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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/15379

Title: 不同海洋環境下不同粒徑沉降顆粒POC/ 234Th 比值之探討
Ratios of POC and 234Th in different size classes of particles collected by sediment trap in different oceanic environments
Authors: 謝鈞盛
Contributors: NTOU:Institute of Marine Environmental Chemistry and Ecology
國立臺灣海洋大學:海洋環境化學與生態研究所
Keywords: 沉積物收集器;顆粒性有機碳;釷-234;顆粒性有機碳與釷-234比值;黑潮;湧升區
Sediment trap;POC;Th-234;POC/ Th-234 ratio;Kuroshio;upwelling
Date: 2010
Issue Date: 2011-06-30T08:11:53Z
Abstract: 沉積物收集器是最直接量測顆粒性有機碳通量的方法。然而此方法會受到水動力、浮游動物及顆粒溶解的影響。除了沉積物收集器外,海洋學家也常用釷-234/ 鈾-238不平衡法來估算顆粒性有機碳通量(也就是以水體估算的釷-234通量乘以下沉顆粒之POC/ 234Th 比值)。然而,釷鈾不平衡法所推導的碳通量也產生了極大的誤差,主要是來自釷-234通量的估算與POC/ 234Th比值的選擇,其中,以POC/ 234Th比值對顆粒性有機碳通量的計算影響最大。傳統上幫浦過濾的大顆粒(>50 mm)是被假設為下沉顆粒,但是這個假設並沒有經過驗證。本研究於台灣東北湧升區與黑潮測站在不同季節的航次中,量測不同粒徑(1~10 mm, 10~50 mm, 50~150 mm, >150 mm, 本文定義<50 mm為小顆粒,>50 mm為大顆粒)沉降顆粒之顆粒性有機碳濃度與釷-234活度,發現小顆粒的碳通量與釷-234通量分別占沉降顆粒(bulk, > 1 mm)碳通量與釷-234通量的26~67 %與39~91 %,這與一般認為下沉顆粒被大顆粒 主導有很大的不同。除了碳與釷-234通量的數據外,在未經過連續過濾的沉降顆粒掃描式電顯圖片中也證實了小顆粒的存在。此外,POC/ 234Th比值在大顆粒的變化(湧升區:1.2~31.1, 黑潮:3.2~12.6)較小顆粒(湧升區:0.6~8.0, 黑潮:0.8~3.0)大,若是以大顆粒的POC/ 234Th 比值估算顆粒性有機碳通量可能會造成較大誤差。因此,本研究建議要選擇總沉降顆粒的POC/ 234Th比值來估算顆粒性有機碳的通量,而不是單單使用大顆粒的POC/ 234Th 比值去估算碳通量。
Sediment trap is directly used to determine particulate organic carbon (POC) flux, while the problem of zooplankton and the solubilization of material after collection. 234Th has been increasingly used as a tracer to estimate POC flux in the surface ocean using the product of the POC/ 234Th ratio from sinking particles (e.g. trap-collected) times the 234Th ratio flux. However, the 234Th-derived POC flux may be significantly biased due to two factors : large uncertainties in estimates of the 234Th flux, and the great variability of POC/ 234Th ratio. The POC/ 234Th ratio from large, pump- collected (>50 mm), particles are considered to be representative of sinking particles, but this hypothesis has not been thoroughly tested. In this study, we present POC and 234Th data for various particle size classes (>150, 50-150, 10-50 and 1-10 mm, (here in we defined <50 mm is the “small particle”, >50 mm is the “large particle”) from trap-collected particles in the upwelling region of northeastern Taiwan and the Kuroshio. Within the trap-collected POC pool, the small particles contained the largest proportion of POC (bulk, >1 mm)(26-67%) and 234Th (39-91%) fluxes. SEM images of bulk (without sequential filtration) sinking particles evidence that sinking particles contained many small particles. In variation of POC/ 234Th ratio in the large particle (upwelling area: 1.2~31.1, Kuroshio: 3.2~12.6) was higher than that of POC/ 234Th ratio in the small particle (upwelling area: 0.6~8.0, Kuroshio: 0.8~3.0). The results indicate that 234Th-derived POC flux will be significantly overestimated of POC/ 234Th ratio in the large particle is used. Therefore, we suggest that the POC/ 234Th ratio in bulk sinking particles should be used in estimating POC flux when using the 234Th approach.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M97830003
http://ntour.ntou.edu.tw/ir/handle/987654321/15379
Appears in Collections:[海洋環境與生態研究所] 博碩士論文

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