Collaborative Research: Establishing Process Links Between Streamflow, Sediment Transport/Storage, and Biogeochemical Processing of Mercury

拟议的工作是对河流系统中汞（Hg）的调查，这些系统经历了大量人为输入这种有毒物质（例如，上游采矿）。这个跨学科项目将确定河流系统中汞输入食物网风险增加的关键位置，并阐明这种情况发生的过程。该研究将侧重于美国北加州尤巴-费瑟-萨克拉门托河系统内和通过该系统在内华达山脉水力金矿和海岸山脉汞矿开采产生的沉积物吸附汞的纵向（下游）运输和生物地球化学处理。它将记录汞污染对萨克拉门托山谷和海湾三角洲低地生态系统的主要来源（海岸山脉和内华达山脉），以及每个来源的相对贡献和风险。我们将：1)建立河流廊道洪水淹没的数学模型，以确定氧化/还原高潜力的区域；2)通过基于事件的冲沙输运数值模拟，确定沉积优先带；3)通过沉积物汞稳定同位素分析，识别不同的低地污染源；4)研究汞物种形成与汞物种同位素特征的变化，这些特征与氧化还原条件和沉积物来源有关。在受大气沉降或人为开采汞污染困扰的河流流域，沉积物运移、沉积和再活化之间的相互作用以及汞反应性的演变对淹没状态和环境化学的响应存在很大的不确定性。这些因素对沉积物吸附汞在食物网中的生物利用度有重要影响，因为它会传播到甲基化潜力高的敏感下游生态系统。这项研究将解决这一问题，并为威胁敏感的低地生态系统的物理和生物地球化学过程提供新的认识。来自遗留矿山的沉积物沉积物的重要性，特别是在海湾三角洲流域，最近有所增加，因为人们意识到它们可能含有高水平的汞，可能会进入食物网。负责流域管理的各种政府机构和非营利组织正在调查这些因素。研究小组与美国有关方面的人员建立了密切联系和关系，并将与他们分享研究结果。

The proposed work is an investigation of mercury (Hg) in river systems that have experienced large anthropogenic inputs of this toxic substance (e.g., by upstream mining). This interdisciplinary project will identify critical locations in river systems where the risk of Hg input to food webs increases and elucidate the processes by which this occurs. The study will focus on the longitudinal (downstream) transport and biogeochemical processing of sediment-adsorbed Hg derived from hydraulic gold mining in the Sierra Nevada and mercury mining in the Coast Ranges within and through the Yuba-Feather-Sacramento River system of Northern California, USA. It will document the primary sources (Coast Range v. Sierra Nevada) of Hg contamination to lowland ecosystems in the Sacramento Valley and Bay-Delta and the relative contribution and risks of each. We will: 1) mathematically model flood inundation in river corridors to identify areas of high potential of oxidation/reduction; 2) identify preferential zones of sedimentation through numerical modeling of event-based washload transport; 3) identify distinct contamination sources to lowlands by conducting Hg stable isotopic analysis of sediment; and 4) investigate Hg speciation in conjunction with changes in Hg species isotopic signatures, associated with redox conditions and sediment source. In river basins beset by Hg contamination from atmospheric deposition or anthropogenic inputs from mining, there is great uncertainty about the interplay among sediment transport, deposition, and remobilization and the evolution of Hg reactivity in response to inundation regimes and ambient chemistry. These factors have important implications for bioavailability of sediment-adsorbed Hg to food webs, as it travels to sensitive downstream ecosystems where methylation potential is high. This research will address this problem and provide new understanding into the physical and biogeochemical processes that threaten sensitive lowland ecosystems. The importance of sediment deposits originating from legacy mines, especially in the Bay-Delta watershed, has recently increased due to realizations that they may contain high levels of Hg that may be available to food webs. These factors are being investigated by various government agencies and nonprofit groups responsible for river basin management. The research team has developed close contacts and relations with personnel from interested parties in the US with whom findings will be shared.