Chamber Flux and Porewater Concentration of CH4, CO2 and N2O, 2018, Columbia River bank at the Hanford site, WA, USA

This is the corresponding observations data for the paper: Jorge A Villa; Garrett J Smith; Yang Ju; Lupita Renteria; Jordan C Angle; Evan Arntzen; Samuel F Harding; Huiying Ren; Xingyuan Chen; Audrey H Sawyer; Emily B Graham; James C Stegen; Kelly C Wrighton; Gil Bohrer (2020) Methane and nitrous oxide porewater concentrations and surface fluxes of a regulated river. Science of the Total Environment. Greenhouse gas (GHG) emissions from rivers are a critical missing component of current global GHG models. Their exclusion is mainly due to a lack of in-situ measurements and a poor understanding of the spatiotemporal dynamics of GHG production and emissions, which prevents optimal model parametrization. We combined simultaneous observations of porewater concentrations along different beach positions and depths, and surface fluxes of methane and nitrous oxide at a plot scale in a large regulated river during three water stages: rising, falling, and low. Our goal was to gain insights into the interactions between hydrological exchanges and GHG emissions and elucidate possible hypotheses that could guide future research on the mechanisms of GHG production, consumption, and transport in the hyporheic zone (HZ). Results indicate that the site functioned as a net source of methane. Surface fluxes of methane during river water stages at three beach positions (shallow, intermediate and deep) correlated with porewater concentrations of methane. However, fluxes were significantly higher in the intermediate position during the low water stage, suggesting that low residence time increased methane emissions. Vertical profiles of methane peaked at different depths, indicating an influence of the magnitude and direction of the hyporheic mixing during the different river water stages on methane production and consumption. The site acted as either a sink or a source of nitrous oxide depending on the elevation of the water column. Nitrous oxide porewater concentrations peaked at the upper layers of the sediment throughout the different water stages. River hydrological stages significantly influenced porewater concentrations and fluxes of GHG, probably by influencing heterotrophic respiration (production and consumption processes) and transport to and from the HZ. Our results highlight the importance of including dynamic hydrological exchanges when studying and modeling GHG production and consumption in the HZ of large rivers.本数据集为下述论文的配套观测数据：Jorge A Villa; Garrett J Smith; Yang Ju; Lupita Renteria; Jordan C Angle; Evan Arntzen; Samuel F Harding; Huiying Ren; Xingyuan Chen; Audrey H Sawyer; Emily B Graham; James C Stegen; Kelly C Wrighton; Gil Bohrer (2020) 受控河流的孔隙水甲烷与一氧化二氮浓度及地表通量. 《整体环境科学（Science of the Total Environment）》. 河流温室气体（GHG）排放是当前全球温室气体模型中关键的缺失环节。目前未将其纳入模型的主要原因在于缺乏原位实测数据，且对温室气体产生与排放的时空变化规律认知不足，这阻碍了模型参数化的优化。 本研究针对一条大型受控河流，在涨水、退水及枯水三个水文阶段，于样地尺度上同步观测了不同滩涂位置与深度的孔隙水浓度，以及甲烷与一氧化二氮的地表通量。本研究旨在探究水文交换与温室气体排放之间的相互作用，并阐明可指导未来关于潜流带（HZ）内温室气体产生、消耗与运移机制研究的可行假说。 研究结果表明，该研究区域为甲烷的净排放源。在三个滩涂位置（浅滩、中滩与深滩）的河流水文阶段中，甲烷地表通量与孔隙水甲烷浓度呈显著相关。但在枯水阶段，中滩位置的甲烷通量显著更高，这表明较短的停留时间提升了甲烷排放。 甲烷的垂向分布在不同深度出现峰值，表明不同河流水文阶段下潜流带混合的强度与方向，会对甲烷的产生与消耗过程产生影响。该研究区域对一氧化二氮的作用表现为汇或源，取决于水柱的高程。 在所有水文阶段中，孔隙水中一氧化二氮的浓度均在沉积物上层达到峰值。河流水文阶段显著影响了温室气体的孔隙水浓度与地表通量，这可能是通过影响异养呼吸（即产生与消耗过程）以及潜流带内外的物质运移实现的。 本研究结果强调，在大型河流潜流带内开展温室气体产生与消耗的相关研究及模型构建时，纳入动态水文交换过程的重要性。