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s ~ Coriti~iued from page 1 found in Twin City lakes by document- ing seasonal trends that show chloride increasing in lakes during and after the snowplowing season. The researchers also found evidence that some of the salt applied each winter remains in lakes and produces chloride concentrations that have been increasing since road salt came into heavy use in the 1960s. The research, parts of which were published in November by the journal Science of tT1e Total Environment, will be presented Feb. 3 at the eighth annual Road Salt Symposium, sponsored by the Freshwater Society. The research team consisted of. Heinz Stefan, a civil engineering professor at the university's St. Anthony Falls Labo- ratory; Eric Novotny, a doctoral student; Andrew Sander; a master's degree stu- dent; Omid Mohseni, a former research fellow who now works for Barr Engi- neering Co.; and Dan Murphy, who now works for HDR Engineering Inc. Key Findings of their work are: About three-fourths of the chloride in the road salt applied each winter in the Twin Cities remains in the soil, lakes; wetlands and ground water after spring arrives; the remainder is flushed down the Mississippi River to the Guif of Mexico. Chloride concentrations in many metro lakes are 10 to 25 times higher than in similar lakes throughout Minne- sota each autumn, when chloride levels are at their lowest. Chloride concentra- tions in the urban lakes increase in the winter and after the spring snow melt, evidence that road salt is causing the chloride contamination. Chloride levels measured in the bottom layers of some urban lakes in the winter and spring of 2005 and 2008 exceeded state water-quality standards. Chloride concentrations in 38 Twin Cities lakes from which water regularly has been tested over 20 years have been steadily increasing-by an average of 1.7 percent per year. Novotny and Ste- fan found a strong correlation between the rate at which chloride has increased in those lakes and the increase in annual road salt purchases in Minnesota over the last 20 years. "The overall. conclusion has to be that some deterioration of the water quality of Twin Cities metro area lakes due to increasing chloride levels is in progress," states the one-paragraph conclusion of the paper summarizing the recent research. "No acute problems have been documented yet, but present trends will lead to violations of water quality standards in some urban lakes. Similarly, shallow ground water in the Twin Cities metro area appears to receive sufficient salt input annually so that water quality deterioration is likely to be evident in the next decade." In an interview, Stefan said the research. did not attempt to explore the environmental damage caused by chlo- ride. Nor did the research find fi•equent or widespread instances of chloride concentrations that exceed water-quality standards. What the research did vas demonstrate that chloride concentra- tions in some Twin Cities lakes exceed those standards some of the time and that chloride concentrations in urban lakes have been steadily increasing. x "Fortunately, we don't have to turn on the red light and say ,~. _ 'This is a catastrophe ~ ~., "'_, right here and now,"' ~ ~_ „=;, Stefan said. "But ~ -^; things are moving in the wrong direction. Chloride and sodium are accumulating ' - s in our urban water resources. It is the ` rates of change that ~ we find alarming." The studies conducted by the '. University of Min- ;~"~"~`~~~~~~~ ~~~ nesota team focused mostly on surface Road salt potlutes... Continues or7 page 4 Rock salt used as a road de-icer is mostly sodium chloride. It works by significantly lower- ing the freezing point of water. U.S. consumption of road salt has increased from about 163,000 tons in 1940 to more than 23 million tons in 2005. The State of Minnesota, which purchases salt for the state Department of Transportation and for many cities and counties, bought 500,926 tons last year. Most of the road salt applied in Minnesota is mined in Louisiana and shipped up the Missis- sippi River by barge. A number of studies have blamed road salt for concentrations of chloride in water that hinder plant and invertebrate growth. Canada's environment and health agency conducted a comprehensive review of those studies and con- cluded in 2001 that road salts "have or may have an immediate or long-term harmful effect on the environment or its biological diversity...or may constitute a danger to the environment on which life depends." + In Minnesota, seven streams or rivers are on the state's 2008 list of "impaired waters" because of high chloride levels. So far, no lakes have been formally identified as contaminated by chloride. .f` k r ~,. Heinz Stefan, a civil engineering professor at the University's St. Anthony Falls Laboratory FACETS December 2008 `• r~ ,::~ . ~,; ~ ,