| 海水溶解磷酸盐氧同位素组成的测定 |
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| 关键词:seawater dissolved inorganic phosphate oxygen isotope method |
| 基金项目:由国家自然科学基金(编号: 11075221, 41006072, 40706033) |
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| The Measurement of Oxygen Isotope Composition of Dissolved Inorganic Phosphate in Seawater |
| The oxygen isotope fractionation between biogenic phosphate and water is primarily controlled by temperature and biological activity, so the oxygen isotope composition of phosphate (δ18OP) has been used to measure the paleotemperature and trace phosphorus biogeochemical cycles. Recently the study of δ18OP has attracted much attention. In addition to traditional biogenic apatite paleotemperature measurements, the studies are mostly concentrated on the phosphorus cycle. δ18OP of dissolved inorganic phosphate (DIP) is an effective proxy for tracing sources and biogeochemical cycle of phosphorus. Seawater composition is very complex, so the seawater sample must be separated and purified before the δ18OP measurement. Professor Paytan of University of California (Santa Cruz), and Professor Blake of Yale University have established their respective δ18OP measurement methods of seawater DIP, but the two method have their respective advantages and disadvantages. The authors combined the advantages of the two methods and modified some procedures to establish an improved δ18OP measurement method of seawater DIP. In this method, DIP in water samples is concentrated through Mg(OH)2-PO4 co-precipitation, which can exclude a portion of the dissolved organic material (DOM) and interfering ions; then the resulting solution is converted to CePO4 precipitate to further separate Pi from dissolved salts, especially Cl-, and subsequently the solution is purified through a batch mode cation resin to remove Ce3+ from the solution and through anion resin column treatment to remove the dissolved organic material. Phosphate is converted to silver phosphate ultimately, which is in turn pyrolitically decomposed to CO at 1350℃ and δ18O is analyzed with continuous-flow isotope ration mass spectrometry (IRMS). The results show that this procedure can remove the interfering compounds effectively and preserve the initial oxygen isotope composition. The sample amount needed is 0.3 mg (Ag3PO4), with an average standard deviation between 0.2‰ and 0.3‰. |
| LU Yang-yang,ZHENG Zhen-zhen,YIN Xi-jie,CHEN Zhi-gang,CAI Yi-hua,LIU Guang-shan,HUANG Yi-pu.2012.The Measurement of Oxygen Isotope Composition of Dissolved Inorganic Phosphate in Seawater[J].Acta Geoscientica Sinica,33(6):961-966. |
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