Inwinter, we often use large amounts of salt to remove dangerous ice from roads -组卷网

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In winter, we often use large amounts of salt to remove dangerous ice from roads and walkways. But when the spring arrives, all that salt can really damage plants along the way. Salt is the chemical sodium chloride.

Salt pulls water from living cells, like plant roots and the healthy ground soil around them. So, spring growth may show up lighter in color than normal, or, in the worst cases, plants may simply die. Rain can wash away much of the salt, permitting some older plants to live. But overusing it unavoidably brings great damage to plants.

There are, of course, other things that can be used in place of sodium chloride. One is the chemical calcium chloride, which does less damage to plants. Calcium chloride can quickly change the melting (融化) point of ice and absorb water, making a much quicker acting agent. It also works when the temperature is below negative 17 degrees Celsius. Salt only keeps its effectiveness at temperatures above negative 12 degrees Celsius. Yet, it’s more expensive and can do more damage to cars.

Calcium magnesium acetate, also called CMA, is a more popular alternative than salt and calcium chloride. It is made by combining limestone, a type of rock, and vinegar. It breaks down naturally so it does not damage plants or soil. It stays on roads and does not hurt cars. CMA does have problems, however. It is most effective at around negative 9 degrees Celsius. And it is better at stopping ice from forming rather than removing it.

Some materials-such as sand or very small pieces of wood-can also work against ice. They might be very messy, but in the interests of plants grown in the ground near a road or where a car is parked, all of them could be a better choice than salt.

【小题1】What advantage does calcium chloride have over salt?