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首页> 外文期刊>Estuarine Coastal and Shelf Science >Fluxes and sources of suspended organic matter in an estuarine turbidity maximum region during low discharge conditions
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Fluxes and sources of suspended organic matter in an estuarine turbidity maximum region during low discharge conditions

机译：低排放条件下河口浊度最大区域的悬浮物和悬浮有机物来源

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Water column concentrations of total suspended solids (TSS), particulate organic carbon (POC) and particulate nitrogen (PN) were measured at three different depths in four different locations bracketing the estuarine turbidity maximum (ETM) along the main channel of a temperate riverine estuary (Winyah Bay, South Carolina, USA). Measurements were carried out over full tidal cycle (over 24 h). Salinity, temperature, current magnitude and direction were also monitored at the same time throughout the water column. Tidally averaged net fluxes of salt, TSS, POC and PN were calculated by combining the current measurements with the concentration data. Under the extreme low river discharge conditions that characterized the study period, net landward fluxes of salt were measured in the lower part of the study area, suggesting that the landward transport through the main channel of the estuary was probably balanced by export out through the sides. In contrast, the net fluxes of salt in the upper reaches of the study area were near zero, indicating a closed salt balance in this part of the estuary. In contrast to salt, the net fluxes of TSS, POC and PN in the deeper parts of the water column were consistently landward at all four sites in Winyah Bay indicating the non-conservative behavior of particulate components and their active transport up the estuary in the region around the ETM. The carbon contents (%POC), carbon:nitrogen ratios (org[C:N]a) and stable carbon isotopic compositions (δ~(13)C_(POC)) of the suspended particles varied significantly with depth, location and tidal stage. Tidally averaged compositions showed a significant increase up the estuary in the %POC and org[C:N]a values of suspended particles consistent with the preferential landward transport of carbon-rich particles with higher vascular plant debris content. The combination of tidal resuspension and flood-dominated flow appeared to be responsible for the hydrodynamic sorting of particles along the estuary that resulted in denser, organic-poor particles being transported landward less efficiently. The elemental and isotopic compositions indicated that vascular C_3 plants and estuarine algae were the major sources of the particulate organic matter of all the samples, without any significant contributions from salt marsh C_4 vegetation (Spartina alterniflora) and/or marine phytoplankton.
机译：在四个不同位置的三个不同深度处测量了总悬浮固体（TSS），颗粒有机碳（POC）和颗粒氮（PN）的水柱浓度，将沿河温带河口主要通道的河道浊度最大值（ETM）括起来（美国南卡罗来纳州，温雅湾）。在整个潮气周期（超过24小时）内进行测量。在整个水柱中也同时监测盐度，温度，电流大小和方向。通过将电流测量值与浓度数据相结合，计算出盐，TSS，POC和PN的潮汐平均净通量。在表征研究期的极端低河流量条件下，在研究区域的下部测量了盐的净陆运通量，这表明通过河口主河道的陆运可能与两侧的出口平衡。 。相反，研究区域上游的净盐通量接近于零，表明该河口部分盐分平衡。与盐形成对比的是，水柱深部中TSS，POC和PN的净通量始终在Winyah湾的所有四个站点上向陆降落，表明颗粒成分的非保守行为及其在河口的向上的主动迁移。 ETM周围的区域。悬浮颗粒的碳含量（％POC），碳：氮比（org [C：N] a）和稳定的碳同位素组成（δ〜（13）C_（POC））随深度，位置和潮汐阶段而显着变化。 。潮汐平均组成显示出河口中悬浮颗粒的％POC和org [C：N] a值显着增加，这与具有较高维管植物碎片含量的富碳颗粒的优先陆运相吻合。潮汐重悬和洪水为主的流动相结合，似乎是对沿河口的颗粒进行水力分选的原因，导致较稠密的，有机质较差的颗粒向陆运的效率较低。元素和同位素组成表明，维管束C_3植物和河口藻类是所有样品中颗粒有机物的主要来源，盐沼C_4植被（互花米草）和/或海洋浮游植物没有任何显着贡献。

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