Adsorption experiment of water-soluble rare earth elements in atmospheric depositions and implications for source tracing in South China

Abstract

The distribution patterns of rare earth elements (REEs) in fine-grained materials in various depositions were often found to be similar to those of the aeolian sediments deposited in the Loess Plateau in North China and the fine-grained materials were suggested to be derived from wind-blown dust. However, increasing evidence indicated that the REEs in the water-soluble portion of atmospheric depositions also displayed similar patterns to those of aeolian sediments. In this study, water-soluble REEs in three atmospheric depositions collected from different climatic zones in China were adsorbed with two adsorbents with distinct adsorption capacity, glass powder, and co-precipitated iron hydroxide. The results showed that the REEs adsorbed by the two adsorbents displayed patterns similar to those of the original atmospheric depositions. The typical characteristics of the REE patterns of atmospheric deposition can be well reproduced in the adsorbed REEs. The higher the REE concentrations in the atmospheric depositions, or the higher adsorption efficiency of the adsorbents, the better reproducibility of the REEs patterns. The results suggest that the REEs of the fine-grained materials in various sediments, which have a high adsorption capacity, especially those deposited in South China, may come from the water-soluble REEs in atmospheric deposition, and may not be appropriate tracers of wind-blown dust from North China.