Soil Development and Climate Trends in Some Parts of China Inferred from 10Be Isotope

Abstract:

The cosmogenic isotope ¹⁰Be has been proved as a potential source for the understanding of soil and landscape development and climate change in a variety of Earth’s surface terrestrial archives such as soils, loess and ice sheets. After being produced in the atmosphere, the deposited ¹⁰Be by precipitation and dust enters mainly the inorganic cycle and accumulates on the surface of soil particles with little loss to the subsurface. Most of the estimates for the preipitaion-¹⁰Be input were performed for archives stretching back in time without a region wide data on ¹⁰Be atmospheric deposition. Although not entirely reflecting atmospheric depositional flux, the bulk of the isotope concertation strongly indicates atmospheric input and soil development processes. In the report presented here, measurement of ¹⁰Be in surface soils (top 5-10 cm) from China are combined with data on atmospheric flux (wet and dry) to estimate present soil development and correlation to precipitation rates. The results indicate variability in ¹⁰Be concentration from 0.27×10⁸ to 35.38×10⁸ atoms/g and show that higher concentrations are found in high precipitation region while regions with extensive precipitation show a possible dilution effect. Also it seems that mature soils along river pathways retain more ¹⁰Be than soils on dry lands and high elevation. A positive correlation between average precipitation rate and ¹⁰Be distribution suggests ¹⁰Be-precipitation relationship if the dilution effect can be eliminated. In addition, estimate of ¹⁰Be deposition using atmospheric flux models suggest differences between regions, with the highest values comparable to trend shown by the empirical data. Although, the data do not cover depth profiles that can reflect past time processes in the soils, the distribution pattern and correlation with precipitation suggest high potential for using ¹⁰Be as proxy of precipitation back in time.