Complexation state of iron and copper in ambient particulate matter and its effect on the oxidative potential

Ambient PM;transition metals;complexation state;oxidative potential

Wei, Jinlai ; Verma ; Vishal

关键词: Ambient PM;    transition metals;    complexation state;    oxidative potential;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/101236/WEI-THESIS-2018.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Transition metals have long been recognized as an important component contributing to the toxicological property of ambient particulate matter (PM). Various methods of assessing this toxicity have been applied, including measuring the capability of PM components to generate reactive oxygen species (ROS), and the capability of consuming antioxidants. However, whether transition metals are complexed with organic compounds or free in ambient PM, which could be an important factor determining their ability to generate ROS, is not well understood. We target to investigate the complexation states of important atmospheric metals in this study. A novel fractionation scheme is developed to separate Fe and Cu from ambient PM into hydrophilic, hydrophobic and inorganic fractions. The scheme has been validated by applying it on a mixture of Suwannee River fulvic acid (SRFA) and Fe or Cu. SRFA is selected as a model compound as it represents the humic-like substances present in ambient PM, which are believed to be complexed with Fe and Cu. The results show that a significant amount of iron pre-mixed with SRFA is detected in both hydrophobic and hydrophilic fractions, indicating potential complexation with both types of organic substances. Similar tests conducted with the ambient PM show up to 70-80% of iron complexed with organic compounds. Fe and SRFA show strong synergistic effect in the generation of hydroxyl radical in different antioxidants systems (surrogate lung fluid, ascorbic acid and dithiolthreitol), which is attributed to the higher efficiency of Fe-SRFA complexes to convert H2O2 to ∙OH (Fenton reaction) than Fe alone. Although, Cu and SRFA show additive effect in ∙OH production, while they are antagonistic in the consumption of antioxidants (ascorbic acid and glutathione). Overall, the organic complexation of metals in ambient PM could significantly alter the oxidative potential of ambient PM and needs to be accounted for apportioning the contribution of metals in aerosol toxicity.