Scientists hung clean moss beside three Russian highways, and the plants began collecting metals linked to traffic pollution

Researchers in Russia hung bags of moss beside three busy highways to see how much traffic pollution the plants would soak up. Published in the Journal of Hazardous Materials, the study exposed moss collected from a clean background site to roadside air along the Leningradskoye, Yaroslavskoye, and Dmitrovkoye highways in central Russia. After analysing the moss for sixteen elements, the researchers found that traffic-related metals had built up in the plants, with pollution levels varying sharply between the three roads.

Why scientists hung moss bags beside three Russian highways

The study, titled ‘Impact of traffic-related emissions on air quality assessed via moss bags technique,’ used Sphagnum girgensohnii moss, a species widely recommended for air pollution biomonitoring. Researchers collected clean moss from a background site in Russia’s Tver region in May 2023, cleaned it, dried it, and packed it into bags before hanging the bags beside stretches of highway not exposed to any other major pollution sources. The approach let the team isolate the effect of traffic alone on air quality, rather than the mix of industrial and vehicle sources found in most previous moss-bag studies conducted in urban settings.

What metals the moss bags collected beside the highways

After exposure, the moss bags were analysed using Inductively Coupled Plasma Optical Emission Spectroscopy and a direct mercury analyser to measure sixteen elements, Al (Aluminium), Ba (Barium), Co (Cobalt), Cd (Cadmium), Cr (Chromium), Cu (Copper), Fe (Iron), Mn (Manganese), Ni (Nickel), P (Phosphorus), Pb (Lead), Sr (Strontium), S (Sulphur), V (Vanadium), Zn (Zinc) and Hg (Mercury). Except for phosphorus, the content of every element in the exposed moss matched or exceeded that of the unexposed samples, showing clear uptake of traffic-related pollutants. These elements typically originate from vehicle exhaust, tyre and brake wear, engine corrosion, and dust thrown up from the road surface, all of which the moss absorbed directly from the surrounding air over the exposure period.

metals came from vehicle exhaust, tyre and brake wear, engine corrosion, and dust thrown up from the road surface, all of which the moss absorbed directly from the surrounding air (Image: Canva)

Why the Leningradskoye highway showed the most pollution

Pollution levels differed sharply between the three highways. The most pronounced uptake of elements was recorded at Leningradskoye highway, followed by Yaroslavskoye and then Dmitrovkoye, a ranking researchers linked to differences in traffic density. Aluminium, cobalt, cadmium, manganese, and lead were significantly higher in moss exposed at Leningradskoye than at the other two roads. Statistical analysis also showed that concentrations of aluminium, copper, cobalt, chromium, iron, nickel, and vanadium changed with distance from the road edge, generally falling off the further the moss bags were placed from passing traffic, underscoring how closely tied the contamination was to the highway itself.

Moss bags prove an effective tool for tracking Russian highway pollution

The research was carried out by Inga Zinicovscaia, Omari Chaligava, Nikita Yushin, Dmitrii Grozdov, Konstantin Vergel, and Pavel Nekhoroshkov, based at the Department of Nuclear Physics at the Joint Institute for Nuclear Research in Dubna, Russia. The team concluded that moss biomonitoring, already widely used across Europe and Asia, proved an effective and inexpensive tool for tracking traffic-related air pollution along stretches of highway free from other contamination sources. Their findings point to vehicle emissions, tyre wear, and brake wear as key contributors to roadside metal pollution, with implications for how such contamination could be monitored more cheaply in the future.