The uptake of salts by the roots of roadside trees is a common problem wherever sodium chloride, calcium chloride, and magnesium chloride are applied to de-ice highways in the winter or for dust abatement in the summer. Most of the time symptoms are insignificant and limited to tip burn, where the bases of the needles remain green and trees recover. However, a surprising amount of mortality may occur when magnesium chloride or calcium chloride is applied for dust abatement during or shortly before heavy rainstorms. Salts are leached off the road in heavy rains and travel into drainages where subsequent tree damage and mortality take place.

References:  6, 82, 92