Evaluation of Pb phytoremediation potential in Buddleja asiatica and B. paniculata

The phytoremediation potential for Pb of Buddleja asiatica (a wild species) and a closely related cultivated species, B. paniculata, was investigated by means of field survey, hydroponic and pot experiments, and field trial experiments. Field surveys showed that B. asiatica had an extraordinary accumulation capacity and tolerance for Pb. Plants grown in soil with 2,369.8-206,152 mg kg^-1 total Pb accumulated 1,835.5-4,335.8 mg kg^-1 Pb in their shoots. Under hydroponic conditions (10, 20 mg l^-1 Pb), both B. asiatica and B. paniculata showed unusually high concentrations of Pb in their roots (12,133-21,667 mg kg^-1) and increased biomass production. A pot experiment in a greenhouse without any soil amendments was conducted on three different soils with various Pb contents (10,652, 31,304, 89,083 mg kg^-1) for 3 months. The results showed that both species of Buddleja had an increase in the biomass similar to the control plants. There was a slight decrease in survival rates of plants grown in soil with 89,083 mg kg^-1 Pb content. A field trial experiment was conducted for 6 months at three sites around the Pb mine area in which plants were provided with Osmocote fertilizer. Both Buddleja species showed 100% survival, increased biomass production and phytoextraction capacity (TF 1.1-2.3) when grown in soil with Pb content of 94,584-101,405 mg kg^-1. Plants accumulated 2,273-3,675 mg kg^-1 Pb in their shoots. The results suggest these Buddleja plants are suitable for use in the phytoremediation of Pb-contaminated soil.