Chemical characterization and speciation of the soluble fraction of Arctic PM10.

The chemical composition of the soluble fraction of atmospheric particulate matter (PM) and how these components can combine with each other to form different species affect the chemistry of the aqueous phase dispersed in the atmosphere: raindrops, clouds, fog, and ice particles. The study was focused on the analysis of the soluble fraction of Arctic PM10 samples collected at Ny-Ålesund (Svalbard Islands, Norwegian Arctic) during the year 2012. The concentration values of Na+, K+, NH4+, Ca2+, Mg2+, Mn2+, Cu2+, Zn2+, Fe3+, Al3+, Cl-, NO2-, NO3-, SO42-, PO43-, formate, acetate, malonate, and oxalate in the water-soluble fraction of PM10 were determined by atomic spectroscopy and ion chromatography. Speciation models were applied to define the major species that would occur in aqueous solution as a function of pH (2-10). The model highlights that (i) the main cations such as Na+, K+, Mg2+, and Ca2+ occur in the form of aquoions in the whole investigated pH range; (ii) Cu2+, Zn2+, and, in particular, Fe3+ and Al3+ are mostly present in their hydrolytic forms; and (iii) Al3+, Fe3+, and Cu2+ form solid hydrolytic species that precipitate at pH values slightly higher than neutrality. These latter metals show interesting interactions with oxalate and sulfate ions, too. The speciation models were also calculated considering the seasonal variability of the concentration of the components and at higher concentration levels than those found in water PM extracts, to better simulate concentrations actually found in the atmospheric aqueous phase. The results highlight the role of oxalate as the main organic ligand in solution.

Phototransformation of Vanillin in Artificial Snow by Direct Photolysis and Mediated by Nitrite.

The photodegradation of vanillin, as a proxy of methoxyphenols emitted by biomass burning, was investigated in artificial snow at 243 K and in liquid water at room temperature. Nitrite (NO2-) was used as a photosensitizer of reactive oxygen and nitrogen species under UVA light, because of its key photochemical role in snowpacks and atmospheric ice/waters. In snow and in the absence of NO2-, slow direct photolysis of vanillin was observed due to back-reactions taking place in the quasi-liquid layer at the ice-grain surface. The addition of NO2- made the photodegradation of vanillin faster, because of the important contribution of photoproduced reactive nitrogen species in vanillin phototransformation. These species triggered both nitration and oligomerization of vanillin in irradiated snow, as the identified vanillin by-products showed. Conversely, in liquid water, direct photolysis was the main photodegradation pathway of vanillin, even in the presence of NO2-, which had negligible effects on vanillin photodegradation. The results outline the different role of iced and liquid water in the photochemical fate of vanillin in different environmental compartments.

Assessing the photodegradation potential of compounds derived from the photoinduced weathering of polystyrene in water.

Benzoate (Bz-) and acetophenone (AcPh) are aromatic compounds known to be produced by sunlight irradiation of polystyrene aqueous suspensions. Here we show that these molecules could react with •OH (Bz-) and •OH + CO3•- (AcPh) in sunlit natural waters, while other photochemical processes (direct photolysis and reaction with singlet oxygen, or with the excited triplet states of chromophoric dissolved organic matter) are unlikely to be important. Steady-state irradiation experiments were carried out using lamps, and the time evolution of the two substrates was monitored by liquid chromatography. Photodegradation kinetics in environmental waters were assessed by a photochemical model (APEX: Aqueous Photochemistry of Environmentally-occurring Xenobiotics). In the case of AcPh, a competitive process to aqueous-phase photodegradation would be volatilisation followed by reaction with gas-phase •OH. As far as Bz- is concerned, elevated dissolved organic carbon (DOC) levels could be important in protecting this compound from aqueous-phase photodegradation. Limited reactivity of the studied compounds with the dibromide radical (Br2•-, studied by laser flash photolysis) suggests that •OH scavenging by bromide, which yields Br2•-, would be poorly offset by Br2•--induced degradation. Therefore, photodegradation kinetics of Bz- and AcPh should be slower in seawater (containing [Br-] ~ 1 mM) compared to freshwaters. The present findings suggest that photochemistry would play an important role in both formation and degradation of water-soluble organic compounds produced by weathering of plastic particles.

Solar photodegradation of irinotecan in water: optimization and robustness studies by experimental design.

Irinotecan, a widely prescribed anticancer drug, is an emerging contaminant of concern that has been detected in various aquatic environments due to ineffective removal by traditional wastewater treatment systems. Solar photodegradation is a viable approach that can effectively eradicate the drug from aqueous systems. In this study, we used the design of experiment (DOE) approach to explore the robustness of irinotecan photodegradation under simulated solar irradiation. A full factorial design, including a star design, was applied to study the effects of three parameters: initial concentration of irinotecan (1.0-9.0 mg/L), pH (5.0-9.0), and irradiance (450-750 W/m2). A high-performance liquid chromatography coupled with a high-resolution mass spectrometry (HPLC-HRMS) system was used to determine irinotecan and identify transformation products. The photodegradation of irinotecan followed a pseudo-first order kinetics. In the best-fitted linear model determined by the stepwise model fitting approach, pH was found to have about 100-fold greater effect than either irinotecan concentration or solar irradiance. Under optimal conditions (irradiance of 750 W/m2, 1.0 mg/L irinotecan concentration, and pH 9.0), more than 98% of irinotecan was degraded in 60 min. With respect to irradiance and irinotecan concentration, the degradation process was robust in the studied range, implying that it may be effectively applied in locations and/or seasons with solar irradiance as low as 450 W/m2. However, pH needs to be strictly controlled and kept between 7.0 and 9.0 to maintain the degradation process robust. Considerations about the behavior of degradation products were also drawn.

Biomimetic photooxidation of noscapine sensitized by a riboflavin derivative in water: The combined role of natural dyes and solar light in environmental remediation.

Noscapine (NSC) is a benzyl-isoquinoline alkaloid discovered in 1930 as an antitussive agent. Recently, NSC has also been reported to exhibit antitumor activity and, according to computational studies, it is able to attack the protease enzyme of Coronavirus (COVID-19) and thus could be used as antiviral for COVID-19 pandemic. Therefore, an increasing use of this drug could be envisaged in the coming years. NSC is readily metabolized with a half-life of 4.5 h giving rise to cotarnine, hydrocotarnine, and meconine, arising from the oxidative breaking of the CC bond between isoquinoline and phthalide moieties. Because of its potentially increasing use, high concentrations of NSC but also its metabolites will be delivered in the environment and potentially affect natural ecosystems. Thus, the aim of this work is to investigate the degradation of NSC in the presence of naturally occurring photocatalysts. As a matter of fact, the present contribution has demonstrated that NSC can be efficiently degraded in the presence of a derivative of the natural organic dye Riboflavin (RFTA) upon exposure to visible light. Indeed, a detailed study of the mechanism involved in the photodegradation revealed the similarities between the biomimetic and the photocatalyzed processes. In fact, the main photoproducts of NSC were identified as cotarnine and opianic acid based on a careful UPLC-MS2 analysis compared to the independently synthesized standards. The former is coincident with one of the main metabolites obtained in humans, whereas the latter is related to meconine, a second major metabolite of NSC. Photophysical experiments demonstrated that the observed oxidative cleavage is mediated mainly by singlet oxygen in a medium in which the lifetime of 1O2 is long enough, or by electron transfer to the triplet excited state of RFTA if the photodegradation occurs in aqueous media, where the 1O2 lifetime is very short.

Investigation of the Aquatic Photolytic and Photocatalytic Degradation of Citalopram.

This study investigated the direct and indirect photochemical degradation of citalopram (CIT), a selective serotonin reuptake inhibitor (SSRI), under natural and artificial solar radiation. Experiments were conducted in a variety of different operating conditions including Milli-Q (MQ) water and natural waters (lake water and municipal WWT effluent), as well as in the presence of natural water constituents (organic matter, nitrate and bicarbonate). Results showed that indirect photolysis can be an important degradation process in the aquatic environment since citalopram photo-transformation in the natural waters was accelerated in comparison to MQ water both under natural and simulated solar irradiation. In addition, to investigate the decontamination of water from citalopram, TiO2-mediated photocatalytic degradation was carried out and the attention was given to mineralization and toxicity evaluation together with the identification of by-products. The photocatalytic process gave rise to the formation of transformation products, and 11 of them were identified by HPLC-HRMS, whereas the complete mineralization was almost achieved after 5 h of irradiation. The assessment of toxicity of the treated solutions was performed by Microtox bioassay (Vibrio fischeri) and in silico tests showing that citalopram photo-transformation involved the formation of harmful compounds.

Photocatalytic degradation of drugs in water mediated by acetylated riboflavin and visible light: A mechanistic study.

There is a current concern, among the scientific community, on the pollutants classified as "persistent organic pollutants (POPs)". Pharmaceuticals and personal care products (PPCPs) belong to this family of contaminants; therefore, it is necessary to find more efficient techniques able to achieve their removal from the environment. This study focuses on two different pharmaceuticals: carbamazepine and atenolol, chosen for their widespread use and their different chemical and medical properties. In this work, an organic dye, acetylated riboflavin, has been used in combination with visible light to achieve the photodegradation of these two POPs in <2 h. Moreover, photophysical experiments demonstrated the involvement of the singlet and triplet excited states of acetylated riboflavin and the generated singlet oxygen in the removal of these drugs. Besides, a detailed UFLC-MS-MS analysis of the photoproducts confirmed the oxidation of the drugs. Finally, a plausible mechanism has been postulated.

Evaluation of Fenton and modified Fenton oxidation coupled with membrane distillation for produced water treatment: Benefits, challenges, and effluent toxicity.

Membrane distillation is a promising technology to desalinate hypersaline produced waters. However, the organic content can foul and wet the membrane, while some fractions may pass into the distillate and impair its quality. In this study, the applicability of the traditional Fenton process was investigated and preliminarily optimized as a pre-treatment of a synthetic hypersaline produced water for the following step of membrane distillation. The Fenton process was also compared to a modified Fenton system, whereby safe iron ligands, i.e., ethylenediamine-N,N'-disuccinate and citrate, were used to overcome practical limitations of the traditional reaction. The oxidation pre-treatments achieved up to 55% removal of the dissolved organic carbon and almost complete degradation of the low molecular weight toxic organic contaminants. The pre-treatment steps did not improve the productivity of the membrane distillation process, but they allowed for obtaining a final effluent with significantly higher quality in terms of organic content and reduced Vibrio fischeri inhibition, with half maximal effective concentration (EC50) values up to 25 times those measured for the raw produced water. The addition of iron ligands during the oxidation step simplified the process, but resulted in an effluent of slightly lower quality in terms of toxicity compared to the use of traditional Fenton.

Structural elucidation of bisphenol E and bisphenol S photoinduced by-products by high-resolution electrospray ionisation mass spectrometry and tandem mass spectrometry.

RATIONALE: Bisphenol E (BPE) and bisphenol S (BPS) have recently replaced bisphenol A as monomers for producing polycarbonates. However, BPE and BPS can pose hazards as they are known to be endocrine disruptors. Despite the huge increase in their use, there is a lack of data regarding the toxicity and effects of BPE and BPS. METHODS: We investigated the photoinduced transformation of BPE and BPS when subjected to sun-simulated radiation and using TiO2 as a photocatalyst. Analyses of BPE, BPS and their by-products were performed by high-performance liquid chromatography/high-resolution mass spectrometry (HPLC/HRMS) using an orbitrap mass analyzer in negative electrospray ionisation (ESI) mode. The chromatographic separations were achieved by employing a C18 reversed-phase column, and the transformation products (TPs) were elucidated structurally using HRMS and multistage MS experiments performed in collision-induced dissociation (CID) mode. RESULTS: The transformation of bisphenol S involved the formation of twelve by-products, while ten TPs were detected following BPE degradation. For bisphenol S, the cleavage of the molecule is a very important transformation route, together with the hydroxylation of the substrate to provide mono- and poly-hydroxylated TPs. For bisphenol E, the two main routes were hydroxylation and ring opening. Acute toxicity for BPS, BPE and their TPs was assessed using the Vibrio fischeri assay, highlighting that their initial transformation involved the formation of TPs that were more toxic than the parent compound. CONCLUSIONS: The HPLC/HRMS method developed was useful for characterising and identifying newly formed TPs from bisphenol E and bisphenol S. This study aimed to examine the structure of twenty by-products identified during TiO2 -mediated photolysis and to evaluate acute toxicity over time.

Waste Cleaning Waste: Combining Alginate with Biowaste-Derived Substances in Hydrogels and Films for Water Cleanup.

Biowaste-derived substances isolated from green compost (BBS-GC) are environmentally friendly reactants similar to humic substances, which contain multiple functionalities, that are suitable for adsorbing different kinds of pollutants in wastewater. Herein, sodium alginate (derived from brown algae) cross-linked with both Ca2+ ions and BBS-GC in the form of hydrogels and dried films are proposed as green, easy-to-form, and handleable materials for tertiary water treatments. The results show that both hydrogels and films are mechanically stable and can effectively remove differently charged dyes through an adsorption mechanism that can be described by the Freundlich model. BBS-GC-containing gels always performed better than samples prepared without BBS-GC, revealing that such unconventional materials can integrate waste valorization and water decontamination, potentially providing social and environmental benefits.

Liquid chromatography/mass spectrometry analytical determination of gabapentin transformation products by heterogeneous photocatalysis and environmental evaluation.

RATIONALE: Gabapentin is a drug used to treat epilepsy and peripheral neuropathic pain. It is an analog of gamma-aminobutyric acid, and it is a selective blocker of voltage-gated calcium channels. The drug is excreted unmetabolized; it is stable in the environment and is classified as a persistent mobile organic contaminant. Because wastewater treatment plants (WWTPs) are not completely efficient, some bioactive molecules may be released unaltered into the environment. The aim of this study was to provide information about degradation pathways of gabapentin in water by studying its photoinduced transformation products (TPs) through laboratory simulation experiments. Gabapentin and its TPs were monitored in influent and effluent water samples from WWTPs in Germany and Italy. METHODS: The laboratory simulation used heterogeneous photodegradation mediated by titanium dioxide (TiO2 ). Chromatographic separation was achieved using a C18 reverse-phase column, and the structural identification of TPs was performed using high-resolution electrospray ionization high-resolution mass spectrometry (ESI-HRMS) and multistage MSn experiments. RESULTS: Several TPs were observed during TiO2 photodegradation. Nine new compounds were detected, and potential structures were assigned by studying the fragmentation pathways of the [M + H]+ ions of these TPs and gabapentin. Gabapentin and some of the newly identified TPs were found in environmental samples from WWTPs. CONCLUSIONS: The developed high-performance liquid chromatography/high-resolution mass spectrometry method was used to identify TPs from gabapentin. It was then successfully applied to real environmental samples to monitor the TPs as potential environmental pollutants.

The role of direct photolysis in the photodegradation of the herbicide bentazone in natural surface waters.

The photochemical fate of the herbicide bentazone was assessed by lab experiments and modeling tools. Experimental and modeling results showed that bentazone is mainly photodegraded by direct photolysis in natural water samples, even in the presence of dissolved organic matter (DOM) that can act as light-screening agent, photosensitizer and scavenger of reactive species. Even when it was dissolved in natural water samples containing different DOM amounts, the phototransformation kinetics of bentazone was unchanged compared to irradiation runs in ultrapure water. This finding suggests that the DOM and the other components of our samples did not affect the direct photolysis of bentazone by light-absorption competition, at least at the experimental optical path lengths, and did not induce significant indirect photodegradation by producing reactive transient species. Photochemical modeling in a lake-water photoreactivity scenario corroborated the observed experimental results, showing the predominant role of direct photolysis in the overall (direct + indirect) photodegradation of bentazone at different water depths and DOM contents. However, the model predicted a minor but non-negligible contribution of indirect photochemistry (i.e., reactions triggered by HO•, CO3•- and 3CDOM*) to the herbicide degradation. This contribution (especially by 3CDOM*) could become crucial in deep and DOM-rich water bodies. Finally, several photoproducts formed by direct photolysis and HO•-induced photodegradation were identified, which should not be particularly toxic for aquatic organisms and Vibrio fischeri bacteria.

Surfactant-Assisted Fabrication of Alumina-Doped Amorphous Silica Nanofiltration Membranes with Enhanced Water Purification Performances.

Surfactant-templated 5 mol% Al2O3-doped silica membranes nanofiltration membranes were synthesized via the sol-gel method, and afterward, were optimized, and tested with respect to the permeability and rejection rate. The disordered silica network was stabilized by doping 5 mol% alumina. Tetraethyl orthosilicate and aluminum isopropoxide were used as the silica and alumina precursors, respectively. Cetyltrimethylammonium bromide (CTAB) was used not only as a pore-forming agent, but also to control the reaction rate of the aluminum isopropoxide, thus obtaining highly homogeneous materials. The results about filtration of model solutions showed that the optimized membranes are featured by both a relatively high water permeability (1.1-2.3 L·m-2·h-1 ·bar-1) and a high rejection for salts (74% for NaCl, and >95% for MgSO4 and Na2SO4) and organic pollutants (e.g., about 98% for caffeine). High rejection of divalent ions and organic molecules was also observed when a real wastewater effluent was filtered. The influence of the synthesis conditions on the membrane performance is discussed.

Evaluation of transformation products from chemical oxidation of micropollutants in wastewater by photoassisted generation of sulfate radicals.

In this research, the degradation of seven different micropollutants (MPs) and the formation of their transformation products (TPs) have been assessed during the application of different advanced oxidation processes: photolytic and photocatalytic activation of peroxymonosulfate (PMS) and persulfate (PS). The results were compared with those obtained from the photolytic experiments using hydrogen peroxide (H2O2) as oxidant. A significant abatement of almost all MPs was achieved, even with very low UV-C contact time (9 and 28 s). The degradation of atenolol (ATN) and caffeine (CFN) ranged from 84 to 100% with a dose of 0.5 mM of any oxidant. The efficiencies for bisphenol-A (BPA), carbamazepine (CBZ), diclofenac (DCF), ibuprofen (IBP), and sulfamethoxazole (SMX) varied depending on the oxidation system and operating conditions (oxidant dose and UV-C contact time), leading to the photolysis of PMS to higher efficiencies than PS and H2O2. In all cases, the abatement of MPs ranged from 63 to 83%, even with the lowest PMS dosage. Moreover, the addition of Fe(II) as a catalyst enhanced the removal efficiency, reaching almost total removal, especially over CBZ, DCF, and IBP. The Dissolved Organic Carbon (DOC) removal ranged between 44 and 62%, suggesting the transformation of MPs in intermediate compounds. The identification of transformation products was carried out for each micropollutant and each oxidation treatment, being observed some transformation products specific of oxidation by sulfate radicals. For example, m/z 165.0432 only appeared after PMS/Fe(II)/UV-C on the degradation of BFA, m/z 251.082 appeared after photolytic activation of PMS and PS on CBZ removal, and m/z 128.0452 was observed after any sulfate radical oxidation treatment, but not after photolysis of H2O2.

Photocatalytic abatement of emerging pollutants in pure water and wastewater effluent by TiO2 and Ce-ZnO: degradation kinetics and assessment of transformation products.

Here, the performances of two different catalysts, Ce-ZnO and TiO2 synthetized in our laboratories, were compared with the commercial TiO2-P25 for degradation of a mixture of seven emerging pollutants under UV irradiation. The investigation included monitoring pollutants abatement in Milli-Q water and in wastewater effluent and identifying their transformation products by HPLC-HRMS. Structural characterization of intermediates supported by data available from literature allowed elucidation of the transformation pathways occurring in the presence of all investigated catalysts in the wastewater effluent. Preliminary results showed a good removal efficacy for almost all examined contaminants, even in real water matrix (i.e. wastewater effluent). The type of matrix and catalyst affects the number and/or the abundance of transformation products, which suggests differences in their transformation routes.

New Insights on the Photodegradation of Caffeine in the Presence of Bio-Based Substances-Magnetic Iron Oxide Hybrid Nanomaterials.

The exploitation of organic waste as a source of bio-based substances to be used in environmental applications is gaining increasing interest. In the present research, compost-derived bio-based substances (BBS-Cs) were used to prepare hybrid magnetic nanoparticles (HMNPs) to be tested as an auxiliary in advanced oxidation processes. Hybrid magnetic nanoparticles can be indeed recovered at the end of the treatment and re-used in further water purification cycles. The research aimed to give new insights on the photodegradation of caffeine, chosen as marker of anthropogenic pollution in natural waters, and representative of the contaminants of emerging concern (CECs). Hybrid magnetic nanoparticles were synthetized starting from Fe(II) and Fe(III) salts and BBS-C aqueous solution, in alkali medium, via co-precipitation. Hybrid magnetic nanoparticles were characterized via X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The effect of pH, added hydrogen peroxide, and dissolved oxygen on caffeine photodegradation in the presence of HMNPs was assessed. The results allow for the hypothesis that caffeine abatement can be obtained in the presence of HMNPs and hydrogen peroxide through a heterogeneous photo-Fenton mechanism. The role of hydroxyl radicals in the process was assessed examining the effect of a selective hydroxyl radical scavenger on the caffeine degradation kinetic.

A model assessment of the potential of river water to induce the photochemical attenuation of pharmaceuticals downstream of a wastewater treatment plant (Guadiana River, Badajoz, Spain).

We predicted the possible direct and indirect phototransformation kinetics of carbamazepine (CBZ), ibuprofen (IBU) and diclofenac (DIC) in river water, based on data of water chemistry obtained for the Guadiana River near Badajoz (Southwestern Spain) during a year-round sampling campaign. The three compounds were chosen, (i) because they occurred at the outlet of the wastewater treatment plant (WWTP) in Badajoz, as well as in river water sampled 1 km downstream of the WWTP, and (ii) because their photochemical fate in surface waters is known well enough to be modelled. The predicted phototransformation kinetics would be negligible in winter and fastest in April-August, with comparable rate constants in April through August despite differences in sunlight irradiance. Favourable water chemistry would in fact offset the lower irradiance, and vice versa. Half-life times of at least three weeks - one month are predicted for CBZ and IBU. Photodegradation may be an important attenuation pathway for biorecalcitrant CBZ, while IBU photochemistry is unlikely to be competitive with other processes including biodegradation. The predicted DIC photochemical half-life times of 7-10 days in April-August would be comparable with the biodegradation kinetics data reported in the literature. Photochemistry might not induce extensive phototransformation of xenobiotics in the Guadiana River under normal flow conditions, but it could become important in the case of low flow produced by water scarcity.

Assessment of the photocatalytic transformation of pyridinium-based ionic liquids in water.

We studied some ionic liquids (ILs) belonging to the pyridinium class under photocatalytic treatment. In particularly, we analysed how the length of the alkyl chain, the kind of inorganic ion and the type of substituents could influence the disappearance rate, the mineralization extent, the acute toxicity and the transformation mechanism. For such, we selected some pyridinium derivatives with different alkyl chain but the same anion, namely tetrafluoroborate (1-ethylpyridinium, 1-butylpyridinium, 1-hexylpyridinium), with two alkyl substituents (4-methyl-1-butylpyridinium) and with a different substituent (1-cyanopropylpyridinium). Then, on a selected IL (1-butylpyridinium), we evaluate the role of different inorganic anions (bromine and chlorine). The results show that irrespective to the alkyl chain or the number of substituents, the transformation involved an attack to the alkyl chain, proceeded through the formation of harmless compounds and the mineralization was easily achieved within 4h. Nitrogen was mainly released as ammonium ion. When introducing a cyano group, the extent of nitrate ions and the number of possible transformation route increased. Conversely, the type of inorganic ion deeply affected the transformation pathways and the extent of mineralization. Actually, in the presence of bromide as anion, IL was only partially mineralized and the formation of highly persistent transformation products occurred.

Effects of the antioxidant moieties of dissolved organic matter on triplet-sensitized phototransformation processes: Implications for the photochemical modeling of sulfadiazine.

Previous studies have shown that the photodegradation of some pollutants, induced by the excited triplet states of chromophoric dissolved organic matter (3CDOM*), can be inhibited by back-reduction processes carried out by phenolic antioxidants occurring in dissolved organic matter (DOM). Here, for the first time to our knowledge, we included such an inhibition effect into a photochemical model and applied the model predictions to sulfadiazine (SDZ), a sulfonamide antibiotic that occurs in surface waters in two forms, neutral HSDZ and anionic SDZ- (pKa = 6.5). The input parameters of the photochemical model were obtained by means of dedicated experiments, which showed that the inhibition effect was more marked for SDZ- than for HSDZ. Compared to the behavior of 2,4,6-trimethylphenol, which does not undergo antioxidant inhibition when irradiated in natural water samples, the back-reduction effect on the degradation of SDZ was proportional to the electron-donating capacity of the DOM. According to the model results, direct photolysis and OH reaction would account for the majority of both HSDZ and SDZ- photodegradation in waters having low dissolved organic carbon (DOC < 1 mgC L-1). With higher DOC values (>3-4 mgC L-1) and despite the back-reduction processes, the 3CDOM* reactions are expected to account for the majority of HSDZ phototransformation. In the case of SDZ- at high DOC, most of the photodegradation would be accounted for by direct photolysis. The relative importance of the triplet-sensitized phototransformation of both SDZ- and (most importantly) HSDZ is expected to increase with increasing DOC, even in the presence of back reduction. An increase in water pH, favoring the occurrence of SDZ- with respect to HSDZ, would enhance direct photolysis at the expense of triplet sensitization. SDZ should be fairly photolabile under summertime sunlight, with predicted half-lives ranging from a few days to a couple of months depending on water conditions.

High-performance liquid chromatography/high-resolution mass spectrometry for the characterization of transformation products of ionic liquids.

RATIONALE: Ionic liquids (ILs) are a subject of active research in the field of alternative solvents. We studied the behaviour of a piperidine IL, 1-butyl-1-methylpiperidinium tetrafluoroborate (BMPA), through the elucidation of its transformation products (TPs) in water. METHODS: The transformation pathways of BMPA were investigated using high-performance liquid chromatography (HPLC) combined with a hybrid LTQ-Orbitrap instrument on the basis of mass defect filtering. TPs of BMPA were identified by fragmentation patterns and accurate mass measurements. RESULTS: The separation and identification of 32 TPs was achieved. BMPA can be oxidized at different positions in the alkyl chains. The ultimate products corresponds to N-methyl-piperidinium and some byproducts involving ring-opening. Tests of acute toxicity, evaluated with Vibrio Fischeri bacteria, show that BMPA transformation proceeds through the formation of slightly harmful compounds. CONCLUSIONS: Results showed that the main transformation pathways of BMPA were alkyl chain hydroxylation/shortening and de-alkylation, and that HPLC/LTQ-Orbitrap can serve as an important analytical platform to gather the unknown TPs of ILs.