According to a research, the underlying presumptions of air quality need to be revised

 By University of Innsbruck

January 18, 2023

 

         

                               The Innsbruck Atmospheric Observatory in Austria's city centre, with a 40-meter-high monitoring tower, continually gives information on the makeup of the atmosphere close to the surface. 36,000 data points are gathered per hour. The eddy covariance method, a unique measurement technique, allows for continuous monitoring of the air component concentration.

With the aid of this information, an international team headed by Thomas Karl from the University of Innsbruck's Department of Atmospheric and Cryospheric Sciences has now thoroughly examined the chemistry of ozone, nitrogen monoxide, and nitrogen dioxide in metropolitan areas. Strong quantities of nitrogen monoxide are caused by the large percentage of diesel automobiles in European towns. This produces nitrogen dioxide when it interacts with ozone. In the environment, nitrogen dioxide breaks down once more into nitrogen monoxide and atomic oxygen, which come together with the oxygen in the air to generate ozone right away.

Common assumption needs to be redefined

In the first textbook on air pollution, written by Philip Leighton more than 60 years ago, this chemical cycle was mathematically defined. The Leighton ratio is the name given to the connection between the two processes. The Leighton ratio, which derives the concentrations of ozone, nitric oxide, and nitrogen dioxide from the concentrations of the other two, is used in computer models of atmospheric chemistry to reduce complexity.

In actuality, this has been applied, for instance, to calculate ozone concentrations in nitrogen oxide-polluted locations. Data from the Innsbruck atmospheric researchers demonstrate that Leighton's computational simplifications provide inaccurate findings when nitrogen monoxide emissions are high. According to Thomas Karl, "this ratio can be exaggerated by up to 50% in cities with significant nitrogen monoxide emissions, which can lead to model estimates overestimating ground-level ozone concentrations in urban regions." Up to 200 metres above the ground, turbulence interactions, a result of chemistry, have a considerable impact on the atmosphere's lowest layer.

Strong turbulence in metropolitan areas combined with significant nitrogen monoxide emissions are to blame for the impact observed in Innsbruck. More ozone is transformed into nitrogen dioxide due to the mixing of the gases and the relatively quick chemical reactions. The researchers' results also demonstrate that, in compared to secondary production, direct emissions of nitrogen dioxide from urban transportation are virtually minor.

It is crucial to remember that environmental rules are based on real observed pollutant concentrations rather than model estimates, according to Thomas Karl.

Under the terms of a Creative Commons licence, this article has been taken from PHYSOORG. Go here to read the original article.