Stir bar sorptive extraction (SBSE) has been developed in 1999 to efficiently extract and preconcentrate volatile compounds, and many applications have been found after that. This technique conforms to the principles of green chemistry. Here, we used an autosampler with an online thermal desorption unit connected to CGC-MS to analyze pesticides. This study describes the development of a highly sensitive extraction method based on SBSE for simultaneous determination of ultra-trace amounts of four pesticides λ-cyhalothrin, α-cypermethrin, tefluthrin, and dimefluthrin in environmental water samples. This method was compared to the standard liquid–liquid extraction. In this study, a totally solventless SBSE was applied to river and tap water samples for the extraction and preconcentration of four pesticides. PDMS-coated SBSEs of 10 mm × 1 mm thickness were used for this purpose, and SBSEs were directly placed into a large-volume injector of a CGC-MS for thermal desorption of the analytes. In all extractions, deltamethrin was used as an internal standard. This method showed linearity in the range of 1.0–200.0 ng L⁻¹ for cyhalothrin, tefluthrin, and dimefluthrin and 10.0–800 ng L⁻¹ for cypermethrin. Preconcentration factors of 179, 7, 162, and 166 were obtained with very low limits of detection of 0.32, 3.41, 0.36m and 0.69 ng L⁻¹ for cyhalothrin, cypermethrin, tefluthrinm and dimefluthrin, respectively. These detection limits are thousands of times lower than that of the standard method of liquid–liquid extraction. Reproducibility of the method, based on the relative standard deviation, was better than 7.5% and recoveries for spiked tap and river water samples was within the range of 87.83–114.45%. The application of PDMS-coated SBSE coupled with CGC-MS equipped with a large volume injector thermal desorption unit can be used for ultra-trace analysis of environmental water samples. Solventless SBSE offers several advantages over conventional traditional liquid–liquid extraction such as being very fast and economical and provides better extraction without requiring any solvents; so it can be considered as a green method for the analysis of pesticides.

Per- and polyfluoroalkyl substances (PFASs) are fluorinated anthropogenic compounds of which numerous have a high thermal stability, high surface tension, water and oil repellence. PFASs are used e.g. as surfactants, in agrochemical products and in fire extinguishing foams. Due to negative effects to the environment and human health some compounds are already declared as Persistent Organic Pollutants (POPs) or Substances of Very High Concern (SVHC). The behaviour of PFASs in environmental matrices can differ dependent on the molecular structure and environmental conditions. Sorption, for example, depends on soil characteristics, compound properties such as the carbon chain length and the functional group. When PFASs are found in soils, the knowledge of factors affecting the leaching behaviour in soil can be helpful to assess plant availability and risk of groundwater contamination.In some contamination cases, e.g. Rastatt/Baden-Baden, Germany, PFASs precursors such as polyfluoroalkyl phosphate diesters (diPAPs) are present in soil and are transformed into PFAAs (perfluoroalkyl acids), a sub-group of PFASs, which are stable in the environment. To study the behaviour of diPAPs in soil, 8:2 diPAP and 6:2 diPAP were applied to 50 cm soil-filled columns with a concentration of 1 mg per kg soil. For two years, the columns are watered on 3-5 days per week with an average weekly natural rainfall of Baden-Württemberg. The leaching water is collected and analysed every two weeks. After the first year, there was no detection of precursors in the leaching water. The main products were, in accordance with literature, PFPeA (Perfluoropentanoic acid) and PFHxA (Perfluorohexanoic acid) for the precursor 6:2 diPAP and PFHpA (Perfluoroheptanoic acid) and PFOA (Perfluorooctanoic acid) for the precursor 8:2 diPAP. The breakthrough peak of PFPeA (864 µg/l) and PFHxA (487 µg/l) was found in week nine after the start of the experiment, the major peak of PFHpA (124 µg/l) in week 15 and the peak of PFOA (303 µg/l) in week 25. Even though the major breakthrough of PFAAs was over after the first year, all of them are still found in leaching water in relatively constant concentrations: ~40 µg PFPeA/l, ~20 µg PFHxA/l (6:2 diPAP) and ~5 µg PFHpA/l, ~50 µg PFOA/l (8:2 diPAP). Thus, as a preliminary result after the first year, there is a higher mass of PFPeA and PFHxA in the leachate compared to PFHpA and PFOA, which can be led back to higher transformation rates of 6:2 diPAP than 8:2 diPAP.After two years, the soil columns will be cut horizontally in sections, and the soil will be analysed for precursors and PFAAs in order to calculate a mass balance. This will provide more insight into the transformation and mobilisation behaviour of investigated diPAPs and PFAAs.

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic substances, which moved to the scientific focus due to their ubiquity in the environment. Several thousands of individual PFAS are known, which differ in chemical structure as well as in their chemical and physical properties. Due to the huge number of substances, the assessment of their environmental behaviour is challenging. Still, more information about these substances, which are partly already declared PBT (persistent, bioaccumulative and toxic), is needed for risk assessments and remediation.The overall aim of this study was to describe the environmental behaviour in soil during leaching of ten different PFAAs (perfluoroalkyl acids), a group of persistent PFAS, and two diPAPs (polyfluoroalkyl phosphate diesters) with physical equations and parameters to gain knowledge about substance-related characteristics. For this purpose, we simulated the leaching of all surveyed PFAAs and of the biodegradable precursors 6:2 diPAP and 8:2 diPAP, which can transform into PFAAs. Soil and percolation data received from two experimental studies, a laboratory soil column study and a field lysimeter study, were used to evaluate the leaching and transformation behaviour using the MACRO model. In both studies the behaviour of diPAPs were simulated, which enables a comparison between natural and unnatural conditions. Modelling results from the laboratory study, in which climate impacts are limited, were used as input for the field study with natural climatic conditions. Parameters used for calibration were substance-related such as the adsorption distribution coefficient (KD). The amount of non-recovered PFAS, which is potentially related to the formation of non-extractable residues (NERs), was described using a first-order degradation equation. The evaluation of simulations was done using the goodness-of-fit function KGE (Kling-Gupta Efficiency) and a fitting score comparing simulated and observed soil and percolation data. Optimisation was done using the caRamel evolutionary algorithm with multi-objectives within the GNU R environment and up to 15,000 runs per substance, which resulted in a pareto front. Results of parameter values were then used to describe their leaching behaviour as transformation products (PFAAs) of diPAPs in two steps: (1) optimisation of leaching and transformation of diPAPs with soil data, (2) simulation of leaching of transformation products using results of PFAA simulations. The preliminary modeling results are promising for simulating the behavior of PFAAs as well as their precursors with MACRO.