The sediments in riverine environments contain notably high concentrations of perfluoroalkyl acids (PFAAs), which may be released into the water body under different hydrodynamic forces, such as those occurring at Y-shaped confluences. The release of PFAAs may pose a significant risk to the surrounding aquatic ecosystems. However, our understanding of the release and transport of PFAAs from sediments at Y-shaped confluences remains unclear. Thus, in this study, we performed a series of flume experiments to explore the effects of discharge ratio and total flow flux on the release and redistribution of PFAAs. The results indicated that these two parameters significantly affected the hydrodynamic features of confluences and the water physicochemical parameters. PFAA concentrations in the dissolved phase and suspended particulate matter (SPM) rose significantly as the discharge ratio and total flow flux increased. The dissolved phase was the predominant loading form of PFAAs, with short-chain PFAAs being the main kind, while long-chain PFAAs were dominant in the SPM. The spatial distribution pattern of PFAAs in sediments at the confluence exhibited a high degree of correspondence with hydrodynamic zones. The separation zone and maximum velocity zone were consistent with sediment regions with low and high capacities to release PFAAs, respectively. The patterns of variation in PFAA distribution were comparable to those observed in hydrodynamic zones as the discharge ratio and total flow flux varied. Furthermore, these two parameters altered the partitioning behaviors of PFAAs; specifically, the PFAAs in sediments tended to be released into the pore-water, while the liberated PFAAs tended to attach to SPM. Linear regression and correlation analyses suggested that the stream-wise and vertical flow velocity components near the sediment-water interface were the primary contributors to sediment suspension and PFAA exchange between the water column and pore-water. These findings will help us to understand the patterns of PFAA release in sediments at Y-shaped confluences and assist in the management of PFAA-contaminated sediments at these locations.

中文翻译：

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Y型汇流处流量比和流量影响下沉积物中全氟烷基酸的释放


河流环境中的沉积物含有极高浓度的全氟烷基酸（PFAA），它们可能在不同的水动力作用下释放到水体中，例如在 Y 形交汇处发生的情况。 PFAA 的释放可能对周围水生生态系统造成重大风险。然而，我们对 Y 形交汇处沉积物中 PFAA 的释放和迁移的理解仍不清楚。因此，在本研究中，我们进行了一系列水槽实验来探讨排放比和总流量对PFAA释放和重新分布的影响。结果表明，这两个参数对交汇处的水动力特征和水体理化参数影响显着。随着排放比和总流量的增加，溶解相和悬浮颗粒物（SPM）中的PFAA浓度显着上升。溶解相是 PFAAs 的主要负载形式，其中短链 PFAAs 是主要种类，而长链 PFAAs 在 SPM 中占主导地位。汇合处沉积物中PFAA的空间分布格局与水动力区表现出高度的对应性。分离区和最大速度区分别与释放PFAA 能力低和高的沉积物区域一致。随着排放比和总流量的变化，PFAA 分布的变化模式与在水动力区观察到的变化模式相当。此外，这两个参数改变了 PFAA 的分配行为；具体来说，沉积物中的 PFAA 倾向于释放到孔隙水中，而释放的 PFAA 倾向于附着在 SPM 上。 线性回归和相关分析表明，沉积物-水界面附近的流向和垂直流速分量是沉积物悬浮以及水柱和孔隙水之间PFAA交换的主要贡献者。这些发现将帮助我们了解 Y 形交汇处沉积物中 PFAA 的释放模式，并协助管理这些地点受 PFAA 污染的沉积物。