An international team of researchers led by the U.S. National Oceanic and Atmospheric Administration NOAA has made a significant step toward understanding the atmosphere's capacity to cleanse itself of pollutants and some gases other than carbon dioxide. This question is a controversial debate for many years.
Some studies suggest the possibility that such an atmosphere of instability and are sensitive to environmental changes, while others have claimed the opposite. In the current study, scientists were able to show the relative stability of the atmosphere's capacity to cleanse itself. The photo Aidan Colton demonstrates the collection of air samples for the observation station near the volcano Mauna Loa in Hawaii.
Published in the journal Science, the new analysis shows that the global level of the hydroxyl radical, a critical matter for atmospheric chemistry, year after year little changed. The level of hydroxyl, which helps to clear the atmosphere of many hazardous pollutants and some important greenhouse gases, except carbon, every year increases and decreases only by a few percent, that number is less than 25 percent of the index, as stated earlier.
"The new hydroxyl measurements give researchers meaningful information about the ability of the atmosphere is oxidized or self-clean — explains Stefan Monttska, team leader and research chemist division NOAA, contributes to global monitoring. — Now we know that the atmosphere's ability to get rid of many pollutants is generally well formed and stable. That is the fundamental feature of the atmosphere, we could not confirm the earlier. "
A new study gives projections for future pollution. Hydroxyl radical, consisting of one oxygen atom and one hydrogen atom, is formed and decomposes in the atmosphere so fast that it was extremely difficult to measure on a global level.
"In the daytime, hydroxyl life is about one second, and its concentration is extremely small — says Monttska. — After his appearance at once there is a substance with which it reacts. "
Radical is a key compound in the chemistry of the atmosphere. It is involved in the formation and decay of surface ozone and pollutants that are harmful to a person's lungs and crops. It also reacts and destroys the essential to the greenhouse gas methane and air pollutants including hydrocarbons, carbon monoxide and sulfur dioxide gases. However, the hydroxyl radical can not remove carbon dioxide, nitrous oxide and chlorofluorocarbons.
To determine the variability of the global level of hydroxyl, and thus, the ability to purify the atmosphere, the researchers decided to study the chemical substances with a long life cycle, which react with hydroxyl.
Industrial chemical methyl chloroform, for example, is destroyed in the atmosphere primarily hydroxyl radical. Comparing levels released into the atmosphere methyl chloroform data on its presence in the air, scientists were able to determine the concentration of hydroxyl and its changes over the years.
With this method to get data about the level of hydroxyl, which vary considerably in the 80's and 90's. Scientists are trying to understand what is the cause of increases and decreases — for example, errors in emissions of methyl chloroform or is it the real fluctuations in hydroxyl. These fluctuations play an important role, significant fluctuations of hydroxyl radicals could mean that the self-cleaning capacity of the atmosphere is very sensitive to human-induced or natural changes in her.
Complicating the case is also the fact that the measurement of concentration levels of hydroxyl radicals compared to other gases such as methane, the researchers obtained data on only a small change in a few years. The same small fluctuation was observed during the testing of standard global chemical models.
Helped to solve the problem of international document. In accordance with the Montreal Protocol — an international agreement to withdraw from the production of chemicals that deplete the protective stratospheric ozone layer — production of methyl chloroform virtually ceased in the mid-90s. As a result, emissions of ozone-depleting gas active stopped abruptly.
Without mixing effect associated with any appreciable methyl chloroform emissions, there was a clearer picture of hydroxyl variability based on the reduction in residual chemical in the atmosphere. Scientists studied by measuring the hydroxyl radical methyl chloroform in the framework of international programs for the collection of air samples NOAA, as well as reproducing the results in the current models.
These results make it possible to make calculations regarding the Earth's atmosphere.
"Suppose we want to know how to reduce anthropogenic emissions of methane, to halve its impact on the climate — explains Monttska. — You will need information on the hydroxyl and its variability. Since our results are based on large changes are unlikely hydroxyl radicals produced estimates of are quite likely. "