Abstract

Deicing salts applied to mountain roads during winter periods provide safe driving conditions but these salts are eventually displaced to roadside areas where they can negatively impact soils, vegetation and water resources. The aim of this study was to confirm the linkage between deicing salt applications and salt accumulation in plants and salt accumulation in soils as a function of distance from roads. We also wantedto determine whether altering the deicing salt composition would lead to a more favorable plant response. In the Mt. Charleston area of southern Nevada, NaCl was applied by the State Department of Transportation in excess of 200 tons per State Highway during the winter prior to this study. Salts sampled with depth and distance from the roads at 15 locations revealed significantly higher salinity levels (p < 0.05) at the 1 m vs. 5 and 10 m distances, with electrical conductivities as high as 37 dSm^-1. In Ponderosa pine, Na and Cl concentrations were found to be elevated in needles revealing visual damage, whereas K concentrations were found to be significantly lower in damaged tissue (p < 0.05), resulting in Na/K ratios as high as 300 to 1. In a companion study we investigated the physiological response of 2 year old seedlings of aspen, Gambel oak and Woods’ rose, to different salt loading rates comprised of different mixes of salts (MgSO₄, CaCl₂ or KCl) at different %NaCl composition (100, 90, 75 and 50%). As the MgSO₄ in the salt mix increased, sulfate concentration increased in the leaves of oak (r = 0.73, p < 0.001), reflecting the shift from Cl to SO₄ availability. The % SO₄ in the leaves of oak revealed a strong linear relationship (r = 0.83 p < 0.001) with leaf weight at final harvest, as well as higher chlorophyll (spad) measurements relative to control (r = 0.89 p < 0.01) and an earlier breaking of dormancy (r = 0.65, p < 0.01), as seedlings with 2.5% SO₄ in leaves at harvest broke dormancy 10 days sooner than those oak seedlings with only 1% SO₄ in the tissue. Based on results of this study , we believe a 25% substitution of MgSO₄ would be worthy of further field evaluations as a significant decline in leaf tissue Na andCl occurred at this level, while  concentrations of Ca and SO₄ increased.

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