Europium anomaly as a robust geogenic fingerprint for the geographical origin of aquatic products: A case study of nori (Neopyropia yezoensis) from the Japanese market

Rare earth element (REE) concentration patterns, while essential in geochemistry for tracing sample histories, have yet to be utilised entirely in food origin authentication. This research analysed 13 heavy metal(oid)s and REEs in Japanese edible seaweed Nori sheet samples (Neopyropia yezoensis), showing that the concentrations mirror the laver cultivation area's geological features (island arc-trench systems vs. continental crust). Thresholds for cadmium (0.5 ppm) and thorium (3.3 ppb) differentiate Japanese products from Korean imports. The slope of REE pattern, gadolinium anomalies, and yttrium/holmium ratios were also examined. However, nori samples significantly conveyed europium (Eu) anomalies, aligning with the mariculture hinterland's geochemistry. Both Japan's major seaweed mariculture areas, the Ariake Sea and the Seto Inland Sea, and Korean imports revealed distinct Eu anomalies (Eu/Eu* = 0.81-0.90, 0.58-0.66, 0.71-0.77), underscoring the potential of Eu anomalies as reliable seafood origin verifiers. This was also confirmed by literature values of Chinese samples.