Cultivation of medicinal and aromatic plants in heavy metal-contaminated soils

Abstract

The growing number of polluted land areas makes the question of rehabilitation and safe/effective use of these areas increasingly imperative. For land polluted by heavy metals, the possibility of transferring the toxic pollutants to humans through the food chain further increases the importance of the safe management of polluted lands. We examined the possibility of using heavy metal-polluted areas for growing specific aromatic plants, which can be used either as food herbs/infusions, or to produce high value products. In a pot experiment, chamomile, sage and thyme plants were exposed to a range of concentrations of Cd, Pb, and Ni in the soil. Toxic metal levels were determined in the roots, leaves and flowers (for chamomile) of the plants. All three plants accumulated relatively high amounts of metals in their roots, whereas the aboveground parts exhibited lower accumulation capacity. Regardless the levels of metal accumulation, the quality of essential oils from chamomile, sage, and thyme was not affected and in all cases the extracted essential oils were free of heavy metals. Our results suggest that the aromatic plants under study cannot be consumed either as food additives or as infusions. However, under strict control of the cultivations, heavy metal-contaminated areas can be used for the production of essential oils from aromatic plants.