Fractional composition of Cd, Pb, and Zn in medicinal plants at the impact territories of a coal-fired power station.

Industrial emissions are a major source of heavy metal (HM) contamination, posing risks to medicinal plants collected for therapeutic use. Assessing HM accumulation in impact territories is critical, as pollutants can enter the food and pharmaceutical chains. The Novocherkassk Thermal Power Station (TPS), one of Russia's largest energy producers, emits Zn, Pb, and Cd, leading to increased metal uptake by local medicinal plants. However, the total content of metals does not reflect actual bioavailability, necessitating detailed fractionation analysis to evaluate contamination levels and the associated health risks. To evaluate the accumulation and bioavailability of HM, eight medicinal plant species were collected in the impact territory during the active vegetation period in June 2024. Achillea setacea Waldst & Kit, Artemisia absinthium L., Matricaria chamomilla L., Plantago major L., Chelidonium majus L., Urtica dioica L., Taraxacum officinale, and Tanacetum vulgare L. were analyzed for metal fractionation using a stepwise extraction scheme to differentiate between bioavailable and strongly bound metal forms: (I) water-soluble, (II) aqueous-alcoholic, (III) hydrochloric acid, (IV) acid-soluble, and (V) silicate-bound fractions. In plants from the impact territory, a proportional rise in metal concentrations is observed across all fractions. The fractionation pattern follows the order: hydrochloric acid (FIII) > acid-soluble (FIV) > silicate (FV) > aqueous-alcoholic (FII) ≥ water-soluble (FI). Pb exhibits the highest extractability in water-based decoctions and tinctures, posing a significant health risk. The highest extraction rates with water (FI) and ethanol (FII) were observed in P. major and M. chamomilla, while the silicate fraction (FV) dominated in the roots and aboveground parts of A. absinthium (Cd, Pb) and M. chamomilla (Zn). Excess HM binding in plants primarily occurs in the aqueous-alcoholic (FII) and hydrochloric acid (FIII) fractions, which exhibit the highest concentrations and variability. In the TPS impact area, high Cd concentrations in plants are mainly found in fractions III and V, while the lowest levels are found in fraction I (aerial parts) and fraction IV (roots). Cd showed a high degree of transfer into decoctions (FI) and alcoholic extracts (FII) from the aerial parts of T. vulgare and A. setacea, accounting for 41% and 44%, respectively. Pb is the most easily extracted HM among those studied, with the sum of fractions FI and FII accounting for 25-59% in the aerial parts and 11-57% in the roots, indicating a high risk associated with medicinal plant materials contaminated with this element. The amount of metals transferring into decoctions and alcoholic infusions varies greatly among plant species and ranges from 5 to 32% in the aerial parts and from 5 to 29% in the roots. The health risks associated with exposure to Cd, Zn, and Pb through herbal infusion intake were evaluated based on the estimated daily intake. In the impact zone, Pb levels in the tincture (fraction II) exceeded the acceptable limits. Increased industrial emissions contribute to elevated metal concentrations in medicinal plant extracts, which may pose a potential risk to human health.