Low-temperature fusion using NHHSO and NHHF for rapid determination of Pu in soil and sediment samples.

Two fusion methods were established for rapid determination of Pu in soil and sediment samples. The methods consisted of NHHSO or NHHF fusion procedures incorporated with procedures for CaF/LaF co-precipitation, extraction chromatography and SF-ICP-MS measurement. The fusion procedures were done on a portable hot plate instead of in a cumbersome muffle furnace and took only 15 min heating-up time from room temperature to 250 °C and 15 min fusion time at 250 °C. Chemical recoveries of Pu after completing the NHHSO and NHHF fusion methods for 0.5-1 g sample were approximately 70% and more than 90%, respectively, and decreased with the increase of sample weight from 0.5 g to 5 g. Sediment samples were pre-ignited at different temperatures ranging from 450 °C to 1000 °C to form refractory fractions of Pu, with which the dissolution rates of Pu by the NHHSO and NHHF fusion were investigated. With the increase of pre-ignition temperature of the sediment samples, the dissolution rates of Pu from the samples prepared by NHHSO fusion declined dramatically from near 100% for 450 °C to 8% for 1000 °C. In contrast, the NHHF fusion was capable of completely releasing Pu from samples that were pre-ignited at temperatures over 450 °C to 1000 °C, which was comparable to releases obtained by the hazardous and time-consuming HNO-HF digestion, and was superior to the conventional HNO digestion. Additionally, because HF is not used in any procedure of the NHHF fusion, a safer and greener alternative to NHHSO fusion and HNO-HF digestion is realized for rapid Pu determination in environmental samples for nuclear emergency response and application in environmental studies.