The Pacific Ocean is a key region for rare earth element (REE) research owing to the occurrence of substantial REE-rich mud deposits on its seafloor. Understanding the sources and biogeochemical cycling of REEs is essential for sustainable resource exploitation and effective environmental risk assessment. However, existing studies rely predominantly on sediment records, while systematic observations of REEs in the overlying water column remain limited, particularly for marine particles that provide a critical link between the water column and sediments. In this study, we investigate the REE distributions in suspended particles collected from 0–4000 m depth across the Northwest Pacific Ocean (125°E-155°E, and 10°N-42°N) during the KK2003 (GEOTRACES GPpr15) and KK2202 cruises aboard R/V Tan Kah Kee. Our results show that Post Archean Australian Shale (PAAS)-normalized REE patterns evolve systematically with depth. In the euphotic zone, they are characterized by negative Ce anomalies (Ce_N/Ce_N^*≈0.7) and heavy REE enrichment relative to light REEs (Yb_N/Nd_N≈1.6), closely resembling dissolved REE patterns and indicating that freshly produced biogenic particles are the dominant carrier of REEs. With increasing depth, particulate REE signatures progressively shift, with Ce anomalies becoming positive (Ce_N/Ce_N^*≈1.6) in the twilight zone as Mn oxide (MnO₂) abundance increases, reflecting enhanced scavenging by MnO₂. In the deep ocean, particulate REE patterns gradually lose their distinct Ce anomalies and heavy REE enrichment, reflecting the increasing dominance of refractory lithogenic phases. Moreover, the degree of REE enrichment relative to PAAS, represented by Nd_N/Al_N, reaches a maximum (10.0~15.0) within the MnO₂ maximum zone before declining markedly in the deep ocean (2.0~3.0). This suggests that direct particle settling may play a limited role in REE enrichment in seafloor sediments. These results provide important constraints on the oceanic transfer of REEs, offering a framework for linking water-column processes with sedimentary REE enrichment.

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