本研究之目的在於了解台灣南部海域冬夏二季水體中釙-210 及鉛- 210
在顆粒態及溶解態中的分佈及變化, 並藉此推算該區顆粒物質對此二核種
的清除速率及其滯留時間。再與前人在東北海域所量測的資料作比較 ,
以了解此二核種在此二海域分佈的異同。 83 年 9 月及 84 年 1 月的採
樣及分析結果, 表水的鉛-210 及釙- 210 其全量及溶解態皆有離岸遞增
的趨勢, 而顆粒態則有遞減的現象。 83 年 9 月之顆粒態鉛-210 活性
較 84 年 1 月者高, 但釙-210 則不論是顆粒態或是溶解態, 84 年 1 月
的活性皆較 83 年 9 月為高。在滯留時間方面, 84 年 1 月全量鉛-210
及釙-210 之滯留時間大致上皆較 83年 9 月為長, 顯示冬夏二季間有明
顯變化。比較三次採樣, 各測站的鉛-210 及釙-210 剖面在各季皆有差
別, 顯示此二核種在水柱中的不平衡狀態會隨著各季的水文狀況變化而改
變。根據鐳-226、鉛-210 及釙-210 三核種的活性不平衡狀態可將水柱分
為二及三層, 用以計算鉛及釙的滯留時間及再循環效率。結果顯示
鉛-210 在上層水中各季的滯留時間相差不大, 但在下層水則因各站之活
性不平衡程度與儲量皆不相同, 故據此計算之滯留時間便有較大的差異。
在各次採樣的上、中、下層水中因水團混合的季節變化, 使釙-210 之剖
面分佈改變,故其滯留時間也隨之改變。在三次採樣中, 下層水鉛-210 均
無再循環現象,而 84 年 1 月時測站 1 及 7 中層水的釙-210 再循環效
率超過 100% ,故應有一側向釙-210 之來源。與東北海域的資料相較,
鐳-226 在此二海域的活性相不大, 但在分佈上則有一明顯差異: 東北海
域在約 100 米處有一極小值, 南部海域則無。鉛-210 在東北海域的活性
較南部海域為高, 但在剖面形態上則大致相似。釙-210 活性在東北及南
部海域的差異並不大,剖面分佈亦相似。因鐳-226、鉛-210 及釙-210 在
東北及南部海域的濃度分佈及活性不平衡類似, 故此二海域的顆粒對
鉛-210 及釙-210 之清除速率或其滯留時間亦相差不大。

The goals of this study were to understand the distributions
and seasonal variations of Pb-210 and Po-210 in both the parti-
culate and dissolved phases at the sea off southern Taiwan and
to estimate the particulate scavenging rates and the mean resi-
dence times of these two nuclides with respect to particulate
scavenging in this area. Dissolved and total Pb-210 and Po-210
in surfacr water inc- reased while particulate Pb-210 decreased
away from the coast for samples collected during September,
1994 and January, 1995. The mean residence times for total
Pb-210 and Po-210 with resp- ect to particulate scavening were
generally longer in January, 1995 indicating distinct
variations between the two seasons. The Pb-210 and Po-210
profiles measured from each station were different for the
three sampling periods, indicating that the radioactive
disequilibrium between the two nuclides in a water column might
be altered by changing hydrographic conditions. The mean
residence times of Pb-210 in the upper layer varied both
spatially and temporally due to different inventories and
variable extent of disequilibrium. The mean residence times of
Po-210 in the upper, intermediate and lower layers were
different for the three sampling periods, reflect- ing the
variable Po-210 profiles produced by mixing of differ- ent
water masses in different seasons. The Po-210 recycling
efficiency at stations 1 and 7 in January, 1995 was over 100%,
requiring a lateral Po-210 source. The activities of Ra-226 at
the seas off northeastern and southern Taiwan were comparable,
but the profile patterns were different. The Pb-210 profiles
off northeastern Taiwan were similar to those off southern
Taiwan, but the former had higher concentrations. The Po-210
profiles off northeastern and southern Taiwan were similar with
comparable activities.