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• Pu tracer is successfully applied to evaluate soil erosion in the Loess Plateau. • Both of natural grassland and artificial forest rehabilitation were effective. • Artificial forest is superior for reducing soil erosion in the short-term. • Natural grass rehabilitation is better for inhibiting soil erosion in the long-term. Soil erosion is a critical threat to the agriculture and ecosystem in the Chinese Loess Plateau area. Ecological rehabilitation has been applied in large area for reduction of the soil erosion. Six soil depth profiles were collected from Nanxiaohegou watershed in the Loess Plateau in northwest China and analyzed for the activity concentrations of plutonium isotopes. The measured 240Pu/239Pu atomic ratios in all these samples (0.186±0.017) showed that the global fallout was the dominant source of plutonium in this region. An exponential decline of 239,240Pu activity concentrations with depth was observed in most of soil profiles. The total inventory of 239,240Pu in the reference site was calculated to be 110 Bq/m2, agreeing well with the reported total fallout value in this latitude. The soil erosion rates were estimated by comparison with the reference site to be 538–941 t/km2/yr in the most of sites. While an excessive inventory of 239,240Pu (186 Bq/m2) compared to the reference site was observed in one site in the base area, indicating a significant accumulation of soil occurred in this area. The soil erosion depths were estimated to be 2.4–4.6 cm in most of sites during 1963–2016, which can be classified as minor erosion. Compared with the erosion rates in the Nanxiaohegou watershed in 1963–2012 which was estimated by other methods, it is suggested that the natural grass is better for long-term ecological restoration, especially in slope area. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Global fallout is the major source of plutonium in the Northeast China. • The topography and precipitation are key factor for the deposition of Pu. • The westerlies and monsoon are important for Pu distribution in north China. • Land use and vegetation are important for reservation of Pu in soil. [ABSTRACT FROM AUTHOR]