Tim Vernimmen: Our Freshwater is Getting Saltier

Scientific American:

Salts that de-ice roads, parking lots and sidewalks keep people safe in winter. But new research shows they are contributing to a sharp and widely rising problem across the U.S. At least a third of the rivers and streams in the country have gotten saltier in the past 25 years. And by 2100, more than half of them may contain at least 50 percent more salt than they used to. Increasing salinity will not just affect freshwater plants and animals but human lives as well—notably, by affecting drinking water.

Sujay Kaushal, a biogeochemist at the University of Maryland, College Park, recounts an experience he had when visiting relatives in New Jersey. When getting a drink from the tap, “I saw a white film on the glass.” After trying to scrub it off, he found, “it turned out to be a thin layer of salt crusting the glass.”

Greg Breining: Road Salt's Problems and Solutions

ENSIA:

A recent study of 371 lakes in North America — most in the northern states and southern Canada — showed chloride concentrations rising in more than a third. More than two dozen were nudging toward levels harmful to aquatic life. Extrapolated to all lakes in the U.S. northern Great Lakes and Northeast regions, about “7,770 lakes may be experiencing elevated chloride concentrations, likely due to road salt runoff,” the study concludes.

U.S. road maintenance departments have been spreading salt on streets and highways to melt snow and ice since the 1940s, but the use of salt skyrocketed over time — from 0.15 metric tons (0.16 tons) per year during the 1940s to about 18 million metric tons (19.8 million tons) per year today. Road salt use is common and growing throughout Canada, Europe, Japan, China and even South America. As much as 60 million metric tons (66 million tons) may be applied worldwide each year. Unlike chemicals that break down into less harmful compounds, road salt persists and may remain in water and soil for years, until it eventually is diluted and carried away by moving water...

...the biggest single change to use less salt is switching to liquid solutions. The brine spreads more evenly, stays put and begins working immediately because the salt is already in solution. As a result, spraying liquid brine is more effective while using less salt.

Scott Johnson: Lakes Soaking up Road Salt

Ars Technica:

Road salt became common in the 1940s, and the amount used has increased over time. The US puts down around 18 million tons of salt each year. Roadsides along highways obviously get dosed with more than their fair share of salt, but salt also runs off (sometimes via storm drains) into streams and lakes where it can accumulate. That makes road salt a common target in local efforts to protect bodies of water. Although this has sometimes been studied on the local scale, there hasn’t been much big-picture analysis. A new study led by the University of Wisconsin-Madison’s Hilary Dugan works to fill in that gap by estimating how widespread salt contamination is in North America.

The researchers used data from 371 lakes that covered at least four hectares and had chloride measurements going back at least 10 years. That’s not a purely random sampling, but it’s the best way to find trends. Most are in the US Midwest and Northeast, with a handful from southern Canada and some spread over the rest of the US. One-third of the 371 lakes showed a significant upward trend in salt concentration.

Matt Sepic: Too Much Salt Reaches Lakes

MPR:

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A recent study found three dozen bodies of water with chloride levels that exceed state standards. Too much salt can harm fish and encourage invasive plants.

The MPCA’s Brian Livingston, who supervises the metro watershed district, said there are ways to reduce salt use without compromising winter road safety. Such methods, he said, include “wetting the salt so it doesn’t bounce off the highways and actually gets applied directly onto the surface, and measuring more accurately the amount of salt that’s being applied, and not over-applying it.”

Road Salt and Urban Streams

National Science Foundation:

Paul Mayer, US EPA

Paul Mayer, US EPA

Urban landscapes are more complex than they seem, but from coast to coast may work in surprisingly similar ways, says Kaushal.

”Urban ecosystems can change relatively quickly in response to human activities,” he says. “These changes can result in rapid losses of ecosystem functions, like flood protection and pollution filtration—or can result in progress toward ecological health and productivity. The difference depends on how they are managed.”

In an overview article, Kaushal, McDowell and Wollheim point out the factors that affect the evolution of urban ecosystems. For example, the streams, lakes and land surfaces that make up cities’ watersheds show consistent patterns of change over time.

Urban waters are becoming saltier, partly due to road salt used for de-icing, and partly because the salt people eat ends up in urban streams.

You will find what you spread on the road and lawn. A cause and effect.

Road Salt Changes Urban Ecosystems

Jason G. Goldman, reporting for Conservation This Week:

Pahz

Pahz

In the urban parts of Minneapolis and St. Paul, Minnesota, around three hundred thousand tons of salt are dumped onto roads each winter. That’s because sodium chloride lowers the freezing point of water, making the formation of ice on the surface of roadways less likely. It keeps drivers safer, since car tires can hold onto imperfect road surfaces better than they can grip slippery, wet ice.

But dumping all that salt into the ecosystem doesn’t just keep drivers safer. It also changes the chemical composition of the soil near roadways, and that added sodium chloride finds its way into plants, into bodies of water, and into animals. And all that added salt could shift the dynamics of natural selection and the animals’ fitness, altering the course of evolution. That’s how natural selection works – it’s neither good or bad – but it’s worth at least being aware of the sometimes nuanced effects that human behavior have on natural ecosystems.

Mudhole? Slimy? Salty? My home this is!