Samples were filtered through a 0.40-μm Whatman membrane. The samples were then acidified to a pH of ~2 with high-purity HCl . From each sample, 15-20 L was placed in acid-cleaned bottles for Nd isotope composition analysis, and 500 mL was collected to determine the REE concentration. The filter membranes were cryopreserved for the determination of SPM. REE concentrations and Nd isotope compositions determined in these filtered waters were treated as dissolved-phase measurements (Nd<0.45μm). An unfiltered water sample was directly acidified to a pH 0.45μm).