HULIS Enhancement of Hydroxyl Radical Formation from Fe(II): Kinetics of Fulvic Acid–Fe(II) Complexes in the Presence of Lung Antioxidants

Abstract

Oxidative stress mediated by reactive oxygen species (ROS) is a hypothesized mechanism for particulate-matter related health effects. Fe(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 Fe(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 Fe(II). For the first time, a chemical kinetics model was developed to explain behavior of Fe(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 to O and destruction of HO to OH to 5.1 ± 1.5 and (4.3 ± 1.4) × 10 M s respectively. Best-fit rates for Citrate-Fe(II) mediated O to O and HO to OH were 3.0 ± 0.7 and (4.2 ± 1.7) × 10 M s 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.

Relationship between chemical composition and oxidative potential of secondary organic aerosol from polycyclic aromatic hydrocarbons

“…Similarly, Hems et al (2017) found that suppression of OH generation (photo-Fenton reaction) occurred, and attributed the decrease to the formation of metal-SOA complex. Although current studies demonstrate such metal-SOA binding leads to a lower OP, other studies (Gonzalez et al, 2017;Yu et al, 2018) have found an increased level of OH radicals through the formation of Fe (II)-HULIS complex. These synergistic/antagonistic metal-organic interactions are relevant to multiple health outcomes.…”

“…) have been shown to be redox-active (Charrier and Anastasio, 2012;Xiong et al, 2017). Metals in ambient particles can range from insoluble substances to soluble cations, leading to var- ious health outcomes after deposition onto the human respiratory tract (Gojova et al, 2007;Oberdörster et al, 2005).…”

Oxidative Potential Associated with Urban Aerosol Deposited into the Respiratory System and Relevant Elemental and Ionic Fraction Contributions

“…(AA, d ai ) displayed the same dimensional profile at the two site: a negligible response below about 1 µm and a coarse mode (maximum at 3.2-5.6 µm), suggesting sensitivity toward redox active components in coarse aerosol, namely to redox active components released by brake abrasion, such as Cu and Fe, to whom OP AA assays is known to be sensitive [14,[27][28][29][30]. ( , ) and ( , ) displayed the same dimensional profile at the two site: a negligible response below about 1 μm and a coarse mode (maximum at 3.2-5.6 μm), suggesting sensitivity toward redox active components in coarse aerosol, namely to redox active components released by brake abrasion, such as Cu and Fe, to whom OP AA assays is known to be sensitive [14,[27][28][29][30].…”

“…The differences between the two tests were evident in terms of total ( ) and ( ) doses as well. ( ) and ( ) were higher at the Ferrara than at the Rome site, whereas the contrary ( , ) and ( , ) displayed the same dimensional profile at the two site: a negligible response below about 1 μm and a coarse mode (maximum at 3.2-5.6 μm), suggesting sensitivity toward redox active components in coarse aerosol, namely to redox active components released by brake abrasion, such as Cu and Fe, to whom OP AA assays is known to be sensitive [14,[27][28][29][30].…”

Development of a chromatographic method to study oxidative potential of airborne particulate matter

“…, and non-radical species such as O3 and H2O2 in the ELF 20 (Kelly and Fussell, 2017;Sies et al, 2017). Although quinones and TMs are widely recognized as being redox-active, other redox-active chemicals, such as those in humic-like substances, are also anticipated to pose OP (Charrier and Anastasio, 2012;Verma et al, 2015;Dou et al, 2015;Gonzalez et al, 2017).…”