Collaborative Research: Determining the Air-Water CO2 Flux in Coastal Systems

在河流、河口和沿海海洋中控制碳运输和转化的过程仍然是区域和全球碳、营养物质和污染物预算的主要不确定性来源。为了准确地评估这些过程，研究需要准确估计空气-水二氧化碳通量。目前，由于无法对物理复杂的沿海系统中控制空气-水-气输送的因素建立令人满意的模型，这些努力受到严重破坏。在这项研究中，哥伦比亚大学和耶鲁大学的研究人员将：(i)确定沿海系统中控制空气-水二氧化碳交换的湍流的时空变异性；（ii）测量控制河流/河口系统中空气-水二氧化碳交换速率的过程，并解决风、潮汐、分层和水深测量在各种河口系统中产生近地表湍流的相对重要性；（三）直接比较梯度通量和浮动穹顶技术；（四）确定空气-水CO2通量相对于沿海系统碳收支中其他项的相对重要性。野外实验将在哈德逊河河口（大潮汐河系统）、帕克河河口（较小的大潮汐河系统）和长岛湾（半封闭沿海海）进行，以研究具有一系列生物地球化学和物理强迫的系统。使用梯度通量和浮动穹顶技术测量CO2的空气-水通量将用于确定这些系统中的气体传输速度。同时，水面湍流（如湍流动能耗散）和产生近水面湍流的物理强迫（如风速、潮流、分层、测深）将被量化。我们的目标是了解在这三个不同的海岸系统中控制二氧化碳通量的过程，这样就可以预测其他海岸系统和海洋中向大气交换的二氧化碳量。由于本研究直接涉及任何具有气相的元素的循环，包括许多生物气体和工业污染物，如N2O，多氯联苯，Hg0 (g)和多环芳烃，因此项目的结果将减少气体交换估算的较大误差。这将使有害挥发性污染物的主要途径得到更仔细的评估。该项目将为研究生和本科生提供支持和培训，并包括k-12科学教师的参与。调查结果将通过一系列教育项目向公众公布。

The processes controlling carbon transport and transformations within rivers, estuaries, and the coastal ocean remain a large source of uncertainty in regional and global budgets of carbon, nutrients, and pollutants. In order to accurately assess these processes, studies require accurate estimates of the air-water CO2 flux. Currently, these efforts are seriously undermined by an inability to satisfactorily model the factors governing air-water gas transfer in physically complex coastal systems.In this study, researchers at the University of Columbia and Yale University will: (i) determine the spatial and temporal variability of turbulence that governs air-water CO2 exchange in coastal systems; (ii) measure the processes controlling the air-water CO2 exchange rate in river/estuarine systems, and resolve the relative importance that wind, tides, stratification, and bathymetry play in generating near surface turbulence in various estuarine systems; (iii) directly compare the gradient flux and the floating dome techniques; and (iv) determine the relative importance of the air-water CO2 flux versus other terms in the carbon budget in coastal systems. Field experiments will be conducted in the Hudson River estuary (large tidal river system), the Parker River estuary (smaller macro-tidal river system), and the Long Island Sound (semi-enclosed coastal sea) to study systems with a range of biogeochemical and physical forcing. Measurements of air-water flux of CO2 using the gradient flux and floating dome techniques will be used to determine the gas transfer velocity in these systems. Simultaneously, turbulence at the water surface (e.g., turbulent kinetic energy dissipation) and physical forcing responsible for generating near surface turbulence (e.g., wind speed, tidal currents, stratification, bathymetry) will be quantified. The goal is to understand the processes controlling the CO2 flux in these three distinct coastal systems, so that the amount of CO2 exchange to the atmosphere in a wide range of other coastal systems and the ocean can be predicted. Because this study relates directly to the cycles of any element with a gaseous phase, including many biogenic gases and industrial pollutants such as N2O, PCBs, Hg0 (g), and PAHs, the results from the project will reduce the large errors in gas exchange estimation. This will allow the dominant pathways of harmful volatile pollutants to be assessed more carefully. The project will provide support and training for graduate and undergraduate students, and include the participation of k-12 science teachers. The results will be available to the public through a number of educational programs.