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首页> 外文期刊>Estuarine Coastal and Shelf Science >The cycling and oxidation pathways of organic carbon in a shallow estuary along the Texas Gulf Coast
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The cycling and oxidation pathways of organic carbon in a shallow estuary along the Texas Gulf Coast

机译：德克萨斯州墨西哥湾沿岸浅河口中有机碳的循环和氧化途径

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摘要

The cycling and oxidation pathways of organic carbon were investigated at a single shallow water estuarine site in Trinity Bay, Texas, the uppermost lobe of Galveston Bay, during November 2000. Radio-isotopes were used to estimate sediment mixing and accumulation rates, and benthic chamber and pore water measurements were used to determine sediment-water exchange fluxes of oxygen, nutrients and metals, and infer carbon oxidation rates. Using ~7Be and ~(234)Th_(XS), the sediment-mixing coefficient (D_b) was 4.3 ± 1.8 cm~2 y~(-1), a value that lies at the lower limit for marine environments, indicating that mixing was not important in these sediments at this time. Sediment accumulation rates (S_a), estimated using ~(137)Cs and ~(210)Pb_(XS), were 0.16 ± 0.02 g cm~(-2) y~(-1). The supply rate of organic carbon to the sediment-water interface was 30 ± 3.9 mmol C m~(-2) d~(-1), of which ～10% or 2.9 ± 0.44 mmol C m~(-2) d~(-1) was lost from the system through burial below the 1-cm thick surface mixed layer. Measured fluxes of O_2 were 26 ± 3.8 mmol m~(-2) d~(-1) and equated to a carbon oxidation rate of 20 ± 3.3 mmol C m~(-2) d~(-1), which is an upper limit due to the potential for oxidation of additional reduced species. Using organic carbon gradients in the surface mixed layer, carbon oxidation was estimated at 2.6 ± 1.1 mmol C m~(-2) d~(-1). Independent estimates made using pore water concentration gradients of ammonium and C:N stoichiometry, equaled 2.8 ± 0.46 mmol C m~(-2) d~(-1). The flux of DOC out of the sediments (DOC_(efflux)) was 5.6 ± 1.3 mmol C m~(-2) d~(-1). In general, while mass balance was achieved indicating the sediments were at steady state during this time, changes in environmental conditions within the bay and the surrounding area, mean this conclusion might not always hold. These results show that the majority of carbon oxidation occurred at the sediment-water interface, via O_2 reduction. This likely results from the high frequency of sediment resuspension events combined with the shallow sediment mixing zone, leaving anaerobic oxidants responsible for only ～10-15% of the carbon oxidized in these sediments.
机译：在2000年11月期间，在加尔维斯顿湾最上层的得克萨斯州三一湾的一个浅水河口地点研究了有机碳的循环和氧化途径。利用放射性同位素估算沉积物的混合和积累速率，以及底栖室。用孔隙水和孔隙水测量来确定氧气，养分和金属的沉积物-水交换通量，并推断碳的氧化速率。使用〜7Be和〜（234）Th_（XS），泥沙混合系数（D_b）为4.3±1.8 cm〜2 y〜（-1），该值处于海洋环境的下限，表明混合目前在这些沉积物中并不重要。利用〜（137）Cs和〜（210）Pb_（XS）估算的沉积物沉积速率（S_a）为0.16±0.02 g cm〜（-2）y〜（-1）。沉积物-水界面的有机碳供应率为30±3.9 mmol C m〜（-2）d〜（-1），其中〜10％或2.9±0.44 mmol C m〜（-2）d〜。 （-1）通过在1厘米厚的表面混合层之下的埋葬从系统中丢失。 O_2的测量通量为26±3.8 mmol m〜（-2）d〜（-1），相当于碳氧化速率为20±3.3 mmol C m〜（-2）d〜（-1）。上限是由于其他还原物种可能被氧化。使用表面混合层中的有机碳梯度，碳氧化估计为2.6±1.1 mmol C m〜（-2）d〜（-1）。使用铵的孔隙水浓度梯度和C：N化学计量比得出的独立估计为2.8±0.46 mmol C m〜（-2）d〜（-1）。 DOC从沉积物中的通量（DOC_（外排量））为5.6±1.3 mmol C m〜（-2）d〜（-1）。通常，虽然达到了质量平衡，表明这段时间内的沉积物处于稳定状态，但海湾和周围地区的环境条件却发生了变化，这意味着该结论可能并不总是成立。这些结果表明，大部分碳氧化是通过O_2还原在沉积物-水界面发生的。这可能是由于高频率的泥沙再悬浮事件和浅层泥沙混合区所致，而厌氧氧化剂仅占这些泥沙中氧化碳的约10-15％。

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