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Remote sensing of sulphur dioxide emissions of sea-going vessels on the Westerscheldt

Zwaveldioxide-uitstoot van zeeschepen op afstand gemeten met lidar


RIVM developed an instrument to measure sulphur dioxide emissions of sea-going vessels. In a five-day pilot study, the emissions of 24 ships on the Westerscheldt estuary were determined. As it turned out, a large number of those ships emitted huge quantities of sulphur dioxide. Sulphur dioxide is a source of acidification and is harmful to the environment. Various measures have driven back emissions from other sources, such as traffic, industry and electricity generation. This causes the share of shipping in the total of the emissions to increase. Sea-going ships are not allowed to use sulphur-rich fuel in territorial waters. This relatively cheap fuel may be on board, though, for use at sea. To what extend ship owners comply with this ban is not known. A breach is difficult to determine using traditional measurement methods because these require boarding the ship. The crew therefore knows a measurement is taking place and can adjust the type of fuel used. The new technique is known as lidar (light detection and ranging) and measures from the shore. The lidar instrument uses a laser beam to scan the exhaust plume of a passing ship and to determine the emission, unnoticed. An advantage of this method is that nearly every passing ship may be measured, instead of only a few. On land, sulphur dioxide emissions of industrial installations are limited by licences. These are granted on the lines of the Dutch emission guideline air (NeR, April 2003), which puts demands on sources that emit more than 2 kgs per hour (0.56 gram per second). The emissions of all measured ships turned out to be higher than that. The highest emission measured was 36 gram per second. This indicates the importance of recognising ocean shipping as a source of air pollution, both when issuing rules and when enforcing them.

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