by applicant): We will develop demonstrable models of the formation ofpolyhalogenated dibenzo-p-dioxins and dibenzofurans (PXDD/F), persistent free radicals, and othertoxic halogenated hydrocarbons from the combustion and thermal reactions of hazardous wastes. Thisincludes polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), polybrominated dibenzo-p-dioxin/dibenzofurans (PBDD/F), mixed bromo/chloro dibeno-p-dioxins/dibenzofurans (PBCDD/F), andpersistent resonance stabilized, surface-associated, semiquinone type radicals that are key reactionintermediates and pollutants. This will be accomplished through a combination of mechanistic studiesusing a high-temperature flow reactor coupled to a gas chromatograph/mass spectrometer (GC-MS)analytical system and reaction kinetic studies using laser-photolysis/laser induced fluorescence andlaser photolysis/laser ionization time-of-flight mass spectrometry. We will: 1) determine the role ofchlorinated benzenes in the formation of PCDD/F, 2) determine how particle size from the nanometer tomicron size regime effects formation rates and product distributions, 3) measure elementary radical-molecule reaction rates of key reactions in formation of PXDD/F, 4) use ab initio and semi-empiricalmodeling techniques to calculate rates of key reactions, and 5) consolidate this information into adetailed, comprehensive model of PXDD/F formation within the CHEMKIN reaction kinetic modelingplatform. We suspect that transition-metal, surface-mediated PCDD/F formation pathways are relatedto formation of persistent, reductive radicals on the surfaces of fine and ultra-fine particles. Thus, inaddition to determining the biodelivery of PCDD/F via exposure to ultra-fine particles, we willcharacterize the formation of persistent free radicals (PFRs) and their role in the toxicity of ultrafineparticles. Our experimental-studies of PCDD/F formation and modeling studies (incorporating theexperimental results of Project 3) will allow us to better elucidate the relative contributions of gas-phaseand surface-mediated processes to the formation of PXDD/F. The models developed in this project will
| Nganai, Shadrack; Lomnicki, Slawo; Dellinger, Barry (2012) Formation of PCDD/Fs from oxidation of 2-monochlorophenol over an Fe2O3/silica surface. Chemosphere 88:371-6 |
| Fahmy, Baher; Ding, Liren; You, Dahui et al. (2010) In vitro and in vivo assessment of pulmonary risk associated with exposure to combustion generated fine particles. Environ Toxicol Pharmacol 29:173-82 |
| Bryukov, Mikhail G; Knyazev, Vadim D; Gehling Jr, William M et al. (2009) Kinetics of the gas-phase reaction of OH with chlorobenzene. J Phys Chem A 113:10452-9 |
| Nganai, Shadrack; Lomnicki, Slawo; Dellinger, Barry (2009) Ferric oxide mediated formation of PCDD/Fs from 2-monochlorophenol. Environ Sci Technol 43:368-73 |
