This is true especially for the organic fraction of fine particles (also called aerosol), much of which forms as organic gases are oxidized by the atmosphere. Computer models under-predict this so-called "secondary" organic aerosol (SOA) in comparison to field measurements, indicating that the models are either missing some important sources or failing to describe the physical processes that lead to SOA formation.
New research from Carnegie Mellon University in collaboration with the National Oceanic and Atmospheric Administration (NOAA) sheds light on an under-appreciated source of SOA that may help close this model-measurement gap. Published in Environmental Science & Technology, the study shows that volatile organic compounds (VOCs) not traditionally considered may contribute as much or more to urban SOA as long-accounted for sources like vehicle emissions and respired gases from tree leaves.
Experiment - Areas - Lot - People - Half
"Our experiment shows that, in areas where you have a lot of people, you can only explain about half of the SOA seen in the field with the traditional emissions from vehicles and trees," said Albert Presto, a professor in mechanical engineering and the study's corresponding author. "We attribute that other half to these non-traditional VOCs."
In 2018, researchers from NOAA made a splash in the journal Science when they detailed how non-traditional VOCs represent half of all VOCs in the urban atmosphere in U.S. cities. Non-traditional VOCs originate from a slew of different chemicals, industries, and household products, including pesticides, coatings and paints, cleaning agents, and even personal care products like deodorants. Such products typically contain organic solvents whose evaporation leads to substantial atmospheric emissions of VOCs.
Lot - Stuff - Presto - Anything - Contains
"It's a lot of everyday stuff that we use," said Presto. "Anything you use that is scented contains organic molecules, which can get out into the atmosphere and react" where it can form SOA.
The prevalence of these VOCs represents a paradigm shift in the...
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