Characteristics of Rare Earth Elements in Groundwaters along the Flow Path in the North China Plain

Groundwater samples collected along the flow path in the North China Plain (NCP) were analyzed for the rare earth elements (REEs), as well as other elements (Fe, Mn, Ba). Results showed that the concentration of total REEs gradually decreased from alluvia fans (Zone I), through alluvial plain (Zone II), to the coastal area (Zone III), which is likely controlled by contaminants due to human activities. Distribution patterns of REEs are different between Zone I and Zone II, while the distribution pattern of REEs in Zone III is similar to that of Zone II. The distribution patterns of REEs in the different zones may be affected by redox conditions, pH, hydraulic characteristics in the groundwater, and mineral composition of the aquifer sediments.