The myth of the healthy sea air

    

    

Doctors newspaper online, 28.08.2019

    

        
        
        

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fine

The air on the coasts is far from being as healthy as widely believed. This is shown by the investigations of an atmospheric physicist at the Helmholtz Center.

By Gesa Coordes

A ferry leaves with thick exhaust cloud from the Baltic Sea resort of Rostock-Warnemünde.

© Bernd Wüstneck

GEESTHACHT. Atmosphere physicist Volker Matthias has a weakness for lighthouses and the North German coast. Often he travels with his wife from Hamburg to Nordfriesland, to relax in tranquil coastal villages. But he has a different view of the merchant ships passing by on the horizon.

The 53-year-old head of department at the Institute for Coastal Research at the Helmholtz Center, together with his team, has precisely calculated in an EU project the impact of the North Sea freighters on air quality. Conclusion: "Around a quarter of the nitrogen oxides on the North Sea coasts come from ship exhaust gases," says Matthias. For the fine dust, it is up to 20 percent.

But that's not all: the exhaust-laden sea air travels hundreds of kilometers far inland, as far as Hesse and Thuringia. And at the same time, the ship's exhaust gases react with other air pollutants – for example from agriculture -, which causes further fine dust to form. The result: According to the World Health Organization, more than 50,000 people die prematurely from ship emissions each year.

Three-Dimensional Computer Models

Volker Matthias has been involved with atmospheric measurements and air quality research ever since his doctoral thesis on measuring methods for aerosol particles. During his studies in physics in Hamburg and his time as a research assistant at the Max Planck Institute for Meteorology, he also traveled on research vessels in the Pacific and in the North Sea: "I'm getting seasick," he admits.

In 2003, he moved to the Helmholtz Center in Geesthacht, where he now heads the Department of Chemical Transport Modeling. Matthias does not investigate the ship's exhaust gases on site. The physicist works with three-dimensional computer models simulating the meteorological and chemical processes in the air. The basis of his calculations are the movement data of all commercially used merchant ships traveling in the North Sea.

Fuel Control by Satellite

Each freighter must have a satellite transmitter on board, which transmits the current position and speed around the clock to the traffic control centers. This allows us to calculate where and how fast each individual vessel is traveling, how high the fuel consumption is and what amounts of nitrogen oxides, particulate matter and other pollutants are expelled. With a so-called chemical transport model, the pollutant distributions in the coastal area are derived.

In 2010 Matthias started the investigations. At that time, the ship's emissions were still little in the eye, because cargo ship transport goods are considered climate-friendly: "There is no more effective way to transport containers," says the researchers. For each tonne and kilometer transported, trucks produce 15 times more carbon dioxide than ships.

The catch: In the case of air pollutants, shipping cuts off worse than any other means of transport. On the high seas, it burns heavy fuel oil, a residue that remains in oil processing at the refinery. Combustion produces large quantities of harmful sulfur and nitrogen oxides.

And even in the ports, ships are a "source of serious stress," says Matthias. Thus, the Port of Hamburg, which was examined by his department, contributed just under one third to the emissions of nitrogen oxides in the Hanseatic city. 70 percent of the exhaust fumes come from lying ships because freighters and crusaders also need energy for cooling or hotel operations in the port. And for that generators are used, which run with ship diesel without catalyst. In the port of Hamburg, therefore, more and more power is to be used by land.

For a research team with colleagues from Rostock, Gdansk, Riga and Gothenburg, Matthias also found high levels of nitrogen oxides in the Baltic Sea. It mainly affects southern Sweden, Denmark and the German Baltic Sea coast, with emissions drifting to Berlin.

Emission limits help

However, the simulations also show that polluting emissions can be effectively reduced by emission limits for ships. In the North Sea and the Baltic Sea, only freighters are now allowed to drive with fuels that contain a maximum of 0.1 percent sulfur. And from 2021 much stricter rules for the emission of nitrogen oxides apply.

From then on, all newly built ships in the North Sea and Baltic Sea have to be equipped with catalytic converters or run on LPG. And then – if you take into account the declining fuel consumption – the emissions by 2040 by about 80 percent, Matthias has calculated: "If the regulations are met, we are actually optimistic."

Burdens of shipping

• According to the World Health Organization (WHO), 50,000 people die prematurely from ship emissions every year.
• Nearly a third of the Port of Hamburg controls nitrogen oxide emissions
• Seventy percent of these emissions come from lying ships because freighters and crusaders also need energy for cooling or hotel operations in the harbor.

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