Researchers from Hokkaido University in Japan reported an advanced laser technology in a research published in Physical Chemistry Letters that allows researchers to observe the process of pollutants decomposing into atmospheric nitrous acid in real time. Nitrous acid plays a key role in the formation of ozone and photochemical smog.
Nitrophenol is a fine particulate matter found in the atmosphere and is the result of fossil fuel burning and forest fires. Suppose that light interacts with nitrophenol and decomposes it into nitroso acid. Nitrous acid in the atmosphere produces hydroxyl radicals that cause ozone to form. Too much ozone and nitrogen oxides can cause photochemical smog and cause respiratory diseases. So far, there is no evidence that nitrophenol is broken down by sunlight into nitrous acid.
The research team has developed an advanced laser technology that uses extreme ultraviolet light with a short wavelength, which is irradiated in femtoseconds and lasts only one billionth of a second. The energy state and molecular changes that occur during the whole process are measured, and the nitrophenol compound decomposes over time.
It was observed that nitrophenol began to form nitrous acid after 374 femtoseconds of light excitation. During the decomposition process, the nitrophenol molecules are distorted under light irradiation, their energy state changes, and finally nitrous acid is formed.
The researchers concluded that “research has shown that exposure of o-nitrophenol to sunlight is one of the direct causes of nitrous acid in the atmosphere.”
