September 8, 2005 4:24 PM PDT
Road salting makes streams more like seawater
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Technology may quench thirst for drinking waterSeptember 2, 2005
After reviewing several years of data on the chemistry of freshwater supplies in three separate regions, University of North Carolina geology professor Lawrence Band and a group of colleagues found that road salting, combined with suburban sprawl, is causing the salinity in streams, lakes and wells in the studied regions to increase.
Many streams in the three regions studied--Baltimore County, Md., the Hudson River Valley in New York and the White Mountains of New Hampshire--contained around 25 percent of the chloride content of seawater. (Chloride is an electrolyte. When combined with sodium it is mostly found in nature as salt.)
"That's like an estuary," Band said Thursday. "That's a pretty dramatic change in the ecology of the system."
The chloride content in some streams in summertime was nearly 100 times greater than in those where road salt runoff was not a factor. Streams entering the Baltimore drinking water reservoir and creeks and rivers of the Hudson River Valley also have shown significant increases in chloride over the past few decades.
If no changes are taken, some communities may end up with water supplies that are undrinkable during this century, Band said.
The increased salinity is due to many factors, he said. Spreading salt rather than sand, of course, brings the material to the ecosystem. Impervious road surfaces ensure that salt runs off with snow or ice into storm drains or seeps into the ground. Either way, the chloride gets into the freshwater system.
The biggest culprit of all, however, is road building associated with sprawl. Baltimore has experienced the most rapid suburban growth of the three, and the salinity of the fresh water kicks up accordingly.
"It depends entirely on the rate of suburbanization," Band said.
The data for water quality goes back several years. Band monitored water chemistry in the Baltimore area for seven years and supplemented his findings with data from local water quality districts.
The actual impact of increased salinity, however, is difficult to gauge. Several environmental factors come into play with suburbanization. Clearing land for roads increases runoff, for instance. Band hopes to do future studies on the changes to other drinking water supplies.
Can anything be done? Replacing salt with sand can reduce the salt content. Deploying water filters, rather than chemical water softeners, could also help, he said. Oddly, global warming could have a beneficial effect by reducing snow and ice, although the phenomenon has other negative side effects, according to many.
Water quality also has become a focus for a few start-ups and venture capitalists in the clean technology space. Michigan's Sensicore, for instance, has developed a handheld device called the WaterPoint that can test for inorganic impurities, such as ammonia, and test water quality in four minutes, according to the director of marketing, Uwe Michalak. Conventional equipment takes about an hour.
The company recently announced that it has received $12 million in third-round funding, has been testing its products with water utilities, and hopes to release its first products in November.
Researchers at the University of California, meanwhile, have crafted a an inexpensive tube for killing germs and biological pathogens in drinking water. It is designed for communities in developing nations.
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