Determination And Analysis Of Rare Earth Elements In Sediment Cores Of East China-Yellow Sea And Suspended Particulate Materials Of Changjiang Estuary With HR-ICP-MS

Rare earth elements have similar chemical properties and low solubilities. They are difficult to be transferred in the processes of weathering, denudation, transportation, deposition and early diagenesis and bring a low fractionation. Rare earth elements are of significance to reveal the sources, formation conditions, provenances and climatic variation.We established the high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) method of rare earth elements in our lab and measured the samples of gravity core sediments and suspended particulate materials. The high resolving capability of the HR-ICP-MS could help us to detach the oxide interferences. Elimination of the spectral interferences, we obtained the results with high credibility. For the optimal precision and sensitivitiy, we optimized the working parameters and detection parameters of the instrument. We got a good effect of the standard reference materials of the sediments which digested by using nitric acid, hydrofluoric acid and perchloric acid in open wide system plus seal system. We measured rare earth elements with external standard method and internal standard method which utilized ¹⁰³Rh (2μg·L^-1) as internal standard. From measuring of the standard reference material GBW07309, the detection limits ranged from 0.37 to 9.36 ng·L^-1 the precision ranged from 0.42 to 2.51 %, the accuracy ranged from -7.9 to 7.9 % and the repeatability ranged from 0.04 to 12.32 mg·kg^-1 for different rare earth elements. The method had an excellence of high accuracy and the measured results of the standard reference sediments in river, estuary and sea showed close agreement with the certified values.We collected E2 core, E4 core and E5 core by the voyage of the Yellow Sea and East China Sea in September 2002. From the rare earth elements' contents, normalized distributions, ratios, anomaly and correlation, some conclusions had been realized: E4 core was in the area with high sedimentation rate of the Changjiang Estuary. The characters of rare earth elements in E4 were similar to the sediments of Changjiang which was the main source of rare earth elements in E4. All layers of E4 had different contents of rare earth elements between each other and varied with water discharge and sediment load of Changjiang during the past fifty years. E4 had a good record of El Nino event. The use of the rare earth fertilizers in recent years had not made rare earth elements changed obviously in sediments of Changjiang Estuary. E5 core was in the mud area which located at the south of Hangzhou Bay and the contents of rare earth elements were controlled by granularity effect. The rare earth elements' characters of normalized distributions, ratio and anomaly in the upper parts (upwards of 200 cm) of E5 were similar to E4 which indicated terrestrial inputs by Changjiang River. The lower parts of E5 had larger average diameter, lower contents of rare earth elements and positive Ce-anomaly which indicated another source. The sediments in the upper parts (upwards of 45 cm) of E2 had gentle distribution patterns, lower contents of rare earth elements and weak positive Ce-anomaly which may indicate mixed sources of Huanghe and deep-sea materials transported by Yellow Sea Warm Current. Correspondingly, the lower parts of E2 had higher contents of rare earth elements and their distribution patterns were very similar to the sediments of Huanghe which indicated terrestrial inputs by old Huanghe.Rare earth elements in suspended particulate materials of Changjiang Estuary in August 2005 indicated obvious characteristic of Changjiang Basin. The contents of rare earth elements in most samples ranged from 200 to 260 mg·kg^-1. All samples had LREE enrichment in chondrite normalized patterns and shale normalized patterns and had no Ce-anomaly with weak Eu-anomaly in chondrite normalized patterns. The constituents of rare earth elements in suspended particulate materials had no correlation with the concentrations of suspended particulate materials but correlated with the particulate concentrations of REEs in water. The south sewage outfall of Shanghai might bring the anomaly of some surface samples. With the increase of salinity, the contents of rare earth elements decreased and the values of 5Ce increased slightly. This might be attributed by desorption on the surface of suspended particulate materials or diluting effect from open sea and the oxidizing of Ce.