What Happens to All the Salt We Dump On the Roads? In the U.S., road crews scatter about 137 pounds of salt per person annually to melt ice. Where does it go after that? By Joseph Stromberg smithsonianmag January 6, 2014 But all that salt has to go somewhere. After it dissolves—and is split into sodium and chloride ions—it gets carried away via runoff and deposited into both surface water (streams, lakes and rivers) and the groundwater under our feet. This chloride can occasionally impact human water use, mostly because some penetrates into the groundwater we tap for drinking purposes. Water utilities most frequently report complaints of salty drinking water during the winter, when chloride concentrations are likely to exceed 250 parts per million (ppm), our tastebuds threshold for detecting it. This is an especially big issue for people on salt restrictive diets. Overall, though, road salt-laced drinking water isnt a widespread problem: A 2009 USGS study found that fewer than 2 percent of the drinking wells sampled had chloride levels that surpassed federal standards. Road salt pollution is generally a bigger issue for the surrounding environment and the organisms that live in it. Its estimated that chloride concentrations above 800 ppm are harmful to most freshwater aquatic organisms—because these high levels interfere with how animals regulate the uptake of salt into their bodies—and for short periods after a snow melt, wetlands nearby highways can surpass these levels. A range of studies has found that chloride from road salt can negatively impact the survival rates of crustaceans, amphibians such as salamanders and frogs, fish, plants and other organisms. Theres even some evidence that it could hasten invasions of non-native plant species—in one marsh by the Massachusetts Turnpike, a study found that it aided the spread of salt-tolerant invasives. On a broader scale, elevated salt concentrations can reduce water circulation in lakes and ponds (because salt affects waters density), preventing oxygen from reaching bottom layers of water. It can also interfere with a body of waters natural chemistry, reducing the overall nutrient load. On a smaller scale, highly concentrated road salt can dehydrate and kill trees and plants growing next to roadways, creating desert conditions because the plants have so much more difficulty absorbing water. In some cases, dried salt crystals can attract deer and moose to busy roads, increasing their chance of becoming roadkill.
Posted on: Wed, 05 Mar 2014 12:54:22 +0000
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