Kemakta has been commissioned by several mining and industrial mineral companies to investigate the occurrence forms of uranium in process water from mining and quarry operations, as well as in receiving waters. Environmental quality standards (MKN) have been established for inland waters through the regulation (HVMFS 2013:19), identifying uranium as a specific contaminant (SFÄ). In many cases, the levels of uranium in both dewatering and process water, as well as in receiving waters, exceed the SFÄ value. However, no toxic effects have been observed in the lakes and watercourses where excess water is discharged.
The purpose of Kemakta’s work is to compare the actual chemical form of dissolved uranium with the chemical form assumed when the SFÄ value was established. Geochemical modeling shows that the uranyl ions in the process water and receiving waters primarily exist as uranyl carbonates, while the SFÄ value was based on studies using uranyl salts of a different composition and under water-chemical conditions that do not correspond to the local conditions in the receiving waters of Swedish mines and industrial mineral quarries.
Kemakta’s investigation provides a description of the properties of different uranium ion forms in various chemical environments, and what is known about the ability of these different forms to pass through biological membranes (bioavailability and bioaccumulation). Calculations on how uranium binds to organic carbon have also been conducted for the process and receiving waters based on available chemical analyses. Investigations into the bioaccumulation of uranium in fish and the risks of toxic effects on top predators consuming these fish have also been carried out. According to Kemakta’s assessment, differences in the chemical form of uranium ions may serve as a basis for arguing that the SFÄ value is often not applicable to the local water-chemical conditions in receiving waters. Kemakta’s findings are used by the companies in their permit applications and in responses to inquiries from authorities.
