Accumulation of Mn and Fe in aromatic plant species from the abandoned Rosalgar Mine and their potential risk to human health

Abstract

The ecophysiological behaviours (translocation and accumulation) of Fe and Mn in three aromatic species spontaneously growing in soils from the abandoned mine in Rosalgar (Setúbal District, SW Portugal) were analysed in order to assess their potential impact on human health. Three different Lamiaceae species (Origanum vulgare subsp. virens, Calamintha nepeta subsp. glandulosa and Lavandula stoechas subsp. luisieri) were selected to determine their chemical compositions. The rhizosphere soil characteristics were also studied. Soils had a slightly acid pH, ranging from 5.6 to 6.4, and a low-medium fertility. The mean total contents of Mn and Fe in these soils were 13,605 mg/kg and 81,870 mg/kg, respectively. These values are higher than the average concentrations in non-contaminated soils in the region (737 mg Mn/kg and 36833 mg Fe/kg). The Mn concentration in the available fraction of these soils was also very high (467–1000 mg/kg). The Fe concentration in the soil available fraction was 69–124 mg/kg. Each species had a different accumulation pattern, as lavender is the only one that translocates Mn to the aerial part, where the concentration reaches a mean value of 890 mg/kg. This concentration is much higher than that observed in the other two species and is higher than the normal range for plants (10–500 mg Mn/kg). Two parameters were used to evaluate the risk posed to human health due to the consumption of O. vulgare and C. nepeta: the estimated daily intake (EDI) and the target hazard quotient (THQ). The EDIs of the studied elements in these two species, which are used for culinary purposes by the inhabitants of the region, were lower than the provisional tolerable daily intake value. Thus, their consumption for alimentary purposes is safe. On the other hand, the THQ values show that inhabitants who consume oregano and calamint may be exposed to health risks as the individual THQ for Mn was higher than unity.