Quantitative estimation of dust transport in the desert region of northwest China by plutonium isotopes.

Dust is an important source of atmospheric pollution, and quantitative estimation of desert dust transport is crucial for air pollution control. In this study, five typical sandy soil profiles in the Tengger Desert were collected and analyzed for ^239,240 Pu concentration and ²⁴⁰ Pu/ ²³⁹ Pu atomic ratios in order to identify the source of ^239,240 Pu in this area and explore the sedimentary characteristics of dust in different profiles. The results revealed that the concentrations of ^239,240 Pu in the soil profiles were between 0.002 and 0.443 mBq/g with an exception of the deep layer soil at one site. The measured atomic ratios of ²⁴⁰ Pu/ ²³⁹ Pu are at the global atmospheric fallout level with a mean of 0.184 ± 0.020, indicating that global fallout is the dominant source of plutonium in this region. The total inventories of ^239,240 Pu in the reference sites in this area were estimated to be 39.2-44.6 Bq/m ² , this is in agreement with the value from the global fallout of atmospheric nuclear weapon tests at the similar latitude (30-40 °N: 42 Bq/m ² ). The estimated erosion rate in the erosion profile utilizing soil erosion intensity mode is 2491 t/km ² /yr and the soil erosion depth is 9.86 cm, While, the stacking rate of the accumulation profile is 1383 t/km ² /yr, and the depth of accumulation is estimated to be 5.48 cm. The difference between the erosion and accumulation profiles indicated that approximately 1107 t/km ² /yr of dust was exported from the Gobi landform area of the Tengger Desert, which might be transported long distance in the downwind direction.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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