Fast determination of coral skeletal rare earth elements in picogram quantities and its application
Date Issued
2009
Date
2009
Author(s)
Wu, Chung-Che
Abstract
Direct measurement of picogram-quantity REE levels in coral samples on an inductively coupled plasma sector field mass spectrometer, ICP-SF-MS, Thermo Electron ELEMENT2, has been developed. A dry introduction system, Cetac ARIDUS, and an ESI micro-nebulizer with an uptake rate 80 μl/min were used to enhance sensitivity, improve detection limit and reduce sample size. A peak hopping mode on a single secondary electron multiplier was used to measure the ion beams of 46Ca, 89Y, 138Ba, 139La, 140Ce, 141Pr, 146Nd, 147Sm, 153Eu, 160Gd, 159Tb, 163Dy, 165Ho, 166Er, 169Tm, 172Yb, and 175Lu. REE/Ca ratios were calculated directly from intensities of ion beams, using external matrix-matched synthetic standards to correct for instrumental ratio drifting and mass discrimination. Every four samples were bracketed with one standard. Internal 2-sigma precision is 0.4-1.4% for all REE/Ca ratios. Replicate measurements made on standards and samples show external precisions of 0.8-1.6% (2σ) can be achieved. The developed was applied to determine REE records of a living coral Porites, collected from Son Tra island (16°12’59.4”N, 108°11’57.1”E), central Vietnam, western South China Sea (SCS) in 2005. The 1991 REE anomalies suggest that a massive mass coral mortality event in the summer and fall of 1991 in the SCS might be enhanced by the volcanic ash fallout following the eruption of Mount Pinatubo on June 15, 1991. This established technique can provide a direct measurement of carbonate REE isotopic composition in picogram quantities without chemical separation steps. The requirement of a small sample size of 10 μg carbonate offers high spatial resolution REE records not only for corals, but for other different natural slow-growth-rate carbonates, such as sclerosponges, tufa and speleothems.
Subjects
REEs
picogram quantities
coral
volcano eruption
Type
thesis
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