Air quality in the Amazon drops significantly in dry periods, when fires associated with deforestation release large amounts of particulate matter — such as soot — into the atmosphere. What surprised the scientists, in an unprecedented study carried out in the forest, is that many of the smoke particles are not from here: they originate in Africa.
The research led by Bruna Holanda, a doctoral student at the Max Planck Institute for Chemistry, in Germany, showed that up to two thirds of the soot found in the Amazon comes from the other side of the Atlantic. “We estimated that the amount of smoke coming from Africa would be around 5 or maybe 15%. In fact, at times it reaches 60%,” says the scientist.
According to the author, the value demonstrates a high efficiency of atmospheric transport between the continents — the particles travel more than 10 thousand kilometers, carried by air masses.
It is possible to differentiate the particles because they have physicochemical characteristics different from each other. Those originating in Africa are larger and contain less organic matter than those originating from fires in the Amazon itself. According to the researchers, this happens because the forest fires that create these particles on the African continent are in savannas, grasslands and open forests, which are drier and less dense than the Amazon biome.
Combustion in the environment there has larger flames, which consume more organic matter. Here, however, wet material leads to combustion with less or no flame, which would act in the opposite way. The research was also able to identify the periods in which particles from Africa are most present in the Brazilian biome: from January to March and from August to November.
The presence of particulate matter in the atmosphere has adverse effects on human health and the environment. Soot particles retain a large amount of solar radiation, in addition, they serve as condensation nuclei for cloud water. A cloud in contact with particulate matter will have an excess of condensation nuclei, which causes the raindrops formed to be smaller – and may even be too small to even fall.
Source: Communications Earth & Environment Via: Max Planck Institute for Chemistry
