Comparative sorption and desorption behaviors of PFHx S and PFOS on sequentially extracted humic substances

The sorption and desorption behaviors of two perfluoroalkane sulfonates（PFSAs）, including perfluorohexane sulfonate（PFHx S） and perfluorooctane sulfonate（PFOS） on two humic acids（HAs） and humin（HM）, which were extracted from a peat soil, were investigated. The sorption kinetics and isotherms showed that the sorption of PFOS on the humic substances（HSs） was much higher than PFHx S. For the same PFSA compound, the sorption on HSs followed the order of HM 〉 HA2 〉 HA1. These suggest that hydrophobic interaction plays a key role in the sorption of PFSAs on HSs. The sorption capacities of PFSAs on HSs were significantly related to their aliphaticity, but negatively correlated to aromatic carbons,indicating the importance of aliphatic groups in the sorption of PFSAs. Compared to PFOS,PFHx S displayed distinct desorption hysteresis, probably due to irreversible pore deformation after sorption of PFHx S. The sorption of the two PFSAs on HSs decreased with an increase in p H in the solution. This is ascribed to the electrostatic interaction and hydrogen bonding at lower p H. Hydrophobic interaction might also be stronger at lower p H due to the aggregation of HSs.

Organophosphate esters in water,suspended particulate matter(SPM)and sediments of the Minjiang River,China

As organic pollutants of emerging concern,organophosphate esters(OPEs)have shown toxicity to organisms after entering the water environment.However,research on OPEs in freshwater in Southwest China is very limited.The levels,distribution and partitioning behavior of OPEs in the Minjiang River and their influencing factors is still unknown.In this study,six OPEs,tri-n-butyl phosphate(Tn BP),tri(2-chloroethyl)-phosphate(TCEP),trichloropropyl phosphate(TCPP),triphenyl phosphate(TPh P),tributoxyethyl phosphate(TBEP),and tris(2-ethylhexyl)-phosphate(TEHP),were determined in surface water,suspended particle matter(SPM)and sediments of the Minjiang River.The results showed that the average concentrations of∑_(6)OPEs in surface water,SPM and sediments of the Minjiang River were 199.32±124.95 ng/L,38463.79±45641.89 ng/g dry weight(dw)and 76.45±28.00 ng/g dw,respectively.High concentrations of OPEs were detected in SPM samples,indicating that more attention should be paid to pollution in SPM.It is worth noting that the variation trend of OPEs in SPM was almost opposite to that in water but basically similar to that in sediment.The proportions of alkyl OPEs in∑_(6)OPEs increased from surface water to SPM and sediments.Alkyl OPEs were the main pollutants in SPM(10.44%–80.88%of∑_(6)OPEs,mean of 54.52%)and sediments(59.08%–81.30%of∑_(6)OPEs,mean of 68.91%),whereas chlorinated OPEs were the most abundant components in surface water(43.16%–75.99%ofδ∑_(6)OPEs,mean of 55.50%).The water-sediment partition coefficient(logKOC)of OPEs was 4.97–7.58,while the water-SPM partition coefficient was 6.71–10.00.No significant correlations were found between log KOW and logKOC.KOW was not the main factor affecting the distribution of OPEs in the Minjiang River,China.