COLLABORATIVE RESEARCH (USC-UW): Evaluating Seawater Circulation Rates Through Permeable Sediments, Using Naturally Occurring Rn and Ra Isotopes

合作研究 (USC-UW)：利用天然存在的 Rn 和 Ra 同位素评估可渗透沉积物的海水循环率

• 批准号: 0623413
• 负责人: Douglas Hammond
• 金额: $ 16.49万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-15 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0623413&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; USC; UW; Evaluating

ABSTRACTOCE-0623413OCE-0623278Evaluating fluid flow rates through permeable sediments, and the impact of this flow on ocean chemistry, has been a challenging problem. Flow may be driven by circulation of seawater through the seabed in response to pressure gradients created by the passage of gravity waves across the sea surface, or by pressure gradients generated as currents flow over irregular bottom topography. In some areas, flow may be driven by terrestrial groundwater discharge into the coastal zone, via bio-irrigation, or physical irrigation. In this study, researcher from the University of Southern California and the University of Washington, will evaluate the fluid circulation rates within offshore sediments off Huntington Beach CA, at sites where circulation is dominated by the influence of waves. Circulation rates and patterns in these permeable sediments will be deduced from reaction/transport modeling of naturally-occurring radioisotope distributions: 222Rn, 223Ra, 224Ra, and 228Ra. Previous work in this region has established regional budgets for Ra isotopes that constrain their overall input from these shallow water sediments. The goal of this study is to define how input varies with water depth and wave characteristics. Observations will provide an in situ calibration point for models describing flow through permeable sediment. In addition to the radioisotopes, oxygen, TCO2, and nutrient profiles will be measured. This data set will be used to establish fluxes of these constituents, based on the model transport parameters developed with radioisotopes. These fluxes will help to constrain the role of these permeable sediments in trapping fine-grained biogenic particles as seawater circulates through the sands. As regards broader impacts, results from this study will be of value to water quality managers who evaluate the ability of nearshore permeable sediments to filter water. The project will also provide research opportunities for undergraduate students to work in laboratory and field settings. The fieldwork component of the research will be done in collaboration with the Aquarium of the Pacific Scientific Diving Program. This collaboration will not only provide an important logistical assistance to carry out the work, but also foster communication between oceanographers and the community of coastal zone recreational users.

Abstractoce-0623413OCE-0623278通过可渗透的沉积物进行流体流速，并且该流动对海洋化学的影响是一个具有挑战性的问题。 流动可以由海水通过海底循环驱动，响应由重力波通过海面而产生的压力梯度，或者是由于电流流过不规则的底部地形而产生的压力梯度。在某些地区，流量可能是由地下水排放到沿海地区，通过生物灌溉或物理灌溉驱动的。在这项研究中，南加州大学和华盛顿大学的研究人员将评估亨廷顿海滩在CA附近的海上沉积物中的流体循环速率，在循环的影响下，波浪的影响。 这些渗透性沉积物中的循环速率和模式将从自然出现的放射性同位素分布的反应/运输模型中推导出来：222222223RA，223RA，224RA和228RA。 该地区的先前工作已经建立了RA同位素的区域预算，从而限制了这些浅水沉积物的总体投入。 这项研究的目的是定义输入如何随水深度和波浪特性而变化。 观察结果将为描述流经可渗透沉积物的流动的模型提供原位校准点。 除了放射性同位素外，还将测量氧气，TCO2和营养谱。 该数据集将基于使用放射性同位素开发的模型传输参数来建立这些成分的通量。这些通量将有助于限制这些渗透性沉积物在海水通过沙子循环时捕获细粒生物颗粒的作用。 关于更广泛的影响，这项研究的结果对评估近海渗透沉积物过滤水的能力的水质经理具有价值。 该项目还将为本科生在实验室和现场环境中工作提供研究机会。研究的现场工作组成部分将与太平洋科学潜水计划的水族馆合作完成。 这项合作不仅将提供重要的后勤援助来进行工作，还可以促进海洋学家与沿海地区娱乐用户之间的交流。