To understand water quality degradation during hypoxia, we need to understand sediment oxygen fluxes, the main oxygen sink in shallow hypolimnia. Kinetic models, which integrate diffusion and consumption of dissolved oxygen (DO) in sediments, usually assume a downward flux of DO from the sediment-water interface (SWI) with a zero-flux condition at the lower boundary of the oxic sediment layer. In this paper, we separately account for the oxidation of an upward flux of reduced compounds by introducing a negative flux of DO as a lower boundary condition. Using in situ measurements in two lakes, kinetic models were fit to DO microprofiles using zero-order and first-order kinetics with both zero and non-zero lower boundary conditions. Based on visual inspection and goodness-of-fit criteria, the negative-flux lower boundary condition, -0.25 g O2 m-2 d-1, was found to more accurately describe DO consumption kinetics. Fitted zero-order rate constants ranged from 50 to 510 mg L-1 d-1, and first-order rate constants ranged from 60 to 400 d-1, which agree well with prior laboratory studies. DO fluxes at the SWI calculated from the simulated profiles with the negative-flux lower boundary condition also showed better agreement with the observed DO fluxes than the simulated profiles with the zero-flux lower boundary condition.

中文翻译：

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湖泊和水库中沉积物氧动力学和通量的改进模型。

要了解缺氧期间水质的下降，我们需要了解沉积物的氧气通量，即浅层低氧的主要氧气汇。动力学模型综合了沉积物中溶解氧（DO）的扩散和消耗，通常假设氧从沉积物-水界面（SWI）向下流动，且在含氧沉积物下边界处为零通量。在本文中，我们通过引入负DO通量作为下边界条件，分别说明了还原化合物的向上通量的氧化。通过在两个湖泊中进行原位测量，使用零阶和非零下边界条件的零阶和一阶动力学将动力学模型拟合到DO微剖面。根据外观检查和拟合优度标准，负通量下边界条件为-0。发现25 g O2 m-2 d-1更准确地描述了DO消耗动力学。拟合的零阶速率常数范围为50至510 mg L-1 d-1，一阶速率常数范围为60至400 d-1，与先前的实验室研究非常吻合。与具有零通量下边界条件的模拟剖面相比，从带有负通量下边界条件的模拟剖面计算得到的SWI处的DO通量也显示出与观测到的DO通量更好的一致性。