Some 'green' road salts release more toxic metal than plain salt
Samaraweera H, Hedberg YS, Power C
Soil Health
If you garden or forage near a road that gets winter deicer, the soil chemistry there is more complicated than 'salt bad, alternative good': one organic deicer studied here mobilized far more lead and cadmium than regular rock salt.
Road crews spread salt every winter to melt ice, and some of that salt washes into nearby soil. Scientists wanted to know whether newer, chloride-free 'organic' salts are actually gentler on soil than old-fashioned salts like table salt or calcium chloride. Surprisingly, one popular organic option, sodium acetate, turned out to release more toxic lead, cadmium, zinc, and copper into the soil water than the traditional salts, because its acetate molecules latch onto metal ions and carry them along, while a different organic blend called calcium magnesium acetate barely disturbed the soil at all.
Key Findings
Sodium acetate-treated soil became strongly alkaline (pH rose from 6.0 to 8.8 at 20°C) and released the most Zn2+, Cu2+, Pb2+, and Cd2+ of all six salts tested, with cumulative release around 2 mg/kg during the first leaching cycle.
At pH 8 and 20°C, roughly 70% of dissolved lead was bound up as lead-acetate complexes, showing organic ligands, not just acidity, drive metal mobilization.
Chloride-based salts (NaCl, CaCl2, KCl) caused only limited trace metal leaching at the tested concentration (~28 mM), and calcium magnesium acetate (CMA) had the smallest overall impact on soil pH, conductivity, chloride, and metal release while still boosting calcium and magnesium levels.
chevron_right Technical Summary
Scientists tested six different road deicing salts on contaminated roadside soil and found that a common 'eco-friendly' organic salt actually pulled more toxic lead and cadmium into the soil water than regular rock salt did, because its acetate molecules bind tightly to the metals and drag them along.
Abstract Preview
Original paper
Influence of inorganic and organic road deicing salts on the mobilization of metals within an agricultural roadside soil.
Seasonal road salt application is vital for winter road safety, but repeated use of chloride (Cl-)-rich salts (e.g., NaCl) releases high Cl- loads to nearby soils. Elevated Cl- levels can mobilize ...
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