Salt in Haarlem

Haarlem is a city and municipality in the Netherlands and the capital of the province of North Holland. The city lies on the river Spaarne and in the Kennemerland region.

Haarlem is one of the medium-sized cities in the Randstad. To the municipality of Haarlem belong the city of Haarlem and the western part of the village Spaarndam. The municipality has 159,340 inhabitants[1] and is after Amsterdam the second largest city of North Holland and the twelfth municipality of the Netherlands. The metropolitan agglomeration of Haarlem (Haarlem, Heemstede and Bloemendaal) has about 200,000 inhabitants[2] and the urban region of Haarlem (Zuid-Kennemerland and IJmond) more than 400,000 inhabitants[3].

Haarlem is mentioned for the first time in a document from the 10th century. In 1245 it received city rights from William II of Holland. By the end of the Middle Ages, Haarlem had become one of the most important cities of Holland. In the early modern period, the city developed industrially as a textile city and culturally as a painter's city.

Sprinkle salt is also a generally accepted de-icing agent in Haarlem. 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 Haarlem
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 Haarlem
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.