“Eco-friendly” road deicers may not be so friendly: assessing the toxicity of beet-juice brine and potassium chloride to <i>Daphnia pulicaria</i>

There is increasing concern over rising salinity in freshwater ecosystems, which is often associated with deicing salt usage in temperate regions that experience cold winters. Negative impacts of deicing salts on the environment include changes to aquatic community composition and loss of biodiversity. Consequently, many municipalities are increasing their usage of alternative deicers that are reported to be "eco-friendly" and require lower application rates. One example of an organic alternative is a beet juice and salt brine mixture that contains degraded beet sugar and chloride salts. There is limited research on the effects of these products on aquatic organisms, including zooplankton, which are critical components of freshwater food webs. To address this knowledge gap, we compared the acute toxicities of a beet-brine product (Fusion 2330) with potassium chloride (KCl, >99% pure) and sodium chloride (NaCl, >99% pure), which are components of beet-juice brine, to a single iso-female line of Daphnia pulicaria using 48-hr median lethal concentration (LC50) toxicity tests. We found that Daphnia pulicaria was more tolerant to NaCl and KCl than beet-juice brine with 48-hr LC50 values of 1,812 mg Cl-/L, 254 mg Cl-/L, and 82 mg Cl-/L, respectively. Considering toxicity related to K+, we determined 48-hr LC50 values of 276.7 mg K+/L and 10.3 mg K+/L for KCl and beet-juice brine, respectively. We also found that dissolved oxygen concentration decreased with increasing concentration of the beet-juice brine product, which may contribute to the negative impact of beet-juice brine application. These results suggest that caution should be taken when using organic deicers, as beet-juice brine is more toxic to D. pulicaria than the commonly used rock salt (NaCl).