Soil-to-plant transfer factors for stable elements in lemon balm (Melissa Officinalis L.) commonly used as a medicinal plant

Abstract

This study evaluated the transfer factors (TF) of stable elements (essential and non-essential) As, Ba, Br, Ca, Cd, Co, Cr, Cu, Fe, Hf, K, La, Mg, Mn, Na, Ni, Pb, Rb, Sb, Sc, Sm, Th, Ti, V and Zn from soil to Melissa officinalis L. (Lemon balm). The transfer factors were calculated by dividing the metal concentration in Lemon balm leaf by the total metal concentrations in the soil. The experiments were conducted from January 2013 to January 2014 at the Municipal Gardening School area, in Ibirapuera Park, São Paulo, Brazil. The experimental design was completely randomized (CRD), with three treatment: control (site soil), organic (2 t ha-1 poultry manure) and conventional (30 t ha-1 of NPK, 6:14:8), and four harvest (April, July, October and January) with four replications. The soil samples collected (0 – 20 cm) were dried at 100 °C and grounded to 100 mesh size particles and homogenized. Lemon balm samples were collected and washed with ultrapure water to remove impurities and soil particles present in all plant structures, air-dried and the leaves were separated. After these processes, the Lemon balm leaves were dried at 100 °C and grounded to 100 mesh size particles. Instrumental neutron activation analysis (INAA), graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES) were applied to determine the elemental concentration in the samples. The results showed that the metals accumulate in species with different intensity. Our findings indicated that Ca, Cd, K, Ni and Rb accumulated the most with the transfer factor of 1.0 – 12, followed by Ba, Br, Co, Cr, Cu, Mg, Mn, Na, Pb, Sb and Zn with TF of 0.1 – 1.0, while As, Fe, Hf, La, Sm, Th, Ti and V had the lowest accumulation with TF usually < 0.1.