By the long-range transport of particles, such as sulfate, across the Atlantic to the Amazon rainforest and to better understand atmospheric cycling. A good opportunity for that arose in 2014. Some of the most active volcanoes worldwide, the Nyamuragira and Mount Nyiragongo volcanoes in Congo in Central Africa, erupted violently.
During this eruption, they emitted a lot of sulfur dioxide (SO2) into the atmosphere. This gas that is later converted to sulfate particles by oxidation. Usually, these particles are diluted in the atmosphere as they mix with other particles. It thus becomes difficult to distinguish them far away from their source. However, the emissions of 2014 were so strong that the sulfate particles originating from the volcanic gas were observed over the Amazon rainforest by ground-based instruments at our ATTO site (specifically at the 80 m tall triangular mast) and by aircraft measurements (during the ACRIDICON-CHUVA campaign). This observation is now being used by ATTO scientists as a case study to understand how gas and particle emissions from Africa are transported over the Atlantic Ocean and reach the Amazon Basin.
For scale, the volcanoes in Congo are almost 10,000 km away from ATTO, and it took the particles around 2 weeks to bridge that distance!