SAPHIR chamber
SAPHIR chamber. Photo: Forschungszentrum Jülich

What: CHANEL experiments (Household Chemicals Amplifying Urban Aerosol Pollution) 2024

Where: Forschungszentrum Jülich SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction chamber)

When: 24 June - 8 August 2024

How: Chamber measurements

Who: Researchers from the NOAA Chemical Sciences Laboratory (CSL), the University of Colorado Cooperative Institute for Research in Environmental Sciences (CIRES), and Forschungszentrum Jülich

Anthropogenic emissions of volatile organic compounds (VOCs) contribute to the degradation of urban air quality. As automotive emissions have decreased in recent decades, the trace gas emissions from lesser-studied sources, including volatile chemical products (VCPs) and cooking, have been shown to contribute substantially to the urban VOC budget. Urban aerosol particles, a major global health hazard, largely consist of secondary organic aerosol (SOA) formed through chemical reactions of emitted VOCs. Despite recent studies highlighting the importance of VOCs from VCPs and cooking as precursors of ozone (O3) and acyl peroxy nitrate (PAN), their potential to form SOA remains largely unknown. Chemical transport models continue to underestimate urban SOA in many cities, highlighting the need for experiments to characterize the contributions of VOCs from VCPs and cooking and their oxidation products to this "missing" SOA to reduce models' uncertainty.

The SAPHIR-CHANEL experiments will utilize a suite of state-of-the-art chemical ionization mass spectrometers to characterize SOA composition resulting from controlled chamber oxidation experiments using atmospheric mixtures containing compounds from VCPs, cooking, and traffic emissions. The precise chemical makeup of these mixtures will be informed by recent ground observations (SUNVEx 2021) and aircraft measurements (AEROMMA 2023) of urban emissions conducted by NOAA, as will the oxidation conditions under which the experiments are performed (e.g., the accompanying levels of nitrogen oxides).

CHANEL experiments

This research will provide novel insights into SOA formation pathways and yields from specific emission urban sources and from realistic urban mixtures under atmospherically relevant conditions. The SOA yields and parameterizations determined from this study will serve as inputs for global chemical transport models to improve their accuracy in forecasting urban SOA formation. Additionally, we will integrate these results with data from the recent AEROMMA aircraft campaign to investigate urban atmospheric chemistry and modeling capabilities.