Between city and sea
AEROMMA focuses on urban air quality, marine emissions, climate feedbacks, and atmospheric interactions at the marine-urban interface.
The sky is blue, the view is good – Georgios Gkatzelis takes a quick photo of the impressive New York skyline, then turns his attention back to his measuring devices. With the instruments on board a NASA aircraft that was converted into a laboratory (see box), he and his colleagues capture the breath of big cities – or, more precisely, its components: mixtures of gases and tiny suspended particles, so-called aerosols.
“Aerosols produced in cities pose a major threat to human health. A well-known example is car exhaust fumes and the soot particles they contain,” says the chemical engineer with a doctorate who heads the “Organic Trace Gases” research group at Jülich. The measurements in the flying lab are part of AEROMMA, a measurement campaign on air quality and climate over North America conducted in the summer of 2023.
More aerosols than expected
Aerosols in the air are not only a result of combustion processes in vehicles or industry, but they also originate from the oxidation of gas-phase emissions from cleaning agents, care and cosmetic products, or cooking. It is these emissions that Gkatzelis is particularly interested in: “Withmeasurements on the ground, we have already been able to prove that, in US cities, household chemicals have replaced car exhaust fumes as the main source of organic vapors,” the Greek scientist explains. Due to their chemical properties, these gas-phase molecules often react in the atmosphere to form the so-called secondary organic aerosol, or SOA for short. “However, household chemicals have hardly been considered in air pollution models so far,” says Gkatzelis. “This could explain why the models always predict less SOA than we measure in reality.”
The flying laboratory
The US space agency NASA converted the aircraft, a Douglas DC-8 built in 1969, from passenger aircraft to research aircraft in 1984. Instead of 175 passengers, it now carries between 30 and 40 researchers and about 30 measuring instruments to measure the quality of the air. In some places, holes were cut in the wall to mount sensors on the outside and connect them to the scientific instruments inside.
Thus, more knowledge regarding the role of household chemicals in urban aerosol pollution is urgently needed. Gkatzelis and his team want to fill this gap. Initial analyses of their AEROMMA measurements over Chicago, for example, show that the concentration of compounds that originate from household chemicals is substantial and contribute to the formation of harmful ozone and SOA. “This example shows how our results could improve air quality prediction models,” says Gkatzelis. He dedicates his research to his scientific mentor, Jülich climate researcher Prof. Astrid Kiendler-Scharr, who passed away in February 2023.
“In order to understand the exact correlations and be able to recommend countermeasures, however, we still need to find out more about SOA formation,” says the researcher. The ERC Starting Grant he received in 2022 will help with this. In the CHANEL project, his team will use the €1.5 million in funding to determine the chemical composition of emissions from household chemicals in European cities. Additional experiments in a controlled atmospheric simulation chamber will help to reconstruct chemical reaction pathways and identify the potential of such sources to form SOA.
The AEROMMA project
Measurements have already been taken at Jülich – in front of the Seecasino canteen. “This is a controlled environment,” explains Gkatzelis. “We knew what was cooked, how many people came to eat, and how often cleaning was done.” This means that emissions could be clearly attributed to sources. In cities, this is more difficult because such information, obviously, does not exist. Only more data can help here, and this is why Gkatzelis will also take to lofty heights in Germany: in addition to measurement campaigns on the ground, he is planning flights over several cities with a zeppelin.
Text: Janosch Deeg | images: jetshoots.com/Jan Vasek; Forschungszentrum Jülich/Ralf-Uwe Limbach; C.J. Moeser, Jetphotos
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Last Modified: 16.02.2024