Study on Ecological and Chemical Properties of Rare Earth Elements in Tropical Marine Organisms

A total of 30 kinds of fish samples, 5 kinds of shellfish samples and 4 kinds of crustacean samples from the Nansha sea area in China were digested using a microwave digestion system with HNO3-H2O2 as the digestion reagent. Then, the contents (ICP-MS determination) and ecological chemical characteristics of rare earth elements (REEs) were studied. The results showed that the method of microwave digestion-ICP-MS for the determination of rare earth elements was perfect, and the linear relationship for each element was good with r ≥ 0.9997. The detection limit reached ng L−1 level with a relative standard deviation (RSD, n = 3) of less than 5.0%. The recovery of REEs was between 91.5% and 106.7%. The total amount of REEs in fishes, shellfishes, and crustaceans were (5.0–34.8) μg kg−1, (30.4–1481) μg kg−1, and (103–863) μg kg−1, individually. The order of the enrichment average contents of the REEs in the three species was crustacean>shellfish>fish. The 14 kinds of REE contents in fish/shellfish/crustacean showed a significantly positive correlation (r > 0.80). The contents of light REEs (from La to Eu) were higher than those of heavy REEs (from Gd to Lu). The light and heavy REEs demonstrated obvious fractionation, and the REE distribution pattern in fish/shellfish/crustacean was consistent with the negative anomaly of Gd. The σEu values had negative anomalies, which were similar to the σEu values in the corresponding area sediment, and σCe values showed positive anomalies, which showed that Ce followed a different oxidation and reduction process in the organism and sediment deposition. At the same time, the enrichment relationship of REEs in sediment and organism was also studied. In this study, the content and distribution of REEs in the tropical marine fish/shellfish/shellfish were analyzed, which could provide basic data for the study of the level, migration, and accumulation of REEs in the environment of South China Sea.