HR: 0830h
AN: OS11A-03    [Abstracts]
TI: 210Po Enrichment Relative to 210Pb in the Planktons Collected from the Northern South China Sea
AU: * Wang, P
EM: ycchung@mail.nsysu.edu.tw
AF: Institute of Marine Geology and Chemistry, National Sun Yat-sen University, Kaohsiung, 80424 Taiwan
AU: Chung, Y
EM: ycchung@mail.nsysu.edu.tw
AF: Institute of Marine Geology and Chemistry, National Sun Yat-sen University, Kaohsiung, 80424 Taiwan
AB: Plankton samples have been collected by net-towing within the top 100m layer from the northern South China Sea (SCS) mainly during a summer (July, 2003) and a winter (February, 2004) cruises. Each of the plankton samples was totally digested with a known 209Po spike and stable Pb as yield tracer, and Po isotopes were auto-plated onto a silver disc for alpha assay of its 210Po activity. The sample was then purified for 210Pb determination by either a second alpha assay of its in-grown 210Po or counting its in-grown 210Bi activity, the energetic beta emitter of 210Pb daughter. 210Po activity was decay-corrected to the sampling date based on the 210Pb activity. The results show significant temporal and spatial variations of 210Po and 210Pb, especially the former. 210Po in the planktons range from about 100 to 350 dpm/g, while 210Pb varies generally between 10 and 20 dpm/g, indicating large enrichment of 210Po relative to 210Pb with 210Po/210Pb ratios being generally about 10 to 15. This is due to a close affiliation of 210Po with the planktons and a repulsion of 210Pb by the planktons. At some of the locations where the particulate 210Po and 210Pb were measured from the filtered samples whose organic matter (POM) contents were estimated (25 to 35 percent), the partition of 210Po and 210Pb in both the planktons and non-planktons (inorganic or aluminosilicate materials) can be evaluated. The 210Po activity ratio between planktons and non-organic matters varies from about 1 to 3, while the corresponding 210Pb ratio is about 0.03 to 0.05. This suggests that 210Po is preferentially enriched in the planktons by a factor up to 3 but 210Pb is strongly repulsed by the planktons, i.e. only 3 to 5 percent of the particulate 210Pb is associated with the planktons. The planktons collected from the area southwest off Taiwan show that the 210Po/210Pb activity ratio is higher, at about 30, with much lower 210Po and 210Pb activities, i.e. 45 and 1.6 dpm/g, respectively. In this area, 210Po in the planktons is about 5 to 8 times high than in the non-organic particulates, but 210Pb in the planktons remains at about 4 percent of the non-organic particulates. Large variation of 210Po and 210Pb activities observed on the planktons collected from different areas may be due to different types and amounts of the planktons and varying particulate matter properties, such as the abundance and size distribution.
DE: 1050 Marine geochemistry (4835, 4850)
DE: 4835 Inorganic marine chemistry
DE: 4850 Organic marine chemistry
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly