How polluted is the air? Experiments with particulate matter and nitrogen oxide

Those taking part in the Elite Academy for Chemistry and Materials Science would probably have happily celebrated the new year by letting off some fireworks. But that wasn't possible because the sale of fireworks was banned. However, at the end of January around 100 school students and students took part in an experimental lecture with Prof. Peter Menzel, held in the chemistry lecture hall at the University of Stuttgart. The topic was "particulate matter and nitrogen oxide". Prof. Menzel explained to the audience that levels of particulate matter are usually at their highest level for the entire year during the first hours of the new year. Setting off fireworks releases about 2,050 tons of particulate matter per year, which accounts for about one percent of the total annual PM10 emissions. So, banning fireworks made a significant contribution to reducing air pollution.

Combatting particulate matter using moss and glue

The city of Stuttgart also has a problem with particulate matter, particularly at the Neckartor measuring station. But what is the city doing to tackle this? It uses a moss wall to remove particulate matter, special street-cleaning vehicles, an adhesive to counter air pollution, filter columns to clean the air and, finally, it has also introduced a ban on diesel vehicles that are classed as Euro 5 and older. Particulate matter (PM10) is defined as particles smaller than ten micrometers. Natural particulate matter includes pollen and viruses, whereas anthropogenic particulate matter is caused by humans, for example particles from tire wear in road traffic. Prof. Menzel demonstrated a simple method for detecting particulate matter. By scattering laser light, he was able to make visible particles created by burning a simple match.

Nitrogen oxide in exhaust fumes, candles or cigarettes

In addition to particulate matter, nitrogen oxides are also examples of air pollutants that can have a detrimental effect on health. Using nitrite/nitrate test strips, Prof. Menzel was able to easily prove the presence of nitrogen oxides because the azo dye produced has a characteristic coloration. He took various measurements using different exhaust gas samples taken from his car. He also demonstrated the formation of nitrogen oxides with a candle and an arc lighter. Only the attempt to detect nitrogen oxides in the gas mixture inhaled when smoking a cigarette resulted in just a small amount of nitrogen oxide. However, the appearance and color of the gas mixture alone should discourage students from reaching for a cigarette. The pollutants are literally visible here. In his experimental lecture, Prof. Menzel was able to show his audience that even a simple experiment is sufficient to conduct chemical reactions.

The Elite Academy for Chemistry and Materials Science [de] is a project of the School for Talents at the University of Stuttgart. This is funded by the German Research Foundation (DFG) as part of the Excellence Strategy of the German federal and state governments.