Partitions and vertical profiles of 9 endocrine disrupting chemicals in an estuarine environment: Effect of tide, particle size and salinity

Phenolic endocrine disrupting chemicals (EDCs) in an estuarine water column in a depth profile of five water layers (0.05 D, 0.20 D, 0.60 D, 0.80 D and 0.90 D, D = Depth, 10.7 ± 0.7 m) and their corresponding environmental parameters (tide, salinity and particle size) were investigated over a year. Water sample from each layer was further separated into three fractions, which were dissolved, coarse (SPM-D, Φ ≥ 2.7 μm) and fine (SPM-F, 2.7 μm > Φ ≥ 0.7 μm) suspended particulate matters. Most of EDCs in the water column were presented in the dissolved fraction. Vertical profiles of salinity fluctuations showed that the upper water layer was most influenced by upstream flow. Estriol (E₃), mestranol (Mes) and 17α-ethynylestradiol (EE₂) concentrations were significantly higher in ebb tide than in flood tide, indicating that EDCs mainly came from terrestrial source, the upstream flow. Dissolved EDCs also exhibited high levels in the surface layer (0.05 D) due to the upstream source and atmosphere deposition, followed by the bottom layer (0.90 D) owing to the re-suspension of EDCs-containing sediment. Compared to the dissolved phase, the contents of BPA, Mes and EE₂ in the solid phase were affected by particle size and exhibited a trend of SPM-F > SPM-D > sediment. On the other hand, the concentrations of octylphenol (OP) and t-nonylphenol (NP), the degradation products from common nonionic surfactants, in sediment were higher than those in suspended particles, and NP concentration was higher in flood tide than that in ebb tide. For both SPM-D and SPM-F, their corresponding EDCs concentrations were negatively related to SPM concentrations due to particle concentration effect (PCE). Owing to the "salting-out effect", salinity pushed EDCs from dissolved fraction to particulate or sedimentary phase.