re unaffected by Ni toxicity, the rates of Ni translocation from roots to shoots were the same in both the hyper- and nonaccumulator species. Our data suggest that Ni tolerance is sufficient to explain the Ni hyperaccumulator phenotype observed in hydropo nically cultured T. goesingense when compared with the Ni-sensitive nonhyperaccumulator T. arvense.
Descriptors: soil-pollution bioremediation- microbial-degradation rhizosphere.
Abstract: It has long been recognized that microorganisms have distinct and unique roles in the detoxification of polluted soil environments and, in recent years, this process has been termed bioremediation or bioreclamation. The role of microorga nisms and their limitations for bioremediation must be better understood so they can be more efficiently utilized. Application of the principles of microbial ecology will improve methodology. The enhancement of microbial degradation as a means of bringing about the in situ clean-up of contaminated soils has spurred much research. The rhizosphere, in particular, is an area of increased microbial activity that may enhance transformation and degradation of pollutants. The most common methods to stimulate deg radation rates include supplying inorganic nutrients and oxygen, but the addition of degradative microbial inocula or enzymes as well as the use of plants (phytoremediation) should also be considered.
Descriptors: contaminants- selenium- brassica- landraces- concentration- tolerance- bioremediation- soil-pollution pollution-control bioaccumulation-
Descriptors: rhizosphere- soil-pollution organic-compounds toxic-substances microbial-degradation bioremediation- roots- interactions- metabolic-detoxification nitrogen-fixing-bacteria plant-microbial-interactions
Abstract: The rhizosphere provides a complex and dynamic microenvironment where bacteria and fungi, in association with roots, form unique communities that have considerable potential for detoxication of hazardous organic compounds. Detoxication m ay result from degradation, mineralization, or polymerization of the toxicant in the rhizosphere. These detoxication processes are influenced not only by the rhizosphere microbiota, but also by unique properties of the host plant, soil properties, and env ironmental conditions. Understanding the interactions among plants, rhizosphere microbial communities, and organic toxicants will facilitate the successful use of vegetation to remediate chemically contaminated soils.
Descriptors: phytotoxicity- metal-tolerance bioremediation.
Abstract: The toxicity of Zn and Cu in three species from the genus Brassica was examined to determine if these plants showed sufficient tolerance and metal accumulation to be used to phytoremediate a site contaminated with these two heavy metals. Hydroponically grown 12 d-old plants of Brassica juncea, B. rapa, and B. napus were grown for an additional 14 d in the presence of either elevated Zn (6.5 mg L-1), Cu (0.32 mg L-1), or Zn+Cu to quantify the toxic effects of these metals on several diffe rent growth parameters. With few exceptions, both root and shoot dry weight for all three species decreased significantly in the presence of heavy metals. Cu inhibited lateral root elongation in B. rapa, B. napus, and, to a lesser extent, B. juncea, while Zn tended to decrease only lateral root diameter. Both metals reduced shoot Fe and Mn concentrations in all three Brassica spp. to levels associated with Fe and Mn deficiencies. These deficiencies, however, did not correlate with observed patterns of le af chlorosis. Nonetheless, heavy metal-induced inhibition of Fe and Mn accumulation may have been a significant factor in reducing plant growth. In terms of heavy metal removal, the Brassica spp. were more effective at removing Zn from the nutrient solut ion than Cu. The extent of Zn and Cu removal was reduced in the presence of both metals, as compared to the single heavy metal treatments. The implications of these results for phytoremediation are discussed.
Descriptors: populus-deltoides populus-nigra hybrids- soil- hydroponics- explosives- contaminants- bioremediation- phytoremediation- 2,4,6-trinitrotoluene-
Descriptors: daucus-carota spinacia-oleracea lycopersicon-esculentum soil- rhizosphere- weeds- trichloroethylene- metabolites- contaminants- soil-pollution groundwater-pollution groundwater- bioremediation- uptake- transformation- binding- isot
ope-labeling bioreactors- phytoremediation- synthetic-groundwater
Descriptors: triticum-aestivum contaminants- bioremediation- waste-water-treatment pollution-control
Descriptors: polluted-soils heavy-metals contamination- rehabilitation- acidification- sulfur- cadmium- solubility- bioavailability- sinapis-alba ion-uptake soil-ph biomass- removal- phytoremediation- hyperaccumulating-plants
Abstract: To a soil artificially contaminated with cadmium, orthorhombic sulphur flower and a hydrophillic microbially produced elemental sulphur were added to induce the soil acidification. The soil was incubated in pots under open-sky conditions . pH, sulphate, and cadmium solubility were recorded in time. Soil acidification with microbially produced sulphur proceeded without any delay and at considerably higher rates, compared to the sulphur flower. Cadmium solubilization was solely controlled b y the soil pH during the experiments. Similar experiments with cultivation of common mustard (Sinapis alba, cultivar JARA) were performed, evaluating both changes of cadmium solubilization and uptake by biomass. Cadmium concentration in shoots increased w ith decreasing pH. However, biomass was negatively affected by the decreasing pH. Combining these two effects, a pH-optimum for maximum cadmium removal from the soil by plants was found at pH = 5-5.5.
Use of whole plants to enhance the biodegradation process in contaminated soils.
Beck, Mary Jim. and Tennessee Valley Authority.
[Knoxville, Tenn.? : Tennessee Valley Authority, 1995] 15 p.: Caption title. Distributed to depository libraries in microfiche. Shipping list no.: 97-0169-M. "March, 1995." Includes bibliographical references (p. 11-15). SUDOCS: Y 3.T 25:2 P 69/5.
NAL Call #: Fiche--S-133-Y-3.T-25:2-P-69/5-
Descriptors: Soil-remediation Bioremediation- Plant-soil-relationships
Abstract: Biostimulation is a successful method for remediation of soils and other matrices contaminated with a wide range of xenobiotics. Use of the appropriate soil amendments can enhance the biodegrading potential of indigenous soil microbia l populations. Plant materials have been studied by others as biostimulating amendments for soils contaminated with a wide range of herbicides. Our previous studies indicated that annual ryegrass (Lolium multiforum L.) residue was the most effective amend ment for enhancing cyanazine (2-[[4-chloro-6-(ethylamino)-1,3,5- triazin-2yl]amino]-2 methyl-propanenitrile) and fluometuron (N,N-dimethyl-N'-(trifluoromethyl)- phenyl]urea) degradation in soils. Thus we pursued a comparative study of various crop residue s on the degradation of fluometuron in soil. In this study we investigated the effects of amending soil with hairy vetch (Vicia villosa Roth), rice (Oryza sativa L.), or ryegrass residues on the degradation of a high concentration (500 mole kg-1 soil) of fluometuron (technical grade or commercial formulation). Initially, all three amendments enhanced fluometuron degradation in soil treated with technical material or commercial formulation. Hairy vetch transiently enhanced degradation, while the two grass residues stimulated degradation during the entire study (60 d). Rice straw had the greatest stimulation. In short term studies (21 d), ryegrass had the greatest effect on stimulating soil bacterial populations and several enzyme activities. Use of the app ropriate plant residue is a promising approach for enhancing the remediation of herbicide-contaminated soils.
Descriptors: naphthalene- contamination- soil-pollution microbial-degradation volatilization- mineralization- grasses- soil- interactions- bioremediation.
Abstract: The potential for vegetation-enhanced biodegradation of naphthalene in artificially contaminated soil was studied in laboratory microcosms. Microcosms containing soil without plants and soil supporting two-month old Bell Rhodesgrass were treated with naphthalene and spiked with [7-14C]naphthalene. Compressed air was continuously passed through each microcosm, through a trap to collect volatile organics, and through a trap for CO2. The microcosms were incubated under artificial lighting w ith a 16 h photoperiod for 25 days. After incubation, soil was solvent extracted and combusted to recover bound radiolabel. Volatilization losses during operation and analysis prevented reaching a mass balance of the radiolabel. Naphthalene volatilization was enhanced by vegetation but mineralization was decreased in vegetated microcosms in comparison to those without vegetation.
Descriptors: biological-indicators bioremediation- water-pollution waste-water-treatment
Descriptors: polluted-soils heavy-metals bioremediation- cadmium- metal-tolerance schizosaccharomyces-pombe genes- gene-transfer gene-expression transgenic-plants bioaccumulation-
Descriptors: thlaspi- silene-vulgaris lycopersicon-esculentum zinc- cadmium- heavy-metals uptake- varietal-tolerance species-differences phytotoxicity- polluted-soils bioremediation- mineral-content shoots- roots- leaves- source-sink-relations
Abstract: Phytoremediation of heavy-metal-contaminated soils can be an inexpensive means to remove hazardous metals from soil. Two metallophytes, Thlaspi caerulescens (J.& C. Presl, a Zn and Cd hyperaccumulator) from Prayon, Belgium, and a Zn- tolerant ecotype of bladder campion [Silene vulgaris (Moench.) Gareke L.] from Palmerton, PA, were compared with tomato [Lycopersicon lycopersicum (L.) Karsten, metal intolerant] in nutrient solution to characterize Zn and Cd uptake and tolerance. Zinc an d Cd were added to solutions at a 50:1 molar ratio to simulate concentrations often found on contaminated sites. Seven treatment concentrations were used, ranging (in half-log increments) from 3.16 micromolar Zn + 0.063 micromolar Cd to 10 000 micromolar Zn + 200 micromolar Cd. Thlaspi caerulescens showed much greater tolerance to Zn/Cd treatments than the other species, with toxicity stress only apparent at the 10 000 micromolar Zn/200 micromolar Cd treatment. In this treatment, shoot concentrations of Z n and Cd were 33 600 and 1140 mg kg-1, respectively. Thlaspi caerulescens was also more effective at translocating both Zn and Cd from solution to shoots. Zinc concentration in shoots of T. caerulescens was higher than the other species at all Zn/Cd treat ments. Cadmium concentration in shoots of T. caerulescens were significantly higher than in bladder campion only at the 316 micromolar Zn/6.32 micromolar Cd treatment. This genotype of T. caerulescens may not hyperaccumulate Cd. However, extreme Zn and Cd uptake and tolerance is evident in T. caerulescens, with >25 000 mg Zn kg-1 and 1000 mg Cd kg-1 before yield is reduced. Results suggest that T. caerulescens may be a candidate for the phytoremediation of Zn-contaminated soils.
Descriptors: thlaspi- zinc- mineral-uptake nutrient-uptake mineral-nutrition trace-elements nutrient-nutrient-interactions roots- shoots- mineral-content nutrient-content growth- dry-matter-accumulation nutrient-availability
Abstract: Thlaspi caerulescens, a metallophyte that is able to accumulate up to 4% zinc (Zn) in leaf dry matter, has attracted much attention for its possible use in phytoremediation of metal contaminated soils. In the present study, the influence of Zn supply on mineral nutrition in T. caerulescens was investigated, in order to establish the extent to which growth stimulation by high Zn supply is related to changes in the levels of other essential nutrients. The plants were exposed to nutrient so lutions containing 1.5, 100, 500, 750, 1000, or 1500 micromolar Zn. Zinc supply significantly influenced root and shoot concentrations of essential nutrients, but excepting Zn, the concentrations stayed within the range considered adequate for optimum gro wth in Brassicaceae crops. Best performance was achieved with the supply of 500 micromolar Zn. Growth stimulation by this treatment was accompanied by increased translocation of iron (Fe) from root to shoot and a significant correlation between shoot dry weight and Fe concentrations in shoots was found.
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