The Amazon rainforest is a mystery of many sorts. We’ve heard of the rare and unique flora and fauna of the place, and here’s another intriguing aspect there: the Amazon is self-sufficient in rain as well!
The technique of “cloud seeding” used by rain-starved nations to induce rain is used naturally by the fungi and trees in the Amazon to produce rain. Scientists have discovered that trees and fungi release minute amounts of potassium-rich salt which is the cause of a large amount of rain in the area. Since they deflect light from the sun, it helps in cooling the Earth too.
Normally, water vapour molecules collect around a core to form raindrops. The core can be salt spray, soot, dust, airborne organisms, droplets of chemicals from volcanoes etc. The scientist for atmospheric research studies at the German Max Planck Institute, Christopher Pöhlker says that though their studies found out that these particles were seeds for the rainfall in the Amazon, they had yet to know what kicked off the development of these particles.
Recent analyses by Pöhlker and his team have found a small amount of salt rich in potassium at the center of a large number of the particles. The salty core measured about 20% of the particle’s weight for aerosols with a diameter of around 0.15 micrometers. The proportion of this weight decreased in larger aerosols. This shows that the minute amounts of salt serves as catalysts for the rich haze particles to grow.
Though Pöhlker and his team have narrowed down numerous sources of these salts, many of them do not fit the bill. While potassium-rich particles are found in smoke from forest fires, their samples did not have any soot particles which would be found in smoke. Satellite images also did not show any fires in the vicinity of the research area. Secondly, the potassium-rich particles couldn’t arrive from the oceanic salt spray beyond the Atlantic Ocean, since the research area was one thousand kilometers away from the study area. The chemical composition of the particle core was dissimilar from that of sea salt.
Studies by Pöhlker and his team have shown that the center of the aerosols had origins in the forest. Fungi and plants disseminate salts into the atmosphere, with fungi also expelling droplets with carbohydrates, cholride and potassium ions along with spores. The samples collected by the team comprised numerous fungal spores as well.
Encouraging Pöhlker’s work, scientist Markku Kulmala, from Helsinkiand University, who studies atmosphere said that their findings on the new source for these aerosol particles and improving the concentration of cloud droplets is significant. The association between the emission of these particles and properties of clouds in the ecosystem found in such rainforests is gaining importance and strength.
Considering the impact of tropical rainforests on the chemistry of the atmosphere, the Amazon’s particle-discharging entities have and will play a significant role in the future, according to Kulmala. They research will also help understand the formation of secondary organic aerosols when the core can be soot, dust or artificial pollutants.