Research of marine geochemical cycles of novel trace metals.

为了了解海洋生物地球化学循环，我们研究了海洋中新型微量金属的分布和行为。首先，研究了新型微量金属银的全球分布，从白令海到南大洋。用“管道模型”分析了银在海洋中的分布，揭示了银在海洋中的生物地球化学过程。从高纬度地区银浓度升高的情况来看，地表水中的银主要通过中水垂直混合供给。其次，将阴离子交换树脂浓度法与同位素稀释电感耦合等离子体质谱法（ID-ICPMS）相结合，建立了天然水体中铂的测定方法。利用ID-ICPMS法测定东京湾河口的铂金，结果表明，河口地区的铂金被强烈清除。并与阴极溶出伏安法（CSV）进行了比较。CSV法测定的铂浓度较低，说明城市河流中铂与有机化合物络合较强。为了估计东京湾铂的来源，采用ID-ICPMS方法对雨水和农村河水进行了分析。这两个水域的铂浓度都很低，不可能是东京湾的主要来源。来自城市地区的人为输入和（或）河口颗粒物的溶解被认为是东京湾铂浓度升高的原因。在开阔海域，采用ID-ICPMS方法对日本海沟附近海域采集的海水样本进行了分析。该站铂的垂直剖面为准营养型，分布范围为0.3 ~ 1 pM。以往沉积圈闭实验表明，造岩物质的侧向搬运可能影响深水铂浓度的升高。

In order to understand the biogeochemical cycles in the ocean, we investigated the distributions and behaviors of the novel trace metals in the ocean.Firstly, the global distribution of silver, one of the novel trace metals, was studied from the Bering Sea to the Southern Ocean. The distribution was analyzed with a "pipe model" to reveal the biogeochemical process of silver in the ocean. Judging from the elevated silver concentrations in high-latitude regions, silver in the surface water is mainly supplied via vertical mixing from mid-water.Secondly, a determination method of platinum in natural waters was established by combining anion-exchange resin concentration method and isotope-dilution inductively coupled plasma mass spectrometry (ID-ICPMS). By determining platinum in the estuary of Tokyo Bay with this ID-ICPMS method, it is shown that platinum is scavenged at the estuary region vigorously. The results were also compared with those by cathodic stripping voltammetry(CSV). The lower platinum concentrations with CSV method imply that platinum is complexed strongly with organic compounds in the urban rivers. To estimate the sources of platinum into Tokyo Bay, the rain water and rural river water were analyzed with the ID-ICPMS method. The platinum concentrations in both waters were so low that both waters cannot be the main source for Tokyo Bay. Anthropogenic input from urban areas and (or) dissolution of particulate matter in the estuary are thought to elevate the platinum concentrations in Tokyo Bay.In the open ocean, the seawater samples collected around the Japan Trench areas were analyzed with this ID-ICPMS method. The vertical profile of platinum shows a quasi-nutrient type, ranged from 0.3 to 1 pM, in this station. Lateral transport of lithogenic materials, indicated from previous sediment trap experiments, may affect the elevated platinum concentrations in deep waters.