Correction: Determination of ultra-low level of 239, 240 Pu in grass/vegetable sample by compact accelerator mass spectrometry

A simple and sensitive method was developed for 239, 240 Pu determination of sub-femtogram level in grass/vegetable sample using compact accelerator mass spectrometry (AMS). Pu was leached with HNO 3 -H 2 O 2 after ashing, and purified with AGMP-1 M resin column from grass matrix. After target preparation using mixed titanium/iron oxides, the final sample was measured by 300 kV AMS. The average recovery was higher than 80% for large-size (> 20 g ) grass sample in the entire procedure. 20 g environmental grass samples spiked with known amounts of 239 Pu standard solution or certified reference materials were measured for method evalution, good agreement between the expected values and measured results has been achieved. The detection limits were estimated to be 1.5 × 10 –16 g (0.34 µBq) for 239 Pu and 9 × 10 –17 g (0.8 µBq) for 240 Pu, demonstrating the feasibility of AMS for the determination of the sub-femtogram level of 239,240 Pu in environmental grass with global fallout signatures. Grass samples collected from China natural environment were successfully analyzed, and 239+240 Pu concentration down to 1.6 × 10 − 4 Bq/kg were measured in these samples. This improvement can stimulate environmental monitoring, ecological migration process and biological availability studies of Pu in the biosphere.