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Over the past decades, the growth of our societies has induced a traffic increase, both on roads and airports, with an extension of the existing infrastructures and an easier access to vehicles (SETRA, 2011). Along with these structural changes, citizen expectations has become greater. For instance, the wish of an “always open road” is now widely installed in the western countries, and traffic disruptions are poorly accepted by road users. As a result, in winter time, infrastructure managers have to cope with economic, political and media pressures. In order to avoid traffic disruption during winter, roads are therefore the subject of a specific maintenance based on the application of de-icing products (Transportation association of Canada, 2003) in solid or liquid (brine) form. On the whole, between 800.000 and 2 million tons of road deicers (mainly sodium chloride) are applied each year over the French road network.
Previous studies have shown that large quantities of de-icing products spread on roads are transferred to the roadside surrounding environment (splashed out by the vehicles or blown away by the wind) (Hunt, Mitchell, & Richardson, 2004; Thunqvist, 2002). In order to lower road water losses, retention ponds are constructed at road vicinity to collect road water flows and diminish the seasonal, chronic and accidental road pollutions. Even though deicers are considered to be a seasonal pollution, nowadays it is not known at which extent these retention ponds collect the de-icing products. Furthermore, these systems do not treat road deicers, thereby eventually rejecting into the environment a part of road deicers that entered in the retention pond. The road deicers can thus end up in the surrounding environment either directly or by passage through the ponds used for road water runoff remediation and flow control (Kimura, Namikawa, Sone, & Kuwabara, 2006; Thunqvist, 2002).
Deicer input sources in the environment are numerous. Some studies led by the CÉTÉ de l'Est estimated that for a storage area of a conventional size (300 – 400 tons) 5 to 8% of the total deicer stored in an open-air area can be lost by dissolution under a pluviometry of 750mm/year. Furthermore, during the transfers from the deicer stock to the spreaders, 50 to 100 kg/spreader are lost (SETRA, 2011). However, the same study showed that the main sources of deicer rejection are not the storage areas, but the roads.
De-icing products used for road winter maintenance are considered to be a seasonal pollution and their impacts have become a real issue (Blomqvist, 2002; Gustafsson, & Blomqvist, 2004). Indeed, numerous studies have shown that they have adverse effects on groundwater, surface water, soils and biodiversity (Ramakrishna, & Viraraghavan, 2005; Trahan, & Peterson, 2007; Lundmark, 2005; Robidoux, & Delisle, 2001; Hendricks, & Paul, 1981). For instance, Dobson (1991) showed that, in Western Europe, over 700 000 trees die each year because of the usage of de-icing products. In addition, studies on aquatic organisms have shown that de-icing products may affect the balance between the present species. This was observed in the lake of Luitel (France) where chloride concentration significantly increased between 1955 and 1999 (passing from 3.7 to 49 mg/L). As a result, over 50% of alga species extincted and new species, normally developing only in salty waters, appeared (Desplanque, 2007). Moreover, it was shown that these products increase the mobility of trace elements (Norrström, 2005).