Level, distribution and sources of plutonium in the northeast and north China

Concentrations of ²³⁹Pu and ²⁴⁰Pu in 163 surface soil samples and five soil cores collected from the northeast and north China were analyzed using the radiochemical separation combined with inductively coupled plasma mass spectrometry measurement. The average ²⁴⁰Pu/²³⁹Pu atomic ratios (0.185 ± 0.018) for all surface soil samples indicated that the global fallout is the major source of plutonium in the studied region. The ^239,240Pu concentrations of the surface soil ranged from 0.002 mBq/g to 4.82 mBq/g, lying in the range of the reported results in the areas with similar latitude, except for a few samples. The distribution of ^239,240Pu in this region is controlled by the deposition of plutonium in the atmosphere and its preservation in the soil, which were affects by multi-factors such as topography, climate, utilization of the land and vegetation coverage. The analytical results could be used as the baseline data for the assessment of the impact of nuclear activities in the past and the future.