Sodium accumulation in calcareous roadside soils: Fid-Bau Portal

Sodium accumulation in calcareous roadside soils

Eimers, M. Catherine / Croucher, Kelli-Nicole / Raney, Shanel M. / Morris, Melinda L.

Abstract Sodium chloride (roadsalt) is routinely applied to roadways during the winter in many parts of the world to reduce ice formation and improve winter driving conditions. While increases in chloride ($ Cl^{−} $) levels in waterways influenced by roads and $ Cl^{−} $ impacts on roadside vegetation have been widely reported, there has been relatively little research on the fate of sodium ($ Na^{+} $) and its impact on soils. Soils in the most heavily populated area of southern Ontario, Canada, are typically rich in calcium ($ Ca^{2+} $) and we predicted that high native $ Ca^{2+} $ levels in this region would limit $ Na^{+} $ accumulation in roadside soils. In order to investigate the extent of $ Na^{+} $ accumulation in calcareous soils, we compared soil $ Na^{+} $ levels adjacent to roads of three different classes but having the same parent material, including a Freeway, three High Capacity Arterial roads and three Low Capacity Collector roads, as road salt loadings are highly dependent on traffic volume. Soil $ Na^{+} $ levels were significantly higher adjacent to the two-lane (mean 0.22–0.50 meq/100 g) compared with the single-lane minor roads (0.013–0.10 meq/100 g), and exchangeable soil $ Na^{+} $ was negatively correlated with $ Ca^{2+} $, $ Mg^{2+} $ and $ K^{+} $, suggesting that not only does $ Na^{+} $ accumulate in calcareous soils, but it also displaces all three nutrient base cations. Nevertheless, relatively low soil $ Na^{+} $ levels adjacent to the Low Capacity Collector roads, which are similar to levels reported for control soils in other studies, suggest that high base saturation in these soils may limit $ Na^{+} $ accumulation, and that road salt application rates at the minor roads are not high enough to cause $ Na^{+} $ accumulation.