Green suburbs can be more polluting than city centres

Recreational parks can pose as much of a pollution threat as city centres due to the weaker barrier functions of the soil. Traditional approaches to urban soil pollution monitoring don’t take into consideration the barrier function of the soil.

Using Moscow as an example, new research has shown that not only polluted downtown districts but also recreational parks and forest zones can pose a threat to people. This is due to the fact that the barrier functions of the soil are weaker in green suburbs.

Industrial soil pollution with heavy metals poses a threat to human health. From the soil, harmful substances get into the water, dust, and plants. The intensity of these processes depends on the properties of the soil, namely its organic content, acidity, and texture. For example, clay and loam soils act as a geochemical barrier: they retain harmful substances and don’t let them spread.

However, traditional approaches to ecological monitoring assess risks based only on the concentration of contaminating agents, explains a statement from the researchers at RUDN University.

The experiment covered nine administrative districts of Moscow. The main sources of contamination were industrial facilities and automobiles. The researchers took soil samples from 224 points in public spaces, residential areas, and industrial zones.

In over 30% of the samples, heavy metal concentrations exceeded the norms of the Russian Agency for Health and Consumer Rights. The most polluted soils were the ones taken from public places downtown. However, loam soil with alkaline acidity that is typical for the center of Moscow has a high barrier activity index, which means it can retain the pollution.

“In some cases, the ability of the soils to bind down heavy metals compensates for high pollution levels. On the other hand, in some green zones topsoils are unable to contain even the smallest amounts of pollutants,” said Olga Romzaykina, a researcher from RUDN University, in the statement.

Photo credit: Matthias Ripp/ Flickr Creative Commons CC BY 2.0

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