Geochemical characteristics and source analysis of rare earth elements in Qinghai Lake sediments

Abstract

This study investigates the distribution, geochemical behavior, and potential anthropogenic influences of rare earth elements (REEs) in the surface sediments of Qinghai Lake, the largest saline lake in China. A total of 36 surface sediment samples were analyzed for REE concentrations with a combination of self-organizing maps (SOM) and positive matrix factorization (PMF). Results indicate distinct enrichment patterns, with light REEs (LREEs) exhibiting higher concentrations than heavy REEs (HREEs), reflecting natural abundances and geochemical behaviors. The minimum value was found in Lu as low as 0.091 mg/kg, and the maximum concentration was exhibited in Ce at 78.877 mg/kg. Geoaccumulation index (I_geo) analysis reveals minor to moderate enrichment of specific REEs of Sm and Nd, suggesting possible localized anthropogenic inputs, particularly near river mouths. Spatial analysis using inverse distance weighting (IDW) and self-organizing maps (SOM) highlights significant correlations between REE distributions and riverine inputs, underscoring fluvial transport's role in sedimentary REE dynamics. PMF identifies mixed natural and anthropogenic sources, with agricultural and industrial activities contributing to elevated REE levels in sediment. These findings provide critical insights into the geochemical behavior of REEs in saline lake systems and offer a foundation for pollution control and sustainable resource management in sensitive environments like Qinghai Lake.