Metallomics of dill: Influence of environmental stress and contamination of commercial samples

Dill (Anethum graveolens), an annual species, was used to study the impact of metallic pollution potentially spreading from the nickel smelter dump in Dolná Streda (Slovakia) by monitoring 55 elements. Despite the proximity of this dump (1 km), only soil Ni (54.8 mg/kg) or Pb (47.3 mg/kg), but not Cr, Mn, Fe or Co (main elements of the dump's sludge) was elevated in given garden soil compared to two control sites. Mainly flowers and/or leaves contained significantly higher amounts of Ni, Cr, Pb, Cu, As, Sb, Sn, V, W, and some rare earth elements at the site close to the dump. Correlation between elements in organs and soil was significant mainly in stem or root but the bioaccumulation factor was typically low (<0.02) for most elements. A positive finding was that the 2022/2024 comparison revealed a decline in most elements in dill leaves, even at the dump site, which may reflect a decrease in the content of air PM particles. Soluble phenols were less accumulated in plants close to the nickel smelter dump, but flavonols showed the opposite trend, and free amino acids were positively correlated with many elements in the stem and root. An evaluation of commercial dill samples revealed variability (e.g., up to 0.7 mg Cd/kg dry weight) but subsequent NCA and PCA analyses clearly separated the dump locality from other samples. However, significant differences in the content of Cd, Ni, Pb, As, and other elements encourage precise control of commercially available dill dry matter.