Measurement of Oxygen Uptake from Marine Sediments by Eddy Correlation

在自然海洋环境中，氧气向沉积物中的输运是由覆盖在其上的大块溶液的湍流输运运动尺度所介导的，分子扩散速度要慢几个数量级，几乎是一个微不足道的项。沉积物的耗氧量通常是通过回收岩心的实验室测量或原位封闭实验来量化的，它是评估有机物分解速率的关键参数，也控制着厌氧呼吸过程中产生的沉积物还原剂（如NH4+、Mn2+、Fe2+、HS-、FeS等）的氧化。通过波浪诱导泵送或生物扰动活动对沉积层进行通风和灌溉，也是可以通过更可靠的沉积物氧吸收测量来潜在量化的过程。该提案将扩展和探索PI与马克斯普朗克海洋微生物研究所（不来梅）的同事共同开发的最近提出的方法。该技术涉及将沉积物边界层中溶解氧随时间变化的浓度（由快速响应微电极测量）与当地感知的垂直速度分量（也通过声波多普勒测速法（ADV）以高频采样）相关联。涡旋相关方法与大气科学家测量行星边界层中标量（如热量、水分（动量）和微量气体）通量的类似技术有直接的相似之处。讨论了将基本方法应用于水生系统的理论和实践考虑因素，并将在丹麦（奥胡斯湾）的浅海岸线现场进行探索。

ABSTRACTOCE-0221259Oxygen transport into sediments in natural marine environments is mediated by the turbulent transport scales of motion of the bulk overlying solution, molecular diffusion being orders of magnitude slower and a virtually insignificant term. The oxygen consumption by sediments, conventionally quantified by either laboratory measurements on recovered cores or by the artifice of an in-situ enclosure experiment, is a key parameter in assessing organic matter decomposition rates and also controls the oxidation of sediment reductants such as NH4+, Mn2+, Fe2+, HS-, FeS etc produced during anaerobic respiration. Ventilation and irrigation of sedimentary layers either by wave induced pumping or bioturbation activity are also processes that could potentially be quantified by more reliable measurements of sediment O2 uptake.This proposal will extend and explore a recently suggested approach being jointly developed by the PI together with colleagues at the Max Planck Institute for Marine Microbiology (Bremen). The technique involves correlating the time varying concentration of dissolved oxygen, measured by fast response microelectrodes, in the sediment boundary layer within a few cm of that surface with locally sensed vertical velocity components also sampled at high frequency by acoustic Doppler velocimetry (ADV). An eddy correlation approach has direct analogues with similar techniques that are used by atmospheric scientists measuring scalar (e.g. heat, moisture (momentum) and trace gas) fluxes in the planetary boundary layer. Theoretical and practical considerations for the adaptation of the basic approach into aquatic systems are discussed and will be explored at shallow coastal field sites in Denmark (Aarhus Bay).