Accumulation of heavy metals from soil in medicinal plants

Medicinal plants accumulate heavy metals from contaminated soil, and their consumption can cause poisoning. Our objective was to determine the levels of Pb, Cd, Zn, Cu, Fe, and Mn in four medicinal plant species (Achillea millefolium, Hypericum perforatum, Plantago lanceolata, and Urtica dioica) and their native soil, all sampled at a former smelter. The highest soil Cd, Pb, and Zn levels surpassed the maximum allowed limit 75-fold, 48-fold, and 14-fold, respectively. Their soil levels correlated with those in the plants, but this was not the case with Cu, Fe, and Mn. Heavy metal accumulation seems to depend on the plant species, yet even so, medicinal herbs should be cultivated and gathered only from controlled (uncontaminated) areas. Polluted areas should be monitored on a regular basis, while further research should investigate the connection between the heavy metal levels in the soil, their levels available for plants, and the levels extractable from plants.
Težke kovine iz onesnaženih tal se kopičijo v zdravilnih rastlinah, zaradi česar lahko njihovo uživanje privede do zastrupitev. Namen naše raziskave je bil ugotoviti vsebnosti svinca, kadmija, cinka, bakra, železa in mangana v vzorcih tal ter v vzorcih navadnega rmana (Achillea millefolium), šentjanževke (Hypericum perforatum), ozkolistnega trpotca (Plantago lanceolata) in velike koprive (Urtica dioica), nabranih na osmih lokacijah v Mežiški dolini. Koncentracije kadmija, svinca in cinka so kritično presegale mejne vrednosti. Vsebnost teh treh težkih kovin je značilno korelirala z njihovo vsebnostjo v proučevanih rastlinah, ki pa posamezne težke kovine kopičijo v različnem obsegu. Različen je bil tudi obseg njihove ekstrakcije v vročo vodo. Naša raziskava prispeva pomembne rezultate za nadaljnje proučevanje povezav med prehajanjem težkih kovin iz (onesnaženih) tal v rastline in rastlinske izvlečke. Poleg tega nakazuje tudi na izjemen pomen rednega spremljanja stanja tal, zlasti na področjih kritične onesnaženosti, saj je nabiranje zdravilnih rastlin v naravi v današnjem času izjemno priljubljeno.