Effect of water–sediment regulation of the Xiaolangdi Reservoir on the concentrations, bioavailability, and fluxes of PAHs in the middle and lower reaches of the Yellow River

Abstract

Keywords:Bioavailability Polycyclic aromatic hydrocarbons (PAHs) Suspended sediment (SPS) Dams Water conservation project Water quality s u m m a r yThe water-sediment regulation of the Xiaolangdi Reservoir is conducted to control the relationship between riverine runoff and sediment transport of the Yellow River; however, there is no research about the effect of water-sediment regulation on the bioavailability and fluxes of hydrophobic organic compounds (HOCs). In this study, water and suspended sediment (SPS) samples were collected downstream of the Xiaolangdi Reservoir before, during, and after the water-sediment regulation in 2013. The 16 priority polycyclic aromatic hydrocarbon (PAH) concentrations of freely dissolved, total dissolved, and SPS-associated were determined. During water regulation, water discharged from the reservoir at a high flow rate led to the resuspension of downstream sediment. During sediment regulation, the sediment ejected from the reservoir resulted in higher SPS concentrations than that during water regulation. Both the freely and total dissolved PAH concentrations in river water during sediment regulation were the highest, followed by the concentrations during water regulation and before regulation. The freely dissolved PAH concentrations in river water during the water-sediment regulation were 2-11 times higher than those before water-sediment regulation. This was due to the fact that the resuspended sediment during water-sediment regulation could release PAHs into water phase, and more contaminants were released from the SPS during sediment regulation than during water regulation. The fluxes of sediment and the 16 priority PAHs (R 16 PAHs) during water-sediment regulation contributed to 32.4% and 35.7% of their annual fluxes, respectively, which were higher than the contribution (22.6%) of water discharge. This study suggested that the water-sediment regulation might reduce the long-term retention of sediment and PAHs in the reservoir. However, the environmental risk of PAHs as well as other contaminants downstream of the reservoir and in the estuary might increase during that period. Therefore, the effect of water-sediment regulation on the bioavailability and environmental risk of HOCs should be considered in the operation and management of the Xiaolangdi Reservoir in the future.

Effect of recurrent sediment resuspension-deposition events on bioavailability of polycyclic aromatic hydrocarbons in aquatic environments

“…After 4-h deposition, both the total and freely dissolved PAH concentrations decreased sharply with time. This was resulted from the re-sorption of PAHs in the water phase by the smaller SPS particles with large specific surface areas (Chalhoub et al, 2013;Dong et al, 2015;Feng et al, 2008). The PAH concentrations in the overlying water decreased slightly with time after 8-h deposition and remained relatively unchanged after 26-h deposition due to the very low SPS concentration (Fig.…”

High‐turbidity events in Western Lake Erie during ice‐free cycles: Contributions of river‐loaded vs. resuspended sediments

“…Resuspension is initiated by the combined effects of currents, surface-gravity waves, and high-frequency linear internal waves, among which the surface-gravity waves predominate in shallow lakes and coastal zones (Hawley and Eadie 2007;Green and Coco 2014;Valipour et al 2017). During the resuspension, resuspended materials can alter the biomass distributions by reintroducing and redistributing nutrients throughout the water column (Zamparas and Zacharias 2014;Dong et al 2015Dong et al , 2016Paytan et al 2017;Li et al, 2018), which in turn can impact the dissolved oxygen levels (Moriarty et al 2017). Given that suspended sediments from river loading and resuspension have distinct ecological functions and driving mechanisms, it is critical to understand their relative contributions to HTEs by tracking their origins explicitly.…”

Sedimentary Record of Polycyclic Aromatic Hydrocarbons from the Shuanglong Catchment, Southwest China

“…And they were less polluted than Xidayang catchment [61] and Feitsui catchment [62]. However, the sampling sites represented a higher contamination than that in Xiaolangdi catchment [53] and Manwan catchment [54].…”