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Information on how plutonium (Pu) isotopes associate with natural soil particles of different size is very important for the interpretation involved in the application of Pu isotopes as soil erosion tracers. This work investigated the association of Pu isotopes with different particle size fractions of natural soils and compared it with that of 137 Cs. Ten bulk soils collected from two different areas were separated into different particle size fractions by a combination of wet sieving and centrifugation techniques and the sub-samples were analyzed for 137 Cs, 239 Pu and 240 Pu. Results showed that the concentrations of both 239 + 240 Pu and 137 Cs increase with decreased particle sizes and are closely related to the specific surface areas of soil particles, which demonstrated a similar preferential association of Pu with finer soil particles as 137 Cs. The activity ratios of 239 + 240 Pu/ 137 Cs in soil fractions increasing with increased particle size further indicated a less preferential transport of Pu with fine particles compared to 137 Cs. These results not only highlight the suitability of Pu isotopes as soil erosion tracers, but also provide useful information for assessing the migration behavior of Pu in contaminated environments. [ABSTRACT FROM AUTHOR]

Ecological restoration of terrestrial ecosystems facilitates environmental protection and enhances sustainable development of land resources. With increasingly severe land degradation, new and effective methods must be developed for the restoration of ecological functions. In this study, we developed a regional risk assessment approach to support the planning of ecological restoration of a terrestrial ecosystem located in the Daye area in central China. The study area was divided into six sub-regions where ecological risks were characterized by building a non-linear model to represent ecological interactions among the risk components there. Socio-economic conditions in the areas were evaluated and presented using an analytic hierarchy process. Assessment of different stakeholders there was conducted based on multiple-criteria decision analysis. Then, integrated assessment was performed using the technique of order preference for an ideal solution. We divided the degraded land in Daye into areas with different priorities for restoration or rectification and presented corresponding sequential time intervals for the action. The results are as follows: (i) the top priority rectification areas (totaling 358 km2) are mainly distributed in northeast and northwest regions; (ii) the high priority rectification areas are concentrated in the central region spanning 226 km2; (iii) the medium priority rectification areas comprised a large amount of arable and forest land spanning 605 km2; and (iv) the low priority rectification areas cover the rest part of the Daye area spanning 195 km2. The assessment tool was proven to be useful in planning regional ecological restoration in terrestrial ecosystems. Unlabelled Image • Integrated assessment used in study of ecological restoration was the first attempt. • RRA expanded the methods for ecological restoration of terrestrial ecosystems. • Multi-factor investigation enabled comprehensive restoration of terrestrial ecosystem. • Nonlinear model reduced the uncertainty of risk calculation. • MCDA methods reflected practical limits of restoring the terrestrial environment. [ABSTRACT FROM AUTHOR]