Variations in rare earth elements with environmental factors in lake surface sediments from 17 lakes in western China

Numerous lakes in western China are excellent sites for understanding environmental change. However, what dominates rare earth element (REE) variations are still under debate in the lake environmental research. In this study, we selected 28 surface sediment samples from 17 lakes (i.e. large-scale lakes, small water bodies, etc.) in the Qinghai-Tibet Plateau and Xinjiang area. These samples were analyzed to reveal the behavior of the REEs and major elements. These REE patterns are characterized by light rare earth element (LREE) enrichment, weak Ce anomaly (0.84–0.98, 0.94 on average) and negative Eu anomaly (0.53–1.00, 0.67 on average). The homogeneous REE patterns may reflect similar REE of the source lithologys. However, the REE abundances showed some significant differences. In this study, water chemistry data analyses inferred that the highly REE values appear possibly in the saltwater lake, and also related to carbonate mineral, whereas pH played a minor role in REE concentrations. In large-scale lakes (e.g. Lake Bosten and Lake Ulungur), the results showed that the relatively larger REE values are in the margins of lakes. Moreover, lower REE contents are towards the central region. Comprehensive study suggested that five major factors control the REE contents: (1) The REE tends to increase with the increase of the weathering intensity. (2) Likewise, heavy mineral (i.e. rutile, anatase, zircon, etc.) are probably primary in these sediments because they are highly enriched in the REE. (3) The contribution of Fe-Mn oxides is significant in sediments because their concentrations highly correlate with the REE. (4) The carbonate mineral (mainly calcite) played a significant role on the REE values in the lakes because the REEs are incorporated into the carbonate minerals generating the low REE concentrations. (5) Major element analysis, mineral analysis, and grain-size data analysis showed that the REE distribution is chiefly influenced by finer grain-size component of lake sediments due to the decreasing proportion of quartz and feldspar than coarser one. Moreover, the clay minerals in finer grain-size sediments can highly absorb the REE.