IVL Swedish Environmental Research Institute

This report presents a screening study commissioned by the Swedish Environmental Protection Agency to assess the occurrence and concentration of flotation chemicals downstream of sulfide mining operations in Sweden. Flotation chemicals, particularly xanthates and carbamates, are widely used in ore processing and may pose ecological risks if released into the environment via effluent from tailings ponds.

The project developed and validated a robust analytical method using solid-phase extraction and LC-MS/MS to detect five target compounds at low concentrations. Sampling was conducted at four mining sites during fall 2024 to spring 2025. In total, 85 analyses were made on surface water samples collected under variable hydrological conditions, with 34 analyses showing detectable levels.

Detected concentrations ranged from 0.2 to 250 µg/L, with butyl and amyl xanthate being most frequently observed. Over 70% of detections were below 10 µg/L, which is lower than most reported toxicity data from tests with aquatic organisms. However, the ecotoxicological foundation is scattered, which is reflected in predicted no effect concentrations (PNEC) for aquatic organisms ranging between 1 and 1500 µg/L Previous studies on synergistic effects between xanthates and metals (e.g., cadmium, copper) showed a substantial increased toxicity, and this should be considered also at low xanthate concentrations.

This screening focused only on snapshot conditions in surface water to ensure robust analysis methods. Xanthate and carbamate occurrence in other environmental media such as sediment and biota remain unclear and surveying their degradation products was not included in the screening project. To gain a better understanding of xanthate and carbamate prevalence and potential ecological risk in downstream water, further seasonal monitoring is needed, as well as additional ecotoxicological studies for sublethal endpoints.