Post-lockdown auto emissions can't hide in the grass
University of California scientists have a new way to demonstrate which neighborhoods returned to pre-pandemic levels of air pollution after COVID restrictions ended.
Vehicle emissions are the biggest source of carbon dioxide in Southern California's air. As people drove their cars far less in 2020 compared to 2019 due to the pandemic, there was a major drop in CO2 on regional highways. A new study published in AGU Advances using a mobile laboratory shows the CO2 drop was roughly 60%.
By analyzing grass samples from across the state, the same study also showed in fine detail that some parts of California were back to high levels of emissions by 2021, while others—generally in more affluent areas—were not.
"Community scientists sent us hundreds of wild grass samples. We analyzed them for radiocarbon content, which is a proxy for fossil fuel emissions," said Francesca Hopkins, UC Riverside assistant professor of climate change and study co-author.
"Plants absorb CO2 during photosynthesis and incorporate it into their tissues, recording a snapshot of local fossil fuel inputs in the process," said study lead Cindy Yañez, formerly of UCR, now an Earth System Sciences doctoral student at UC Irvine.
Graduate student Cindy Yañez taking inventory of plant samples mailed in by community scientists for radiocarbon dating. Credit: C. Czimczik/UCI