Saltpåverkan på vegetation, grundvatten och mark utmed E20 och Rv 48 i Skaraborgs län 1994 = The influence of de-icing salt on vegetation, ground water and soil along the highways E20 and 48 in Skaraborg county during 1994.

The extensive damage to vegetation that occured along the Highways E20 and 48 in Skaraborg County, Sweden, during 1994 can probably be attributed to three interacting factors: the large amount of deicing 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 chloride concentration in needles from both years was >8,000 ppm. Brown needles from the previous year taken from a dying pine tree contained 1,7% sodium and 2,0% chloride. The concentrations decreased rapidly with increasing distance from the road. The needles had higher salt concentrations in branches turned towards the road than in branches in other directions. Needles from a tall pine tree and a tall spruce tree had higher salt concentrations in their lower branches than in their upper branches. The damage (affecting coniferous and deciduous trees as well as bushes) manifested itself as sparse foliage, bare or dead branches and shoots, lack of budding and (in pines) red-brown needles from the previous year. The damage decreased with increasing distance from the road. Exposure was of major significance for the salt concentration and the extent of the damage. Extensive road salt during winter 1992/93 may have contributed to the vegetation damage in 1994. The groundwater and soil (down to 165 cm) from an area along the E20 showed greatly increased sodium and chloride concentrations, especially next to the road, compared with 1978, 1979 and 1988. The concentrations decreased rapidly with increasing distance. The increased concentration can only be explained by the heavy increase in road salting. In another area, the concentrations were lower, but still on the high levels measured earlier. Both areas have unfavourable hydrogeological conditions, with permeable surface soil layers, high groundwater level and poor rate of water renewal (flat terrain). (A) This report has also been published in English as VTI Meddelande 775A: The influence of de-icing salt on vegetation, ground water and soil along the highways E20 and 48 in Skaraborg county during 1994 (see C 8057 S).