| Perfluorinated compounds(PFCs) are a new type of persistent organic pollutants(POPs). They are widely used as surfactants and surface protectors in the industrial and civil fields, such as textile, paper, packing, pesticides, carpets, leather, floor sanding, wash hair shampoo and fire-fighting foam due to the PFCs having oleophobic and hydrophobic properties. Perfluorinated carboxylic acids(PFCAs) and perfluorinated sulfonic acids(PFSAs) are the most typical PFCs that have attracted an intense scientific and regulatory interest because of their persistence, bioaccumulation and toxicity. In particular, PFOS and its salts and perfluorooctane sulfonyl fluoride have been officially classified as emerging POPs in superior control lists in the fourth conference of the parties of the Convention which was held in Geneva on May 2009. Therefore, the establishment of an efficient and rapid method for the determination of the natural environment of PFCs is very important. The impact of the migration and conversion of PFCs in the natural environment of the entire ecosystem can not be ignored, so its adsorption behavior in sediments will also have a very important significance.The concentrations of perfluorinated compounds(PFCs) in water and sediment samples were determined using the validated ultra-performance liquid chromatography tandem mass spectrometry(UPLC-ESI-MS/MS) method. The results showed that the total concentrations of PFCs ranged from 1.9 to 13.2 ng·L-1 in water samples of Hun River(HR) and Daliao River(DLR), where PFHx A, PFHpA, PFOA, PFOS and PFDA were major pollutants; the total concentration of PFCs were 27~50 ng·L-1 in water samples of Xi River(XR) with PFPA, PFOA, PFOS and PFDA as dominant pollutants. PFHx A was only detectable PFCs in the sediments of HR and DLR with concentrations between 0.13 and 0.49 ng·g-1 dry weight. Apart from PFHxA, PFOS was also detected in the sediments of XR, with the concentration range of 0.07 ~ 0.22 ng·g-1 for PFHxA and 0.18 ~ 0.83 ng·g-1 dry weight for PFOS. In addition, the risk quotient method was used for the ecological risk assessment of PFOA and PFOS in water and sediment based on the measured concentration of PFOA and PFOS in environment and the predicted no-effect concentration(PNEC). The assessment results suggested that PFOA and PFOS in water and sediment of HR, DLR and XR had no risk to ecological environment.PFOA/PFOS and sediment samples from Hun-Liao River were choosed as adsorbate and adsorbent, respectively, in order to study the adsorption kinetics and thermodynamics adsorbed on sediments. We also discussed the effect of the solution pH, concentration of Ca2 +, the particle size and organic content of their absorption rate to the adsorption, the conclusions show that:(1)The experimental results of adsorption kinetics showed that: the adsorption kinetics of PFOA and PFOS in the adsorption stage can be divided into fast and slow phase adsorption and adsorption equilibrium phase. The time to reach adsorption equilibrium was 10-24 h.(2)The experimental results of adsorption thermodynamics showed that: Henry, Langmuir, Freundlich adsorption model can be fitted to the PFOA and PFOS adsorption behavior on the sediments in the concentration range of this experiment. For PFOA, Freundlich adsorption model was superior to the other two models; for PFOS, Henry adsorption model was better than the other two models.(3)Researches showed that the pH and ionic strength of the solution, the grain size and organic matter content of the sediment had a certain influence on the adsorption of PFOA and PFOS through the factor experiments: acidic or alkaline solutions were all helpful for the adsorption rate; adsorption rate increased with increasing concentration of Ca2+; the absorption rate would rise as the the particle size of the sediment shrink; the more the sediment organic matter content, the greater the adsorption rate. |
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