碩士 / 國立臺灣大學 / 海洋研究所 / 84 / The study area of this thesis encompasses the continental shelf and the slope of the southern East China Sea, ranging from 26°20''N, 120°30''E to 25°10''N, 122°25''E. Large volume seawater was collected at four stations for dissolved and paniculate 234Th determinations in May(OR386) and November(OR405C) 1994. Colloidal 234Th distributions at two stations and in the surface water were also determined.
The results of two cruises show that TSM concentration decreases from the shelf to the open ocean while τd, τp and τT show an inverse trend. τd, τp and τT in the euphotic layer of the study area increase from 2~5 to 215~242 days, 2~7 to 66~94 days, and 8~9 to 765~892 days, respectively, from the shelf to the open ocean. In this thesis, we try to use 234Th as a tracer to estimate the carbon flux in the euphotic zone. The results show that the value of fratio is 0.24~0.43 on the shelf (stations 1 and 8) and less than 0.1 in the oligotrophic Kuroshio. The flux of 234Th directly measured by sediment trap about three times higher than calculated from the irreversible model. Dissolved 234Th is scavenged to a minimum value of 1.17 dpm/L at the depth of 700~1000m of the Okinawa Trough, which is due to the lateral transport of resuspended particles from the shelf/slope. The dissolved 234Th activity is 1.68~1.91 dpm/L in the bottom water of the Okinawa Trough and an enhanced scavenging caused by the hydrothermal system is suspected for this unusual phenomenon. Wall adsorption of 234Th in the filter cartridge of the ultrafiltration system was observed. For the colloidal phase, an amount of ~0.1 dpm/L 234Th was lost when separating colloids from the samples. However, the two sets of data, ultrafiltration and dead-end filtration, result in a similar distribution pattern in the study area.
| Identifer | oai:union.ndltd.org:TW/084NTU03274004 |
| Date | January 1996 |
| Creators | 李佳明 |
| Contributors | 魏慶琳 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 70 |
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