1 research outputs found
HULIS Enhancement of Hydroxyl Radical Formation from Fe(II): Kinetics of Fulvic Acid–Fe(II) Complexes in the Presence of Lung Antioxidants
Oxidative
stress mediated by reactive oxygen species (ROS) is a
hypothesized mechanism for particulate-matter related health effects.
FeÂ(II) is a key player in ROS formation in surrogate lung fluid (SLF)
containing antioxidants. Humic-like substances (HULIS) in particulate
matter such as biomass burning aerosol chelate FeÂ(II), but the effect
on ROS formation in the presence of lung antioxidants is not known.
We use Suwanee River Fulvic Acid (SRFA) as a surrogate for HULIS and
investigate its effect on OH formation from FeÂ(II). For the first
time, a chemical kinetics model was developed to explain behavior
of FeÂ(II) and SRFA in SLF. Model and experimental results are used
to find best-fit rate coefficients for key reactions. Modeling results
indicate SRFA enhances Fe-mediated reduction of O<sub>2</sub> to O<sub>2</sub><sup>–</sup> and destruction of H<sub>2</sub>O<sub>2</sub> to OH to 5.1 ± 1.5 and (4.3 ± 1.4) × 10<sup>3</sup> M<sup>–1</sup> s<sup>–1</sup> respectively.
Best-fit rates for Citrate–FeÂ(II) mediated O<sub>2</sub> to
O<sub>2</sub><sup>–</sup> and H<sub>2</sub>O<sub>2</sub> to
OH were 3.0 ± 0.7 and (4.2 ± 1.7) × 10<sup>3</sup> M<sup>–1</sup> s<sup>–1</sup> respectively. The kinetics
model agrees with both the experimental results and thermodynamic
model calculations of chemical speciation for 0 and 5 μg/mL
SRFA, but both models are less successful at predicting further enhancements
to OH formation at higher SRFA Concentrations