Biogeochemical Processes along the Lower Amazon River Continuum

这项研究致力于二氧化碳从河流到大气的移动，这一现象被称为放气。最近修订的对河流排放气体的估计表明，它是全球碳循环的重要组成部分。但到底发生了多少排气，以及是什么因素控制了排气速度，人们仍然知之甚少，特别是在热带大河潮汐较低的河段。大多数排出气体的测量都是在远离海洋上游的地方进行的，海洋学研究仅限于近海区域。这留下了一个重大的知识鸿沟，几乎没有关于上游测量站和海洋考察船在海上接收信号的近海站点之间的大片河流范围的数据。这个以亚马逊河为重点的项目将提供更多关于河流碳循环如何运作的见解，并最终对它们对全球循环的影响提供更多的见解。为该项目开发的耦合模型将提供给政策制定者，用于评估不断变化的亚马逊盆地的更广泛的水资源问题。该项目将支持培训一名研究生和一名从代表不足的少数民族中招聘的本科生。这项研究将使用内河船探险、遥感和建模相结合的方法来检验这一假设，即整个下游河流和烟羽内侧的溶解二氧化碳水平保持在大气饱和以上。在这种情况下，如果充分考虑淡水和低盐度水域，亚马逊河羽流将成为大气中二氧化碳的净来源。碳的气态、溶解和颗粒浓度随潮汐变化的假设将通过潮汐周期的详细测量来评估。为了深入了解调节有机物分解和能量产生的生物机制，将结合微生物代谢的蛋白质组学特征和利用超高分辨率质谱仪表征溶解有机物。最后，一个详细的水动力学模型，包括生物过程和来自盆地水文学模型的输入，将被用来提供整个项目的综合。这个奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This research addresses the movement of CO2 from rivers to the atmosphere, a phenomenon referred to as outgassing. Recently revised estimates of riverine outgassing suggest that it is a significant component of the global carbon cycle. But precisely how much outgassing occurs and what factors control the rates of outgassing remain poorly understood, especially in the lower, tidal reaches of large tropical rivers. Most measurements of outgassing are made far upstream of the ocean, and oceanography studies are restricted to zones that are offshore. This leaves a major knowledge gap, with little or no data available for extensive river reaches between upstream gauging station and offshore sites where oceanographic research vessels pick up the signal at sea. This project, with a focus on the Amazon River, will provide greater insights into how riverine carbon cycles function, and ultimately their influence on global cycles. The coupled models developed for the project will be available to policy makers for use in evaluating broader water resource issues of the changing Amazon basin. The project will support the training of one graduate student and an undergraduate student recruited from an underrepresented minority. This research will use a combination of river boat expeditions, remote sensing, and modeling to test the hypothesis that dissolved CO2 levels remain above atmospheric saturation along the entire lower river and in the inner reaches of the plume. Under those conditions the Amazon River plume would act as a net source of CO2 to the atmosphere when freshwaters and low salinity waters are fully considered. The hypothesis that gaseous, dissolved, and particulate concentrations of carbon vary consistently with the tide will be evaluated through detailed measurements over tidal cycles. To obtain insights into the biological mechanisms regulating organic matter decomposition and energy production a combination of proteomic signatures of microbial metabolism and dissolved organic matter characterization by ultra-high-resolution mass spectrometry will be employed. Finally, a detailed hydrodynamic model, that includes biological processes and inputs from a basin hydrology model, will be used to provide synthesis across the project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.