Cadmium phytoextraction efficiency of hyperaccumulator as affected by harvest stage in three continuous years

Phytoremediation which mainly using hyperaccumulator is a very popular and environmental-friendly clean method. Long term continuous test is very important due to its low remediation efficiency in a growth period. Cd hyperaccumulator Rorippa globosa (Turcz.) Thell. Was used to explore the effect of two remediation modes (harvests at flowering and maturity stages) on the continuous remediation efficiency in a 3-year experiment using pot experiment with real Cd contaminated soil. The results showed that the biomass in maturity-harvest treatments was 1.12 times of that in flowering-harvest treatments due to the short vegetation time. Shoot Cd concentrations in the flowering-harvest treatments were on average 15.4% lower compared to the maturity-harvest treatments either. However, the Cd phytoextraction efficiency (PE) in the flowering-harvest treat-ments was 13.8% higher compared to the harvests at the maturity stage due to the growth cycle of R. globosa harvested at the flowering was 34.5% of shorter compared to those in the maturity harvest treatments. After three consecutive years of R. globosa phytoextraction, the concentration of extractable Cd decreased on average by 28.7% and corresponding PEs lower either. It was suggested that cultivation modes of R. globosa and low- accumulation crop rotation, or three times flowering harvests of R. globosa per year seemed to be a good choice in practical solution.

Automated summary

Phytoremediation using hyperaccumulators is a popular and environmentally-friendly clean method. Long-term continuous testing is crucial due to its low efficiency during the growth period. An experiment using Cd hyperaccumulator Rorippa globosa was conducted over a 3-year period to investigate the effect of two remediation modes on continuous efficiency. The results showed that biomass was higher in maturity-harvest treatments, while shoot Cd concentrations were lower in flowering-harvest treatments. However, Cd phytoextraction efficiency was higher in the flowering-harvest treatments due to the shorter growth cycle. After three years of R. globosa phytoextraction, the concentration of extractable Cd decreased and corresponding phytoextraction efficiencies were lower. It is suggested that cultivation modes and rotation with low-accumulation crops, or three times flowering harvests per year, could be practical solutions.