Nontargeted Analysis Reveals Organic Compounds That Drive Oxidative Potential in Ambient Particulate Matter

Area of Science:

• Environmental Chemistry
• Atmospheric Science
• Toxicology

Background:

• Air pollution, particularly fine particulate matter (PM), poses significant health risks.
• Understanding the differential toxicity of PM components is crucial for effective mitigation.
• Oxidative potential (OP) is a key indicator of PM's adverse health effects.

Purpose of the Study:

• To investigate the oxidative potential (OP) of water-soluble organic compounds in fine particulate matter.
• To differentiate the toxic contributions of metals versus organic compounds in ambient PM.
• To identify specific organic compounds associated with PM's oxidative potential.

Main Methods:

• Analysis of 42 ambient PM filter samples from Frankfurt and Beijing.
• Measurement of OP using the dithiothreitol (DTT) assay.
• Quantification of metals via ICP-MS and organic compounds via UHPLC-HRMS.
• Utilized a chelating agent to isolate the OP contribution of organic components.

Main Results:

• Identified specific organic compounds, including quinones and oxidation products of xylenes and trimethylbenzenes, linked to OP.
• Phthalic acid (biomass burning/vehicular exhaust tracer) and nitrosalicylic acid were found to enhance OP.
• A significant volume-normalized OP (up to 4 nmol DTT min⁻¹ m⁻³) was observed from organic compounds after metal removal.

Conclusions:

• Stable organic compounds, beyond metals, significantly contribute to the oxidative potential of ambient fine particulate matter.
• Secondary organic aerosol products derived from aromatic precursors are key drivers of PM toxicity.
• Differentiating the roles of metals and organics is essential for accurate PM risk assessment and control strategies.