Which aerosol components and processes control the toxicity of ambient particulate pollution? Targeted studies of aerosol oxidative potential

Duration: 2020-2024
Funding: Swiss National Science Foundation (SNSF)
Contact: Rob Modini (robin.modini@psi.ch)

Table of Contents

Particulate matter air pollution is damaging to human health and responsible for millions of premature deaths each year worldwide. Some types of particulate matter are more toxic for humans than others. The goals of this project are to identify these most toxic aerosol species and to examine how they are formed. To achieve this we have measured the ability of particulate matter to induce oxidative stress within cells (so called aerosol oxidative potential) in near real-time with a new instrument developed for the project. To link these measurements to specific aerosol components, we also made combined measurements of metals, soot and organic aerosol species. The measurements were performed in the polluted megacity of Beijing, China, as well in an atmospheric simulation chamber at the Paul Scherrer Institute. The simulation chamber allowed us to artificially generate many different types of aerosol pollution.

The project is a Sino-Swiss Joint Research Project that benefits from a close collaboration with partners at Peking University in China. The Chinese side of the project is led by Professor Jing Shang.

Major source categories of aerosol oxidative potential in wintertime Beijing, China

We successfully operated our new instrument for measuring aerosol oxidative potential in wintertime Beijing and surroundings for a period of 2 months in winter 2021. These are the first online dithiothreitol-based field measurements of PM_2.5 oxidative potential ever conducted in China. In combination with these measurements we performed a detail characterization of the aerosol chemical composition. The resulting data were analyzed with advanced analytical techniques to link the measurements together and identify major source categories of aerosol oxidative potential. Two major pollution episodes were identified -- one natural (dust storm) and one anthropogenic (spring festival celebrations) -- in order to highlight the differential toxicity of PM_2.5. On average over the whole measurement period, both primary PM and aged, oxygenated organic aerosols were found to make substantial contributions to the aerosol oxidative potential.

Effects of atmospheric aging on the oxidative potential of different types of carbonaceous aerosols

Carbonaceous aerosols are emitted directly into the atmosphere from a variety of sources (e.g. combustion processes) or formed from the atmospheric oxidation of biogenic and anthropogenic precursors. Atmospheric aging processes continue to alter the chemical and physical properties of carbonaceous aerosols, thus also influencing their oxidative potential. We have performed over 30 smog chamber experiments in order to measure these changes under a wide variety of simulated atmospheric conditions. Specifically, we measured hourly-resolved oxidative potential as a function of aging for different types of carbonaceous aerosols including residential wood burning, open biomass burning, and coal combustion emissions, as well as alpha-pinene and naphthalene-derived secondary organic aerosols. In combination we also performed detailed measurements of the physical and chemical properties of the aerosols. This large database of measurements is currently being analyzed to quantify and compare the toxicity of the different types of carbonaceous aerosols under different atmospheric ageing scenarios.

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