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Title: POC/234Th ratio在沉降顆粒與懸浮顆粒之比較
Comparison of POC/Th-234 in sinking particles and suspended particles
Authors: Po-Kai Hu
胡博凱
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: 碳通量;沉積物收集器;釷-234
POC flux;sediment trap;Th-234
Date: 2011
Issue Date: 2011-11-25T03:27:09Z
Abstract: 釷鈾不平衡法(234Th / 238U disequilibrium)是用來估算顆粒性有機碳通量的方法之一,在過去的研究,是假設現場幫浦過濾得到的大顆粒(>50 m)為下沉顆粒,Hung and Gong(2010)用不同粒徑的濾膜來分析下沉顆粒之有機碳與釷-234含量,發現小顆粒(<50 m)是不可忽略的,但是他們並未同時比較幫浦收集的有機碳與釷-234的含量。本研究於2010年間在西北太平洋深水海域,利用”採後過濾法”、”自然分相法”、”幫浦過濾法”,同時測量水體中不同粒徑(1-50 m、50-355 m,本文定義>50 m為大顆粒,<50 m為小顆粒)的沉降顆粒與懸浮顆粒之有機碳與釷-234濃度。 結果顯示“採後過濾法”所得小顆粒(<50m)分別佔總沉降顆粒碳通量與釷-234通量的34~78%與48~91%,而”自然分相法”的小顆粒分別佔總沉降顆粒碳與釷-234通量的11~68%與11~66% 。”幫浦過濾法”所得的小顆粒分別佔總碳含量(濃度)與釷-234濃度的88~98%與43~98%。此結果顯示幫浦收集的大、小顆粒有機碳與釷-234的含量確實是與下沉顆粒有很大的不同,因此,若是以幫浦收集大顆粒的POC/234Th比值來估算顆粒性有機碳通量可能會造成較大誤差。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,而不是僅僅採用”幫浦過濾法”所收集的大顆粒POC/234Th比值來計算碳通量。
234Th/238U has been increasingly used as a tracer to estimate particulate organic carbon(POC)fluxes by calculating product of the POC/234Th ratio of sinking particles and the 234Th flux. Large(>50 m)pump-collected particles are assumed to be representative of sinking particles. Hung and Gong(2010)in the Northwestern Pacific found that small(<50 m)sinking particles(collected by sediment traps)dominated the bulk POC flux, but they did not simultaneously measure the contents of POC and Th-234 in both trap- and in situ pump-collected particles.  Here we present POC and 234Th data from the N Pacific for two particle size classes(1-50 and 50-355 m)from both trap- and pump-collected particles in the northwestern Pacific using three methods:trap-collected particles with gravity filtration(PGF), trap-collected particles with natural filtration(PNF), and pump-collected particles with sequential filtration(PSF). POC in small(<50 µm)particles using PGF, PNF and PSF accounted for 34-78%, 30-75% and 88-98%, respectively. Th-234 in small(<50 µm)particles using PGF, PNF and PSF showed a similar range, i.e., it accounted for 44-89%, 11-75% and 43-98%, respectively. These results clearly show that pump-collected large and small particles are not only different from trap-collected particles in terms of POC and Th-234 concentrations, but also POC and Th-234 contents in small(pump-collected)particles are significantly larger than large(pump-collected)particles.These results suggest that the contribution of particles smaller than 50 m to the settling flux is larger than previously thought. Thus, POC/234Th ratios conventionally derived from large pump-collected particles may not be appropriate for esti-mating POC flux. Instead, we suggest that POC/234Th ratios in sinking particles should be used for estimating POC flux.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M98830005
http://ntour.ntou.edu.tw/handle/987654321/29936
Appears in Collections:[海洋環境與生態研究所] 博碩士論文

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