Geochemistry of Rare Earth Elements in Surface Water from the Red Beds of the Nanxiong Basin of China

The concentrations of the dissolved rare earth elements and main ions were determined in 16 samples of surface water at the Red Beds of the Nanxiong Basin by using the inductively coupled plasma mass spectrometry (ICP-MS),inductively coupled plasma atomic emission spectrometry (ICP-AES) and ion chromatography. The results show that the surface water samples in the Hongshaling area of Nanxiong are weakly alkaline, with a pH range of 7.02 to 9.46, and the cation is mainly Ca²⁺. The average total content of rare earth elements is 0.6014 ng/mL, which is relatively high compared with the main rivers and surface water bodies in China. The La/Sr ratio in shale (PAAS) is predominantly below 1, with an average value of 0.74. The PAAS-normalized rare earth element (REE) distribution pattern exhibits a slightly right-skewed trend, with a moderate enrichment in the middle rare earth elements, suggesting their relative accumulation in the water body. Additionally, Ce and Eu display negative anomalies, whereas Gd exhibits a positive anomaly. The total concentration of rare earth elements (REEs) exhibits a weak negative correlation with pH and a significant positive correlation with the concentrations of Fe and Mn. It is inferred that the desorption or dissolution of Fe-Mn colloids or suspended particles constitutes one of the primary factors influencing REE behavior in the studied system.