The Relative Toxicity of Road Salt Alternatives to Freshwater Mussels; Examining the Potential Risk of Eco-Friendly De-icing Products to Sensitive Aquatic Species

The negative impact of road salt on freshwater ecosystems has led to an interest in eco-friendly de-icing products. Biota, including freshwater mussels that have heightened salt sensitivity, would be expected to benefit from a transition to alternative de-icing products. However, it was unknown whether the alternatives themselves pose a risk. The toxicity of three road salt alternatives including a salt brine, a beet juice, and a brine-beet juice product were examined. Lampsilis fasciola glochidia (larvae) were exposed to dilutions (0-2%) of de-icing products. On a per volume basis, beet juice products were significantly more toxic than brine with 48 h EC50s (95% confidence intervals) as follows: brine, 0.42% (0.35-0.50%); beet juice, 0.020% (0.018-0.022%); and brine-beet juice, 0.034% (0.028-0.039%). Unlike brine, beet juice toxicity did not correspond with the concentration of chloride in the exposure. While elevated trace metals (Cu, Fe, Zn) and reduced water quality occurred in the 1% and 2% beet juice exposures, toxicity occurred at much lower dilutions (<= 0.05%). The toxicity of beet juice products aligned with glochidia potassium EC50s. Based on toxicity and application rates, beet juice deicing products pose more of a hazard to early life stage mussels than traditional products and could contribute substantial potassium to receiving environments.

Automated summary

The research found that on a per volume basis, beet juice products were significantly more toxic than brine, and the toxicity of beet juice did not correspond with chloride concentration. The toxicity of beet juice products aligned with glochidia potassium EC50s, indicating that beet juice deicing products could pose a greater hazard to early life stage mussels.