Growth Ability and Phytoremediation of Water Mint (Mentha aquatica), Eryngo (Eryngium caucasicum) and Froriepia (Froriepia subpinnata) in Soil Contaminated with Lead

Phytoremediation is one of the most eco-friendly and inexpensive methods that can be used to clean toxic soil pollutants such as lead (Pb). The choice of medicinal and aromatic plants under such conditions has received much attention. In order to study the potential of lead phytoremediation by three native and medicinal plants of water mint (Mentha aquatica L.), eryngo (Eryngium caucasicum Trautv.) and froriepia (Froriepia subpinnata Ledeb.), three separate experiments were designed.  

The experiments were performed in the greenhouse of Sari Agricultural Sciences and Natural Resources University in 2017, in a completely randomized design (CRD) with four replications. The levels of lead were included 0 (control), 125, 250, 375 and 500 mg Pb.kg-1 soil from source of lead nitrate. Shoot and root dry weight, lead concentration in shoot and root, tolerance index, transfer factor, bioaccumulation factor, bioconcentration factor and lead uptake in shoot were calculated.  

Results showed that biomass decreased in all three plants by increasing lead concentration; while, all three plants transferred lead to shoot and root. Concentrations of lead in the root of water mint were higher than shoot. Also, water mint with a bioconcentration factor higher than one and a transfer factor lower than one can be used to phytostabilization of lead heavy metal. In froriepia the bioaccumulation factor and transfer factor was higher than one, indicating that it could be used for phytoextraction of lead. Eryngo had the highest lead uptake in shoot (0.24 mg of lead in pot).  

In general, the results showed that lead uptake and transport depend on species, biomass production and soil lead concentration, and all three plants in lead contaminated soil have phytoremediation ability; while, eryngo showed a higher ability to phytoextraction based on higher amount of lead uptake in shoot due to higher shoot dry weight than froriepia.