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Uncontrolled use and disposal of per- and polyfluoroalkyl substances (PFASs) in recent decades has resulted in extensive soil and groundwater contamination, necessitating counteraction. Electrokinetic remediation (EKR) offers a promising approach to in-situ soil remediation. Two novel modifications to conventional EKR were tested for the first time in a laboratory-scale study, to explore the capacity of EKR for PFAS removal. The first modification was a two-compartment setup designed for PFAS extraction from soil to an electrolyte-filled chamber. The second was a single-compartment setup designed to transport and confine contaminants in a chamber filled with granular activated carbon (GAC), thus, combining extraction with stabilisation. Electromigration varied for individual compounds, based mainly on perfluorocarbon chain length and functional group. The results indicated up to 89% concentration and extraction of ∑PFASs for the two-compartment setup, with removal efficiency reaching 99% for individual PFASs with C ≤ 6. Removed PFASs were concentrated adjacent to the anode at the anion exchange membrane, while short-chain compounds were extracted in the anolyte. The single-compartment setup achieved 75% extraction and accumulation of ∑PFASs in GAC. This demonstrates, for the first time, good effectiveness of coupling EKR with AC stabilisation for PFAS removal from soil. Perfluorocarbon chain length was a dominant factor affecting treatment efficiency in both setups, with very high removal rates for short-chain PFASs.

Contamination of soils with organic pollutants is an increasing global problem, so novel soil remediation techniques are urgently needed. One such technique is electrokinetic remediation, in which an electric field is applied over the soil to extract contaminants. Previous evaluations of the technique have been limited to a few specific compounds. In this study, we integrated the latest advances in high-resolution mass spectrometry (HRMS) to identify molecular fingerprints, and used the results to improve the mechanistic understanding necessary for successful remediation. A laboratory-scale 0.38 mA cm-2 electrodialytic treatment was applied for 21 days to a contaminated soil from a firefighter training facility in Sweden. Non-target analysis allowed generic evaluation of changes in the soil organic fraction by tentatively determining the elemental composition of compounds present. The results showed that smaller oxygen-rich molecules were significantly transported to the anode by electromigration, while larger hydrogen-saturated molecules were transported to the cathode by electroosmotic flow. Wide suspect screening with >3000 per- and polyfluoroalkyl substances (PFASs) tentatively identified seven new PFASs in the test soil, including perfluoroheptanesulfonic acid (PFHpS), and PFASs with butoxy, ethoxy, ethanol, and ethylcyclohexanesulfonate functional groups.

Contamination of soils with organic pollutants is an increasing global problem, so novel soil remediation techniques are urgently needed. One such technique is electrokinetic remediation, in which an electric field is applied over the soil to extract contaminants. Previous evaluations of the technique have been limited to a few specific compounds. In this study, we integrated the latest advances in high-resolution mass spectrometry (HRMS) to identify molecular fingerprints, and used the results to improve the mechanistic understanding necessary for successful remediation. A laboratory-scale 0.38 mA cm−2 electrodialytic treatment was applied for 21 days to a contaminated soil from a firefighter training facility in Sweden. Non-target analysis allowed generic evaluation of changes in the soil organic fraction by tentatively determining the elemental composition of compounds present. The results showed that smaller oxygen-rich molecules were significantly transported to the anode by electromigration, while larger hydrogen-saturated molecules were transported to the cathode by electroosmotic flow. Wide suspect screening with >3000 per- and polyfluoroalkyl substances (PFASs) tentatively identified seven new PFASs in the test soil, including perfluoroheptanesulfonic acid (PFHpS), and PFASs with butoxy, ethoxy, ethanol, and ethylcyclohexanesulfonate functional groups.

Contamination of soils with per- and polyfluoroalkyl substances (PFASs) is a global problem, in particular at fire-fighter training sites due to the usage of PFAS-containing aqueous fire-fighting foams (AFFFs). In this study, an electrodialytic remediation method was applied for the first time to remove PFASs from contaminated soil. The electrodialytic remediation system was evaluated in a laboratory-scale experiment with current densities of 0.19 mA cm−2 and 0.38 mA cm−2 over 21 days, using PFAS-contaminated soil from a fire-fighter training site at Stockholm Arlanda Airport, Sweden. Of the 23 PFASs targeted, significant (p < 0.05) PFAS electromigration towards the anode was observed for C3-C7 perfluoroalkyl carboxylates (PFCAs) (PFBA, PFPeA, PFHxA, PFOA) and C4, C6, and C8 perfluoroalkane sulfonates (PFSAs) (PFBS, PFHxS, PFOS) since these PFASs were predominantly negatively charged. In contrast to the electromigration of the charged PFASs, N-methyl perfluorooctane sulfonamide (MeFOSA), perfluorooctane sulfonamidoacetic acid (FOSAA) and ethyl FOSAA (EtFOSAA) showed significant (p < 0.05) transport towards the cathode, which is probably attributed to electro-osmotic flow of these predominantly neutral PFASs. Mass balance calculations showed that for the shortest-chained PFASs (i.e., PFBA, PFPeA, PFHxA, PFBS, and PFHxS), up to 20% was extracted from the soil to the anolyte, which showed that electrodialysis is a possible in-situ remediation technique for PFAS-contaminated soil.

Multiple segmented rating curves have been proposed to better capture the variability of the physical and hydraulic characteristics of river-floodplain systems. We evaluate the accuracy of one- and two-segmented rating curves by exploiting a large and unique database of direct measurements of stage and discharge data in more than 200 Swedish catchments. Such a comparison is made by explicitly accounting for the potential impact of measurement uncertainty. This study shows that two-segmented rating curves did not fit the data significantly better, nor did they generate fewer errors than one-segmented rating curves. Two-segmented rating curves were found to be slightly beneficial for low flow when there were strong indications of segmentation, but predicted the rating relationship worse in cases of weak indication of segmentation. Other factors were found to have a larger impact on rating curve errors, such as the uncertainty of the discharge measurements and the type of regression method.

River discharge estimation is the basic hydrological information for most hydrological applications in various socioeconomic planning. Increasing the accuracy of the traditional rating curve in relation to river discharge estimation would be very valuable to hydrological applications. Suggestions have been made that the traditional power function rating curve should be divided into several segments because this is often motivated by the physical characteristics of the river. Each curve is commonly constructed by regression and each requires 3 estimated parameters. However stage-discharge data is often scarce, and this scarcity could lead to overparametrization and deterioration of accuracy. By constructing many unsegmented and segmented rating curves accounting for measurement uncertainty, the models can be validated, it can be determined if segmented rating curves suffers from overparametrization. The results showed that two-segmented rating curves did not yield better fits to data, and nor did it generate larger errors than unsegmented rating curves in extrapolation. Segmentation only reduced errors in low flow interpolation, when there is a clear segmentation. It could also be concluded that unsegmented rating curves were slightly more robust when extrapolating. The biggest impact on rating curve errors was shown not to be determined by segmentation, but rather much more dependent on the amount of discharge measurement uncertainty or choice of regression method. With a mean discharge uncertainty of ±5 %, the errors from in high flow was 60 % in interpolation and 35 % in extrapolation. For low flows, the interpolation errors were around 95 % end extrapolation error estimation was 250 %. Conclusions could also be made that the relative errors from rating curves increased with lower discharges. Other important regression factors, such as heteroscedasticity, sometimes showed to have substantial impact on rating curve regressions, generally reduced from 59 % occurren, Uppskattning av vattenflöden i vattendrag är den grundläggande informationen för de flesta hydrologiska applikationer vid olika typer av socioekonomisk planering. Att förbättra noggrannheten i avbördningskurvor då vattenflödet uppskattas vid en mätstation skulle vara värdefullt för de flesta tillämpningar där vattenflöden används. Tidigare studier har föreslagit att avbördningskurvor borde delas upp i flera segment, eftersom vattendrag inte sällan har olika segment med olika fysikaliska karaktärer. Varje segment kräver dock att 2-3 regressionsparametrar bestäms, men flödesmätningar vid olika vattennivåer är ofta få, och knappheten kan göra att en utökad modell blir överparametriserad och än mer osäker. Genom att konstruera många avbördningskurvor, segmenterade och osegmenterade, kan dessa valideras mot valideringsdata och var det möjligt se om segmenterade avbördningskurvor blev överparametriserade. Studien visade att segmenterade avbördningskurvor vid kalibrering, interpolation och extrapolation generellt inte gav bättre prediktion än osegmenterade avbördningskurvor. Vid låga flöden och tydligt motiverade segmenteringar gav segmenterade avbördningskurvor en bättre interpolation, men dock inte vid extrapolation, vilket är en indikation att segmenterade avbördningskurvor var något överparametriserade. Den största inverkan på att minska felen i avbördningskurvor var var att minska mätosäkerheten i flödesmätningarna. Med en genomsnittlig mätosäkerhet i flödesmätningarna på ±5 % kunde osäkerheten kvantifieras till kring 60 % för interpolerade osegmenterade avbördningskurvor vid höga flöden och kring 95 % vid låga flöden. Variansen var dock stor. Osäkerheten från modellvalideringen av extrapolation för osegmenterade avbördningskurvor vid höga flöden kvantifierades till kring 35 % vid höga flöden och kring 250 % vid låga flöden. Resultaten visade att de relativa felen från avbördningskurvor blev större för ju lägre flödet blir. Heteroskedastitet, som kan generera osäk, Avbördningskurva, icke-linjär regression, flöde, flödesmätning, osäkerhet, validering, hydrologi, överparametrisering, vattenstånd