Seasonal variation of rare earth elements in Taraxacum officinale as an indicator of changes in urban pollution.

Taraxacum officinale has been identified as a potential rare earth elements (REEs) accumulator, making it a promising bioindicator for urban environment. However, the influence of seasonal variation on the bioavailability, transport, and accumulation of REEs in plant tissues remains poorly understood. This knowledge gap is crucial, especially in the context of development of reliable bioindicators for urban pollution and managing urban ecosystems sustainably. The aim of this study was to evaluate seasonal changes in the content and distribution of Sc, Y and 14REEs in soils and dandelion roots and leaves from urban areas. Ten research sites typical for urbanised areas were designated and samples of soils and plants were collected in the spring and autumn season. The assessment of the level of studied elements combined with statistical analysis was performed. Variation in REEs accumulation in soil was found. Due to the lack of heavy industry in the city, the major source of REEs contamination in soils might be related to transportation and local agrotechnical and nutrition treatments. Our research on dandelion showed a decrease in REEs content in roots and leaves during autumn compared to spring. Slightly higher translocation efficiency was observed in autumn, possibly due to the plant's age and tolerance mechanism.