Abstract
Complex tidal processes and suspended particulate matter (SPM) behavior influence the land-sea transport of terrestrial contaminants in estuaries. Contaminants are generally trapped within the estuarine maximum turbidity zone (MTZ), where SPM concentrations peak, misleading flux estimation. Here, we conducted high-resolution continuous sampling over two tidal cycles within the MTZ of a semidiurnal estuary. Tidal variations of per- and polyfluoroalkyl substances (PFAS), a class of persistent organic pollutants, were analyzed in dissolved water and size-fractionated SPM. Results showed that variations in dissolved PFAS may related to the mixing of upstream and downstream. The predominant size range for SPM was found in 1-31μm (75%, mainly 10-31μm), but the PFAS tended to be sorbed by 0.22-1μm (60%) and>31μm (37%) fractions. Except during periods of sediment resuspension when particulate PFAS concentration decreased, the PFAS concentration in the 1-31μm increased during flood tides and decreased during ebb tides, which may not be related to organic carbon/elemental carbon levels. The hourly dynamic flux of dissolved-phase and particulate-phase PFAS transport to the sea in the MTZ was calculated by combining it with a hydrodynamic model. This study first highlights the size-fractionated PFAS transport under tidal influences and provides hourly flux estimation with a hydrodynamic model.
Published Version
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