Salt in Amsterdam
Amsterdam is the (titular) capital and by population the largest municipality in the Netherlands. The city, also called Mokum in Amsterdam (from Yiddish), is located in the province of North Holland, on the IJ, the North Sea Canal and the estuary of the Amstel river.
The municipality of Amsterdam has 853,312 inhabitants (30 April 2017, source: CBS). Greater Amsterdam had 1,353,972 inhabitants. The number of different nationalities in the municipality is among the highest in the world..
Amsterdam owes its name to its location near a dam in the Amstel river, built in the 13th century. The place received city rights shortly after 1300, became a place of pilgrimage in 1345 by the Miracle of Amsterdam and grew in the Golden Age to one of the most important port and trading cities in the world. An influx of foreigners, especially from the Southern Netherlands, Germany and the Scandinavian countries, led to urban expansion from the end of the 16th century onwards, including the last canals of the fortification, which is now known as a ring of canals and was added to the UNESCO World Heritage List in 2010.
Road salt is also a widely accepted defrosting agent in Amsterdam. It lowers the freezing point of water. The salt (almost always sodium chloride, NaCl, sometimes calcium chloride, CaCl2) mixes with the water present (ice or snow) to form brine. Because brine has a lower freezing point than water, it will freeze less quickly so that less slipperiness occurs. After sprinkling salt, there must be sufficient traffic to get a good mixture. Brine is a mixture of water and salt. When a substance is dissolved in water, the freezing point of the solution drops. For example, if water contains 1 molal of sodium chloride, the freezing point will be lowered by about 1.86°C. The freezing point reduction can be calculated using cryoscopic constant. At lower and lower temperatures sodium chloride becomes less effective. To still melt ice, calcium chloride can be used, which is however much more expensive.
Wet salt in Amsterdam
Nowadays wet salt is mostly used. In that case, the spreading machine is equipped with liquid tanks (usually on the side), in which pre-mixed brine is stored. The dry salt is mixed with brine before it is released, where the salt grains clump together. The advantage of this is that the mixture is more homogeneous than dry salt, allowing it to be scattered much more accurately. In addition, much less dust is created behind the spreader. It is therefore possible for the spreader to drive faster, up to 70 km/h (against a maximum of 40 km/h with dry salt spreading). Wet salt also adheres better to the road surface due to crystallization and because wet salt blows less quickly, it is also suitable for preventive spreading.
Effects of brine in Amsterdam
Spreading salt is not without risk. For example, car bodies need to be well protected against oxidation because brine reacts strongly with metals.
Another influence is the salinization of the soil next to the road, which affects the flora's environment. For example, salt-loving plants, such as English grass, can be found along many roads, far from the coasts where they are normally found.
However, due to increasingly sophisticated equipment and new techniques, such as wet salt spreading, the accuracy with which the salt is brought onto the road has been greatly increased in recent years, which has resulted in a lower environmental impact. Not only is the dosage used a lot lower than before (often only 10 g/m2 is spread), also much less is spread on the verge.