RESUMEN
The distribution and fate of microplastics in different water sources and their treatment plants (seawater, three municipal wastewaters, a pharmaceutical factory wastewater, and three drinking waters) in France were studied. Currently, research in this field is still under exploration since almost no relevant standards or policies have been introduced for the detection, the removal, or the discharge of microplastics. This study used an improved quantitative and qualitative analytical methodology for microplastic detection by µ-FTIR carried out with siMPle analytical software. By investigation, wastewater was determined to contain the most abundant microplastics in quantity (4,203-42,000 MP·L-1), then followed by surface water/groundwater (153-19,836 MP·L-1) and seawater (around 420 MP·L-1). Polyethylene was the dominant material in almost all water types followed by polypropylene, polystyrene, and polyethylene terephthalate. Almost all treatment technologies could remove microplastics whatever the feed water types and concentration of microplastics, though some treatment processes or transport pipes could cause additional contamination from microplastics. The four WWTPs, three DWTPs, and SWTP in France provided, respectively, 87.8-99.8%, 82.3-99.9%, 69.0-96.0% removal/retention of MPs in quantity, and provided 97.3-100%, 91.9-99.9%, 92.2-98.1% removal/retention of MPs in surface area. Moreover, ultrafiltration was confirmed to be an effective technology for microplastic retention and control of dimensions of microplastics in smaller ranges both in field-scale and lab-scale experiments. The 200 kDa ultrafiltration membrane could retain 70-100% and 80-100% of microplastics in quantity and in surface area, respectively.
Asunto(s)
Agua Potable , Contaminantes Químicos del Agua , Aguas Residuales , Microplásticos , Plásticos , Contaminantes Químicos del Agua/análisis , Agua Dulce , Agua de Mar , Monitoreo del AmbienteRESUMEN
Microplastics of millimeter dimensions have been widely investigated in environmental compartments and today, studies are mainly focused on particles of smaller dimensions (< 500 µm). However, as there are no relevant standards or policies for the preparation and analysis of complex water samples containing such particles, the results may be questionable. Therefore, a methodological approach for 10 µm to 500 µm microplastic analysis was developed using µ-FTIR spectroscopy coupled with the siMPle analytical software. This was undertaken on different water samples (sea, fresh, and wastewater) taking into consideration rinsing water, digestion protocols, collection of microplastics, and sample characteristics. Ultrapure water was the optimal rinsing water and ethanol was also proposed with a mandatory previous filtration. Although water quality could give some guidelines for the selection of digestion protocols, it is not the only decisive factor. The methodology approach by µ-FTIR spectroscopy was finally assessed to be effective and reliable. This improved quantitative and qualitative analytical methodology for microplastic detection can then be used to assess the removal efficiency of conventional and membrane treatment processes in different water treatment plants.
Asunto(s)
Microplásticos , Contaminantes Químicos del Agua , Plásticos/análisis , Aguas Residuales , Espectroscopía Infrarroja por Transformada de Fourier , Monitoreo del Ambiente/métodos , Contaminantes Químicos del Agua/análisis , Agua Dulce/química , Agua de MarRESUMEN
In the present study, the photolysis of carbofuran has been undertaken under sunlight conditions and at the surface of model supports such as clay films and different soils collected from two different sites in Morocco (Tirs and Dahs). In all conditions, an efficient degradation occurred owing to direct light absorption and also to photoinduced processes involving either clays or natural organic matter moities. On kaolin films, the photodegradation kinetics appears to follow a first-order process that clearly depends on the film thickness. The diffusion of carbofuran from the lower part to the illuminated surface was found to be negligible when compared to the photolysis process within the range of 20-70 µm. Thus, the photolysis rate constant at the surface of the solid support, k (0), was evaluated to be 7.0 × 10(-3) min(-1). Under these experimental conditions, the quantum yield was found equal to 2.1 × 10(-4). On soil surfaces, the disappearance rate constant was mainly attributed to photoinduced processes arising from natural organic matter. From the analytical point of view, the products were formed through (1) hydroxylation on the aromatic ring, (2) homolytic scission of the carbamate C-O bond leading to radical species formation, and (3) photohydrolysis of the carbamate C-O bond.
Asunto(s)
Carbofurano/efectos de la radiación , Insecticidas/efectos de la radiación , Caolín/efectos de la radiación , Contaminantes del Suelo/efectos de la radiación , Carbofurano/química , Insecticidas/química , Fotólisis , Contaminantes del Suelo/química , Luz SolarRESUMEN
RATIONALE: Sulfonamides such as sulfaquinoxaline (SQX) are among the most important antibiotic families due to their extensive use in veterinary medicine. The prediction of their fate under solar irradiation through the identification of the generated metabolites is required. However, unambiguous structural characterizations often remain a challenge particularly when several isomers could match with the same MS(2) data. METHODS: Liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI-Q-TOFMS) in the positive ion mode, leading to the formation of the protonated forms of the studied compounds, [M + H(+)] ions, was employed. Collision-induced dissociation tandem mass spectrometry (CID-MS/MS) of the protonated molecules was carried out, and the effect of the collision energy as well as the elemental compositions of the product ions were used to propose chemical structures. Validation of the hypothesized structures was performed by the calculation of key fragmentation pathway energies using density functional theory (DFT) calculations (B3LYP/6-31 G (d,p)). RESULTS: The photoproducts were identified as 2-aminoquinoxaline, SQX isomers, 2-(N-parabenzoquinoneimine)quinoxaline and isomers resulting from SO(2) extrusion. The direct fragmentations of [SQX + H](+) and its protonated isomers mostly occurred through the loss of 2-aminoquinoxaline and/or the 4-sulfoaniline radical ion, while their rearrangements involved the migration of H and/or O atoms. For the desulfonated byproducts in their protonated forms, the main neutral losses were of the quinoxaline radical, aminoquinoxaline and NH(3). The fragmentation of the protonated 2-aminoquinoxaline mainly involved the elimination of NH(3) and HCN. CONCLUSIONS: LC/ESI-Q-TOFMS and DFT calculations have been shown to be useful and complementary methods for the identification of unknown isomeric compounds and the elucidation of fragmentation patterns, in the case of the sulfaquinoxaline veterinary antibiotic.
Asunto(s)
Cromatografía Liquida/métodos , Espectrometría de Masa por Ionización de Electrospray/métodos , Sulfaquinoxalina/análogos & derivados , Sulfaquinoxalina/química , Luz Solar , Agua/química , Isomerismo , Procesos Fotoquímicos , Quinoxalinas/química , Sulfaquinoxalina/análisis , Sulfaquinoxalina/efectos de la radiación , Espectrometría de Masas en TándemRESUMEN
This study concerns the elimination of methabenzthiazuron (MBTU) photocatalysed by sodium decatungstate salts W10O32(4-)·(DTA) in aqueous solution under irradiation at 365 nm. Ninety percentage of MBTU (10(-4) M) is mineralised in the presence of the photocatalyst (2×10(-4) M) after 7 d under exposure and the formation of nitrate, sulphate and ammonium confirmed this phenomenon. In aerated conditions, the photodegradation rate of MBTU clearly increased in the presence of DTA by a factor of 40 when compared to direct photolysis with ΦMBTU=2.5×10(-2) and t1/2 (MBTU)=1.4 h. Oxygen appeared essential since 2 times inhibition of MBTU disappearance and the photocatalytic cycle interrupt were observed in the absence of oxygen. The degradation mechanism has been elucidated through the photoproducts identification by LC-ESI-MS analysis. Two processes were implied in the degradation: electron transfer and H atom abstraction reactions both involving W10O32(4-∗) excited state species. In the primary steps of the degradation, the aromatic ring hydroxylation was observed by electron transfer leading to OH-MBTU isomers and H atom abstraction reaction gave benzthiazuron and a supposed demethylated product. Secondary oxidations permitted the hydroxylation of both products.