Effects of Road Distance and Protective Measures on Deicing NaCI Deposition and Soil Solution Chemistry in Planted Median Strips
Lars Bo Pedersen, Thomas B. Randrup, and Morten Ingerslev
Abstract: The deposition pattern of deicing salt and the resulting concentrations in the soil water were determined in planted median strips of two major approach roads with speed restrictions of 70 kmh (43.5 mph) in Copenhagen, Denmark. The objectives were to evaluate the effect of distance from the roadside and to test different straw mat protective measures. Deposition and soil water concentrations of sodium chloride (NaCI) decreased significantly within 2 m (6.6 ft) from the roadside compared to areas farther away. Straw mats mounted like a skirt around the tree stem did not constitute a proper protection against salt spray or splash and high salt concentrations in the soil water. In contrast, protection with straw mats on all sides of the trees resulted in a small but measurable effect. The highest concentrations of NaCI in the soil water were seen during the winter. However, there was a strong tendency of elevated concentrations persisting throughout the subsequent summer, which suggests that serious salt stress exists on the trees during the growing season. We concluded that planting at a distance of more than 2 m from the roadside is more effective than using straw mats in reducing the undesirable effects of salt spray deposition on trees as well as the salt concentration in the soil water.
Keywords: Road salt; deicing salt; salt stress; median strips; protective measures; roadside distance; soil water; deposition.