Effects of Road-salt on Vegetation
Through the primary focus of this project is on the interaction between road salt and the surrounding aquatic ecosystem, the effects of road salt exposure on vegetation surrounding the road as well as the riparian areas around the aquifer in question play an important role in the health of the habitat as a whole. Thus it is important to better understand the interaction between salt mixtures and vegetation in order to better prepare and maintain areas where deicing is necessary.
Indirect dangers through soil alteration:
Excessive salt exposure can take a toll on local plant life in several ways, foremost, in its interaction with soil. When salt filters through soil, especially in the high quantities often associated with de-icing, a portion of the sodium ions held within the mixture are held in the soil through ionic attraction. When these sodium ions bond with the soil, they replace existing phosphorus and potassium. This increases the soil density as well as its susceptibility to compaction which in turn lead to poorer drainage and aeration, both of which are vital for sustaining healthy plant growth. The presence of excess calcium and chloride, such as that found in common salts and mixes, can further hamper local vegetation by increasing the mobilization of heavy metals contained within the soil which deter plant development.
The overabundance of sodium and calcium in the soil surrounding a plant can also affect that plant's mineral nutrition. In areas of excessive salinity, plants will often absorb the introduced ions in the place of the phosphorus and potassium that they replaced, this can lead to a severe potassium and phosphorus deficiency which in turn further stunts the plant's growth.
Direct dangers posed by high salt exposure:
Salt ions trapped within the root zone of a plant bond tightly with surrounding water, this makes it difficult for the roots to absorb the bonded water and, in areas of significant salinity contamination, can lead to an artificial drought.
While sodium ions are too large to be effectively absorbed by the root ball, chlorine ions surrounding the roots are often taken in by the plant alongside required minerals. Because plants do not have a way of excreting chloride other than through the loss of leaves or needles, the amount of chlorine imbibed by vegetation can quickly pass the critical threshold for damage to occur. For this reason, solutions with a high chloride concentration, such as dissolved road salt, often lead to overexposure in the surrounding vegetation. This overexposure in turn causes leaf burn, loss, and the death or "die back" of twigs.
Similarly, salt and chlorine applied directly to a plants leaf can eat away at the cell structure of the leaf, effectively burning it. This is commonly seen within 15 feet of a de-iced roadway where dissolved road salt has been splashed onto bordering vegetation by the passage of vehicles. This danger can be mitigated through vegetative structuring, or planting vegetation around roads in such a way that plants with a greater salt tolerance such as white poplar are placed nearer to the road and thus able to protect less tolerant local species.
*Sources*
https://plant-pest-advisory.rutgers.edu/impact-of-road-salt-on-adjacent-vegetation/