碩士 / 國立中山大學 / 海洋地質及化學研究所 / 101 / 234Th/238U has been used to estimate particulate organic carbon (POC) export fluxes, based on the POC/234Th ratio of sinking particles and the 234Th flux, in the ocean. However, the 234Th-derived POC flux may be significantly biased due to the variation of use POC/234Th ratios from large particles (>50μm). More recently, some studies use particle size distributions in the upper ocean to calculate POC flux. Although Hung and Gong (2010) and Hung et al. (2012) have measured the size distributions in sinking particle, but their experiments were limited in some regions. Therefore, the size distributions in sinking particle are not clearly. In this study, we collected sinking particles with three different instruments (Laser in-situ Scattering and Transmissometry (LISST-100X), cylindrical and conical sediment traps) from the northern South China Sea, the upwelling region off the northeast Taiwan (where diatoms are the most dominant group) and the Northwestern Pacific (where picoplanktondominated), measured POC and 234Th data for various particle size classes (1-50 μm, 50-330 μm and >330 μm, (herein we defined that < 50μm is the “ small particle”). The results show the small particles, investigated by-cylindrical and conical traps, contained the largest proportion of POC (46~66%, by cylindrical traps) and (37~75%, by conical traps) and the distribution of particle size measured by LISST-100X howed small particles had the elevated shares of total particle volume. SEM images of bulk (without sequential filtration) sinking particles also evidence that sinking particles contained many small particles. Besides, the model-derived POC flux in small particles using particle size distribution is quite comparable with the measured POC flux by sediment trap, while the POC fluxes measured by both methods show pronounced difference suggesting that it is worthy for studying in the future. Overall, our results suggest that the contribution of particles smaller than 50 μm to the sinking POC flux can be a major fraction of the total sinking flux, and thus, particles smaller than 50 μm cannot be ignored when using Th-234/U-238 disequilibrium to estimate POC flux in the water column.
| Identifer | oai:union.ndltd.org:TW/101NSYS5271004 |
| Date | January 2013 |
| Creators | Ying-Hsueh Chien, 錢映學 |
| Contributors | Chin-Chang Hung, 洪慶章 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 96 |
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