Human activities continue to emit a variety of pollutants into the atmosphere. If there is no molecule called hydroxyl radical to oxidize and degrade pollutants, they will continue to accumulate in the atmosphere. A recently released international study has deeply described a special generation mode of hydroxyl radical, and the discussion of this process is expected to reshape people's understanding of atmospheric self purification and air pollution mitigation. In the near ground atmosphere, gaseous pollutants are generally degraded or removed by oxidation reaction with hydroxyl radical, which is called "atmospheric cleaner". How are hydroxyl radical formed in the atmosphere? A previous view in the scientific community was that sunlight was the main driving force behind its formation. However, a new study carried out by researchers from the University of California, Irvine and other institutions found that the strong electric field between the surface of a water drop and its surrounding air can generate hydroxyl radical through some mechanism. The research results are published in the Journal of the National Academy of Sciences in the United States. The research team used two test tubes to track the production of hydroxyl radical in the dark - one containing water and air, and the other containing only water and no air. They put a "probe" molecule in two kinds of test tubes, which will emit fluorescence when it reacts with hydroxyl radical. The researchers found that the generation rate of hydroxyl radical in the dark is similar to or even exceeds that in sunlight and other conditions. This means that hydroxyl radical is still generated in the night without photochemical effect, and the amount generated is not lower than that generated by other known methods. The researchers said that this discovery will change people's understanding of the formation mechanism of hydroxyl radical and atmospheric self purification, and may change the way researchers predict the computer modeling of air pollution. (New News Agency)