Research of marine geochemical cycles of novel trace metals.

为了了解海洋中的生物地球化学循环，我们研究了新型痕量金属银在海洋中的分布和行为。首先，研究了从白令海到南大洋的全球分布。用“管状模型”分析了银在海洋中的分布，揭示了海洋中银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，地表水中的银主要是通过中层垂直混合提供的。其次，建立了阴离子交换树脂浓缩法和同位素稀释电感耦合等离子体质谱(ID-ICPMS)相结合测定天然水中铂的方法。用ID-ICPMS法测定了东京湾入海口中的铂，结果表明，在入海口区域，铂被强烈地清除。并与阴极溶出伏安法(CSV)进行了比较。CSV法测得的较低的铂浓度表明，城市河流中的铂与有机化合物有很强的络合作用。为了估计进入东京湾的铂的来源，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，因此这两个水域不可能是东京湾的主要来源。城市地区的人为输入和(或)河口颗粒物的溶解被认为提高了东京湾的铂浓度。在公海上，用ID-ICPMS方法对日本海沟周围采集的海水样品进行了分析。该站铂的垂向剖面呈准营养型，变化范围为0.3~1 pm。以前的沉积物捕集实验表明，致岩物质的横向运移可能会影响深水中铂浓度的升高。

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.