碩士 / 臺灣大學 / 海洋研究所 / 98 / A total of 85 surface seawater samples were collected for the determination of dissolved and particulate 210Pb and 210Po as part of the Joint Hydrographic Survey project from 31 May to 11 June 2007. Sampling tasks were carried out on board R/V Ocean Researcher I (OR1-833), II and III (OR2-1444 and OR3-1226), and Fishery Researcher I (FR1-9605). The results provide the first synoptic picture of the spatial distributions of 210Pb and 210Po in the surface waters surrounding Taiwan. About with the hydrographic data, it is evident that the spatial distributions of the two radionuclides are controlled by the current system and particle scavenging force in the seas surrounding Taiwan.
A tongue structure with relatively low dissolved 210Pb extends northwardly in the region off the eastern Taiwan, where the Kuroshio pathway is found. The lowest dissolved 210Pb was found in the coastal water of China and the coastal water of western Taiwan whereas the highest value was found in the region off eastern Taiwan. Along the Peng-Hu channel, the mixture of Kuroshio Branch Water and the northern South China Sea surface water formed a tongue of relatively high dissolved 210Pb, which extends northwardly into the Taiwan Strait. The dissolved 210Pb in this water lie between the value in the Taiwan Strait and that in the region off eastern Taiwan. The particulate 210Pb was significantly lower than dissolved 210Pb, and its spatial distribution is not as systematic as that of dissolved 210Pb.
The contour lines of dissolved and particulate 210Po off eastern Taiwan revealed a meandering feature, where the Kuroshio flows through. Compared with hydrographic data, the contour of 6 dpm/100L dissolved 210Po matches with the S=34.2 contour, indicating 210Po scavenging rate is affected by the interaction of the Kuroshio and the coastal water off western Taiwan. An elevation of particulate 210Po in the region is due to the increased primary production off northeastern Taiwan, in which the scavenging of 210Po by the biological particles is enhanced.
Both 210Pb and 210Po in the region to the west of the northern South China Sea were lower than that in the Kuroshio, indicating enhanced removal of the two radionuclides after the Kuroshio intrusion through the Luzon Strait. Moreover, the tongues of high 210Pb and 210Po originated from the northern South China Sea extend along the Peng-Hu Channel, depicting the important of lateral transport plays an important role in the distributions of the two radionuclides.
The residence times of 210Pb and 210Po in the surface water surrounding Taiwan were estimated by the irreversible scavenging model. The residence time of 210Po was 600 days in the shelf area and 200 days in the Kuroshio. The residence time of 210Pb was highly related to the atmospheric 210Pb flux. If 0.6 dpm/cm2/y of atmospheric 210Pb flux was assumed, the residence times of 210Pb were 50 days and 200 days in the coastal region and in the open ocean, respectively. If a higher atmospheric 210Pb flux of 1.6 dpm/cm2/y was assumed, then the residence times would be 25 days and 100 days in the coastal and in the open ocean, respectively.
| Identifer | oai:union.ndltd.org:TW/098NTU05279001 |
| Date | January 2010 |
| Creators | Pin-Ruei Chen, 陳品叡 |
| Contributors | Ching-Ling Wei, 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 | 50 |
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