Noticed something “off” in the air past few days? A lot of us thought it smelled of, to put it bluntly, poop. But don’t blame the local wastewater treatment plant.
According to MPCA staff meteorologist Daniel Dix, it’s a common occurrence in the late fall.
Daniel says once temps are below 50F, farmers apply anhydrous ammonia or manure to fertilize the soil, to prep for the spring season. This produces better yields for the following season when applied in cooler temps in late October/November. When the temps dip below freezing, it locks in the good stuff. But when the weather warms up, the odors and nitrates are released.
“It wasn’t just Minneapolis, but St. Paul and the whole Twin Cities metro area, and pretty much anywhere in the transport path from where the fields have the fertilizers being applied,” Daniel said of the recent odors. That includes all of southern Minnesota and neighboring states, even as far as Illinois.
“It’s nothing new,” Daniel said, “happens every year. Welcome to Minnesota!” He added that once this short shoulder season of variable temps ends and soils freeze solid or get snow-covered, our usual wintertime regime of more stagnant air will kick in and the odors should dissipate.
A meteorological note: Last night’s cold front with its northwest winds ended the transport of smells into the Twin Cities. However, we’ll warm up again with winds becoming southerly on Thanksgiving and Friday, which may bring another round of smells before the next cold front sweeps through the state on Saturday.