Research Explores Impact of Road Salt

The leafless trees in our area signal the return of winter and its entire splendor — festive decorations, tempting treats and snowmen … but also snow shovels and bags of salt. How much of an impact will the way this winter’s icy roads are cleared have on your post-holiday diet? More than you would like to imagine.

“When someone is trying to control their diet and sodium intake, they never would have thought about salt in their water,” said Dr. Jonathan Husch, professor and chair of Rider’s Department of Geological, Environmental, and Marine Sciences (GEMS).

Yet, several studies from the GEMS department have found that high levels of sodium are retained in our watersheds due to the application of sodium chloride (NaCl) or road deicing salt. In fact, Dr. Hongbing Sun, lead researcher of the studies and a professor of Geological and Environmental Sciences, said sodium concentrations has exceeded the 20 mg/1 level recommended by the United States Environmental Protection Agency and the American Heart Association in the downstream of Delaware River for many years, and he expects that number to increase.

For more than 10 years, Sun, a GEMS faculty member, has led teams of student researchers to examine the impact of sodium from road deicing salt in the Delaware River Basin (DRB). Recently, Sun, Husch and alumni Kelli Lucarino ’07 and Maria Huffine ’10 co-authored and presented the paper “Retention of sodium in a watershed due to the application of winter deicing salt” (2010) for the 10th International Symposium on Stochastic Hydraulics and 5th International Conference on Water Resources and Environmental Research in Quebec, Canada.

In the paper, they describe how they used sodium and chloride concentration data in the Delaware River collected by the United States Geological Survey, as well as  the amount of salt applied within the DRB from 1981 to 2008, according to records provided by the New Jersey, New York and Pennsylvania Departments of Transportation. They also collected water samples from surface runoff water along Interstate 95 and on Rider’s Lawrenceville campus before conducting experiments with an artificial watershed in a laboratory setting in order to measure sodium input and output, and to quantify sodium retention.

Overall, the group found that the annual average sodium concentration in the Delaware River increased 2.8 times from 1944 to 2007. Chloride concentrations increased more than 5 times, according to the United States Geological Survey.

While they noted a number of sources of sodium, including precipitation, agricultural areas and chemical weathering of rocks, they determined that the primary source is the sodium chloride distributed in the Delaware River Basin from salt trucks. They also found that concentrations of sodium and chloride are highest from the end of January to March when snow and ice are removed from local roads. Sun, Huffine and Husch also recently submitted another paper about the topic to the scientific journal, Water Resources Research.

According to the Delaware River Basin Commission, about 750 water companies get their water supply from the Delaware River Basin. The Delaware River Basin supplies water to more than 15 million people for drinking, agriculture and industrial use. Since sodium levels are expected to increase, it’s becoming a greater concern for water supply companies because of the health threat to people. While these levels will alter the results of crash diets, there are greater implications for individuals with diabetes and heart problems, who are more at risk for complications due to high sodium levels.

The process for filtering water with high salt concentrations is expensive, Husch said.

“This cannot go on indefinitely. It’s not sustainable,” Husch said. “The state and its counties need to limit the use of sodium chloride. There are other chemicals out there that can be used to melt ice.”

For example, Rider uses the salt alternative, calcium chloride (CaCl2), to remove ice from its parking lots, roads and walkways. Calcium chloride is an ecologically friendly salt, but it is more expensive than sodium chloride.

Currently, Leeann Sinpatanasakul, a senior Environmental Sciences and Political Science dual major; Nicholas Mazza, a junior Geosciences major; and Jessica Horton, a junior Marine Sciences major, are examining how the two different salts, NaCl and CaCl2, are mixing and storing in the artificial watershed in Sun’s lab in order to allow a better understanding of how the two products interact in a large, natural watershed, such as the Delaware River Basin.

“Our understanding of the interaction between salt and water will have implications to environmental policies not only in the Delaware River Basin but also in other basins of north eastern states, including Rhode Island where salt problems have been much worse,” Sun said.