Magnetic field enhance decontamination efficiency of Noccaea caerulescens and reduce leaching of non-hyperaccumulated metals

Hyperaccumulators can accumulate high amounts of specific metals and have been widely used to remediate metal polluted soil. However, organic acid secretion and soil acidification (two important mechanisms for hyperaccumulators to mobilize and extract metals) can also activate non-hyperaccumulated metals and then increase the leaching risk. The decontamination efficiency and leaching risk of using Noccaea caerulescens (formerly Thlaspi caerulescens) and Thlaspi arvense were compared in the present study. Although N. caerulescens accumulated significantly more Cd and Zn than T. arvense, it increased the leaching risk of Pb and Cu as well. Under magnetic fields of 30, 60, 120 and 150 mT, the biomass production of N. caerulescens was increased by 18.5, 48.9, 80.4, and 29.3% respectively, but decreased by 21.7% under 400 mT. Comparing with the control, plants raised from seeds pre-treated by magnetic fields accumulated 37.8-250.1% more metals and reduced the leachate volume and leached metals by 1.1-32.9% and 4.6-48.1% respectively. Considering remediation efficiency, environmental risk alleviation and energy consumption, N. caerulescens treated by 120 mT magnetic field is suited to remediate multi-metal polluted soil.