Is a Road Stormwater Retention Pond Able to Intercept Deicing Salt?

The amount of deicing salt spread on the road during cold periods increased since the 1940s even though its impact on water quality is well-known. In France, an average of 0.75 tons of salt per kilometre is spread during a winter in order to ensure the users security. The salt is carried by runoff from the road to a retention pond. One of the role of these ponds is to reduce road pollution before runoff joins the environment. The efficiency of the Azerailles retention pond collecting road runoff was assessed regarding NaCl retention. Indeed, an increase in Mg 2+ , K + , Ca 2+ , and SO 4 2 − concentrations correlated to an increase in Cl − and Na + concentrations was observed. These observations were directly linked to the presence of deicing salt on the roadway. Forty-eight percent of the spread salt was collected by the retention pond during the winter maintenance period from December 2016 to April 2017. The high intensity of rainfall during this period had a strong influence on the amount of salt leached from the pond. Almost all of the deicing salt entering the basin was evacuated at the end of March (91%). The sediment analysis showed that sodium from the road flux was not retained in the sediment neither during nor after the salting period.