During spring 1994, vegetation damage, of a remarkable and previously unknown extent, was observed along many heavily used roads in southern Sweden. The purpose of the present investigation was to determine the cause of vegetation damage along the Highways E20 and 48 by means of a damage survey and measurement of sodium and chloride concentrations in pine and spruce needles, ground water and soil. At the same time, changes in salt concentration in ground water and soil in two previously studied areas close to the E20 were documented. The extensive damage to vegetation can probably be attributed to three interacting factors: the large amount of de-icing salt applied during winter 1993/94, the lateness of the last salting and the hot, dry weather during the budding season. This conclusion is supported by the damage observations and the very high sodium and chloride concentrations in pine and spruce needles along the roads. In extreme cases, the sodium concentration was >1,000 ppm (dry wt.) in current-year needles and >5,000 ppm in needles from the previous year. The concentrations decreased rapidly with increasing distance from the road and similarly, the needles in branches turned towards the road had higher salt concentrations than needles in branches in other directions. The ground water and soil from an area along the E20 showed greatly increased sodium and chloride concentrations, especially next to the road, compared with previously measurements. The increased concentration can only be explained by the increase in road salting. (A)
Abstract