Environmental Photochemistry of Polybrominated DiphenylethersEPA Grant Number: R830398
Title: Environmental Photochemistry of Polybrominated Diphenylethers
Investigators: Jafvert, Chad T. , Filley, Timothy , Hua, Inez
Institution: Purdue University
EPA Project Officer: Carleton, James N
Project Period: January 1, 2002 through December 31, 2003
Project Amount: $234,586
RFA: Futures Research in Natural Sciences (2001) RFA Text | Recipients Lists
Research Category: Futures , Ecological Indicators/Assessment/Restoration , Land and Waste Management , Hazardous Waste/Remediation
The overall objective of the proposed research is to investigate photochemical transformation of several polybrominated diphenylether (PBDE) congeners under conditions of environmental relevance. Specific congeners to be investigated include decabromodiphenylether (DeBDE) and 2,2',4,4'-tetrabromodiphenylether (2,2'4,4'-TeBDE). Reaction rates and product distributions will be determined with both solar light (West Lafayette, IN, 40_ 26' N, 86_ 55' W) and artificial light in aqueous systems. Our primary hypothesis is that solar illumination can reductively debrominate DeBDE to congeners that are more mobile in the environment and to those that have been shown to act as thyroid function disruptors (i.e., a type of endocrine disruptor) in several vertebrate species.
Photochemical experiments with DeBDE and Bromkal 70-5DE (containing 2,2'4,4'-TeBDE) as starting materials will be conducted (a) with solar light and (b) within a Rayonet photochemical reactor equipped with various lamps. Lamps to be used are PRP 3000, 3500 and 4190 Å lamps (Southern New England Ultraviolet Company). By using the range of lamps, we will observe some of the wavelength dependencies in parent compound decay and intermediate product decay. In solar light and with 3000 Å lamps, for example, some intermediates may not appear due to their own reactivity with light at these energies, whereas they may appear at significant concentrations using the 3500 Å lamps. Due to the ultra-low water solubility of DeBDE and its affinity for any solid surface, we intend to conduct the solar and reactor experiments with DeBDE and Bromkal 70-5DE adsorbed onto materials suspended in aqueous solution. These materials are: (1) organic free silica particles, (2) natural organic matter (NOM) isolated from the Wabash River, (3) NOM-coated silica, and (4) a commercially available humic acid (Aldrich) coated onto silica. Although PBDEs are not expected to undergo direct photolysis with the 4190 Å lamps, experiments with humic substances may lead to indirect photochemical decay at the longer wavelengths.
Our experiments will test whether DeBDE released to the environment is a long-term source of more mobile and more bioavailable lower-brominated diphenylether congeners via photoreductive debromination. Through our experimental design, we hope to determine how significant this process may or may not be in the natural environment. This research will provide technical information that will lead to more scientifically defensible regulatory policy decisions regarding the safe use of these chemicals in our society.