Dissolved rare earth elements (REEs) distribution in marginal sea is of significant importance to understand geochemical cycling of REEs in the ocean. We determined REEs concentrations of four vertical profiles of seawater collected by KK1803 cruise (R/V Jiageng) from April to May 2018 in the northern South China Sea (SCS), the largest marginal sea of the western Pacific Ocean. These seawater stations are located from the northern to the central SCS that allow to evaluate the REEs sources of surrounding rivers and water masses from the western Pacific Ocean to the SCS. All seawater samples were filtered on board by using 0.45 mm membrane. (MilliPore Corp.). The results show that surface seawater REEs concentration are higher than the subsurface water indicating that surface seawater REEs distribution is likely impacted by terrigenous input through river discharges. Below the subsurface water, REEs concentrations generally increase with depths and are similar to what has been observed in open oceans.

Dissolved rare earth elements (REE) concentrations were measured by ThermoScientific XseriesII Inductively Coupled Plasma-mass Spectrometer (ICP-MS) at Laboratoire des Sciences du Climat et de l'Environnement (LSCE) in France. During measurement, REE concentrations were corrected of any sensitivity drift of the machine using In and Re as internal standards. The BCR-2 standard solution was diluted by 47,200 times during the measurement.