Precipitation plays a key role in the processes of accumulation, retention and re-suspension of particulate matter on Betula pendula, Tilia cordata and Quercus robur foliage

Particulate matter (PM) is one of the most dangerous air pollutants. Urban vegetation, especially trees, can accumulate PM and reduce its concentration in the air. However, knowledge about the dynamics of PM accumulation, retention and re-suspension is limited. This study examined the effects of rainfall on the dynamics of PM (0.2–2.5, 2.5–10 and 10–100 μm, surface PM, wax-embedded PM) accumulation, wash off and re-accumulation on Betula pendula, Tilia cordata and Quercus robur trees throughout the growing season. Irrespective of the species, rain affected PM deposited on plants, reducing the amount of PM on foliage by 17%, 24%, and 37% for B. pendula, Q. robur and T. cordata respectively. Rain had a lesser effect on the amount of wax-embedded PM washed off than on the amount of surface PM. After each rainfall event, PM re-accumulation was recorded. If the amount of PM washed off from the foliage were taken into consideration, the amount of PM that plants actually removed from the air would be 55% (B. pendula), 66% (T. cordata) and 62% (Q. robur) greater than the amount deposited on leaves at the end of growing season. Thus, many studies underestimate plants’ potential for air purification.