Is it raining PFAS in France? An analysis of 52 PFAS at nanogram per liter levels in French rainwaters during autumn season.

Per- and polyfluoroalkyl substances (PFAS) are of increasing concern due to their pervasive nature, high persistence, and their impacts on human health and the environment. Many studies have attempted to assess the presence of PFAS along the water cycle, but few have analyzed rainwater PFAS content and its contribution to water contamination. The present study aims to improve knowledge by providing the first analysis of PFAS rainwater samples from France. A total of 52 PFAS were analyzed at nanogram per liter levels in rainwater samples collected in 14 locations in France using a cutting-edge liquid chromatography-tandem mass spectrometry (LC/MS/MS) method for multiresidue determination. Depending on the quantity of rainwater collected, the PFAS concentrations were analyzed either by direct injection or after solid-phase extraction (SPE), allowing to quantify 20 PFAS with a limit of quantification (LOQ) ≤ 100 ng/L and 52 PFAS with a LOQ ≤ 1 ng/L, respectively. For the five locations for which the collected samples were analyzed by direct injection, no PFAS could be detected (i.e., their concentrations in the samples were below the LOQs of the method). The samples from four locations out of the nine analyzed by SPE-LC/MS/MS show results above the method's LOQs for up to 10 PFAS. Among the quantified PFAS, three compounds (perfluorononanoic acid, perfluoroundecanoic acid, and perfluorohexanoic acid) have been found to be of most significance. These results bring out the presence of PFAS in rainwater samples in France, highlighting the need for PFAS environmental surveillance and risk assessment and the necessity of continuous improvement of existing analysis methods.

Photostability of l-tryptophan in aqueous solution: Effect of atmosphere and antioxidants addition.

l-Tryptophan (l-Trp) is an amino acid important in nutrition, and mainly provided by food supplements. However, it is known to be unstable under light irradiation, which is an issue for the nutrition and feed industry. In the present study, the photostability of l-Trp was studied in acidic aqueous solutions under air and under an inert atmosphere, N2. The photodegradation was followed using UV-visible and fluorescence spectroscopy after photolysis. Moreover, molecular orbitals and bond dissociation energies calculations, and electron spin resonance spectroscopy were performed. From all these results, a photodegradation occurring through a free radical pathway was suggested. Interestingly, several antioxidants were tested to improve the photostability of l-Trp, especially during irradiation under air, since the l-Trp was evidenced to be much less stable under air than under N2. The results showed that sodium benzoate or EDTA were not efficient, but antioxidants such as chlorogenic acid, ascorbic acid or potassium sorbate improved significantly the photostability of l-Trp in acidic solutions.

Ascorbic Acid Derivatives as Potential Substitutes for Ascorbic Acid To Reduce Color Degradation of Drinks Containing Ascorbic Acid and Anthocyanins from Natural Extracts.

Ascorbic acid is widely used in the food industry as a source of vitamin C or as antioxidant. However, it degrades quickly in beverages at acidic pH and can accelerate the degradation of anthocyanins, natural dyes used in beverages, leading to a loss of color. In this work, we investigated the possibility to replace ascorbic acid by ascorbic acid derivatives to prevent its degradation effect on anthocyanins from natural extracts (black carrot, grape juice, and purple sweet potato). For this, the thermal and photolytic stabilities under air and under N2 of ascorbic acid (as reference) and of some ascorbic acid derivatives (3-O-ethyl-l-ascorbic acid, 2-O-α-d-glucopyranosyl-l-ascorbic acid, l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate, l-ascorbyl 2,6-dibutyrate, glyceryl ascorbate, (+)-5,6-O-isopropylidene-l-ascorbic acid), soluble in aqueous model beverages, were studied alone and in the presence of anthocyanins from the natural extracts in citrate buffer at pH 3. The stability was followed by UV-visible spectrometry. To extend the investigation, some properties of the ascorbic acid derivatives (pKa, oxidation potential, bond dissociation energy, ionization potential) were also determined. Moreover, the addition of chlorogenic acid was examined to further stabilize the mixture of anthocyanins with 2-O-α-d-glucopyranosyl-l-ascorbic acid, a promising ascorbic acid derivative.

Concentrations and Adsorption Isotherms for Amphiphilic Surfactants in PM1 Aerosols from Different Regions of Europe.

Predicting the activation of submicrometer particles into cloud droplets in the atmosphere remains a challenge. The importance of surface tension, σ (mN m-1), in these processes has been evidenced by several works, but information on the "surfactants" lowering σ in actual atmospheric particles remains scarce. In this work, PM1 aerosols from urban, coastal, and remote regions of Europe (Lyon, France, Rogoznica, Croatia, and Pallas, Finland, respectively) were investigated and found to contain amphiphilic surfactants in concentrations up to 2.8 µg m-3 in the air and 1.3 M in the particle dry volume. In Pallas, correlations with the PM1 chemical composition showed that amphiphilic surfactants were present in the entire range of particle sizes, supporting recent works. This implied that they were present in hundreds to thousands of particles cm-3 and not only in a few large particles, as it has been hypothesized. Their adsorption isotherms and critical micelle concentration (CMC) were also determined. The low CMC obtained (3 × 10-5-9 × 10-3 M) implies that surface tension depression should be significant for all the particles containing these compounds, even at activation (growth factor ∼ 10). Amphiphilic surfactants are thus likely to enhance the CCN ability of submicrometer atmospheric particles.

Properties of Seawater Surfactants Associated with Primary Marine Aerosol Particles Produced by Bursting Bubbles at a Model Air-Sea Interface.

Surfactants account for minor fractions of total organic carbon in the ocean but can significantly influence the production of primary marine aerosol particles (PMA) at the sea surface via modulation of bubble surface tension. During September and October 2016, model PMA (mPMA) were produced from seawater by bursting bubbles at two biologically productive and two oligotrophic stations in the western North Atlantic Ocean. Total concentrations of surfactants extracted from mPMA and seawater were quantified and characterized via measurements of surface tension isotherms and critical micelle concentrations (CMCs). Surfactant CMCs in biologically productive seawater were lower than those in the oligotrophic seawater suggesting that surfactant mixtures in the two regions were chemically distinct. mPMA surfactants were enriched in all regions relative to those in the associated seawater. Surface tension isotherms indicate that mPMA surfactants were weaker than corresponding seawater surfactants. mPMA from biologically productive seawater contained higher concentrations of surfactants than those produced from oligotrophic seawater, supporting the hypothesis that seawater surfactant properties modulate mPMA surfactant concentrations. Diel variability in concentrations of seawater and mPMA surfactants in some regions is consistent with biological and/or photochemical processing. This work demonstrates direct links between surfactants in mPMA and those in the associated seawater.

Thermal and Photochemical Stability of Anthocyanins from Black Carrot, Grape Juice, and Purple Sweet Potato in Model Beverages in the Presence of Ascorbic Acid.

Anthocyanins are natural dyes widely used in the food industry, but their chemical stability in beverages can be affected by the presence of additives. In the present paper, the interaction between anthocyanins and ascorbic acid (AA) is more particularly investigated. Ascorbic acid is an ubiquitous component in food products. In this study, the thermal stability at 43 °C and the photolysis stability in air and in an inert atmosphere (N2) of anthocyanins extracted from black carrot (BC), grape juice (GJ), and purple sweet potato (SP) were studied in the presence and absence of ascorbic acid (in citrate buffer at pH 3). Discriminating the main environmental factors (i.e., heat and light) affecting anthocyanin stability is a key point for better understanding the degradation pathways. The stability of the anthocyanins was followed by UV-vis spectrometry. Moreover, to understand the degradation mechanisms in both the presence and absence of ascorbic acid, various techniques such as fluorescence quenching, cyclic voltammetry, and electron-spin-resonance (ESR) spectroscopy were also used to furnish a full coherent picture of the chemical mechanisms associated with the anthocyanin degradation. In addition, molecular orbitals and bond-dissociation energies (BDE) were calculated to extend the investigation. Moreover, the effects of some supplementary stabilizers (chlorogenic acid, sinapic acid, tannic acid, fumaric acid, ß-carotene, isoquercitrin, myricitrin, green coffee bean extract, and rosemary extract) and sugars (sucrose, fructose, and glucose) on anthocyanins stability in the presence of ascorbic acid were examined.

Citral Photodegradation in Solution: Highlighting of a Radical Pathway in Parallel to Cyclization Pathway.

Citral, a lemon flavor molecule often used in the beverage and fragrance industry, is known to be unstable under light irradiation. Its deterioration is considered to be an important issue for the stabilization of lemon-flavored drinks. The aim of this study is to understand the degradation mechanisms of citral under light irradiation with the variation of three parameters: the solvent (citrate buffer solution at pH 3 vs ethanol), the atmosphere (air vs N2), and the concentration of citral. The photodegradation has been studied using UV-visible spectroscopy after photolysis, nuclear magnetic resonance spectrometry, and electron spin resonance spectroscopy. To extend the investigation, molecular orbitals and bond dissociation energies have also been calculated. They give an insight into the light absorption properties and the possible cleavage of citral molecular bonds. In addition, UV-light absorption and radical scavenging activities of two additives, potassium sorbate and ascorbic acid, have been studied for the inhibition of the citral photodecomposition by UV-light irradiation. Both theoretical and experimental results highlight a new degradation pathway involving free-radical intermediates in parallel to the already reported cyclization one, which could be prevented by the addition of stabilizers such as ascorbic acid or sorbate.

Extraction and Characterization of Surfactants from Atmospheric Aerosols.

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in the Earth's atmosphere, a central process in meteorology, hydrology, and for the climate system. But because specific extraction and characterization of these compounds have been lacking for decades, very little is known on their identity, properties, mode of action and origins, thus preventing the full understanding of cloud formation and its potential links with the Earth's ecosystems. In this paper we present recently developed methods for 1) the targeted extraction of all the surfactants from atmospheric aerosol samples and for the determination of 2) their absolute concentrations in the aerosol phase and 3) their static surface tension curves in water, including their Critical Micelle Concentration (CMC). These methods have been validated with 9 references surfactants, including anionic, cationic and non-ionic ones. Examples of results are presented for surfactants found in fine aerosol particles (diameter <1 µm) collected at a coastal site in Croatia and suggestions for future improvements and other characterizations than those presented are discussed.

Anionic, Cationic, and Nonionic Surfactants in Atmospheric Aerosols from the Baltic Coast at Askö, Sweden: Implications for Cloud Droplet Activation.

Recent analyses of atmospheric aerosols from different regions have demonstrated the ubiquitous presence of strong surfactants and evidenced surface tension values, σ, below 40 mN m(-1), suspected to enhance the cloud-forming potential of these aerosols. In this work, this approach was further improved and combined with absolute concentration measurements of aerosol surfactants by colorimetric titration. This analysis was applied to PM2.5 aerosols collected at the Baltic station of Askö, Sweden, from July to October 2010. Strong surfactants were found in all the sampled aerosols, with σ = (32-40) ± 1 mN m(-1) and concentrations of at least 27 ± 6 mM or 104 ± 21 pmol m(-3). The absolute surface tension curves and critical micelle concentrations (CMC) determined for these aerosol surfactants show that (1) surfactants are concentrated enough in atmospheric particles to strongly depress the surface tension until activation, and (2) the surface tension does not follow the Szyszkowski equation during activation but is nearly constant and minimal, which provides new insights on cloud droplet activation. In addition, both the CMCs determined and the correlation (R(2) ∼ 0.7) between aerosol surfactant concentrations and chlorophyll-a seawater concentrations suggest a marine and biological origin for these compounds.

Microemulsions with the ionic liquid ethylammonium nitrate: phase behavior, composition, and microstructure.

In this study, we investigate properties of microemulsions which consist of the ionic liquid (IL) ethylammonium nitrate (EAN), the nonionic surfactant C12E3 and an n-alkane, namely n-dodecane or n-octane. The compositions of the coexisting phases are calculated from the densities and volumes of the respective phases. Since the interfacial tension between the water-rich and the oil-rich phase in traditional microemulsions (containing water and oil) relates to the microstructure, spinning drop tensiometry is used to measure the interfacial tension σab and to estimate the domain sizes. Finally, measuring the self-diffusion coefficients of all components via the Fourier Transform Pulsed Gradient Spin Echo (FTPGSE) NMR technique allowed distinguishing between continuous and discrete structures. Our results indicate that the general principles underlying water-n-alkane-CiEj microemulsions can indeed be transferred to oil-in-EAN droplet and the respective bicontinuous microemulsions, while differences are observed for EAN-in-oil droplet microemulsions.