Scientists measuring the breath of megacities onboard an aircraft over North America
How is urban air pollution changing as traffic emissions decrease? Scientists from the United States, Austria, and from the Institute of Energy and Climate Research (IEK-8: Troposphere) are trying to answer this question by utilizing measurements of trace gases onboard the world’s largest airborne chemical laboratory.
The AEROMMA (Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas) campaign jointly organized and directed by the US National Oceanic and Atmospheric Administration (NOAA) and NASA aims to investigate emerging emissions from four megacities: New York, Chicago, Toronto, and Los Angeles. AEROMMA's primary objective is to comprehensively explore the extent of the present-day contribution of urban sources to air pollution and assess their influence on the formation of secondary pollutants, including hazardous ozone and organic aerosols. “As emissions from traffic decrease in magnitude, the significance of volatile chemical products (VCPs) originating from sources such as perfumes, cosmetics, cleaning products and solvents gain importance in the mixture of organic compounds that are released into the atmosphere due to human activities”, explains Georgios Gkatzelis, a scientist at IEK-8. Gkatzelis, who was recently honored with a Starting Grant from the European Research Council (ERC), intends to leverage this grant to conduct further investigations into the role of VCPs in the atmosphere.
The campaign spans over seven weeks of measurements during which the aircraft is partly stationed in Ohio and partly in California. "This provides an excellent opportunity for both young and experienced scientists to collaborate, engage in scientific discussions, and mutually benefit from each other’s expertise”, says Anna Novelli, a scientist affiliated at IEK-8. Master and PhD students from IEK-8 took up the challenge of operating cutting-edge instrumentation within a challenging environment. The NASA DC- 8 aircraft predominantly operated at altitudes lower than 3 km within the lowest layer of the atmosphere to capture ground-level emissions. However, flying at low altitude is not without difficulties; the cabin temperature frequently exceeded 30°C, and the scientists and their instruments experienced constant vibrations throughout the journey.
IEK-8's contributions to the extensive range of aircraft measurements include the support for VCP measurements through mass spectrometer instruments, measurements of radiation responsible for photolysis reactions in the atmosphere as well as measurements of the total hydroxyl radical reactivity, which gives a measure of the total air pollutant concentration, with a newly developed instrument. Furthermore, the aircraft is equipped with instrumentation covering the detection of both gas-phase compounds as well as aerosol properties. Measurement will be compared with results from satellite measurements and regional air quality models with the goal of improving the chemical mechanisms used and the emissions inventory databases.