Grantee Research Project Results
Final Report: Mechanistic Role of Plant Root Exudates in the Phytoremediation of Persistent Organic Pollutants
EPA Grant Number: R829405Title: Mechanistic Role of Plant Root Exudates in the Phytoremediation of Persistent Organic Pollutants
Investigators: White, Jason C. , Smets, Barth F. , Mattina, MaryJane Incorvia , Gage, Daniel J. , Gent, Martin P.N.
Institution: Connecticut Agricultural Experiment Station , University of Connecticut
EPA Project Officer: Aja, Hayley
Project Period: November 1, 2001 through October 31, 2004 (Extended to December 14, 2005)
Project Amount: $401,241
RFA: Phytoremediation (2001) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The overall objective of this research project was to investigate the role of root exudates in the plant uptake of persistent organic pollutants (POPs) from soil. Preliminary data had shown that two weathered organic pollutants (2,2-bis(p-chlorophenyl1)-1,1-dichloroethylene [p,p'-DDE] and chlordane) were readily translocated from soil to the roots of a very narrow range of plant species. These findings contradicted a significant body of scientific evidence indicating time-dependent reductions in contaminant availability in soil (i.e., sequestration). The specific objective of this research project was to determine the mechanism by which the uptake occurs. The following hypotheses were being tested:
- The root exudates of certain plant species facilitate the mobility and subsequent availability of weathered organic pollutants. Plant root exudates were isolated and characterized from plants shown to have differential pollutant uptake/remediation abilities in the field. A series of abiotic assays comparing contaminant release in the presence and absence of these exudates tested the central hypothesis. Biosensors were to be constructed for visual detection of the spatial and temporal release of critical exudate constituents from roots.
- Contaminant solubilization by exudates occurs by direct or indirect mechanisms. In direct enhancement, the exudate molecules directly induce contaminant release from the soil. Possible mechanisms include the formation of exudate/contaminant complexes or the partial solubilization/reformation of soil structure organic fractions through chelation of polyvalent metals (iron and aluminum). A second hypothesis considers indirect enhancement, where root exudates stimulate a microbial community that promotes contaminant availability to the plant. The microbial communities of plants with differential uptake/remediation potentials were characterized by 16s ribosomal RNA (rRNA)-targeted terminal restriction fragment length polymorphism (T-RFLP) profiling, and critical microbial exudates were investigated for their role in promoting pollutant availability.
Summary/Accomplishments (Outputs/Outcomes):
Year 1
Connecticut Agricultural Experiment Station (CAES). A series of field and greenhouse studies were completed in the first year. In the field experiments, the uptake and translocation of weathered DDE was assessed in several species of Cucumis (melon and cucumber) and Cucurbita (zucchini, squash, pumpkin) genera. Data from the literature were contradictory on the ability of these plants to accumulate weathered POPs. We observed significant variability in the phytoextraction of weathered DDE between the different genera. Root to soil bioconcentration factors (BCFs), defined as the contaminant concentration in the roots (dry weight) divided by that in the soil (dry weight), were up to 1.8 for the Cucumis sp. but ranged up to 16 for the Cucurbita sp. Large variability in uptake existed within the Curcubita genera (BCFs of 0.47-16) and even within a single species (C. pepo zucchini BCF was 16; C. pepo winter squash was 2.0). The percent of contaminant removed from soil by the “non-accumulator” Cucumis sp. was low (0.03%), but Cucurbita pepo removed up to 2.4 percent of the highly weathered contaminant in a single growing season.
In greenhouse studies, seedlings of zucchini were amended with citric or oxalic acid periodically during their 1-month growth period in DDE-contaminated soil. Parallel laboratory studies had shown that organic acids could increase the desorption of weathered DDE by up to 80 percent through soil matrix destruction mediated by chelation of inorganic soil constituents. Plants receiving water alone were able to extract 1.7 percent of the contaminant, but in soils receiving citric and oxalic acid amendments, the plants removed 2.1 and 1.9 percent of the DDE, respectively. In addition, the aboveground biomass of plants grown with organic acid amendments was greater, resulting in up to 66 percent more DDE in the aerial tissue as compared to plants grown in soil receiving water alone.
University of Connecticut (U. Conn.). Lettuce, wheat, zucchini, and pumpkin were grown in polycyclic aromatic hydrocarbon (PAH)-contaminated soil from a manufactured gas plant (MGP) site. The amount of contaminated soil was varied as follows: 0 percent, 0.3 percent, 3 percent, and 30 percent contaminated soil in the potting media. After 3 months of growth the plants were harvested and the root-associated bacteria were dislodged from the roots by sonication. The bacteria were separated from the soil particles through a series of centrifugation and filtration.
PAH-degrading bacteria were isolated by spreading the rhizobacteria on minimal media plates amended with a layer of PAH on the surface of the plate. Four PAHs were used but anthracene and chrysene provided the best discernable selection. Colonies capable of degradation were chosen based upon clearing zones of the PAH. Over 300 anthracene or chrysene-degrading rhizobacteria were isolated from the four host plants’ rhizospheres and the bulk contaminated soil. Twenty isolates were taken from each selection plate and selection plates for anthracene and chrysene were incubated for each cell sample. Presently, we are differentiating among these isolates using the BOX-PCR method that provides a band pattern that can be used as a fingerprint to differentiate among isolated bacteria.
Some work has begun looking at how the availability of iron can impact PAH degradation. A microplate assay using the tetrazolium salt dye WST-1 has been used to indicate growth of incubating cells. A range of iron to anthracene ratios was used to observe when iron was limiting and when it was in excess for a specific anthracene-degrader based upon the growth indicated by adding the WST-1 stain. For the first anthracene-degrader analyzed, the best growth was exhibited when the iron concentration to anthracene concentration ratio was 0.6 x 10-3.
Microbial community analysis is being performed on all the rhizosphere samples collected for the four different plant types grown in the PAH-contaminated soils. A 16s rDNA targeted T-RFLP method is being employed. Samples are being loaded on native gel and run on ABI 377 sequencer in GeneScan mode. The profiles then are visualized in GeneScan software (ABI) and are being analyzed in BioNumerics software (Applied-Maths, Belgium) using principal component analysis.
A biosensor for detecting plant-released dicarboxylic acids was constructed by fusing the dctA promoter from Sinorhizobium meliloti to the gene for green fluorescent protein (GFP). The dctA gene is a member of the dicarboxylate transport system and this transport system is responsible for the facilitated movement of the C4-dicarboxylate acids across the cell membrane. The dctA gene specifically encodes a gene for the permease that allows the movement of the carbon into the cell. The dctA promoter region was amplified by polymerase chain reaction (PCR) using lab-designed primers and this was cloned in front of a gene from a bright variant of gfp. The final biosensor plasmid also contained a trp terminator and stop codons in all three reading frames in front of the promoter, and gfp gene, respectively to prevent any transcriptional and translational read-through from the plasmid vector. The plasmid construction was done in an Escherichia coli host and then transferred to our wild-type S. meliloti strain Rm1021 for expression. The final plasmid, pPG12, was tested on a variety of carbon sources and showed the highest GFP fluorescence with fumaric acid, followed by maleic, succinic acids. Alfalfa (Medicago sativa) roots were inoculated with the biosensor, and fluorescence was apparent along the root during plant growth indicating that the organic acids were released from roots and that the biosensor was functional in an applied setting.
Year 2
CAES. A field experiment was designed to address the uptake and translocation of highly weathered DDE by two separate subspecies within Cucurbita pepo; subspecies pepo (which includes “true” zucchini and pumpkin) and subspecies texana (which includes other summer and winter squash). Twenty-one cultivars were grown for 3 months; 10 cultivars of ssp pepo and 11 cultivars of ssp texana. Root and stem BCFs varied widely but much of the variability was explained by the subspecies level dichotomy. For example, the average root and stem BCFs for DDE by ssp pepo were 7.4 and 5.4, whereas the values for texana were 2.4 and 0.54, respectively. The ssp pepo cultivars also removed nearly 5 times more contaminant than did texana cultivars. Lastly and perhaps most importantly, the two subspecies also differed in their ability to remove phosporus from the soil. As predicted by our hypothesized relationship between phosphorous acquisition and POP phytoextraction, ssp pepo was significantly more efficient at removing phosphorous from the soil. Interestingly, pepo cultivars were able to remove a number of inorganic elements from the soil to a greater extent than ssp texana, including cadmium and zinc. In fact, one pepo cultivar had a leaf BCF for cadmium of 38.
A second set of experiments investigated the uptake and translocation of DDE by zucchini (C. pepo ssp pepo) and cucumber (Cucumis sativus) under three different cultivation conditions; field (2-3 plants in an estimated 789 kg soil), non-dense (1 plant in 80 kg soil), and dense (5 plants in 5 kg soil) conditions. Under field conditions, the two species behaved as observed in previous studies; zucchini phytoextracted 1.3 percent of the contaminant with 98 percent in the aerial tissues. Conversely, cucumber removed 0.09 percent of the contaminant with 83 percent in the shoot system. Under dense cultivation, cucumber phytoextraction increased to 0.78 percent but most of the contaminant (94%) was retained in the root tissue. Under dense cultivation, removal of DDE by zucchini actually decreased to 0.59 percent, although nearly half of the pollutant was translocated to the aboveground tissues. For both plants, the concentrations of organic acids in soil increased with increasing proximity to the root system (rhizosphere > near-root > bulk) and across cultivation regimes (dense > non-dense > field conditions). Interestingly, under dense cultivation the rhizosphere concentrations of low molecular weight organic acids (LMWOAs) were significantly greater for cucumber than for zucchini. Clearly zucchini exhibits its best phytoextraction potential under field conditions, where root to soil contact is far from maximized.
A series of hydroponic trials were undertaken to investigate organic acid exudation in ssp pepo and other plant species and to assess how that exudation is impacted by nutrient status. In a continuous flow experiment comparing texana and pepo cultivars, adequate phosphorous nutrition resulted in greater exudation of succinic, lactic, and formic acids. Upon phosphorous starvation, citric acid exudation increased for both ssp but increased to a significantly greater extent for the pepo cultivars. In a batch-style hydroponic experiment, phosphorous starvation caused cucumber and zucchini to increase their citric acid release by 2 and 59 times, respectively. When the exudates of P-starved C. pepo cultivars were used as the aqueous phase in abiotic batch-style desorption assays, they increased the release or desorption of weathered DDE from soil significantly more than by distilled water alone.
U. Conn. Rhizobacteria were isolated from the root systems of lettuce, wheat, zucchini, and pumpkin growing in a soil contaminated with PAHs. The soil was from an MGP and contains approximately 750 mg/kg total PAH. Over 300 anthracene or chrysene-degrading organisms were isolated from the plant rhizospheres, characterized by BOX-PCR techniques and plotted on dendrograms. For both the anthracene and chrysene-degrading isolates, the organisms found in the rhizosphere differ from those present in the bulk soil and in the case of the anthracene isolates, the organisms from zucchini rhizosphere differ from those of wheat. These findings suggest that vegetation will select for a specific population of microbes and that the selection process may be plant-specific.
A second fundamental question focused on the degradative range of these individual isolates. Presumably condensed PAHs are not their preferred carbon and energy source and it has been hypothesized that aromatic root exudates may actually prime these organisms for degrading the PAHs, as well as potentially being involved in the selection process described in the preceding paragraph. A colorimetic, well-type system was used to investigate the ability of the anthracene and chrysene-degrading isolates to degrade a number of other PAHs, aromatic root exudates, phytohormones, and pathway intermediates. Initial results indicated that the degradative range of these organisms is indeed quite broad.
Years 3 and 4
CAES. Field experiments were conducted to assess the effects of nutrient amendments on the phytoextraction of field-weathered p,p’-DDE by eight cultivars of cucurbits, including both accumulators Cucurbita pepo ssp pepo (zucchini and pumpkin) and non-accumulators (Cucurbita pepo ssp ovifera [summer squash] and Cucumis sativus [cucumber]). The non-amended accumulators phytoextracted 1.0 percent of the DDE and had a translocation factor (contaminant concentration ratio of stems to roots, TF) of 0.44, and the non-accumulators removed 0.16 percent of the contaminant and had a TF value of 0.09. The accumulators and non-accumulators responded differently to the nutrient treatment. When normalized to respective control plants, the root and stem DDE BCFs of the accumulator cultivars were significantly greater than that of the non-accumulator cultivars under most nutrient regimes. The biomass of accumulators tended to decrease with nutrient amendment and resulted in mixed effects on the amount of DDE extracted from the soil. Nutrients resulted in significantly greater biomass for the non-accumulators, and increased the amount of DDE extracted from soil by 75 percent. Although it is generally assumed that fertilizer amendments to vegetation will enhance phytoremedial potential, as evidenced here by the non-accumulators, additions of certain macronutrients may reduce the phytoextraction of weathered POPs by Cucurbita pepo ssp pepo. These findings support our hypothesis that ssp pepo’s unique ability to remove sequestered organic contaminants is governed by evolved nutrient acquisition mechanisms.
In a parallel field experiment, 10 plant species previously shown to accumulate inorganic elements effectively from soil were grown under field conditions in DDE-contaminated soil. The plant species were rye, mustard, canola, vetch, pigeonpea, clover, peanut, and three cultivars of white lupin. The plants varied widely in their ability to phytoextract and translocate weathered DDE. The percentage of contaminant phytoextracted ranged from 0.06 percent (white lupin) to 0.22 percent (clover, vetch), and the TFs ranged from 0.04 (clover, white lupin) to 0.37 (canola). An inverse relationship exists between the root BCF and the TF. Each species was also amended with nutrients. The effect of nutrient regime on plant biomass, DDE uptake and translocation, and inorganic element content varied greatly among the species. For some species (rye, vetch, pigeonpea, clover, white lupin), reductions or non-significant changes in DDE uptake were observed with nutrients and were not correlated with biomass effects. For mustard, canola, and peanut, the DDE phytoextracted with nutrient amendment was more than doubled and was directly correlated with increased biomass. Although it is generally assumed that fertilizer amendments will enhance the phytoremediation of organic and inorganic pollutants, the data here suggests that such effects are highly species specific.
In a final set of field experiments, the effects of two soil amendments, mycorrhizae or a biosurfactant, on DDE accumulation was determined. Also, DDE uptake was assessed at four stages of plant growth (12, 26, 38, and 62 days). Cucurbita pepo ssp pepo accumulated large amounts of the contaminant from soil, having stem BCFs, amounts of DDE translocated, and overall percent contaminant phytoextracted that were 14, 9.9, and 5.0 times greater than C. pepo ssp ovifera, respectively. Over 62 days, the stem BCF for DDE in ssp pepo remained constant and the percent of contaminant phytoextracted was correlated with plant biomass. For ssp ovifera, the stem BCF was highest at 12 days(1.0) but decreased to 0.38 by 62 days, and DDE removal was not correlated with plant biomass. Mycorrhizal inoculation and biosurfactant amendment increased DDE accumulation by both subspecies, although the amendments reduced ssp ovifera biomass. Soil amendments or patterns of root exudation that enhance the mobility of weathered POPs will significantly increase the amount of contaminant phytoextracted by Cucurbita pepo.
A series of small and large pot trials were conducted to assess the phytoextraction potential of several plant species for weathered polychlorinated biphenyls (PCBs). In small pots (one plant, 400 g soil), three cucurbits (zucchini, squash, and cucumber) accumulated up to 270 μg PCB/g in the roots and 14 μg/g in the stems. Periodic citric acid amendments increased the stem and leaf PCB concentration by 330 and 600 percent, respectively. Two large pot trials were conducted in which the same cucurbits and white lupin were grown in 70 kg of PCB-contaminated soil. White lupin was the poorest accumulator of PCBs, with 20 μg/g in the roots and 1 mg/g in the stems. Both summer squash and cucumber accumulated approximately 65-100 mg/g in the roots and 6.0-10 mg/g in the stems. Zucchini accumulated the greatest level of PCBs, with 430 μg/g in the roots and 22 μg/g in the stems.
Experiments were conducted to assess the uptake of weathered PAHs by plants. Three species were cultivated for four consecutive growing cycles in PAH-contaminated soil. During the first growth period, zucchini tissues contained significantly greater quantities of PAHs than cucumber and squash. During the first growth cycle, zucchini plants accumulated up to 5.5 times more total PAH than did the other plants, including up to three orders of magnitude greater levels of the six-ring PAHs. Over growth cycles 2 to 4, PAH accumulation by zucchini decreased by 85 percent, whereas the uptake of the contaminants by cucumber and squash remained relatively constant. Over all four growth cycles, the removal of PAHs by zucchini was still twice that of the other species.
To investigate the mechanism by which shoots of zucchini accumulate various hydrophobic contaminants from soil while cucumber does not, we presented DDE in low concentration in hydroponics solution. A mixture of DDE bound to Tenax™ beads stirred with a solution of water passing through an air-tight polyethylene mobile-phase reservoir provided a flowing solution with DDE at about 2 μg/L. The DDE supplied in solution was bound tightly to the roots of both cucumber and zucchini. Some DDE moved from the roots to the shoot of both species, but the fraction translocated in zucchini was 10 fold greater than that translocated in cucumber. There was a gradient of DDE concentration in zucchini, root >> stem > petiole > leaf blade, indicating the movement was in the transpiration stream. The ability of zucchini to translocate DDE to the shoot is independent of its ability to release DDE from soil or bind it to roots.
Zucchini, squash, and cucumber were grown in rhizotrons containing soil contaminated with highly weathered chlordane, DDT/DDE/DDD, and PAHs. Movement of the contaminants through the soil/plant system was studied in the bulk soil, the soil pore water, the xylem sap, and aerial tissue. In addition, concentrations of LMWOA as well as organic and elemental pollutants were determined in the plant rhizospheres. Zucchini exuded greater quantities of organic acids than the other plants and some significant correlations between the porewater acid concentrations and the porewater contaminant concentrations were evident. The BCF for chlordane was 36, 40, and 23 for zucchini, squash, and cucumber, respectively. The BCFs for the DDT/DDE/DDD residues were 19, 4, and 0.8, respectively. Differences in the in planta movement of three- and four-ring PAHs also were observed. The movement of heavy metals was cultivar-dependent with cadmium BCF values 9.5, 3.5, and 0.62 for zucchini, squash, and cucumber, respectively; the analogous BCFs for zinc were 9, 11, and 2. Thus, passage from ex planta to in planta regions of the soil/plant system is dependent on plant and pollutant properties.
U. Conn. Characterization of indigenous PAH-degrading bacteria (Pahdegs) in the rhizospheres of the four plant species grown in the various levels of PAH-contaminated soil was completed. A total of 139 isolates were collected from the selection plates for all plant types and were characterized by BOX-PCR. Clustering analysis of the band patterns from BOX-PCR found 10 unique strains among the 139 Pahdegs, which then were further characterized by 16s rRNA PCR and sequencing. Alignment with reference species in the ribosomal database project (RDP) showed that seven strains belong to the Burkholderia sp. (Burk) and three strains belong to Pseudomonas sp. (Pseud). Interestingly, the noncontaminated soil and the highest contaminated level (750 ppm) both showed a different Pahdeg community, indicating a highly specific relationship between rhizosphere Pahdeg community and plant species. Both Burk and Pseud strains carry genes encoding ring-hydroxylating dioxygenases for pyrene (nidA) and biphenyl (bphA1) but not for naphthalene (nahAC). These results suggest that these rhizosphere Pahdegs are well suited for degradation of three- and four-ring PAHs but not naphthalene.
Work assessing the significance of iron to PAH degradation also was completed. Previous work showed that Pahdegs from the plant rhizosphere carry a suite of genes that encode PAH catabolic enzymes. These enzymes, called dioxygenases, require an excess of iron for optimal stability of the ferrodoxin component of the enzyme. Therefore, we assessed the importance of iron in the utilization of PAHs (anthracene and chrysene) by rhizosphere Pahdegs and also the methods by which these bacteria could acquire iron. An isolated Pseudomonad grew best at the iron/ anthracene ratio of 1/1000, twice that of the optimal iron/toluene ratio of 0.5/1000. Pahdegs from plants grown in the PAH-contaminated soil were assessed for ability to produce siderophores. These chelating agents are produced by both bacteria and plants, especially monocots like wheat, under iron-scarcity. At 0 percent MGP soil (no contamination), 90 percent of Pahdegs produce siderophores; at 3 percent MGP soil, 80 percent produce siderophores; and at 30 percent MGP soil, 25 percent produce siderophores. These results suggest that another mechanism for iron acquisition also may be employed at higher contamination levels in the rhizosphere. For example, Dicots, like pumpkin, zucchini, and lettuce, exude phenolic compounds from their roots to scavenge iron.
Experiments assessing the degradative range of these isolates were completed. All Pahdegs tested, utilized caffeic acid, cinnamic acid, coumaric acid, naringenin, quercetin, and morin, suggesting that these rhizosphere bacteria are familiar with these aromatic plant exudates and are not affected by their antimicrobial properties. In addition, we probed these Pahdegs for two enzymes involved in flavonoid synthesis/degradation, flavonol synthase (FLS), which is a plant enzyme, and quercetinase, which is a bacterial enzyme. All strains tested showed the presence of quercetinase but not FLS. These results suggest that iron signaling is a possible mechanism whereby plants stimulate the presence of PAH-degrading bacteria in the rhizosphere.
Lastly, we utilized rhizobacteria community analysis to assess how plant/microbe interactions change due to PAH contamination level and plant species. The whole bacterial community and the cultured PAH-degrading bacteria community were analyzed for the rhizospheres of the four plants. Whole community analysis performed through T-RFLP shows that the bacterial community is influenced more by contamination level than by the plant species. Community analysis for cultured, abundant Pahdegs also showed greater influence by the contamination level in the rhizosphere rather than the host plant type. Both communities, whole and cultured Pahdegs, differ from that of non-vegetated soils (PAH-contaminated and pristine). Cultured Pahdegs show a significant shift in community at the highest treatment level where several species of Gram positive and α- Proteobacteria bacteria appear. The diversity of the Pahdegs increases as the level of PAH contamination increases. For this cultured community, plants did show a difference in distribution of different Pahdegs. Wheat has an even distribution of strains, whereas pumpkin and zucchini predominantly carry 1-2 strains of Pahdegs at the different contamination levels. Cucurbits are then more specific in the type of Pahdeg associated with their roots.
Conclusions:
We are grateful to the U.S. Environmental Protection Agency’s Science To Achieve Results (STAR) Program for its award and because of that funding, feel that we have made significant contributions to the field of phytoremediation research and development. Investigations conducted as a direct result of this funding have resulted in 15 peer-reviewed scientific publications and presentations at nearly two-dozen scientific meetings or seminars. With regard to our hypotheses at the outset of this project, how did we do? Zucchini/pumpkin are effective at accumulating weathered POPs from soil. Perhaps they exude large quantities, or unique mixtures of, LMWOAs as an evolved nutrient acquisition mechanism. These acids are known to chelate inorganic elements in soil, resulting not only in the desired increase in nutrient availability to the plant but also soil matrix deconstruction/disarticulation. Thus, any POPs previously sequestered in that soil matrix may actually now be more available for uptake. One disappointment in the project was the failure of the biosensor bacteria that would be capable of providing a visualization of LMWOA release from plant roots in situ. This did force us, however, to develop alternative methods for soil-based exudation measurements, as described in our rhizotron experiments. As such, in both hydroponic and soil-based experiments, we have shown that zucchini/pumpkin do indeed exude larger amounts of LMWOAs and that correlates with higher levels of the contaminant in the plant. Our hydroponic data and our experiments with soil amendments, however, have shown us that zucchini/pumpkin also have a unique set of in planta processes that goes along with the ex planta exudation uniqueness. For example, you can add surfactants or organic acids to soil and increase the availability of weathered POPs and if plants (any plant) are growing at the time, you get increased contaminant levels on/in the roots. We use “on/in” the roots because regardless of how much contaminant you associate with the root system, plants (at least most plants) cannot translocate a highly hydrophobic contaminant from roots to shoots in the xylem stream, which is largely water. Zucchini/pumpkin are the exception and they can indeed move these contaminants upward. The mechanisms controlling that process are the makings of several additional proposals and are of significant practical and scientific interest.
Journal Articles on this Report : 14 Displayed | Download in RIS Format
Other project views: | All 39 publications | 15 publications in selected types | All 15 journal articles |
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Gent MPN, Parrish ZD, White JC. Nutrient uptake among subspecies of Cucurbita pepo L. is related to exudation of citric acid. Journal of the American Society for Horticultural Science 2005;130(5):782-788. |
R829405 (Final) |
not available |
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Kelsey JW, Colino A, Koberle M, White JC. Growth conditions impact DDE accumulation in Cucurbita pepo. International Journal of Phytoremediation. |
R829405 (Final) |
not available |
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Lee WY, Iannucci-Berger W, Eitzer BD, White JC, Mattina WI. Plant uptake and translocation of air-borne chlordane and comparison with the soil-to-plant route. Chemosphere 2003;53(2):111-121. |
R829405 (Final) R828174 (2002) R828174 (Final) |
Exit Exit Exit |
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Mattina MI, Iannucci-Berger W, Musante C, Mattina MI. Concurrent plant uptake of heavy metals and persistent organic pollutants from soil. Environmental Pollution 2003;124(3):375-378 |
R829405 (2003) R829405 (Final) |
not available |
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Mattina MI, Eitzer BD, Iannucci-Berger W, Lee WY, White JC. Plant uptake and translocation of highly weathered, soil-bound technical chlordane residues: Data from field and rhizotron studies. Environmental Toxicology and Chemistry 2004;23(11):2756-2762. |
R829405 (Final) R828174 (Final) |
not available |
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Mattina MJI, Iannucci-Berger W, Eitzer BD, White JC. Rhizotron study of Cucurbitaceae: Transport of soil-bound chlordane and heavy metal contaminants differs with genera. Environmental Chemistry 2004;1(2):86-89. |
R829405 (Final) |
not available |
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Parrish ZD, White JC, Iseleyen M, Gent MP, et al. Accumulation of weathered polycyclic aromatic hydrocarbons (PAHs) by plant and earthworm species. Chemosphere2005. |
R829405 (Final) |
not available |
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White JC. Differential bioavailability of field-weathered p,p’-DDE to plants of the Cucurbita and Cucumis genera. Chemosphere 2002;49(2):143-152. |
R829405 (2002) R829405 (Final) |
not available |
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White JC, Mattina MJI, Lee W-Y, Eitzer BD, Iannucci-Berger W. Role of organic acids in enhancing the desorption and uptake of weathered p,p'-DDE by Cucurbita pepo. Environmental Pollution 2003;124(1):71-80. |
R829405 (2002) R829405 (Final) |
not available |
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White JC, Wang XP, Gent MPN, Iannucci-Berger W, Eitzer BD, Schultes NP, Arienzo M, Mattina MI. Subspecies-level variation in the phytoextraction of weathered p,p’-DDE by Cucurbita pepo. Environmental Science & Technology 2003;37(19):4368-4373. |
R829405 (2003) R829405 (Final) |
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White JC, Parrish ZD, Iseleyen M, Gent MPN, Iannucci-Berger W, Eitzer BD, Mattina MI. Influence of nutrient amendments on the phytoextraction of weathered 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene by cucurbits. Environmental Toxicology and Chemistry 2005;24(4):987-994. |
R829405 (Final) |
not available |
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White JC, Parrish ZD, Iseleyen M, Gent MPN, et al. Phytoextraction of weathered PCBs by cucurbita and lupinus species. International Journal of Phytoremediation. |
R829405 (Final) |
not available |
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White JC, Parrish ZD, Iseleyen M, Gent MPN, Iannucci-Berger W, Eitzer BD, Mattina MJI. Uptake of weathered p,p’-DDE by plant species effective at accumulating soil elements. Microchemical Journal 2005;81(1):148-155. |
R829405 (Final) |
not available |
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White JC, Parrish ZD, Iseleyen M, Gent MPN, et al. Soil amendments, plant aged, and intercropping impact DDE bioavailability to C. pepo. Journal of Environmental Quality. |
R829405 (Final) |
not available |
Supplemental Keywords:
phytoremediation, plant-based remediation, bioremediation, cleanup, risk assessment, bioavailability, environmental microbiology, remediation, chlordane, bioaccumulation, biological treatment, contaminant removal, in situ bioremediation, in situ remediation, organic contaminants, organic pollutants, risk assessment, sequestration, soil contaminants, soil microbes, soil pollution,, RFA, Scientific Discipline, Waste, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Environmental Chemistry, Contaminated Sediments, Remediation, Chemistry, Environmental Microbiology, Ecology and Ecosystems, Bioremediation, risk assessment, sequestration, plant-based remediation, organic pollutants, rhizospheric, in situ remediation, biological treatment, contaminated sediment, plant uptake studies, contaminated soil, soils, toxicity, contaminants in soil, in situ bioremediation, bioremediation of soils, persistent organic pollutants, phytoremediation, bioacummulation, soil microbes, organic contaminants, soil reclamationProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.