Assessment of Scandium Ecotoxicity Based on the Dynamics of Changes in Biological Parameters of Haplic Chernozem

The increasing demand for scandium (Sc) has accelerated the growth of its production, raising concerns about its environmental and soil-related impacts. This model experiment aimed to evaluate the ecotoxicity of Sc and its impacts on changes in the biological parameters of Haplic Chernozem. Haplic Chernozem was contaminated with varying doses of Sc (3, 30 and 300 times the background concentration). The study revealed that increasing Sc concentrations in the soil reduced radish seed germination and root length, decreased the abundance of Azotobacter sp., and inhibited catalase, dehydrogenase, and cellulolytic activity. Biological parameters reached their lowest values 30 days after Sc contamination. However, extending the exposure period to 90 days facilitated the recovery of soil conditions to near-control levels. Among the biological parameters tested, the abundance of Azotobacter sp. bacteria was the most sensitive to Sc contamination, while cellulolytic activity proved to be the most informative indicator of Sc contamination. The threshold value of Sc in soil was determined to be 82 mg kg–1. These findings provide a valuable framework for diagnosing and assessing the ecological state of soils contaminated with Sc.