Silver: Concentrations, Sources, Processes in Fresh Water

淡水中银的浓度、来源、过程

• 批准号: 9406373
• 负责人: Gaboury Benoit
• 金额: $ 9.24万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-08-15 至 1996-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9406373&HistoricalAwards=false
• 关键词: Silver; Concentrations; Sources; Processes; Fresh

9406373 Benoit Silver is one of the most toxic metals in the aquatic environment, yet, because of past contamination artifacts, there are currently no reliable data on its concentration, transport, and fate in fresh waters. Based on lab experiments that simulate estuarine conditions, silver at moderate levels can be directly toxic to plankton and invertebrates while low levels can influence estuarine community structure and reduce bivalve growth rates. Fresh waters, having more silver sources and less complexation by chloride than do estuaries, are likely to have an even greater problem with silver toxicity. Silver's naturally low abundance means that it may derive almost entirely from anthropogenic sources, and can serve as a non-degradable tracer of pollution, free from obfuscation by natural background concentration variations. An equally important reason to study silver is that it is one of the few pure class B metals, and as such, its study can help to delineate one end of the total range of metal behavior. At present the aquatic chemistry of silver is poorly understood. Because of the almost complete lack of reliable information on freshwater silver, this proposal is designed as a reconnaissance to explore the biogeochemical context of silver cycling and to position researchers for more detailed studies of specific processes in the future. The research comprises three main components: 1) to initiate establishment of benchmark Ag levels in freshwater, 2) to identify and quantify natural and anthropogenic sources, and 3) to specify and begin to investigate processes and mechanisms that control silver's transport, bioavailability, and fate. The research will use ultra-clean methods to avoid contamination artifacts that have plagued nearly all previous studies on trace metals in fresh waters. An important goal is to prompt additional freshwater studies that use these methods. The investigation will be conducted along the entire length of the once highly- industrialized Quinnipiac River, including a mid-stream lake. A mass balance approach will be used, providing the opportunity to compare natural, point, and nonpoint sources of silver, and to quantify removal rates. Based on preliminary measurements, headwaters of the Quinnipiac are extremely clean, while the lower river is badly contaminated. Two other rivers, the Naugatuck and Connecticut, will be studied in less depth in order to increase the generality of the findings within the constraints of a modest budget. Of these two, the Naugatuck has a history of severe metal pollution, while the Connecticut does not. Techniques that will be used are: 1) conventional membrane filtration (to separate particulate and non-particulate fractions), 2) ultrafiltration (for colloidal forms), 3) anodic stripping voltammetry (to appraise silver -organic matter complexes), 4) thermodynamic calculations (to estimate dissolved ion speciation), 5) measurement of pore water (to evaluate diffusive flux from sediments), and 6) Ag concentration and 210Pb geochronology of sediments (to assess resuspension fluxes and document contamination history).

9406373 Benoit 银是水生环境中毒性最大的金属之一，然而，由于过去的污染人工制品，目前还没有关于其在淡水沃茨中的浓度、运输和归宿的可靠数据。 根据模拟河口条件的实验室实验，中等水平的银可对浮游生物和无脊椎动物直接有毒，而低水平的银可影响河口群落结构并降低双壳类的生长速率。 与河口相比，淡水沃茨具有更多的银来源和更少的氯化物络合作用，可能具有更大的银毒性问题。银的天然低丰度意味着它可能几乎完全来自人为来源，并且可以作为污染的不可降解示踪剂，不受自然背景浓度变化的混淆。 研究银的一个同样重要的原因是，它是为数不多的纯B类金属之一，因此，它的研究可以帮助描绘金属行为总范围的一端。 目前对银的水生化学知之甚少。 由于几乎完全缺乏关于淡水银的可靠信息，本提案旨在作为一种侦察，以探索银循环的地球化学背景，并定位研究人员在未来对特定过程进行更详细的研究。 该研究包括三个主要组成部分：1）开始建立淡水中的基准银水平，2）识别和量化自然和人为来源，3）指定并开始调查控制银的运输，生物利用度和命运的过程和机制。 这项研究将使用超净方法，以避免污染文物，困扰了几乎所有以前的研究微量金属在新鲜沃茨。 一个重要的目标是促进使用这些方法进行更多的淡水研究。 调查将沿着曾经高度工业化的昆尼皮亚克河的整个长度进行，包括一个中游湖泊。 将使用质量平衡方法，提供比较天然、点和非点银来源的机会，并量化去除率。 根据初步测量，昆尼皮亚克河的源头非常干净，而下游则受到严重污染。 另外两条河流，诺格塔克河和康涅狄格州，将进行较深入的研究，以增加在有限的预算范围内的调查结果的一般性。 在这两条河中，诺格塔克河有严重金属污染的历史，而康涅狄格河没有。 将使用的技术是：1）常规膜过滤（分离颗粒和非颗粒部分），2）超滤（用于胶体形式），3）阳极溶出伏安法（评价银-有机物络合物），4） 热力学计算（估计溶解离子形态），5）孔隙水测量（评估沉积物的扩散通量），6）沉积物的Ag浓度和210 Pb地质年代学（评估再悬浮通量和记录污染历史）。