Paleoclimatological records of the Great Ghost Lake in Taiwan

Distinctive white laminations appear in the black sediments of the Great Ghost Lake in Taiwan. Compared with the black sediments, these white laminations have lower porosity, organic matter content and C/N ratio, but higher C/S and N/S ratios, and with organic matter characterized by the phytoplanktons. It suggests that they may be deposited in cooler and drier periods. The organic matter of the black sediments was mainly from land plants, suggesting deposition under warmer and wetter climates. Major white laminations appear in 0 AD, 500 AD, 700 AD, 900 AD, 1 350 AD, 1 500 AD, etc., and correspond to the periods of cold/dry and frequent dust storms from the historical and natural records of China or Peru. These seem to reflect large-scale climatic changes.     

A Seasonally Anoxic Mountain Lake with an Active Fe Cycle in Tropical Taiwan

Variations of temperature and oxygen indicate that the 2150 m high Great Ghost Lake in tropical Taiwan is seasonally stratified and anoxic. Low concentrations of ions and nutrients and the similarity in the distribution of the reduced species in the water column in the early stages of stagnation indicate that the production of the reduced species occurs mainly in the sediments with a subsequent release into the overlying water. In addition, the high organic matter content in the sediments and the short period of water overturn make Fe(II) the most abundant reduced species in the sediments and in the water column. As a result, the annual Fe cycle plays one of the most important roles in regulating the water chemistry and in driving the reduced species from the sediments to the anoxic hypolimnion. The distribution of reduced species during the stagnation is in agreement with the thermodynamic sequence. The accumulation rates of Fe2+, Mn2+, NH4+, sulfide and CH4 in the water column during the early stages of stagnation are about 5.07, 0.059, 1.69, 0.015 and 1.65 mmol m-2 day-1, respectively.     

2600年以来台湾大鬼湖中的金属通量

Sediment cores were collected from the remote subalpine Great Ghost Lake in southern Taiwan. Because the lake is anoxic the sediments are well preserved, distinctive past variations can be dated accurately. The vertical distributions of total and acid-leached metal concentrations for aluminum, arsenic, cadmium, cerium, chromium, cesium, copper, iron, magnesium, manganese, nickel, lead, rubidium, strontium, vanadium and zinc are measured and the fluxes determined. The dates of higher fluxes in the past 2600 years seem to correlate with dry spells. Further, trace metal fluxes show a large increase but Pb-206/Pb-207 ratios show a large decrease since 1950, suggesting a significant anthropogenic input.     

湖泊中溶解氧极大值之成因

本文对位于台湾南部两个次高海拔湖泊－大鬼湖及万山神池进行研究,并试图探讨此二无明显进,出水口之封闭型湖泊中,水体溶解氧垂直分布出现极大值之成因,此二次高海拔湖泊地处偏远,人烟罕至,因此较不受人为干扰,为研究湖泊水体中种种自然作用的良好对象,大鬼湖平均水深约14.8m,最深处约40m,降冬季外,水体均有分层现象,1988年夏季资料显示,水深16m以下水体趋于无氧状态,且于此深度以上的溶氧饱和值,均接近当地的大气饱和值（约78％）,经各种资料推断,此极大值的成因,除水团乃于春季时留下主溶氧值之外,应综合了季节增温效应下使表水向下温合的物理作用（尤其是山区明显的口,夜温差所引起的表水冷却向下混合作用,且其混合深度随季节增温而逐步变浅）,消耗溶解氧的生物作用及跃层存在等影响因素,而非单纯的物理或生物作用所造成,1991年4月万山神池观测资料显示,湖水平均深度约8m,最深可达14m ,其氧饱和程序分布在80％－104％之间,表水接近近当地饱和值（78％）,而于1.5m处往下增加,于2m处有溶解氧及和程度极大值,比当时大气饱合值高约20％,此极大值深度与叶绿素a极大值深度相吻合,主要由生物之光合作用造成,此外,于此深度pH值亦有明显增加现象,更证实了生物作用的存在,此二湖环境背景相似,且水泥中均出现溶氧极大值,但二者间极大值却有不同的成因,经曲两不同成因的比较,将可提供许多相关研究资料。     

中国台湾大鬼湖沉积物所保留之降尘记录

本文以中国台湾大鬼湖沉积物岩芯回推此区过去1600年以来PM10与空飘重金属之变化情形.湖区沉积物主要来自集水区冲刷来的岩屑及植物碎屑,一般为黑色,平均粒径30～50μm,PM10约10%～20%.但在干冷时期,由空飘来的祖国大陆北方沙尘较多,形成相对亮度指数较高的白层,其磁化率较高、平均粒径约10μm,且PM10可达60%;而从1350年以来,无机元素沉积累积速率较前期有所增加,且白层中大部分无机元素皆有较高的累积速率,可能导因于空飘物质输入量增加.较暖湿时期,则以亲有机质元素之沉积累积速率较高.