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The total (239+240)Pu activities and (240)Pu/(239)Pu atom ratios in surface soil samples (0-5 cm) in the Kumtag Desert in western Gansu Province, and in a soil core sample in Lanzhou were investigated using a sector-field ICP-MS. In the surface soil samples, (239+240)Pu activities in fine particles (<150 mu m) were 1.3-2.1 times of those in coarse particles (150 mu m(-1) mm) which ranged from 0.005 to 0.157 mBq/g. Atom ratios Of (240)Pu/(239)Pu in the surface soils ranged from 0.168 to 0.192 with a mean of 0.182 +/- 0.008. The mean ratio was similar to the typical global fallout value although the Kumtag Desert was believed to have received close-in fallout derived from Chinese nuclear weapons tests mainly conducted in the 1970s. (240)Pu/(239)Pu atom Furthermore, the mean ratio observed in the soil core sample in Lanzhou was similar to the typical global fallout value. In the soil core sample, (239+240)Pu activities in the various layers ranged from 0.012 to 0.23 mBq/g, and the inventory of (239+240)Pu (32.4 Bq/m(2), 0-23 cm) was slightly lower than that expected from global fallout (42 Bq/m(2)) at the same latitude. Rapid downward migration of Pu isotopes was observed in Lanzhou soil core sample layers. The contribution of the 10-cm deep top layers of surface soils to total inventory was only 17%, while the contribution of deeper layers (10-23 cm) was as high as 83%. The (239+240)Pu activity levels and (240)Pu/(239)Pu atom ratios in soils in Gansu Province, China are similar to those in atmospheric deposition samples collected in the spring in recent years in Japan. (c) 2009 Elsevier Ltd. All rights reserved.