Progress 05/01/07 to 04/30/10
Outputs
OUTPUTS: Persistent organic pollutants or POPS are contaminants which are known for their long-half lives in the environment, toxicity, and potential to bioaccumulate within biota and biomagnify within food chains. In addition, most remedial options available to engineers are completely ineffective for soils contaminanted with persistent organic pollutants. Chlordane, an organochlorine insecticide belonging to this group, was widely used for many decades, but its use was discontinued in the United States in the late 1980s. However, because of its resistance to breakdown, the chemical can still be found in significant concentrations in both agricultural and residential soils. As mentioned above, remedial options for chlordane-contaminanted soils are quite limited and highly expensive. Phytoremediation, or the use of plants to remove pollutants from soil, is a low cost and environmentally friendly means of reducing contamination. When phytoremediation is applied successfully, operating costs for remediation can be reduced up to 10-fold. Previous work in our laboratory has shown that certain plants, the cucurbit zucchini, in particular, are able to take up chlordane and other persistent organic pollutants from soil exceedingly well. POPs are not required nutrients, but are taken up from the soil opportunistically by pre-existing physiological mechanisms. This study focuses on the mechanism of pollutant uptake at the root/soil interface. Channels known as aquaporins are present in the plasma membranes of most cells and are known to selectively transport water and small solutes, as well as some organic solvents. These pores may also alter the enantiomeric profile of chiral compounds which pass through them. Chlordane uptake, and changes in the chiral ratio of some of its components, were investigated under conditions which would close these pores, or, alternately, permit them to remain open. Initial experiments from the previous reporting period focused on boron acquisition and deficiency as a means to potentially elucidate the role of aquaporins in chlordane uptake in cucurbits. However, findings revealed no relationship between chlordane and boron uptake. Current experiments are evaluating the use of hydrogen peroxide (the peroxide radical) to close aquaporins. If our hypothesis is correct, the closing of aquaporins would dramatically decrease chlordane uptake. In fact, an initial preliminary experiment indeed showed that 18-hour exposure to hydrogen peroxide decreased chlordane content in the xylem sap of hydroponically grown plants by 3-fold. In addition, the chiral signature of one of the chlordane components (MC-5) changed dramatically upon peroxide exposure. This also agrees with our hypothesis as a closed transport channel (aquaporin) would result in exclusive simple diffusion across the plasma membrane and signficantly different enantiomer ratios. Future experiments will attempt to repeat these findings and to address the reversibility of the aquaporin shutdown. PARTICIPANTS: PARTICIPANTS: MaryJane Incorvia Mattina was the principal investigator at The Connecticut Agricultural Experiment Station for the current reporting period. The study was designed by Dr. Mattina and Mr. W. A. Berger. Dr. Mattina supervised the work, while Mr. Berger conducted the growth experiments and performed chlordane analyses by gas chromatography/mass spectrometry. During the current reporting period, Dr. Mattina retired from state service and Dr. Jason C. White took over the Department of Analytical Chemistry as Chief Scientist and served as co-investigator on this project. TARGET AUDIENCES: TARGET AUDIENCES: The first target audience is the scientific community which needs to know the mechanisms by which lipophilic and chiral pesticides are taken up from soil into plants. The environmental community will need the data from these experiments in order to design more rational field solutions for the attentuation of real-world pollution. PROJECT MODIFICATIONS: Dr. MaryJane Mattina retired from State service in July 2009. As such, this project will be terminated.
Impacts
Development of efficient phytoremediation tools for the removal of organic compounds would significantly decrease the cost of cleanup at contaminated sites. Preliminary results indicate that closure of aquaporins in hydroponically grown zucchini plants reduces total chlordane uptake, as well as the degree of change in chiral signature. Boron starvation did not yield significant differences in chlordane uptake. However, the use of hydrogen peroxide, which is known to close aquaporins in green algae, does yield significant differences in both uptake and enantiomeric profile with zucchini. The implication of aquaporins in the chlordane uptake mechanism allows for further study in a model system. The genetic basis of aquaporin expression is even better understood in the brassica, Arabidopsis thaliana, than it is in cucurbits. Arabidopsis is also a chlordane uptaker, albeit not to the extent of zucchini. Further studies of chlordane uptake using A. thaliana may allow for the optimization of aquaporin expression in plant roots. Use of such a well understood genetic model could lead to the development of a commercially viable plant species which could be used for the phytoremediation of organic compounds in soil.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Persistent organic pollutants (POPs) comprise a class of compounds which are known for their long half-lives in the environment, toxicity, and tendency to bioaccumulate. Chlordane, an organochlorine insecticide belonging to this group, has been banned from use in the United States for many years. However, it can still be found in significant concentrations in agricultural and residential soils. Phytoremediation, or the use of plants to remove pollutants from soil, is a low cost and environmentally friendly means of reducing contamination. Previous work in our laboratory has shown that certain plants, the cucurbit zucchini, in particular; are able to take up chlordane from soil exceedingly well. POPs are not needed by the plant, but are taken up from the soil opportunistically. This study focuses on the mechanism of uptake at the root/soil interface. Channels present in the plasma membranes of most biological cells, known as aquaporins, are known to selectively transport water and small solutes, as well as some organic solvents. These pores may also alter the enantiomeric profile of chiral compounds which pass through them. Chlordane uptake, and changes in the chiral ratio of some of its components, were determined under conditions which would close these pores, or, alternately, permit them to remain open. Elucidation of the role of aquaporins in chlordane uptake in cucurbits may allow for its optimization in other plant species which are well-suited to phytoremediation projects. PARTICIPANTS: There was one main investigator on this project: MaryJane Incorvia Mattina (principal investigator at The Connecticut Agricultural Experiment Station). The study was designed by Dr. Mattina and Mr. W. A. Berger. Dr. Mattina supervised the work, while Mr. Berger conducted the growth experiments and performed chlordane analyses by gas chromatography/mass spectrometry. TARGET AUDIENCES: The target audiences are as follows: environmental scientists, state and federal environmental regulators, as well as private remediation companies. Results will be published in peer-reviewed scientific journals and reported to the public at Experiment Station events or invited talks. PROJECT MODIFICATIONS: Experiments are designed and modified on an on-going basis to accomplish the goals of the project.
Impacts
Development of efficient phytoremediation tools for the removal of organic compounds would significantly decrease the cost of cleanup at contaminated sites. Preliminary results indicate that closure of aquaporins in hydroponically grown zucchini plants reduces total chlordane uptake, as well as the degree of change in chiral signature. Boron starvation did not yield significant differences in chlordane uptake. However, the use of hydrogen peroxide, which is known to close aquaporins in green algae, does yield significant differences in both uptake and enantiomeric profile with zucchini. The implication of aquaporins in the chlordane uptake mechanism allows for further study in a model system. The genetic basis of aquaporin expression is even better understood in the brassica, Arabidopsis thaliana, than it is in cucurbits. Arabidopsis is also a chlordane uptaker, albeit not to the extent of zucchini. Further studies of chlordane uptake using A. thaliana may allow for the optimization of aquaporin expression in plant roots. Use of such a well understood genetic model could lead to the development of a commercially viable plant species which could be used for the phytoremediation of organic compounds in soil.
Publications
- No publications reported this period
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Several experiments have been conducted to assess the relationship between physiologically based nutritional uptake and opportunistic uptake of pollutants in Cucurbita pepo using chlordane as a model. Based on several experiments conducted to date, it is not apparent that boron nutrition and the uptake of technical chlordane components are related. However, with the experimental design--hydroponically on glass ballatini--the experiments are non-routine and difficult to conduct. Nevertheless, this approach is considerably closer to conditions that pertain to plants grown in soil as opposed to typical hydroponic conditions. We continue to pursue the hypothesis that opportunistic uptake of the chiral chlordane components reflects transport through the chiral trans-membrane protein channels. In this regard, we are studying the hydroxyl radical and its impact on aquaporin channels to elucidate the mechanisms of chlordane uptake by C. pepo.
PARTICIPANTS: MaryJane Incorvia Mattina and William Berger, Department of Analytical Chemistry, The Connecticut Agricultural Experiment Station.
TARGET AUDIENCES: The first target audience is the scientific community which needs to know the mechanisms by which lipophilic and chiral pesticides are taken up from soil into plants. The environmental community will need the data from these experiments in order to design more rational field solutions for the attentuation of real-world pollution.
Impacts
We have learned that sap samples collected need to be handled extremely carefully so as not to produce artifacts in the concentrations of technical chlordane components measured in the saps. We have also determined that considerable care needs to be taken in setting up the instrument parameters, again so as not to result in artifacts which would skew the conclusions drawn. Nevertheless, despite its technical difficulties, the semi-hydroponic procedure provides the sole means of examining plant parameters at the root membrane which might impact pollutant uptake in the soil-plant system. The practical application of phytoremediation will be influenced by the elucidation of the underlying mechanisms for chlordane uptake.
Publications
- No publications reported this period
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