Moose as fine dust killer

Plants are designed to reduce air pollution in cities and on highways

Does it look so soon on the edges of many highways in Germany? © Jan-Peter Frahm
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Fine dust is poisonous. According to estimates by the European Commission, microparticles in the air cost 300, 000 Europeans each year alone. Now researchers want to tackle the dangerous fine dust with an unusual means: Moose. Like a biological microfiber duster, the plants swallow large quantities of the dangerous air particles.

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According to the scientists from the University of Bonn, many exhaust components are even used as food, others are broken down by bacteria that live on the moss leaves. In the former federal capital, the natural air filters are now to be used for the first time for greening the streets.

Five million tiny leaves

It's a combination of properties that make Moose a fine dust killer. Firstly, there is their huge surface: "A moss cushion of one square meter size has five million smallest leaves, " calculates the Bonn Moos researcher Professor. Jan-Peter Frahm.

Point two: Each of these leaves magically attracts some microparticles from the air. These include ammonium ions, which account for an average of 40 percent of particulate matter. "The whole works electrostatically, " says Frahm; "The moss surface is negatively charged, while an ammonium ion is positive." By the way, the popular microfibre dusters work on a similar principle. display

Point three: Mosses not only capture the dangerous particle load - they even pick up the dust from their leaves and digest it. Because ammonium is an important nutrient that the inconspicuous plants need to grow. Other components of the dust are used by bacteria that live on the moss leaves. "Particulate matter turns into biomass, " commented Frahm dryly.

Laboratory tests a complete success

In the lab, he and his colleague Marko Sabovljevic have already shown how well it works. They tipped lead and barium dust onto various moss cushions. After a few hours of waiting, the plants were washed. From the amount of dust in the washing water, the researchers were able to calculate the binding capacity of the plants. "Up to 20 grams of particulate matter were absorbed by one square meter of moss cushion during this procedure, " explains Sabovljevic. By comparison, on a busy street, only 14 grams of particulate matter per square meter fall to the ground each year.

Decisive for the air purification, however, is that the humidity is right: dry moss has hardly any effect, but it should not be too wet either.

Great career on the fringes of German highways?

In Bonn, the plants will soon be able to prove beyond the laboratory what they are made of: a connecting piece to the Federal Highway 562 will soon be welcomed by mosses. "In the meantime, it is possible to use finished moss mats", explains Frahm. "That reduces the effort." Originally, the mats were developed for roofing - among other things from the Kalk l, you can use these natural humidifiers, the local climate in the interior Improve cities.

Perhaps the inconspicuous plants will now have a great career on the outskirts of German highways. If so, this is certainly due to a final argument that might be worth a lot in times of bad public finances: "Moose do not need much care, " says Frahm. "Their low maintenance makes them even more attractive for highway maintenance companies."

The scientists report on their results in autumn in issue 4/2007 of the magazine "Immissionsschutz", which is published by the Ministry of Environment and Nature Conservation, Agriculture and Consumer Protection of the State of North Rhine-Westphalia.

(idw - University of Bonn, 03.08.2007 - DLO)