Progress 02/03/04 to 02/02/07
Outputs
OUTPUTS: The outputs of this project have been several studies of the plant-soil-air system that have improved our knowledge of how pollutant chemicals move through the environment. These include studies on the phytoaccumulation of persistent organic pollutants by different species of Cucurbitaceae and different eco-types of Arabadopsis thaliana. In both cases, it was shown that differing species of the same family or even differing eco-types of the same species have differing amounts of phytoaccumulation of organic pollutants. This implies that there are specific genetic traits that control the phytoaccumulation of organic pollutants. If these genes can be identified it might be possible to bioengineer the plants to enhance the viability of phytoremediation. We also found that though there were some correlations between the measured concentrations of low molecular weight organic acid exudates of roots and the phytoaccumulation of soil sequestered organic compounds, these
correlations did not appear to be causative. This would indicate that adding these acids to the soil at the levels measured in this study is not likely to enhance phytoremediation. These results have been disseminated to the scientific public through publications and presentations at meetings including those of the Society of Environmental Toxicology and Chemistry, and, the Florida Pesticide Residue Workshop. During this project, a post-doctoral research associate in our laboratory was trained in the use of these techniques. He is currently a professor at a university in Turkey. The techniques have been shown to the general public during laboratory open houses that occur as part of our annual Plant Science in the Spring day at the Connecticut Agricultural Experiment Station and tours of the station by various groups.
PARTICIPANTS: Dr. Brian D. Eitzer was the principal investigator working on the development of methods in this project.
TARGET AUDIENCES: The primary target audience is the scientists and researchers who study phytoremediation and the environmental transport and fate of organic pollutants. A secondary audience would be all the people who are working on the remediation of contaminated sites, as these methods can be used to assist in the evaluation of the contamination of these sites.
Impacts
This project was focused on the development of methods for the analysis pollutants from soil and vegetation. Our goal was to develop methods that could give more detailed information on the location of the pollutants within the soil-porewater-plant-air system so that we could better understand how chemical pollutants move through that system. Three new methods were developed during this project that have been incorporated into the standard procedures used in our studies of the translocation of chemicals by plants. The first of these methods was a procedure for the analysis of low molecular weight organic acids (LMWOA) that are exuded by plant roots. These acids can be collected on small pieces of filter paper. The filter paper is then spiked with an isotopically labeled standard, freeze dried, derivatized and analyzed by gas chromatography/mass spectrometry (GC/MS). The second procedure was a method by which porewater from the plant root/soil interfacial area could be
collected for analysis of both organic pollutants and LMWOA. In this procedure, plant roots were trained to grow through small pipettes containing soil. After the root grew through the pipette it was severed, and the pipette was centrifuged allowing collection of the porewater. The porewater is then split into two portions; one portion is spiked with an isotopically labeled chlordane and analyzed by solid-phase microextraction (SPME) GC/MS to determine the concentrations of semivolatile organic pollutants. The second portion is used for analysis of LMWOA by freeze drying and derivatization GC/MS. The third procedure developed was a method for collection of sap from the severed stem of a cucurbit. The collected sap could then be subjected to analysis of organic contaminants by SPME-GC/MS. The major advantage of these new methods is that they provide concentration data from a very specific location and a very small mass of sample within the plant-soil-water system. These methods provide
these data while maintaining the very high sensitivity that was previously available only with much larger sample sizes.
Publications
- MaryJane Incorvia Mattina, William A. Berger and Brian D. Eitzer. "Factors affecting the phytoaccumulation of weathered soil-borne contaminants: analyses at the ex Planta and in Planta sides of the plant root." Plant Soil, 2007, 291,143-154.
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Progress 01/01/06 to 12/31/06
Outputs
This project has developed methods to analyze persistent organic pollutants (POPs) within the soil-rhizosphere-vegetation-air system. The methods are suitable for the meso-scale allowing the analyses to be conducted with minimal amounts of sample collection. For example POPs can be determined in less than a mL of sap collected from a plant that was severed. These methods have been used in experiments to determine the uptake of soil-borne contaminants by Cucurbitaceae. During these experiments, we have found that although low molecular weight organic acids are exuded from the roots of the plants, and, there are some correlations between the amount of acid exudation and the amount of uptake of POPs by the plants, these correlations do not appear to be causative. Therefore, there are some other factors that impact the ability of plants to uptake POPs. These factors are controlled by plant genotypes. Studies of three Cucurbitaceae have shown that the uptake of POPs is
dependent on the genotype and pollutant. The three genotypes not only differed in bioconcentration factors for different pollutants but also differed in the enantioselective profile of the chiral components. Recent experiments in which the aerial tissue of one genotype was grafted to the rootstock of a different genotype demonstrated that the enantioselective profile for these chiral components in the aerial tissue is solely dependant on the genotype of rootstock; transport of the POPs from the root to the aerial tissue does not affect the enantioselective profile in the aerial tissue. Differences in uptake by ecotypes of the same species have also been shown in Arabadopsis thaliana plants. Seven different eco-types of Arabadopsis thaliana were grown in a chlordane contaminated soil. During three different trials using different growing conditions, the same ecotype always had the highest bioconcentration, though the relative amount of bioconcentration changed between trials.
Impacts
There are numerous locations where the environment is contaminated by persistent organic pollutants. These sites need to be remediated so that the land can be put back to productive use. A typical remediation strategy requires the removal of the contaminated material followed by treatment or disposal elsewhere. This strategy can be quite costly. Alternate strategies, such as phytoremediation, can potentially deal with the contamination in situ at a much lower cost. The methods developed during this project will lead to improved understanding of the mechanisms underlying the phytoremediation strategies. In addition, understanding the genetic control of these mechanisms could lead to plants engineered to maximize their phytoremediation potential. Together this can allow phytoremediation to become a much more accepted practice for remediation, thus providing economic savings to those paying for the remediation.
Publications
- MaryJane Incorvia Mattina, Mehmet Isleyen, Brian D. Eitzer, William Ianucci-Berger, and Jason C. White. Uptake by Cucurbitaceae of Soil-Borne Contaminants Depends upon Plant Genotype and Pollutant Properties. 2006 Environ. Sci. Technol. 40, 1814-1821.
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Progress 01/01/05 to 12/31/05
Outputs
During the past year, this project has continued to develop methods to analyze persistent organic pollutants (POPs) within the soil-rhizosphere-vegetation-air system. Methods have now been established so that low molecular weight organic acids (LMWOA), metals, and POPs, can be determined in soil, soil porewater, roots, sap, and aerial vegetation. The methods include sampling procedures that allow for a small volume of sample to be collected from a specific spot within the system. These physical procedures include the growing of roots within mini-rhizotrons to allow for centrifugation and collection of porewater from the rhizosphere. A second procedure has been developed to allow the collection of sap from plants that had grown in rhizotrons. The stem is carefully severed just above the point at which the plant emerges from the soil and the rhizotron is laid on its side with the bottom slightly raised. A small vial is placed underneath the stem tip and is used to
collect sap while the rhizotron remains watered. Once the sap is collected, it is analyzed by solid-phase microextraction/gas chromatography mass spectrometry for POPs then digested for the analysis of metals. These procedures were used in the rhizotron based experiments where we determined POPs, LMWOA, and metals in the various compartments of rhizotrons grown with one of three Cucurbit species. Previously we had thought that the LMWOA exuded from the roots of the cucurbits might play a role in making the POPs sequestered in the soil more bioavailable. The results of our study showed that though there were some correlations between the LMWOA and the concentration of POPs in the rhizosphere porewater, these correlations did not appear to be causative. Comparison of the rhizosphere porewater concentrations to sap concentrations allows bioconcentration factors to be determined. These factors allowed us to show that the movement of chemicals from porewater through the root into the sap
is dependant on both plant species and chemical indicating that this transport is not solely determined by physico-chemical properties.
Impacts
There are numerous locations where past useage of chemicals has led to contaminated environmental sites. Protection of the environment requires that those sites be remediated. One remediation strategy requires the removal of all the contaminated material to be treated or disposed of elsewhere. This strategy can be quite costly. Alternate strategies, such as phytoremediaiton, can potentially deal with the contamination in situ at a much lower cost. However, use of these alternate strategies requires detailed knowledge of the mechanisms by which the contaminants can be translocated to alternate environmental compartments. These mechanisms are not well understood particularly, as regards to the uptake of sequestered pollutants by plant species. The methods being developed by this project will enhance our understanding of the mechanisms of translocation and thus help to insure a healthy environment.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
This project is focused on the development of methods for the analysis of persistent organic pollutants (POPs) that will enhance our ability to understand the mechanisms by which those pollutants translocate within the soil-rhizosphere-vegetatation-air system. During the past year we have developed a procedure which has allowed us to collect rhizosphere porewater and developed methods which allow us to analyze low molecular weight organic acids (LMWOA), metals and persistent organic pollutants in the collected porewater. Rhizosphere impacted porewater is generated by placing root tips of plants growing in a rhizotron at the head of small pipettes that are packed with the same soil as in the rhizotron. As the root grows through the pipette it is watered daily until the root tip starts to emerge from the other end of the pipette. At this point the root is severed at either end of the pipette and the pipette is removed from the rhizotron. Centrifugation of the pipette in
a glass vial collects porewater from the pipette. This procedure allows us to collect between 200 and 1000 microliters of root impacted porewater from a pipette packed with approximately 6 grams of soil. The porewater is split into two portions for subsequent analyses. The first portion is analyzed for the LMWOAs by adding a dueterated succinic acid internal standard, freeze drying the acids and derivatizing them to form volatile esters which are analyzed by gas chromatography/mass spectrometry. The second portion has carbon-13 labeled POPs added as an internal standard with reverse osmosis water added to bring the sample volume to 1 milliliter. The solution is then analyzed by a solid phase microextraction/ chiral gas chromatography mass spectrometry procedure, after which the solution is digested for analysis of metals by inductively coupled plasma atomic emission spectrometry. Together these procedures allow us to measure low concentrations of LMWOAs, POPs, and metals in the same
small sample of porewater.
Impacts
One aspect of the protection of the environment is to clean-up contamination which has occurred in the past. One possible route for that clean-up is phytoremediation, the use of plants to remove the contaminant from soil. Understanding the mechanism by which soil-bound pollutants translocate into the aerial tissue of plants is essential if we are to devise strategies to phytoremediate contaminated soil. Elucidation of those mechanisms is only possible if we are able to examine the multiple compartments of the soil-rhizosphere-vegetatation-air system for the contaminants and chemical species impacting the contamination. In addition these analyses will need to be done on the micro-scale. The methods developed by this project will allow some of these measurements to be performed and will therefore assist in the understanding of those mechanisms.
Publications
- MaryJane Incorvia Mattina, Brian D. Eitzer, William Iannucci-Berger, Wen-Yee Lee, and Jason C. White. "Plant Uptake and Translocation of Highly Weathered Soil-Bound Technical Chlordane Residues from Field and Rhizotron Studies." Environ. Toxicol. Chem. 2004, 23, 2756-2762.
- MaryJane Incorvia Mattina, Brian D. Eitzer, William Iannucci-Berger, and Jason C. White. "Rhizotron Study of Cucurbitaceae: Transport of Soil-Bound Chlordane and Heavy Metal Contaminants Differs with Genera." Environ. Chem. 2004, 1, 86-89.
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