by Murray Carpenter
Some say the Romans used to salt their enemies' fields. These days, we salt our own. In 1999 more than 16.5 million tons of rock salt was used to de-ice roads in the United States.
Two salt detectives, University of Maine professors Steve Norton and Steve Kahl, are often called upon to determine whether
a Mainer's tainted well has been contaminated by intruding seawater or by road salt. The pair had studied a single salt stockpile
that had contaminated more than 15 wells. Norton says that improved salt storage and application have lessened the problems, but
that when salt gets into groundwater it may linger for decades. "When you pile up road salt," he says, "you can sure trash a groundwater source."
"Salt burn" on roadside vegetation is the most visible effect of road salting, and plants suffer to varying degrees.
Sugar maples and black walnuts, for example, are more sensitive than white ashes and jack pines. Furthermore, salt-induced chemical
changes alter nutrient balances in soil and water, making some roadside wetlands more vulnerable to invasive plants.
Canada uses more than 5 million tons of road salt annually, and so Environment Canada, that country's equivalent of the U.S. Environmental Protection Agency,
recently proposed that the substance be designated "toxic" under the Canadian Environment Protection Act. The agency noted that some birds are poisoned directly
by salt. Others, including crossbills, grosbeaks, and siskins, are known in some areas as "grill birds" because they get it by cars when eating roadside snow laden with salt. Bigger
creatures are not immune either; road salt attracts bighorn sheep, elk, and moose to roads, where they risk being hit. Environment Canada is
advocating better road-salt management and more consideration of alternatives.
One option is using calcium magnesium acetate (CMA), which is less corrosive than road salt and does not harm
wildlife, although it costs 20 times as much. Another option is pre-storm applications of relatively benign anti-icing
agents, such as CMA or calcium chloride. Still, this winter, as paved areas continue to grow, it looks as if more salt than ever
will be spread on North American roads.
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