Predicting steady state concentrations of chloride in groundwater and surface water.

Author(s)
Thunqvist, E.-L.
Year
Abstract

A road in operation with its traffic can pose a serious pollutant threat to groundwater and surface water in its vicinity. Examples of pollutants are salt for de-icing and dustbinding; metals from corrosion of vehicles and wear of road surface and tires; hydrocarbons from the wear of road surface, tires, exhaust, oils; and hazardous goods discharged in the case of an accident. In Sweden about 300000 tonnes of sodium chloride are used annually by the Swedish National Road Administration for de-icing purposes. In addition the local municipalities also use salt for de-icing purposes. The use of studs improve the friction but increase the wear and the grinding effect on winter roads. The wear of a wet surface is reported to be two to seven times the wear of a dry surface, and hence, the grinding effect may be further increased by the use of de-icing salt. The movement of pollutants from the road to the surrounding environment will involve runoff from roads, airborne spreading, infiltration from road construction and road area. The chloride ion is a good tracer. It is conservative and highly soluble and not subjected to retardation or degradation. A small part of the sodium may be retained in soil but almost all of the de-icing salt will be either infiltrated and found in groundwater or form runoff and be found in surface water. Other, nondegradable road-related substances may be retained in soil to a greater extent. Eventually, all pollutants from roads, which are not subjected to degradation, will be transported either to surface water or to groundwater. In this paper a method is presented by which the steady state concentration of chloride in groundwater and surface water due to the use of de-icing salts can be calculated. The calculations are based on digital data for catchment areas, net recharge (precipitation with the deduction of evapotranspiration), background deposition and road network with de-icing salt application rates. All data are processed and presented with the GIS-tool Arcview. The method makes its possible to scan an area, e.g. a country, in order to make the decisions on what areas to protect and which measures to adopt. The method can also be used to predict the steady state concentrations of other road related pollutants. (Author/publisher)

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Publication

Library number
C 23455 (In: C 23450 S) /15 /62 / ITRD E207783
Source

In: PIARC 2002 XIth International Winter Road Congress, 28-31 January 2002, Sapporo (Japan) : reprints from proceedings of oral presentations, VTI Särtryck No. 350, 8 p., 10 ref.

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