Science1 publisherNot yet confirmed elsewhere3 min readPublished
Long Island tower measurements trace summer city emissions to paints, cleaners and buildings
Researchers measuring emissions from a Long Island cell tower found paints, cleaners and building materials were major summer sources of urban VOCs. The team says the models cities and states use to forecast and regulate air quality do not accurately include these heat-sensitive sources.
The Scientist · Science desk
What happened
- At the same urban Long Island site, vehicle emissions were the source of most winter pollution, while summer pollution came largely from chemical products and residences.
- The Science Advances paper, first-authored by Purdue's Michael Vermeuel, attributes the strong seasonal swing in urban reactive carbon emissions to surface temperatures.
- Co-author Dylan Millet of the University of Minnesota said cleaner-burning vehicles have made less-studied urban pollution sources more relevant.
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Why it matters
- exposure If these sources rise with heat, as Millet says, the models' shortfall would be largest during heat waves and would widen as the climate warms.
- decision Summer controls aimed only at vehicles would address a smaller part of the problem at this site, pushing regulators toward consumer products and building materials.
- constraint Because the flux method is rare in cities and most studies record only concentrations, few comparable datasets exist to test whether Long Island is typical.
Most urban air-quality studies measure the concentrations of pollutants, to learn what is in the air [11]. This one measured emission rates. The team collected its data from a cellular tower using eddy covariance, a technique that pairs wind data with chemical measurements to calculate emission rates directly for many kinds of pollutants [9]. The method is rarely used in urban field studies. Its measurement requirements are complex, and it has to sample from well above the surrounding buildings [10].
"We used the most direct method available for measuring emissions from the urban surface, combining detailed chemical monitoring with wind measurements to determine what pollutants were actually being emitted and where they were coming from," said Michael Vermeuel, the paper's first author and an assistant professor at Purdue University [12][14]. Machine learning tools helped the team tie the emissions to their sources [11]. "Few field experiments have done this in urban environments, and it revealed a broad chemical fingerprint that changed substantially between summer and winter," he said [13].
The products in question include hairspray, paint, solvents and household disinfectants [16]. The volatile organic compounds they give off are potentially hazardous gases, and they are usually discussed as an indoor air problem [15]. Delphine Farmer, the Colorado State University chemistry professor who helped lead the work, said that "even building materials themselves were major sources of emissions from the city in summer" [7][17].
Dylan Millet, a University of Minnesota atmospheric chemist and co-author, described why these sources now stand out. "Vehicles on U.S. roadways have become much cleaner-burning. As a result, other less-studied sources of urban air pollution are becoming more relevant," he said [8].
The paper's title carries the causal claim: surface temperatures drive strong seasonality in urban reactive carbon emissions [14]. "Many of these emerging pollution sources increase when it is hotter, meaning they are liable to increase during heat waves and as climate warms," Millet said [18]. A summer-against-winter comparison changes more than temperature. People's habits with paints and cleaners can change with the season too, so the heat-wave projection depends on how well the analysis separated heat from everything else that comes with summer. The release does not describe that step, and it does not report each source's share of summer emissions or how far the models fall short of the measured rates.
"These sources are important but are not accurately included in current models that cities and states use to predict and reduce air quality events," Farmer said [1]. The paper notes that current models do not account for the temperature-dependent pollution, so agencies could be missing key information when they manage and regulate air pollution [2]. I think the direction of the finding is sound, because the tower measured emissions directly instead of inferring them from what was in the air [9][11]. The evidence so far comes from one urban area of Long Island, measured in summer and winter [5].
What to watch
- Whether the Science Advances paper's own figures quantify how far current inventories underestimate summer VOC emissions at the Long Island site.
- Flux-tower measurements from other cities that test whether the summer shift toward products and buildings holds beyond Long Island.
- Whether city or state agencies add temperature-dependent product and building emissions to the models behind their air-quality forecasts.