One refinery is responsible for 10-25% of Salt Lake’s winter inversion PM2.5 pollution, NOAA finds

Researchers said they could smell bleach when they flew over US Magnesium on the Great Salt Lake.

(Trent Nelson | The Salt Lake Tribune) US Magnesium, seen across the Great Salt Lake from Stansbury Island on Saturday, March 26, 2022.

When they flew downwind of a Utah magnesium refinery to record its emissions, researchers didn’t need fancy monitoring equipment to figure out when the plane was inside the chemical plume rising from US Magnesium.

“We could smell it,” said Caroline Womack, a scientist working for the National Oceanic and Atmospheric Administration, or NOAA. “It smelled like bleach.”

Womack is the lead author of a peer-reviewed NOAA-led study released this week into US Magnesium’s contribution to Utah’s air quality challenges. Her team discovered the plant’s role could be far larger than previously known because of its vast amount of bromine emissions, which accelerate chemical reactions that form the microscopic droplets known as fine particulate matter, or PM2.5.

“Our measurements of chlorine and nitrogen oxides agree with what the facility reports to regulators,” Womack said. “But what we found suggests that bromine industrial emissions may deserve a closer look.”

The study concluded that the plant is responsible for 10 to 25% of the PM2.5 choking Salt Lake City’s air during winter inversions, making it the single largest driver of Utah’s air quality troubles.

“The bromine was a surprise. Bromine is not in the inventory, because it’s not asked about,” Womack said. Based on its sampling from overflights, the research estimated that the plant emits nearly 2.5 million pounds of bromine compounds a year.

A US Magnesium executive did not immediately respond to a voicemail Thursday.

Situated on the southwest shore of the Great Salt Lake, the Rowley company’s plant is the nation’s largest producer of magnesium compounds, which are extracted from the lake’s brines.

Bromine itself isn’t categorized as a pollutant, but as an oxidizing agent that spurs the chemical reactions that turn other compounds in the atmosphere into the fine particulate that degrades air quality along the Wasatch Front, according to John Lin, a University of Utah atmospheric scientist who participated in the research.

“It’s related to the complexity of the chemical soup that’s our atmosphere,” Lin said. “When you put certain stuff in, it’s sometimes surprising what stuff comes out the other end.”

The chlorine and bromine molecules emitted by US Magnesium are in a class of chemicals known as halogens, which break apart when exposed to sunlight.

In this case, the researchers suspect the bromine radicals react with nitrogen oxides, ammonia and organic compounds emitted from other sources to form ammonium nitrate, a leading component of PM2.5, adding to the pollution that gets trapped in Utah’s valleys during winter.

“We flew both during the day and at night, and we saw these emissions at all times of day,” Womack said. “But they were only accelerating this chemistry during the day because the sunlight is a necessary part of kickstarting that.”

NOAA’s findings have been provided to the Utah Department of Environmental Quality to help find ways to improve Wasatch Front’s air quality. More than 70% of its wintertime PM2.5 is composed of chemical compounds that are formed in the atmosphere, as opposed to pollution directly released into the air.

“We are in the process of reviewing the study and determining how it will impact our modeling, and any actions that may be necessary,” said DEQ spokesman Matt McPherson.

Ammonia and nitrogen oxide are the main “precursor” emissions that are recombined into PM2.5. DEQ has a study underway to identify ammonia sources.

Comments are closed.