Project R-4315

The role of endophytes and carbon nanoparticles in the success or failure of DDE phytoremediation using Cucurbita pepo (Research)

2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) is a pesticide that has been used in agriculture and gardening since 1943. Since 1974, DDT can no longer be used in Belgium because of its high toxicity for wildlife and its hormone disrupting properties. In soils, DDT degrades to 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (DDE). Both DDT and DDE classify as persistent organic pollutants (POPs), but because of the conversion from DDT to DDE over the thirty years since the ban on DDT-usage, the main focus of this project will be on DDE phytoremediation. Soil contamination by DDE is a worldwide problem. There are different conventional techniques for soil remediation, but these are mostly expensive and invasive to the environment and ecosystems. Phytoremediation is a technique which is based on the in situ use of vegetation to remove or stabilize contaminants from soils. This technique exploits the natural ability of plants and their associated micro-organisms to remove nutrients from the soil. A direct consequence of this process is that plants also take up a wide range of natural and man-made toxicants. Several plants including mustard, canola, peanut and zucchini have been found to be accumulators of DDE. In this project, Cucurbita pepo (zucchini) was selected for its high DDE extraction levels on one hand and the remarkable differences in DDE uptake between the Cucurbita pepo ssp ovifera (Squash) and Cucurbita pepo ssp pepo (Zucchini) subspecies on the other hand. Zucchini accumulates DDE while squash lack the ability to accumulate DDE. The reason for this difference in DDE accumulation has yet to be determined. Research has demonstrated that the remediation of organic contaminants can be enhanced by adding bacteria that show a degrading capacity for organic contaminants to the plant. Moreover, bacteria often show plant-growth promoting capacities that counteract the eventual phytotoxicity of the contaminant. I hypothesize that the difference in DDE accumulation might be, at least partly, due to the differences in the plant-associated bacterial populations of both Cucurbita pepo subspecies that might possess the capacity to degrade DDE and promote plant growth. Another factor that may significantly impact DDE uptake are nanoparticles. These nanoparticles have sizes less than 100 nm and exhibit unique electronic states, magnetic properties, and catalytic reactions in comparison to corresponding bulk size materials. Currently, manufactured nanoparticles are used extensively in pesticides and herbicides by plants. Since many of the modern herbicides show analogous structures as many organic contaminants, nanoparticles could also enhance the uptake of persistent organic contaminants. Previous work reports that Cucurbita pepo shows higher DDE-accumulation rates when nanoparticles are added. This property of nanoparticles is used in this project to further optimize bacteria-enhanced phytoremediation of DDE. However, little is yet known about the possible toxicity of nanoparticles to plant-associated bacteria. Therefore, the effects of nanoparticles on the bacterial populations will be investigated before using them in DDE phytoremediation experiments

01 January 2013 - 31 December 2016