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评估穿过可渗透沉积物的流体流速以及该流动对海洋化学的影响一直是一个具有挑战性的问题。 流动可以由响应于重力波穿过海面所产生的压力梯度的海水循环通过海床驱动，或者由水流流经不规则底部地形时产生的压力梯度驱动。在一些地区，流量可能是由陆地地下水通过生物灌溉或物理灌溉排入沿海地区驱动的。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加利福尼亚州亨廷顿海滩附近近海沉积物内的流体循环速率，这些沉积物的循环主要受波浪的影响。 这些可渗透沉积物中的循环速率和模式将从天然放射性同位素分布（222Rn、223Ra、224Ra 和 228Ra）的反应/传输模型中推断出来。 该地区之前的工作已经制定了 Ra 同位素的区域预算，限制了这些浅水沉积物的总体输入。 本研究的目的是定义输入如何随水深和波浪特征变化。 观测将为描述渗透性沉积物流动的模型提供现场校准点。 除了放射性同位素之外，还将测量氧气、TCO2 和营养成分。 该数据集将用于根据放射性同位素开发的模型传输参数来确定这些成分的通量。当海水在沙子中循环时，这些通量将有助于限制这些可渗透沉积物捕获细粒生物颗粒的作用。 就更广泛的影响而言，这项研究的结果对于评估近岸可渗透沉积物过滤水能力的水质管理者来说很有价值。 该项目还将为本科生提供在实验室和现场工作的研究机会。该研究的实地考察部分将与太平洋科学潜水计划水族馆合作完成。 此次合作不仅将为开展工作提供重要的后勤援助，还将促进海洋学家与沿海地区休闲用户社区之间的沟通。