Heterogeneous photochemical reactions of decabromodiphenyl ether

Abstract

Brominated diphenyl ethers are a major class of brominated flame retardants, with production of decabromodiphenyl ether (DBDPE) contributing significantly to this total. Although little is known about the mechanisms and rates of DBDPE decay in the natural environment, photochemical transformation is often suggested as a potentially important fate process. In this study, photochemical reactions of DBDPE precipitated onto hydrated surfaces (quartz glass, silica particles, and humic acid-coated silica particles) were measured. Decabromodiphenyl ether was irradiated within a Rayonet photochemical reactor equipped with lamps having maximum emissions (λmax) at 300 or 350 nm or with sunlight (West Lafayette, IN, USA at 40°26′N, 86°55′W). When DBDPE is plated onto quartz tubes and hydrated with reagent-grade water, phototransformation occurred over a period of days with each light source. With two lamps (λmax = 300 nm), about 31% of the initial mass of DBDPE remained after 60 h in the Rayonet reactor. Decabromodiphenyl ether transformed more slowly when irradiated by sunlight, with 30% of the initial compound recovered from tubes after 72 h. In the presence of humic acid (HA) solution, transformation of DBDPE by solar irradiation is slowed even further: approximately 70% remained after 72 h. Solar irradiation of DBDPE adsorbed to humic acid-coated sand particles resulted in the slowest irradiation rates: approximately 88% of the initial mass was recovered after 96 h of exposure. Although the parent compound exhibited slow transformation, analysis by high-performance liquid chromatography (HPLC) indicated some accumulation of transformation products.