Carbon dioxide model could aid in reducing Utah pollution

By Javan Rivera

Salt Lake City, Utah is facing a very serious problem concerning air pollution.

It’s no secret that Utah winters often cause severe inversions that trap large amounts of dirty air in the Salt Lake Valley. However, what’s less widely known is the cause of the problem and what exactly is being done to rectify the situation.

Enter Carolyn Stwertka, a graduate research assistant at the University of Utah who, along with her advisor, are currently developing a model for measuring carbon dioxide movement in the Salt Lake Valley.

Stwertka’s work, which is funded by a GK-12 National Science Foundation grant http://www.gk12.org/ called Think Globally, Learn Locally http://tgll.utah.edu/home.html, is vital to understanding exactly how carbon dioxide circulates through the greater Salt Lake City area and how exactly carbon dioxide emissions can be accurately measured for future Utah policy and legislation.

According to Stwertka, the main cause of Utah’s inversion problem is that the Salt Lake Valley acts as a natural bowl for collecting dirty air. With the Oquirrh and Wasatch mountain ranges hedging in the valley’s south and east sides, the Great Salt Lake trapping air from the west, and the high elevation of the valley’s north end, very little air is able to escape the valley without the aid of significant weather changes such as storms.

“Studying carbon dioxide in an urban environment is of interest to a lot of people because humans are creating a new ‘urban environment’ and this [modeling] provides a way to verify if emissions are decreasing due to [potential future] policy change,” she said.

Salt Lake City provides a very unique testing ground for this research not only because of its natural, inversion-causing barriers, but also because it is home to “the longest standing, consistently running set of [carbon dioxide measuring] stations in a city in the world,” said Stwertka.

The set of stations, mostly owned and operated by University of Utah professor Jim Ehleringer, is the primary source from which Stwertka drew her carbon dioxide measurements of Salt Lake City’s surface layer of air for her case study of the winter of 2010-2011.

Using carbon dioxide measurements along with a set of data points that account for wind forces, biogenic flux as a result of plant life in the valley, man-made emissions, and entrainment http://en.wikipedia.org/wiki/Entrainment_%28meteorology%29, are all input into Stwertka’s model in an attempt to accurately measure carbon dioxide movement through the valley.

“We have our model data and we can see how well it compares to the carbon dioxide observations around the valley [as measured by Ehleringer’s stations],” Stwertka said.

The real core of Stwertka’s work comes into play when it comes to finding an accurate measurement of not only how carbon dioxide circulates through the valley, but more importantly how those emissions eventually make their way out of the city air, and into the higher parts of the troposphere. Ultimately, what effect that has on the global mean of greenhouse gases.

Based on her observations from her own unpublished research, she’s discovered that in urban environments such as Salt Lake City, carbon dioxide tends to form a concentrated dome over the city similar to the “urban heat island effect.”

“In cities you produce a lot of carbon dioxide because it is concentrated,” Stwertka explained. “This essentially means that cities create a lot of carbon dioxide that stays isolated around the city and doesn’t extend into the surrounding rural environment. The question is, how do you relate the surface measurements to the global mean average?”

If Stwertka’s model can successfully measure carbon dioxide emission dispersal into the greater atmosphere, her model could be vital to creating future Utah policy changes regarding carbon dioxide emission regulation.

Salt Lake City is currently in violation of the Environmental Protection Agency’s National Ambient Air Quality Standards, thanks in part, to the valley’s severe inversion problem. With Salt Lake City currently attempting to create a State Implementation Plan (SIP), in order to regulate emissions, Stwertka’s work presents an opportunity to gain accurate carbon dioxide dissemination measurements for the plan.

Not only does Stwertka’s model hold promise for measuring carbon dioxide levels, but it also holds the possibility of measuring additional air pollutants such as PM 2.5 and PM 10 http://en.wikipedia.org/wiki/Particulates.

“Understanding the broad pattern [of carbon dioxide emissions] can help you understand the traveling of other pollutants,” Stwertka said. “We would like to further develop the model to track other pollutants as well so that our model can be used for the SIP.”

http://www.youtube.com/watch?feature=player_embedded&v=3dxx_RNsbLs

An inversion creeps across the city as Carolyn Stwertka hikes up the Grandeur Trail to gather carbon dioxide density measurements of Salt Lake City’s surface air.

Throughout the hike, the inversion managed to spread all the way to the base of Grandeur Peak, and even enveloped part of the mountain.

Carolyn Stwertka hiked ¾ of the way up the Grandeur Trail during the winter of 2010, carrying a backpack full of electronic equipment designed to take measurements of carbon dioxide emissions throughout the trek.