Partitioning behavior of short-chain legacy and novel perfluorinated substances (PFAS) between dissolved and particulate phases in a river-estuary-coast continuum.

In this study, legacy and novel perfluoroalkyl substances (PFAS) in dissolved and particulate phase samples of Xiaoqing River from the headwater to estuary region were investigated. The downstream area of Xiaoqing River was found to be heavily influenced by discharged wastewater from a fluorochemical industry park and possessed an extremely high total PFAS concentration (as high as 123,000 ng/L for July and 2,170,000 ng/L for December in dissolved phase, and 33,600 ng/g dw for July and 741,000 ng/g dw for December in suspended particulate matter [SPM]). Various PFAS substance were observed in the samples: apart from a high concentration of perfluorooctanoic acid (PFOA), several perfluoropolyether carboxylic acids (PFECAs) were also found in remarkable concentration, constituting ∼17 %-35 % of the dissolved phase. In the particulate phase, hexafluoropropylene oxide trimer acid (HFPO-TrA) was shown to concentrate, and together with PFOA it made up over 95 % of the total PFAS concentration. The distribution behavior of PFAS between dissolved and particulate phases was studied, and we observed that short-chain PFAS species such as perfluorobutanoic acid (PFBA) and perfluoromethoxyacetic acid (PFMOAA) involved in the distribution between dissolved and particulate phase. Such partitioning behavior was found to be seasonal and dependent on various environmental parameters, such as salinity, TOC and nutrients. We propose that this may be due to electrostatic interaction on the particle surface surpassing the classical hydrophobic interaction for certain short-chain PFAS, and it may be associated with the bioconcentration process of PFAS in certain mollusk species in the ocean.