Controlling factors of reactive beryllium in river sediments entering the oceans and implicationsfor weathering intensity

The continental weathering process is an important mechanism for regulating climate changes during the geological history. A variety of chemical weathering indices based on the elemental geochemical composition of silicate sediments have been proposed and widely used to characterize the degree of weathering in various environments. Among them, with the development of the meteoric ¹⁰Be/⁹Be denudation proxy, the proportion of reactive ⁹Be (mainly enriched in Mn-Fe oxides) relative to the bulk ⁹Be in sediments (f_reac) is considered to indicate the dissolution process of primary minerals during chemical weathering and has the potential to reflect the intensity of chemical weathering. However, the reliability of the f_reac proxy in indicating the weathering intensity still lacks a systematic assessment. We compiled the published data on the leachable Be in river sediments worldwide, calculated the f_reac index, and evaluated the controlling factors of f_reac. Results show that although f_reac could be affected, to some extent, by grain size and leaching methods, overall, there is a significant positive correlation between f_reac and commonly used weathering indicators such as the Chemical Index of Alteration (CIA), implying that the Be-based index f_reac can be used to indicate the overall weathering intensity of sediments in neutral or alkaline watersheds. In addition, there is a nonlinear negative correlation between f_reac and the denudation rate on catchment scale, suggesting that the higher the denudation rate, the lower the weathering intensity. In the future, the weathering proxy f_reac can potentially be applied in terrestrial sedimentary archives to reconstruct paleo-changes in Earth surface processes.