Numerous groundwater sites around the globe have been contaminated by aqueous film forming foam (AFFF) as a result of firefighting, fire training activities and the storage and accidental spillage of AFFF.
Hydroxyl
radical (·OH) production from the reaction between
aqueous total sulfide ([H2S]T = [H2S] + [HS–] + [S2–]) and dissolved
oxygen is potentially an environmentally important reaction when anoxic,
sulfidic water is exposed to oxygen. Using hydroxyterephthalate (hTPA)
formation from the reaction of terephthalic acid (TPA) with ·OH
as a probe for ·OH production, hydrogen peroxide was verified
as an essential intermediate, and the production of free ·OH,
versus lower energy hydroxylating agents, was established. The optimal
conditions for the quantification of ·OH production kinetics
and yield were determined by varying TPA and total sulfide concentrations.
An initial total sulfide concentration of 10 μM and TPA concentration
of 2 mM was used to find a yield of 15 mmol of ·OH per mole [H2S]T. Additionally, a pseudo-first-order model elucidated
a maximum rate of production of 1.04 (±0.05) × 10–4 moles of ·OH per hour per mole of [H2S]T. Experiments with sulfidic wetland porewaters containing up to 294
mg/L of dissolved organic carbon (DOC) revealed that [H2S]T, and not reduced DOC, was the dominant source of ·OH.
A simple model considering a water containing [H2S]T, DOC, and methane exposed to a constant concentration of
oxygen (∼50 μM) gave steady state values of [·OH]
ranging from 5.7 × 10–19 to 3.2 × 10–18 M. The results indicate that [H2S]T should be considered a source of dark formation of ·OH
in addition to ferrous iron and reduced DOC.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.