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If you live in a city that gets lots of snow and ice, then you're familiar with road salt. Your city and local government likely has several de-icing trucks that spread road salt on the highways, streets and sidewalks to melt the ice. But how exactly does it work? 如果你生活在一个冰雪多的城市，那么你对道路盐很熟悉。你所在的城市和当地政府可能有几辆除冰卡车，在高速公路、街道和人行道上撒盐融化冰。但它究竟是如何工作的呢? First, road salt is simply halite — rock salt — which is table salt in its natural form. The difference is table salt goes through a lengthy purification process, while rock salt does not. And because rock salt still has impurities, it's brown or gray in color. 首先，道路盐就是岩盐，也就是天然的食盐。不同之处在于食盐要经过漫长的提纯过程，而岩盐则不需要。因为岩盐仍然有杂质，所以它的颜色是棕色或灰色。 Why Salt? 为什么是盐?Ice forms when the temperature of water reaches 32 degrees Fahrenheit (0 degrees Celsius), and that includes ice on roadways. Road salt works by lowering the freezing point of water via a process called freezing point depression. The freezing point of the water is lowered once the salt is added, so it the salt makes it more difficult for water to freeze. A 10-percent salt solution freezes at 20 degrees Fahrenheit (-6 Celsius), and a 20-percent solution freezes at 2 degrees Fahrenheit (-16 Celsius). 当水的温度达到32华氏度(0摄氏度)时，冰就形成了，这包括道路上的冰。道路盐的工作原理是通过一个称为冰点降低的过程来降低水的冰点。一旦加入盐，水的冰点就会降低，所以盐会使水更难结冰。10%的盐溶液在20华氏度(-6摄氏度)结冰，20%的盐溶液在2华氏度(-16摄氏度)结冰。  The key is, there has to be at least a tiny bit of water on the road for freezing point depression to work. That's why you often see trucks pre-treat roads with a brine solution (a mixture of salt and water) when ice and snow is forecast. If the roads are dry and the DOT simply puts down road salt, it likely won't make much of a difference. But pre-treating with a brine solution can help ice from ever forming, and will help reduce the amount of road salt trucks will need to spread to de-ice later. 关键是，道路上至少要有一点点水，才能使冰点降低起作用。这就是为什么在预报有冰雪天气时，你经常看到卡车用盐水溶液(盐和水的混合物)预先处理道路。如果道路干燥，而交通部只是在道路上撒上盐，这可能不会有太大的区别。但是用盐水溶液进行预处理可以帮助防止结冰，并有助于减少道路上的盐卡车随后除冰所需的量。 Pros and Cons 利与弊Rock salt is one of the most widely used road de-icers, but it's not without critics. For one, rock salt does have its limits. If the temperature of the roadway is lower than about 15 degrees F (- 9 C), the salt won't have any effect on the ice. The solid salt simply can't get into the structure of the frozen water to start the dissolving process. In these cases, the DOT typically spreads sand on top of the ice to provide traction. 岩盐是使用最广泛的道路除冰剂之一，但它也不是没有批评者。首先，岩盐确实有它的局限性。如果路面温度低于15华氏度(- 9摄氏度)，盐对冰面没有任何影响。固体盐根本无法进入冻结水的结构，从而开始溶解过程。在这种情况下，交通部通常会在冰面上铺上沙子，以提供牵引力。  Rock salt also has major environmental issues, including the sodium and chlorine that leaches into the ground and water. And as we mentioned earlier, because rock salt isn't purified and contains contaminants — including lead, iron, aluminum and phosphorus — when it's spread, these are spread as well. However, rock salt still remains the most widely used and affordable de-icers available. And while there are other chemical de-icers, too, none are 100 percent risk free. 岩盐也有重大的环境问题，包括渗入地下和水中的钠和氯。正如我们之前提到的，因为岩盐没有经过净化，而且含有铅、铁、铝和磷等污染物，当它扩散时，这些污染物也会扩散。然而，岩盐仍然是使用最广泛、价格最便宜的除冰剂。虽然也有其他化学除冰剂，但没有一种是100%无风险的。 |
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