Society 23/09/2021

Can gas emissions from La Palma volcano be felt in Catalonia?

Barcelona is one of the European capitals with the lowest sulphur dioxide levels

3 min
Total atmospheric sulphur dioxide concentration forecast for Friday midday

BarcelonaIf you are very involved in social networks, surely these days you have started to see maps of sulfur dioxide dispersion (SO₂), animations that draw the possible movement of gas emissions from the La Palma volcano to the Peninsula. To what extent will it be possible to perceive the SO₂ of the eruption in Catalonia? At this stage there is no indication that it will be perceptible for the population. Although the wind dynamics will indeed be part of this sulphur dioxide flow towards the Peninsula, on the way it will be dispersed and will arrive in a much lower concentration than at the source. The levels of this gas will be higher in the upper layers of the atmosphere, but at the surface the increase of SO₂ may not be perceptible.

A not too distant precedent is that of the famous eruption of the Eyjafjallajökull volcano, which forced the cancellation of 100,000 flights in Europe in 2010. According to Xavier Querol, professor at the Institute of Environmental Diagnosis of the CSIC in Barcelona, at that time the pollution measurement stations in Catalonia hardly perceived the phenomenon.

The AEMET has released data on the levels of SO₂ that have been recorded at the observatory of Izaña, located in Tenerife, at an altitude of about 2,400 meters and far from population centres. This Tuesday night there was a punctual peak of 700 ug/m³ of air at this point, but even at this time the alert threshold set by the European Union was not exceeded, which occurs when for three hours in a row there is a concentration above 500 ug/m³ of air. The air quality monitoring stations in the Canary Islands that are located close to the population have not even recorded an increase in sulphur dioxide levels.

Although sulphur dioxide does not reach the surface, only the fact that it is in higher concentrations in the atmosphere could favour the phenomenon of acid rain, but according to Querol this effect is not expected to be relevant at all, since in any case the problem of acid rain comes in cases of very persistent emissions in a particular place, a problem that did occur in some parts of central Europe a few decades ago, due to the presence of thermal power plants that constantly generated this gas.

In Catalonia this problem occurred in less quantity due to thermal power plants such as the old Besòs, which was closed in 2007, and Cercs, which being located in a valley favored the concentration of gases such as SO₂. Today the levels of sulphur dioxide in Catalonia are low and, in fact, Barcelona is currently one of the cities with the lowest levels of sulphur dioxide, according to Querol. The only factor that makes this pollutant rise at times is the marinade, since much of the emissions of this gas currently come from the port.

Will there be a cooling effect?

Another of the issues related to the atmosphere that has been talked about in recent days is the possible transient cooling effect that may result from the eruption. In this sense there are no indications that the eruption will have any noticeable effects beyond the island. Marc Prohom, head of climatology at Meteocat, who wrote his thesis on the effects of large volcanic eruptions on the climate of the peninsula, is an expert on the subject. According to Prohom, it is difficult for the cooling effect to be felt beyond the island itself, since a more global effect would require an explosive eruption that could spread large amounts of sulphur dioxide into the stratosphere. This is not happening now, nor has it happened before in other eruptions in the Canaries. SO₂ is a gas with a high capacity to repel solar radiation, and so in large concentrations in the atmosphere it can cause a drop in temperature.

The International Civil Aviation Organization (ICAO) is keeping an eye on the eruption because of the possible complications it could cause for air traffic. For now, the ICAO's periodic warnings are orange, which is associated with gas and ash emissions that are not significant enough to pose a serious threat to aviation. According to the ICAO, the ash cloud reached 4,000 meters this afternoon, around 2,000 meters above the elevation of the Cumbre Vieja volcanic area.

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