Plasticizers are widely used as additives for the production of PVC and other types of plastics. They have been observed to leach out of the solid matrix over the course of the lifetime of the finished product. These compounds have now been observed across the globe and in different environments. The main focus of this work is the study of the interactions of industrial plasticizers with soil microorganisms including bacteria, yeast and fungi. / This research is concerned with the microbial degradation of plasticizers such as di-2-ethylhexyl phthalate (DEHP) and di-2-ethylhexyl adipate (DEHA). In particular, the study has focused on the stable metabolites produced during biodegradation, including 2-ethylhexanol and 2-ethylhexanoic acid. The first step was to show that these toxic metabolites were found in significant concentrations in the environment. In addition, a series of experiments with a variety of organisms showed how wide spread the ability to produce these metabolites was. Most organisms tested were capable of interacting with the plasticizers and many of these produced the metabolites. / It was apparent that these metabolites could have appreciable stability and an in-depth study with one species of bacteria, R.rhodochrous , showed that the entire initial 2-ethylhexanol component incorporated in the original plasticizers could be accounted for. Some of this was volatile and found in the exit gas of the reactor. This included all of the 2-ethylhexanol and some of the 2-ethylhexanol. These compounds may contribute to the impairment of the quality of indoor air. An overall mass balance showed that while the bacterium could eventually oxidize the 2-ethylhexanol released by hydrolysis to 2-ethylhexanoic acid, it could not degrade this acid. Thus, a summation of the quantities of each of the various metabolites generated equaled the original amount of 2-ethylhexanol in the plasticizer. / A mathematical model was then constructed to include all of the above features of the interaction of R.rhodochrous with the plasticizers DEHA and DEHP. This model included terms for the biological interactions and enzyme kinetics as well as the toxicity and inhibition of bacterial growth by the plasticizers and their metabolites. The increased understanding of the interaction of microbes with plasticizers will lead to a better understanding of the environmental impact of these compounds and their metabolites. The results of this study also demonstrate that when assessing the environmental impact of a compound, it is essential that not only should the impact of the parent compound be considered, but it is essential that the assessment process must also account for impacts associated with degradation products.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.85630 |
| Date | January 2005 |
| Creators | Nalli, Sandro |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002223746, proquestno: AAINR12915, Theses scanned by UMI/ProQuest. |
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