Fog can play an important role in the natural cleansing of the atmosphere. Inside tiny water droplets are active bacterial communities that are not merely carried by the air, but grow, reproduce and take part in chemical processes.
Over two years, researchers studied 32 fog events in central Pennsylvania. The main discovery was the bacteria’s ability to efficiently remove formaldehyde — a toxic compound present in the atmosphere — from the air. The rate of its breakdown was up to 200 times higher than previously observed in clouds, and up to 95% of this process was explained by the biological activity of microorganisms.
A particularly important role is played by the genus Methylobacterium. In fog, they made up almost a third of the total bacterial mass, although they were rarely found in dry air. After the fog dissipated, the number of bacteria in the atmosphere increased by about 45%, indicating that they were actively reproducing inside the water droplets. Scientists believe the microorganisms neutralize formaldehyde primarily to protect themselves from its toxic effects.
The results also have practical significance. Water collected from fog in arid regions may contain large numbers of bacteria, so approaches to its purification and quality control may require additional attention. The study also shows that fog is not just an atmospheric phenomenon, but an active biological environment capable of influencing the chemical composition of the air and the processes of its natural self-cleaning.
