Sorption to sediment black carbon (BC) may limit the aerobic biodegradation of polycyclic aromatic hydrocarbons (PAHs) in resuspension events and intact sediment beds. We examined this hypothesis experimentally under conditions that were realistic in terms of oxygen concentrations and BC content. A new method, based on synchronous fluorescence observations of 14C-pyrene, was developed for continuously measuring the uptake of dissolved pyrene by Mycobacterium gilvum VM552, a representative degrader of PAHs. The effect of oxygen and pyrene concentrations on pyrene uptake followed Michaelis-Menten kinetics, resulting in a dissolved oxygen half-saturation constant (Kom) of 14.1 μM and a dissolved pyrene half-saturation constant (Kpm) of 6 nM. The fluorescence of 14C-pyrene in air-saturated suspensions of sediments and induced cells followed time courses that reflected simultaneous desorption and biodegradation of pyrene, ultimately causing a quasi-steady-state concentration of dissolved pyrene balancing desorptive inputs and biodegradation removals. The increasing concentrations of 14CO2 in these suspensions, as determined with liquid scintillation, evidenced the strong impact of sorption to BC-rich sediments on the biodegradation rate. Using the best-fit parameter values, we integrated oxygen and sorption effects and showed that oxygen tensions far below saturation levels in water are sufficient to enable significant decreases in the steady-state concentrations of aqueous-phase pyrene. These findings may be relevant for bioaccumulation scenarios that consider the effect of sediment resuspension events on exposure to water column and sediment pore water, as well as the direct uptake of PAHs from sediments.
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机译:在重悬事件和完整的沉积床中,对沉积物黑碳(BC)的吸附可能会限制多环芳烃(PAH)的好氧生物降解。我们在氧气浓度和BC含量现实的条件下,通过实验检验了该假设。基于同步荧光观察 14 sup> C-py的新方法,开发了一种连续测量PAHs代表性降解物 Mycobacterium gilvum em> VM552吸收的pyr的方法。氧和pyr浓度对pyr吸收的影响遵循Michaelis-Menten动力学,导致溶解氧半饱和常数( K em> om sub>)为14.1μM和溶解pyr半饱和常数( K em> pm sub>)为6 nM。沉积物和诱导细胞的空气饱和悬浮液中 14 sup> C-py的荧光遵循随时间变化的过程,反映courses的同时解吸和生物降解,最终导致溶解balancing平衡吸收的准稳态浓度投入和生物降解清除。通过液体闪烁法测定,这些悬浮液中 14 sup> CO 2 sub>的浓度不断增加,证明了富BC沉积物的吸附对生物降解速率的强烈影响。使用最佳拟合参数值,我们对氧气和吸附效果进行了积分,结果表明,远远低于水中饱和度的氧气张力足以使水相pyr的稳态浓度显着降低。这些发现可能与考虑到泥沙再悬浮事件对水柱和泥沙孔隙水的暴露以及泥沙中多环芳烃的直接吸收的影响有关的生物富集情景有关。
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