Rare earth elements and neodymium isotopes in dissolved and particulate phases in the Cam River andNam Trieu Estuary, north Vietnam

Dissolved and particulate rare earth elements (REE) were measured in the Cam-Nam Trieu estuary (north Vietnam) to trace land inputs to the ocean and particulate-dissolved phase interactions. This work discusses REE measurements in 19 samples based on the analysis of three phases (dissolved, labile, and refractory) using a quadrispike method. Dissolved REE (dREE) concentrations ranged from 1.16 to 14.7 nmol/kg, while particulate REE concentrations (pREE, including labile and refractory fractions) ranged from 24.6 to 104.6 nmol/kg. In the solid phase, light REEs (LREE) were most abundant (up to 85 % of total REE content), followed by middle REEs (MREE), with heavy REEs (HREE) representing less than 15 %. Calculated anomalies of Ce, Eu, and Gd indicated minimal fractionation. Surprisingly, no significant trace of anthropogenic Gd was detected in this estuary. Neodymium isotopic composition analysis revealed no change in isotopic signals during particle transport from the midstream part of the riverto the estuary. The isotopic signatures of the dissolved and labile values were more radiogenic (${\epsilon }_{Nd}$ = −10.9 ± 0.3) than those of the refractory fraction (${\epsilon }_{Nd}$ = −12.5 ± 0.4).