ABSTRACT
The concentrations and distributions of trace metals and rare earth elements (REE) in sediment and mussel samples collected from the India Ocean hydrothermal area were analyzed.The metal correlation between organisms and sediments was investigated, and the ecological and chemical characteristics of REE were also explored.The results showed that, the trace metals in sediments were mainly Fe (96.6 mg/kg), Mn (1.14 mg/kg) and Zn (322.6 μg/kg), and Fe had high ratio of 98.15% by normalized calculation, which indicated that the available sediments in this studying hydrothermal area mainly consisted of iron ore substances.Trace metals and REE distributions all had good correlation between deep-sea sediments and deep-sea mussels, and the correlation coefficients were 0.991 for trace metals and 0.996 for REE.The contents and distributions of metal elements in deep-sea mussels were different from those in offshore mussels.The REE distributions in sediments and mussels showed obvious fractionation phenomenon, and the enrichment of LREE in mussels was significant.Through the REE patterns, Eu and Gd in sediments and mussels all showed anomalies, and Eu had a significant abnormal phenomenon in deep-sea sediments and deep-sea mussels.Besides, δEu values were 9.50, 10.68 and 0.23 in deep-sea sediments, deep-sea mussels and offshore mussels, respectively, and δCe were 2.21, 2.71 and 4.38, which showed that the enrichment sources of REE in offshore mussels and deep-sea mussels were different, and the REE in sediments and mussels from the India Ocean were homologous.
ABSTRACT
A microwave digestion system was preparation for the digestion of the sediment samples of 16 stations in the Southe mid_Atlantic ridge by using HNO3_H2 O2_HF as the digestion reagent. The rare earth elements ( RE ) in sediments were determined by inductively coupled plasma mass spectrometry, and distribution characteristics of rare earth elements were studied. The microwave digestion_ICP_MS method was used for the determination of rare earth elements with a good linear relationship ( r=0 . 9997-1 . 0000 ) for each element. The detection limit reached ng/L level, the relative standard deviation ( RSD, n=3 ) was less than 3% and the relative error was 6%. The total amount of rare earth elements (ΣRE) in sediment samples from 16 stations varied in the range of 37. 25-134. 77 μg/g, the ratio range of light RE/heavy RE ( LRE/HRE) was 0 . 61-1 . 70 , the average value was 1 . 27 , and the enrichment of light rare earth elements in sediments was slightly obvious. The RE distribution patterns were basically the same in each station with obvious fractionation between LRE and HRE. The RE distribution patterns were also similar in sediments from different sources with slightly difference between terrestrial and marine sediments. The δEu and δCe in the sediments had negative anomaly which showed that the rare earth elements in sediments came from the seawater. This study first analyzed the content and distribution of rare earth elements in the southern Atlantic, providing data and technical support for further study of the distribution of rare earth elements in the Atlantic.
ABSTRACT
BACKGROUND:Absorbable suture with good biocompatibility and mechanical strength has been extensively used in the clinic. OBJECTIVE: To explorein vitro degradation of different absorbable sutures, to analyze the clinical superiority of absorbable sutures and the influential factors for itsin vitro degradation. METHODS: After retrieval of related literatures concerning degradation and application of absorbable suture material, we retrospectively analyzed relevant articles addressing influential factors for performance and degradation of absorbable suture materials, and comparison of clinical absorbable and nonabsorbable sutures, thereby providing theoretical evidence for clinical application. RESULTS AND CONCLUSION: Absorbable sutures can be completely degraded and absorbed by the body, with no adverse reaction and no scars after wound healing. Absorbable sutures overcome the shortcomings of nonabsorbable sutures that cannot break down in the body. The absorption of its degradation products in vivo has two pathways: one is the phagocytosis of giant cels and phagocytes in the body, and the other is that the degradation products enter the body fluids and blood. For example, lactic acid is absorbed and excretedvia the systemic circulation. There is a very complicated physiological environment in the human body, and various factors can affect material properties. In addition, the different kinds of materials have different degradation mannersin vivo. Therefore, it is necessary to design, synthesize and process biodegradable polymer materialswith special properties within a certain range to meet the clinical needs.