Beryllium-7 in vegetation, soil, sediment and runoff on the northern Loess Plateau.

Beryllium-7 (Be), as a potentially powerful tracer, was widely used to document soil redistribution and identify sediment sources in recent decades, but the quantity and distribution of Be in vegetation, soil, sediment and runoff on the Loess Plateau have not been fully described. In this study, we measured Be in vegetation, soil, sediment and runoff on the northern Loess Plateau of China and analyzed its variations during the rainy season to assess the potential of the Be method for documenting soil redistribution and identifying sediment sources in a wide range of environments. The results indicated that vegetation, soil, and sediment samples showed higher levels and larger variations of Be activities during the rainy season. The drying plants showed Be mass activity that was more than three times higher than that of living and semi-decomposed plants. Be mass activity in plants and sediment was much higher than in the soil. Be activity in runoff water with a few submicron suspended particles varied slightly and was far lower than in plant, soil and sediment samples. The cumulative precipitation generally determined Be inventory held by plants and soil. An inverse relationship was found between the Be mass activity in sediment and the sediment amount. Globally, approximate 30% of the total Be was held by plants in both the herbaceous and subshrub plots. Approximate 10% of the total Be was lost with sediment from the bare plot. A very small proportion of Be (1.18%-3.20%) was lost with runoff, and the vast majority of Be was retained in the slope soil at the end of rainy season. Vegetation cover and soil erosion significantly affected the spatial distribution and variations of the Be inventory in soil, providing a necessary condition for the development of a Be method to document soil erosion on slopes with vegetation.