Particulate organic carbon composition, granulometric and geochemical data for suspended sediment from the Rio Bermejo (Argentina) collected in March 2017@en

To study the transformation of organic carbon through long distance transport in rivers, we measured the composition of bulk organic carbon in river suspended sediment of the Rio Bermejo (northern Argentina). This river has a ~1300 km lowland flowpath with no significant tributaries. We collected fluvial suspended sediment in vertical depth profiles at five sampling locations along the length of the Rio Bermejo (northern Argentina) during near-bankfull conditions, when discharge varied between 675 and 1080 m3/s and banks were actively eroding. Additionally, we collected one depth profile from the Rio San Francisco (RSF) and one from the Rio Bermejo 10 km upstream of the RSF confluence. Combining these profiles and weighting them by the relative proportions of their total sediment load input to the mainstem Bermejo serves as a depth profile representing the headwaters. At each depth profile location, we collected water and suspended sediment from the channel thalweg by boat. We used a weighted 8-liter horizontal sampling bottle (Wildco Beta Plus bottle) with an attached pressure transducer to measure sampling depth. We separated sediment from the water using a custom-built 5-liter pressurized filtration unit with a 293 mm diameter, 0.2 µm polyethersulfone filter. In the laboratory, we rinsed sediment off the filters directly into an evaporating dish with ultrapure 18.2 MΩ water (pH~7). Samples were dried in an oven at 40ºC, and subsequently homogenized. Sediment particle size distributions were measured on ~10 mg aliquots using a laser diffraction particle size analyzer (Horiba LA-950). Specific surface area (SSA) of bulk sediment samples was measured on ~4 g aliquots using a Quantachrome NOVAtouch LX gas sorption analyzer and the Brunauer, Emmett, and Teller (BET) theory (Brunauer et al., 1938). Aliquots for organic carbon measurements were first treated with 4% HCl solution to remove inorganic carbon, following Galy et al. (2007, doi:10.1111/j.1751-908X.2007.00864.x). Total organic carbon (TOCPOC) and δ13C of POC was measured in duplicate at Durham University using a Costech elemental analyzer (EA) coupled to a CONFLO III and Thermo Scientific Delta V Advantage isotope ratio mass spectrometer (IRMS). Radiocarbon content was measured using an EA coupled to an accelerator mass spectrometer (EA-AMS) at ETH Zurich. […]为研究河流中有机碳经长距离输运的转化过程，我们对阿根廷北部贝尔梅霍河（Rio Bermejo）的河流悬浮沉积物中的总有机碳组成开展了测定。该河流拥有约1300千米的平原径流路径，且无重要支流汇入。我们在近满岸流量条件下（此时河流流量介于675至1080 m³/s，河岸正处于活跃侵蚀状态），于贝尔梅霍河（阿根廷北部）沿岸的5个采样点位采集了垂向深度剖面的河流悬浮沉积物。此外，我们还采集了圣弗朗西斯科河（Rio San Francisco, RSF）的1组深度剖面，以及位于RSF汇口上游10千米处的贝尔梅霍河沉积物深度剖面。将上述剖面数据整合，并按各点位输入主河道贝尔梅霍河的总沉积物负荷相对占比进行加权，即可得到代表河源区的沉积物深度剖面。 在每个深度剖面采样点位，我们乘船从河道深槽处采集水体与悬浮沉积物。我们采用配备压力传感器的8升加权卧式采样瓶（Wildco Beta Plus型采样瓶）测定采样深度。通过定制的5升加压过滤装置（搭配直径293 mm、孔径0.2 μm的聚醚砜滤膜）实现沉积物与水体的分离。 在实验室中，我们使用超纯水（电阻率18.2 MΩ，pH≈7）将滤膜上的沉积物直接冲洗至蒸发皿中。样品经40℃烘箱烘干后进行均质化处理。取约10 mg的沉积物等分试样，采用激光衍射粒度分析仪（Horiba LA-950）测定沉积物的粒径分布。取约4 g的沉积物等分试样，采用Quantachrome NOVAtouch LX型气体吸附分析仪结合布鲁瑙尔-埃米特-特勒（Brunauer, Emmett and Teller, BET）理论（Brunauer et al., 1938）测定总沉积物样品的比表面积（Specific Surface Area, SSA）。 参照Galy等人（2007, doi:10.1111/j.1751-908X.2007.00864.x）的方法，有机碳测定所用的等分试样首先经4%盐酸溶液处理以去除无机碳。颗粒有机碳（Particulate Organic Carbon, POC）的总有机碳（TOCPOC）与δ¹³C值在杜伦大学采用Costech元素分析仪搭配CONFLO III接口与Thermo Scientific Delta V Advantage型同位素比值质谱仪（Isotope Ratio Mass Spectrometer, IRMS）进行重复测定。放射性碳含量则采用元素分析仪耦合加速器质谱仪（EA-AMS）在苏黎世联邦理工学院（ETH Zurich）进行测定。[…]