❓ Does hydrodynamic dilution always mean reduced environmental toxicity? Not necessarily.
💻 10+ years of empirical monitoring of high-TDS mine water plumes (Svystunova Gully) + thermodynamic speciation in PHREEQC reveal a striking evolution in Cadmium mobility:
🔹 Near the source (dilution 0.00–0.30): Extreme chloride ionic strength sequesters Cd into neutral/anionic chloro-complexes (CdCl₂, CdCl₃⁻), keeping free Cd²⁺ near zero and enabling unretarded transport.
🔹 Migration path (dilution 0.30–0.85): Cationic CdCl⁺ becomes dominant, reaching ~70% of total activity.
🔹 Plume fringe (dilution >0.90): Chloro-complexes dissociate rapidly, triggering a sharp non-linear surge in free hydrated Cd²⁺ — the most bioavailable and toxic form.
🔗 Open-access preprint (v0.80): https://zenodo.org/records/20709306
#Hydrogeology #EnvironmentalGeochemistry #Groundwater #PHREEQC #Geochemistry #WaterQuality #OpenScience #RStats #SvystunovaGully #Cadmium #Toxic #TraceElements #IronOre #Mining