About the sulphur smell felt in a large area who goes through Belgium and the northern regions of France, an article in the Ouest France news tries to give an explication claiming that it was due to multiple factors: sewer brewing, violent electrical activity caused by the storms, a pollution wave and strong North-Est winds.
I'm not expert in this field, but we already know where this smell comes from. The article accounts however for the unusual meteorological activity, but can this explain the sulphur presence ? Again I'm not qualified to debunk the connection, so if someone who knows better can cast a glance at it, here the article in French followed by some excerpts translated into English.
Une odeur de soufre inquiétante s’étend de Lille jusqu’à Nantes : on vous explique ce qui se passe
A worrying smell of sulphur stretches from Lille to Nantes: we explain what's going on
Since last night, a strong smell of sulfur reigns over part of the country, from the Hauts-de-France to the Pays de la Loire, via the Ile-de-France region. This worrying phenomenon has its origins in several factors, some natural, others linked to human activities. We will explain.
During the night of Sunday to Monday, May 11, the telephone did not stop ringing at the fire brigade of the Ile-de-France region. A few hours earlier, it had been the same with their colleagues in the Hauts-de-France. And, since Monday morning, it is the inhabitants of the Pays de la Loire region - and particularly Nantes, Sarthe and Le Mans - who have been calling the firemen.
Each time, they all report a phenomenon that is both unpleasant and worrying: a strong smell of sulphur hovering in the air. Each time, the fear of an industrial accident like the one in Lubrizol, near Rouen, is evoked by the people - sometimes in panic - who make up the 18. Wrongly: No particular intervention is underway," explain the Paris firefighters.
What's this smell?
It's a sign of air pollution. To what? Two main things. NO2 first - translate: nitrogen dioxide. Nitrogen dioxide is a member of the NOx family of compounds, which are oxides of nitrogen formed when oxygen and nitrogen are combined. Remember that NO2 is a very toxic gas when inhaled. It is pungent and stings the eyes because, to make a long story short, it interacts chemically with water (including water in our eyes).
However, this smell can also be a sign of sulphur dioxide (SO2) pollution, with its characteristic rotten egg smell. That said, the air quality monitoring body in the Ile-de-France region, Airparif, has not found high levels of SO2, but points out that this nauseating smell can also be emitted by a component that is very present in wastewater, hydrogen sulphide (H2S), a gas that is very recognizable... but which is not included in its readings.
"It looks like a mixture between a burnt insect in a halogen pole and old Brussels sprout..." an internet user says.
What is the origin of this smell?
- The stirring of the sewers
That's what Paris City Hall said last night. Emmanuel Grégoire, first deputy, says that it could be linked to the mixing of the sewage networks because of the heavy rains that make the decomposition gases rise.
Without being false, on the contrary, the assertion does not seem to be sufficient: certainly, the violent storms of this weekend have led to heavy rainfall, themselves clogging and mixing the network of rainwater and sewage. It seems unlikely that such rotten-egg smells could be produced over such a distance, from Lille to Nantes.
In a tweet, Emmanuel Grégoire announces that "no fire or industrial incident has been reported". He added that "checks are underway.
That sulphur dioxide or hydrogen sulphide has been released into the atmosphere through the sewers of large cities is highly plausible. But these gases alone are not sufficient to create a phenomenon of such geographical scope. So what could have amplified the phenomenon?
- The storms themselves
It is not necessarily known, but thunderstorm phenomena are nitrogen oxide factories (incidentally, the same applies to volcanic eruptions and large forest fires).
More than 1.2 billion lightning bolts occur worldwide every year. Laboratory and field tests have shown that the core of some lightning strikes reach 29,700°C. This is a monstrous heat, at least enough to instantly melt sand and break oxygen and nitrogen molecules into two individual atoms.
Translate: each of these billions of lightning bolts produces a blast of nitrogen oxide (NOx) that reacts with sunlight and other gases in the atmosphere to produce, among other things, ozone.
Or, la France a connu ce week-end une violente activité électrique. Pas des milliards d’éclairs, bien sûr, mais en nombre suffisant pour p
Now
, France experienced a violent electrical activity this weekend. Not billions of lightning bolts, of course, but enough to produce nitrogen oxides, as Mark Parrington explains in a tweet.
- A wave of pollution
We saw it this weekend, and we can only notice it since this Monday morning: after south-westerly flows which brought powerful and long-lasting thunderstorms up over France, a huge cold front, coming from the north-east, quickly pushed back this warm and humid air to bring its cool temperatures as far south as the Loire.
This caused thick fog and mist over the waters of the English Channel, but also over the Cotentin and Northern Brittany from Sunday.
In doing so, this strong wind carried with it, and accumulated along the warm edge, the pollution-laden atmosphere (NO2 and SO2 in particular) that prevailed over Great Britain and Northern Europe (Netherlands, Belgium...), especially over large cities (Antwerp, for example).
This wave of pollution, brought by a sustained north-easterly wind, seems in any case to be the predominant factor here.
