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LC-MS/MS analysis showed the co-occurrence of cyanotoxins (seven microcystin congeners and cylindrspermopsin, at low levels, <1 g/L) with other cyanobacterial peptides (anabaenopeptins, microginins). Cordeiro et al. [[16]] screened 157 strains from the Azorean Bank of Algae and Cyanobacteria (BACA) for cyanotoxin production (microcystins, saxitoxins and cylindrospermopsins) using qPCR, LC-MS/MS and 16S rRNA phylogenetic analysis. Toxic cyanobacteria in freshwater bodies constitute a major threat to public health and aquatic ecosystems [[1]]. Cyanotoxin-producing genes were amplified in 13 strains, and 4 were confirmed as toxin producers by LC-MS/MS. [Extracted from the article]

A 9-week feeding trial was conducted to investigate the effects of dietary Enteromorpha prolifera on the growth performance and body composition of juvenile large yellow croaker ( Pseudosciaena crocea) (Richardson, 1846) (11.41 ± 1.59 g) in floating sea cages (1.5 × 1.5 × 2.0 m). Four isonitrogenous and isoenergetic diets were formulated to contain graded levels (0%, 5%, 10% and 15%) of E. prolifera. Survival ranged from 98.7% to 99.7%, and was independent of dietary treatment ( P>0.05). There were no significant differences in the feeding rate among dietary treatments ( P>0.05). The specific growth rate (SGR) increased with increasing levels of E. prolifera. When the supplementation of E. prolifera was >5%, SGR was significantly higher compared with the control group (0%). The feed efficiency ratio (FER) in fish fed the diet with 5% E. prolifera (diet 2) was higher than that of the other groups, while in fish fed the diet with 10% E. prolifera (diet 3), it was the lowest ( P<0.05). The protein retention (PR) decreased as the level of E. prolifera increased in diets (5%, 10% and 15%). The protein body content displayed a trend similar to that of PR. No significant difference was observed in body moisture and ash among the dietary treatments. An increase in minerals of potassium, magnesium and sodium in body was observed with an increase in dietary seaweed concentrations. On basis of the SGR and FER, supplementation levels of E. prolifera can reach at least 15% without affecting the growth and still maintain a high survival rate for juvenile large yellow croaker. [ABSTRACT FROM AUTHOR]

Polyoxometallates (POMs), i.e. metal oxide clusters of mainly tungsten, are effective homogeneous photocatalysts for the mineralization of organic pollutants. ·OH radicals formed by the reaction of the photo-excited POMs with H 2 O appear to play a key role in the process. POMs are similar to TiO 2 . In this article, the photocatalytic activity of POMs has been presented on several diversified organic pollutants of interest such as phenol, chlorophenols, chloroacetic acids, and pesticides to determine the feasibility of decontamination of aqueous solutions from these pollutants. The results show that aqueous solutions containing the target pollutants, upon photolysis in the presence of POMs, undergo effective degradation to CO 2 , H 2 O, and the corresponding inorganic anions. The intermediates identified give rise to complicated degradation mechanisms prior to mineralization. In addition, photolysis of an aqueous solution of metal ions in the presence of POMs and organic substrate leads to the oxidative degradation of the organic and the simultaneous reduction–precipitation of metals in elemental state. This process has been successful in the removal–recovery of a great variety of metal ions including either toxic metallic compounds (chromium and mercury) or valuable metals (such as copper, silver, gold, palladium, and platinum). Finally, the two pathways were combined into a simple one-pot process for the decontamination of aquatic environment from both organic pollutants and metal cations. [ABSTRACT FROM AUTHOR]

Using the polyoxometallate anions (POM) PW12O403-, SiW12O404-, H2W12O406- or P2Mo18O626- as photocatalysts and propan-2-ol as sacrificial electron donor, Pd2+ can be reduced and recovered in metallic form. The method leads to very low final palladium concentrations (<0.2 ppm) while the soluble POM catalyst is self-separated from the pure precipitated metal that is obtained, retaining its catalytic function.The process is efficient in both one-pot and two-pot system. However, reduced tungstates of the formula XW12O40n-, X = P, Si or H2 that react rapidly with oxygen are preferably photochemically produced in situ in a one pot system, where propan-2-ol/POM/Pd2+ species co-exist. On the other hand, the 2-equivalent reduced P2Mo18O626- is preferably used in a two-pot system, pre-formed upon photolysis of a propan-2-ol/POM system and in turn serves as an easily kept electron storage (since it is inert against reoxidation by oxygen) amenable to reduce Pd2+ ions at will.Some novel results are marked concerning the environmental photocatalysis with POM: i) Upon photolysis of a one-pot system where propan-2-ol/POM/Pd2+ species co-exist and under the same conditions, the rate of photocatalytic reduction of palladium follows the photoxidizing ability of POM (PW12O403->SiW12O404->H2W12O406-). That is, POM catalysts that are more efficient in photo-oxidative degradation of organic compounds are also more effective in reductive recovery of palladium. ii) Selectivity in recovery of palladium among mixture of non-noble metal ions (Cu2+ and Ni2+), can be achieved even when they are in more than 10-fold excess. [Copyright &y& Elsevier]

Recovery of silver ions from aqueous solutions can be obtained through a homogeneous photocatalytic process that involves addition of a polyoxometalate (POM) (POM=PW12O403−, SiW12O404− or P2Mo18O626−) organic substrate, for instance propan-2-ol, and illumination with near-visible and UV-light. The process is effective for a wide range of Ag+ concentration, varying from about 3 to more than 1300 ppm. Prolonged irradiation leads to complete removal of silver up to non detected traces (<0.2 ppm). Silver removal follows thermodynamics, i.e. it depends on the redox potential difference of the photochemically reduced POM and Ag+ in the thermal reaction [POM(e−)+Ag+→POM+Ag]. Air oxygen has no effect on the rate of silver recovery. On the contrary, thiosulfate complexes Ag+, lowers the redox potential and hinders the reduction and precipitation of silver. Unlike TiO2 particulates, POM anions are not contaminated by the precipitated silver retaining their ability to remove large quantities of pure metal. [Copyright &y& Elsevier]

Studies the photocatalytic reduction and recovery of copper by polyoxometalates (POM). Characterization of copper particles; Effect of POM and substrate concentrations; Influences of the dioxygen on the induction period observed before the commencement of copper formation.

Investigates the decomposition of atrazine in the presence of polyoxometalates. Capability of ultrasound to decompose atrazine; Elaboration on sonolysis and photoloysis; Production of cyanuric acid.

Investigates the light-induced catalytic decomposition of several mono-, di-, and trichlorophenols and phenol in the presence of PW12O403- in aqueous solutions. Hydroxylation; Substitution of chlorine by OH radicals mainly in the ortho and para positions; Cleavage of the aromatic ring; Ring-opening products detected.

Focuses on a study which examined the mineralization of 2,4-dichlorophenol and organochlorine pesticides with near ultraviolet and visible light in the presence of a characteristic polyoxometallate catalyst PW...O... Details on the experimental setup; Results; Discussion of findings.

Many water utilities are at least occasionally affected by unpleasant taste and odour (T&O) in drinking water. For decades, aesthetic water quality has been of secondary concern to water producers, with water safety being the primary focus. However, there has been a recent shift towards prioritising consumer satisfaction, encompassing not only services, but also water quality, including T&O issues, which can negatively impact the supplier’s reputation. Starting to address a T&O problem until consumers’ complaints become massive is too late and puts water producers under great stress to take effective action in a timely manner. Rather, a preventive approach is necessary. The most effective approach is to include T&O as a hazard to assess and manage in the context of developing a water safety plan (WSP) for the supply system. The development of a WSP provides an excellent platform for including the stakeholders needed to control the source of T&O events, as this often requires multistakeholder cooperation. Our review provides a comprehensive guide to addressing T&O occurrences and shows how this can be included in the framework of WSP development. It identifies supporting tools and illustrates the information given with a number of examples from water suppliers’ practice. [ABSTRACT FROM AUTHOR]

Hepatotoxic microcystins (MCs) are the most frequently detected group of cyanobacterial toxins. This study investigated the degradation of common MC variants in water, MC-LR, MC-RR, MC-YR and MC-LA, by UV-254 nm-based processes, UV only, UV/H 2 O 2 , UV/ S 2 O 8 2 − and UV/ HSO 5 − . Limited direct photolysis of MCs was observed, while the addition of an oxidant significantly improved the degradation efficiency with an order of UV/ S 2 O 8 2 − > UV/ HSO 5 − > UV/H 2 O 2 at the same initial molar concentration of the oxidant. The removal of MC-LR by UV/H 2 O 2 appeared to be faster than another cyanotoxin, cylindrospermopsin, at either the same initial molar concentration or the same initial organic carbon concentration of the toxin. It suggested a faster reaction of MC-LR with hydroxyl radical, which was further supported by the determined second-order rate constant of MCs with hydroxyl radical. Both isomerization and photohydration byproducts were observed in UV only process for all four MCs; while in UV/H 2 O 2 , hydroxylation and diene-Adda double bond cleavage byproducts were detected. The presence of a tyrosine in the structure of MC-YR significantly promoted the formation of monohydroxylation byproduct m/z 1061; while the presence of a second arginine in MC-RR led to the elimination of a guanidine group and the absence of double bond cleavage byproducts. It was therefore demonstrated in this study that the variable amino acids in the structure of MCs influenced not only the degradation kinetics but also the preferable reaction mechanisms. [ABSTRACT FROM AUTHOR]

Anatoxin-a is a potent alkaloid neurotoxin produced by a number of cyanobacterial species and released in freshwaters during cyanobacterial blooms. Its high toxicity is responsible for several incidents of lethal intoxications of birds and mammals around the world; therefore anatoxin-a has to be regarded as a health risk and its concentration in lakes and water reservoirs should be monitored. Phenylalanine is a natural amino acid, also present in freshwaters, isobaric to anatoxin-a, with a very similar fragmentation pattern and LC retention. Since misidentification of phenylalanine as anatoxin-a has been reported in forensic investigations, special care must be taken in order to selectively determine traces of anatoxin-a in the presence of naturally occurring phenylalanine. A fast LC tandem MS method was developed by using a 1.8 μm 50 × 2.1 mm C18 column for the separation of anatoxin-a and phenylalanine, achieving a 3-min analysis time. Isotopically labelled phenylalanine- d5 was employed as internal standard to compensate for electrospray ion suppression and sample preconcentration losses. Both compounds were preconcentrated 1,000-fold on a porous graphitic carbon solid-phase extraction (SPE) cartridge after adjustment of sample pH to 10.5. The method was validated by using lake water spiked at four different levels from 0.01 to 1 μg L−1. Anatoxin-a recovery ranged from 73 to 97%, intra-day precision (RSD%) ranged from 4.2 to 5.9, while inter-day precision (RSD%) ranged from 4.2 to 9.1%. Limits of detection and quantification were 0.65 and 1.96 ng L−1 respectively. The method was successfully applied for the detection of anatoxin-a in Greek lakes at concentrations ranging from less than 0.6 to 9.1 ng L−1. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The ability of polyoxometallates (POM), molecular-anionic metal oxides, to act as photocatalysts in the electron transfer from organic substrates to metal ions will be presented. In the process, illumination at the O → M charge-transfer band (near-visible and UV regions), renders POM strong oxidants able to abstract electrons from a great variety of organic compounds, including organic pollutants. The photochemically reduced POMs can in turn act as soluble cathodes, able to reduce several metal ions to the elemental state. The process can be implemented for (i) the controlled reductive precipitation and recovery of valuable or toxic metals that can also be combined with the degradation of organic pollutants in a one-pot system and (ii) the synthesis of several metal nanoparticles in a simple and efficient way. To cite this article: A. Troupis et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: The photocatalytic reduction of Cr(VI) to the less toxic Cr(III) is presented in the presence of the polyoxometalates (POM) PW12O40 3− or SiW12O40 4− as photocatalyst and an organic substrate (salicylic acid or propan-2-ol) as electron donor. Cr(VI), as dichromate, is reduced to Cr(III), according to the 6:1 stoichiometry of PW12O40 4− versus Cr2O7 2− indicated from experiments in the dark. Increase of POM or salicylic acid (SA) concentration accelerates, till a saturation value, both the reduction of metal and the oxidation of the organic, suggesting that these two conjugate reactions act synergistically. The photocatalytic action of POM is not so important in the case of highly concentrated solutions of organics that exhibit direct photochemical reduction of Cr(VI), i.e. propan-2-ol (i-prOH), while it becomes important at low concentrations of i-prOH, especially for organics that do not react directly photochemically with Cr(VI), such as SA. Increase of Cr(VI) concentration enhances consumption of SA and Cr(VI) till an optimum value, due to inner filter effect. The method is suitable for a range of chromium concentration from 5–100ppm achieving complete reduction of Cr(VI) to Cr(III) up to non-detected traces (>98%). The presence of oxygen does not influence the efficiency of SA and Cr(VI) consumption. In contrast to the semiconductor-based heterogeneous photocatalysis, the POM-based homogeneous process seems superior in the frame that: (i) it remains catalytic throughout illumination by providing more active sites and (ii) among the two POM used, the one that is more efficient in the degradation of the organic, that is PW12O40 3− compared to SiW12O40 4−, is also more efficient in reducing Cr(VI), due to a kinetic effect, and a compromise is not needed. [Copyright &y& Elsevier]

Photocatalytic reduction of mercury in aqueous solutions using PW12O403- or SiW12O404- as photocatalysts has been studied as a function of irradiation time, concentration of Hg(II), polyoxometalate, and organic substrate in the presence or absence of dioxygen. The photocatalytic cycle starts with irradiation of polyoxometalate, goes through the oxidation of, for instance, propan-2-ol (used as sacrificial reagent), and closes with the reoxidation of reduced polyoxometalate by Hg2+ ions. Mercury(II) is reduced to mercury(I) and finally to Hg0 giving a dark-gray deposit, following a staged one-by-one electron process and a first-order kinetics in [Hg2+]. The process is slightly more efficient in the absence of dioxygen, while the increase of either catalyst or propan-2-ol concentration results in the augmentation of the rate of reduction till a certain point where it reaches a plateau. The results show that this method is suitable for a great range of mercury concentration from 20 to 800 ppm achieving almost complete recovery of mercury up to nondetected traces (<50 ppb). In addition, this homogeneous process demonstrates advantages such as the lack of necessity for separation of the zero state metal from the catalyst and ensures that the precipitation of metal will not poison the catalyst or hinder its photocatalytic activity. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of the organophosphorus insecticide diazinon in aqueous suspensions has been studied by using titanium dioxide as a photocatalyst. The degradation of the insecticide was a fast process and included the formation of several intermediates that were identified using GC/ion-trap mass spectrometry with EI or CI in positive and negative ionization mode and HPLC/electrospray-QqTOF mass spectrometry. Since primarily hydroxy derivatives were identified in these aqueous suspensions, the mechanism of degradation was probably based on hydroxyl radical attack. The initial oxidative pathways of the degradation of diazinon involved the substitution of sulfur by oxygen on the P&z.dbnd6;S bond, cleavage of the pyrimidine ester bond, and oxidation of the isopropyl group. Exact mass measurements of the derivatives allowed the elemental formula of the molecules to be determined confidently. Similarities to the metabolic pathways occurring in living organisms were observed. [Copyright &y& Elsevier]

Microbial fuel cells (MFCs) are an emerging technology that holds promise for renewable energy production and the mitigation of environmental challenges. This research paper introduces a single-compartment MFC reactor that utilizes transparent conducting oxides (TCOs), such as fluorine-doped tin oxide (FTO) and indium tin oxides (ITO), as the working electrodes. The effectiveness of MFCs based on FTO and ITO was evaluated by characterizing the transparent electrode and examining its performance during biofilm cultivation. Additionally, the optical properties of the biofilm grown directly on these electrodes were investigated using LEDs as a light source. The impressive average current density of 200 μA cm−2 over 100 days demonstrates the efficiency of the see-through electrodes in bioenergy extraction. The correlation between spectroscopic and microscopic analyses substantiates the feasibility of employing transparent electrodes for accurate quantification of biofilm thickness, with an initial accuracy of ±10 μm in the initial cycle, ±22 μm in the subsequent cycle, and a maximum of ±31 μm after seven days of growth. This innovative approach holds great potential for advancing our understanding of MFCs and their application in environmentally friendly energy generation and optical-based monitoring. [ABSTRACT FROM AUTHOR]

• Effects of five whole-lake treatments with hydrogen peroxide were studied. • Cyanobacteria drastically declined after every H 2 O 2 treatment. • Eukaryotic phytoplankton and copepods were much less sensitive to H 2 O 2. • Rotifers strongly declined after H 2 O 2 treatments ≥ 2 mg L−1. • Microcystins and anabaenopeptins were released, but disappeared after a few days. Cyanobacteria can reach high densities in eutrophic lakes, which may cause problems due to their potential toxin production. Several methods are in use to prevent, control or mitigate harmful cyanobacterial blooms. Treatment of blooms with low concentrations of hydrogen peroxide (H 2 O 2) is a promising emergency method. However, effects of H 2 O 2 on cyanobacteria, eukaryotic phytoplankton and zooplankton have mainly been studied in controlled cultures and mesocosm experiments, while much less is known about the effectiveness and potential side effects of H 2 O 2 treatments on entire lake ecosystems. In this study, we report on three different lakes in the Netherlands that were treated with average H 2 O 2 concentrations ranging from 2 to 5 mg L−1 to suppress cyanobacterial blooms. Effects on phytoplankton and zooplankton communities, on cyanotoxin concentrations, and on nutrient availability in the lakes were assessed. After every H 2 O 2 treatment, cyanobacteria drastically declined, sometimes by more than 99%, although blooms of Dolichospermum sp., Aphanizomenon sp., and Planktothrix rubescens were more strongly suppressed than a Planktothrix agardhii bloom. Eukaryotic phytoplankton were not significantly affected by the H 2 O 2 additions and had an initial advantage over cyanobacteria after the treatment, when ample nutrients and light were available. In all three lakes, a new cyanobacterial bloom developed within several weeks after the first H 2 O 2 treatment, and in two lakes a second H 2 O 2 treatment was therefore applied to again suppress the cyanobacterial population. Rotifers strongly declined after most H 2 O 2 treatments except when the H 2 O 2 concentration was ≤ 2 mg L−1, whereas cladocerans were only mildly affected and copepods were least impacted by the added H 2 O 2. In response to the treatments, the cyanotoxins microcystins and anabaenopeptins were released from the cells into the water column, but disappeared after a few days. We conclude that lake treatments with low concentrations of H 2 O 2 can be a successful tool to suppress harmful cyanobacterial blooms, but may negatively affect some of the zooplankton taxa in lakes. We advise pre-tests prior to the treatment of lakes to define optimal treatment concentrations that kill the majority of the cyanobacteria and to minimize potential side effects on non-target organisms. In some cases, the pre-tests may discourage treatment of the lake. [ABSTRACT FROM AUTHOR]

The production of β-Ν-methylamino-L-alanine (BMAA) in cyanobacteria is triggered by nitrogen-starvation conditions and its biological role, albeit unknown, is associated with nitrogen assimilation. In the present study, the effect of BMAA (773 μg L−1) on nitrogen metabolism and physiology of the non-diazotrophic cyanobacterium and non-BMAA producer, Synechococcus sp. TAU-MAC 0499, was investigated. In order to study the combined effect of nitrogen availability and BMAA, nitrogen-starvation conditions were induced by transferring cells in nitrogen-free medium and subsequently exposing the cultures to BMAA. After short-term treatment (180 min) and in the presence of nitrogen, BMAA inhibited glutamine synthetase, which resulted in low concentration of glutamine. In the absence of nitrogen, although there was no effect on glutamine synthetase, a possible perturbation in nitrogen assimilation is reflected on the significant decrease in glutamate levels. During the long-term exposure (24–96 h), growth, photosynthetic pigments and total protein were not affected by BMAA exposure, except for an increase in protein and phycocyanin levels at 48 h in nitrogen replete conditions. Results suggest that BMAA interferes with nitrogen assimilation, in a different way, depending on the presence or absence of combined nitrogen, providing novel data on the potential biological role of BMAA. • β-Ν-methylamino-L-alanine effect οn the cyanobacterium Synechococcus was investigated. • Short-term (180 min)/long-term exposure (24–96 h) with or without nitrogen. • β-Ν-methylamino-L-alanine affects the nitrogen assimilation pathway in Synechococcus. • The effect depends on nitrogen availability or scarcity in the culture medium. [ABSTRACT FROM AUTHOR]

Cyanobacterial diversity associated with sponges remains underestimated, though it is of great scientific interest in order to understand the ecology and evolutionary history of the symbiotic relationships between the two groups. Of the filamentous cyanobacteria, the genus Leptolyngbya is the most frequently found in association with sponges as well as the largest and obviously polyphyletic group. In this study, five Leptolyngbya‐like sponge‐associated isolates were investigated using a combination of molecular, chemical, and morphological approach and revealed a novel marine genus herein designated Leptothoe gen. nov. In addition, three new species of Leptothoe, Le. sithoniana, Le. kymatousa, and Le. spongobia, are described based on a suite of distinct characters compared to other marine Leptolyngbyaceae species/strains. The three new species, hosted by four sponge species, showed different degrees of host specificity. Leptothoe sithoniana and Le. kymatousa hosted by the sponges Petrosia ficiformis and Chondrilla nucula, respectively, seem to be more specialized than Le. spongobia, which was hosted by the sponges Dysidea avara and Acanthella acuta. All three species contained nitrogen‐fixing genes and may contribute to the nitrogen budget of sponges. Leptothoe spongobia TAU‐MAC 1115 isolated from Acanthella acuta was shown to produce microcystin‐RR indicating that microcystin production among marine cyanobacteria could be more widespread than previously determined. [ABSTRACT FROM AUTHOR]

Highlights • Neurotoxicity of BMAA and its most common isomers DAB and AEG. • Occurrence of BMAA/DAB/AEG in cyanobacteria cultures and environmental samples. • Occurrence of neurotoxic amino acids in cyanobacteria-based dietary supplements. • Extensive information for sample preparation, analytical methods and validation data. • Inconsistencies in results due to inadequate analytical methods and bound fractions. Abstract Cyanobacteria are photosynthetic microorganisms distributed globally in aquatic and terrestrial environments. They are also industrially cultivated to be used as dietary supplements, as they have a high nutritional value; however, they are also known to produce a wide range of toxic secondary metabolites, called cyanotoxins. BMAA (β-methylamino- l -alanine) and its most common structural isomers, DAB (2,4-diaminobutyric acid) and AEG (N -2-aminoethylglycine) produced by cyanobacteria, are non-proteinogenic amino acids that have been associated with neurodegenerative diseases. A possible route of exposure to those amino acids is through consumption of food supplements based on cyanobacteria. The review critically discusses existing reports regarding the occurrence of BMAA, DAB and AEG in cyanobacteria and cyanobacteria-based food supplements. It is shown that inconsistencies in reported results could be attributed to performance of different methods of extraction and analysis applied and in ambiguities regarding determination of soluble and bound fractions of the compounds. The critical aspect of this review aims to grow awareness of human intake of neurotoxic amino acids, while results presented in literature concerning dietary supplements aim to promote further research, quality control as well as development of guidelines for cyanotoxins in food products. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First C. raciborskii strain from Greece assessed for phylogeography and toxicity. • Presence of microcystin synthetase genes in a C. raciborskii strain. • Faint peak of MC-LR in Cylindrospermopsis raciborskii TAU-MAC 1414. • Common ancestor between C. raciborskii strains from Mediterranean and America. • Strains from C. Europe/Portugal, Asia, and Australia cluster with Africa strains. Abstract The cyanobacterium Cylindrospermopsis raciborskii represents a challenge for researchers and it is extensively studied for its toxicity and invasive behaviour, which is presumably enhanced by global warming. Biogeography studies indicate a tropical origin for this species, with Greece considered as the expansion route of C. raciborskii in Europe. The widening of its geographic distribution and the isolation of strains showing high optimum growth temperature underline its ecological heterogeneity, suggesting the existence of different ecotypes. The dominance of species like C. raciborskii along with their ecotoxicology and potential human risk related problems, render the establishment of a clear phylogeography model essential. In the context of the present study, the characterization of Cylindrospermopsis raciborskii TAU-MAC 1414 strain, isolated from Lake Karla, with respect to its phylogeography and toxic potential, is attempted. Our research provides new insights on the origin of C. raciborskii in the Mediterranean region; C. raciborskii expanded in Mediterranean from North America, whilst the rest of the European strains may originate from Asia and Australia. Microcystin synthetase genes, phylogenetic closely related with Microcystis strains, were also present in C. raciborskii TAU-MAC 1414. We were unable to unambiguously confirm the presence of MC-LR, using LC–MS/MS. Our results are shedding light on the expansion and distribution of C. raciborskii , whilst they pose further questions on the toxic capacity of this species. [ABSTRACT FROM AUTHOR]

This paper presents the first report of cyanobacteria and cyanotoxins from the South Caucasus region, in particular from Lake Yerevan (Armenia). Microcystis, Dolichospermum and Planktothrix were the key genera identified during the growing season. A trend of a remarkable increase in cyanobacterial densities was observed from 2012 to 2013 exhibiting bloom formation in June (by Nostoc linckia ) with the highest values in June and August 2013, reaching up to 695.9*10 3  cells mL −1 . Seasonal dependence of cyanobacterial density on temperature, and temperature as a driver for cyanobacterial cells growth and development were suggested. Biogenic nutrients were identified as co-drivers determining species richness and dominance, as well as the distribution of phytoplankton in different parts of the reservoir. Cyanotoxin concentrations in the filtered biomass were reported during July 2012 for both stations of the reservoir (left and right bank). Microcystin-RR (MC-RR) was the most abundant and the most frequently observed cyanotoxin. Lower MC-LR concentrations were identified in all samples from both stations, with the highest values observed at the right bank in July 2012. [D-Asp 3 ]MC-RR, MC-YR, MC-HtyR, [D-Asp 3 ]MC-LR, MC-HilR, MC-WR, MC-LY and MC-LW were also identified in trace levels. Anatoxin-a (ANA) was reported in the samples from both stations during August 2012. Cylindrospermopsin (CYN) was present in trace concentrations in samples from both stations during July and in the sample from the left bank during September. [ABSTRACT FROM AUTHOR]

5′,8-Cyclo-2′-deoxyadenosine (cdA) and 5′,8-cyclo-2′-deoxyguanosine (cdG) in their two diastereomeric forms, 5′Sand 5′R, are tandem lesions produced by the attack of hydroxyl radicals to the purine moieties of DNA. Their formation has been found to challenge the cells’ repair machinery, initiating the nucleotide excision repair (NER) for restoring the genome integrity. The involvement of oxidatively induced DNA damage in carcinogenesis and the reduced capacity of some cancer cell lines to repair oxidised DNA base lesions, intrigued us to investigate the implication of these lesions in breast cancer, the most frequently occurring cancer in women. Using liquid chromatography tandem mass spectrometry (LC-MS/MS), we measured the levels of diastereomeric cdA’s and cdG’s in estrogen receptor-alpha positive (ER-α) MCF-7 and triple negative MDA-MB-231 breast cancer cell lines before and after exposure to two different conditions: ionising radiations and hydrogen peroxide, followed by an interval period to allow DNA repair. An increase at the measured levels of all four lesions, i.e. 5′S-cdA, 5′R-cdA, 5′S-cdG and 5′R-cdG, was observed either afterγ-irradiation (5 Gy dose) or hydrogen peroxide treatment (300 μM) compared to the untreated cells (control), independently from the length of the interval period for repair. For comparison reasons, we also measured the levels of 8-oxo-2′-deoxyadenosine (8-oxo-dA), a well-known oxidatively induced DNA damage lesion and base excision repair (BER) substrate. The collected data indicate that MCF-7 and MDA-MB-231 breast cancer cells are highly susceptible to radiation-induced DNA damage, being mainly defective in the repair of these lesions. [ABSTRACT FROM PUBLISHER]

Cyanobacterial and algal toxins comprise a large group of harmful metabolites, belonging to different chemical classes, with a variety of chemical structures, physicochemical properties and toxic activities. In this study, a fast, simple and sensitive analytical method was developed for the simultaneous determination of multi-class cyanobacterial and algal toxins in water. The target compounds were: Cylindrospermopsin, Anatoxin-a, Nodularin, 12 Microcystins ([D-Asp3]MC-RR, MC-RR, MC-YR, MC-HtyR, [D-Asp3]MC-LR, MC-LR, MC-HilR, MC-WR, MC-LA, MC-LY, MC-LW and MC-LF), Okadaic acid and Domoic acid. Analytes were determined using liquid chromatography–tandem mass spectrometry (LC–MS/MS). A dual Solid Phase Extraction (SPE) cartridge assembly was applied for the extraction of target compounds from water. Optimized SPE parameters included cartridge material, initial sample pH, sequence of the cartridges in the SPE assembly as well as composition and volume of the elution solvent. The method was validated, providing acceptable mean recoveries and reproducibility for most analytes. Limits of detection were at the ng L −1 level. The method was successfully applied in real lake water samples from Greece, where a wide range of Microcystins were detected for the first time, at concentrations ranging from 0.034 to 63 μg L −1 . [ABSTRACT FROM AUTHOR]

Lake Karla (Central Greece) is a unique example - at European scale - of a shallow lake ecosystem that was dried in the 1960s and in 2009 started to be restored. The lake is listed in the network of the Greek protected areas as it is considered a vital aquatic ecosystem, in terms of biodiversity. It has, however, already been adversely affected by both agricultural and industrial land uses in the surrounding area, leading to eutrophication and shifting algal community towards bloom-forming toxic cyanobacterial species. After repeated heavyblooms, cyanotoxin occurrence and mass fish kills, the local ecosystem management authority has implemented a water quality monitoring program (July 2013 - July 2015) to assess environmental pressures and the response of aquatic biota in the lake. Microscopic, immunological, and molecular techniques combined with physico-chemical parameters, complemented by liquid chromatography tandem mass spectrometry (LC-MS/MS), were used to monitor cyanobacteria blooms and the associated cyanotoxin production from three different sites in Lake Karla and from the adjacent Kalamaki Reservoir. Water quality was also assessed by the structure of benthic invertebrate community on the sediment. Cyanobacteria were the main phytoplankton component, representing more than 70% of the total phytoplankton abundance; dominant taxa belonged to Cylindrospermopsis raciborskii, Limnothrix redekei, Anabaenopsis elenkinii, and Microcystis spp. Euglenophytes (Euglena), diatoms (Nitzschia), and chlorophytes (Scenedesmus) were also important phytoplankton constituents. LC-MS/MS confirmed the co-occurrence of microcystins, cylindrospermopsin, saxitoxin, neo-saxitoxin and anatoxin-a. The occurrence of cyanotoxins in relation to the persistent and dominant cyanobacteria and the impact of cyanobacterial harmful algal blooms on the newly constructed lake along with the land uses and the emergent mitigation measures are discussed. [ABSTRACT FROM AUTHOR]

This review aims to summarise the outcomes of some recent European research concerning toxic cyanobacteria and cyanotoxins, with an emphasis on developments within the framework of the CYANOCOST Action: COST Action ES1105, Cyanobacterial Blooms and Toxins in Water Resources: Occurrence, Impacts and Management. Highlights of the Action include phycological and ecological studies, development of advanced techniques for cyanotoxin analysis, elucidation of cyanotoxin modes of action, management techniques to reduce cyanobacterial mass development, and research on methods and practices for cyanotoxin removal during drinking water treatment. The authors have identified a number of gaps in knowledge. Proposed directions for future research on toxic cyanobacteria and cyanotoxins are also discussed. [ABSTRACT FROM AUTHOR]

Cyanobacteria produce a plethora of structurally diverse bioactive secondary metabolites, including cyanotoxins which pose a serious threat to humans and other living organisms worldwide. Currently, a wide variety of mass spectrometry-based methods for determination of microcystins (MCs), the most commonly occurring and studied class of cyanotoxins, have been developed and employed for research and monitoring purposes. The scarcity of commercially available reference materials, together with the ever-growing range of mass spectrometers and analytical approaches, make the accuracy of quantitative analyses a critical point to be carefully investigated in view of a reliable risk evaluation. This study reports, a comparative investigation of the qualitative and quantitative MCs profile obtained using targeted and untargeted liquid chromatography–mass spectrometry approaches for the analyses of cyanobacterial biomass from Lake Kastoria, Greece. Comparison of the total MCs content measured by the two approaches showed good correlation, with variations in the range of 3.8–13.2%. In addition, the implementation of an analytical workflow on a hybrid linear ion trap/orbitrap mass spectrometer is described, based on combining data-dependent acquisition and a powerful database of cyanobacterial metabolites (CyanoMetDB) for the annotation of known and discovery of new cyanopeptides. This untargeted strategy proved highly effective for the identification of MCs, microginins, anabaenopeptins, and micropeptins. The systematic interpretation of the acquired fragmentation patterns allowed the elucidation of two new MC structural variants, MC-PrhcysR and MC-Prhcys(O)R, and proposal of structures for two new microginins, isomeric cyanostatin B and MG 821A, and three isomeric micropeptins at m / z 846.4715, 846.4711 and 846.4723. [Display omitted] • Comparison between untargeted LC-HRMS and targeted LC-MS/MS for microcystins quantitation. • First finding of S-propylhomocysteine-containing microcystins. • HRMS2-based structural elucidation of new microcystins. • A novel data dependent acquisition-based workflow for cyanometabolites profiling. • HRMS2-based structural insights of new microginins and cyanopeptoline-type peptides. [ABSTRACT FROM AUTHOR]

Visible light (VIS) photocatalysis has large potential as a sustainable water treatment process, however the reaction pathways and degradation processes of organic pollutants are not yet clearly defined. The presence of cyanobacteria cause water quality problems since several genera can produce potent cyanotoxins, harmful to human health. In addition, cyanobacteria produce taste and odor compounds, which pose serious aesthetic problems in drinking water. Although photocatalytic degradation of cyanotoxins and taste and odor compounds have been reported under UV-A light in the presence of TiO 2 , limited studies have been reported on their degradation pathways by VIS photocatalysis of these problematic compounds. The main objectives of this work were to study the VIS photocatalytic degradation process, define the reactive oxygen species (ROS) involved and elucidate the reaction mechanisms. We report carbon doped TiO 2 (C–TiO 2 ) under VIS leads to the slow degradation of cyanotoxins, microcystin-LR (MC-LR) and cylindrospermopsin (CYN), while taste and odor compounds, geosmin and 2-methylisoborneol, were not appreciably degraded. Further studies were carried-out employing several specific radical scavengers (potassium bromide, isopropyl alcohol, sodium azide, superoxide dismutase and catalase) and probes (coumarin) to assess the role of different ROS (hydroxyl radical OH, singlet oxygen 1 O 2 , superoxide radical anion O 2 • − ) in the degradation processes. Reaction pathways of MC-LR and CYN were defined through identification and monitoring of intermediates using liquid chromatography tandem mass spectrometry (LC-MS/MS) for VIS in comparison with UV-A photocatalytic treatment. The effects of scavengers and probes on the degradation process under VIS, as well as the differences in product distributions under VIS and UV-A, suggested that the main species in VIS photocatalysis is O 2 • − , with OH and 1 O 2 playing minor roles in the degradation. [ABSTRACT FROM AUTHOR]

Research on the development of new TiO 2 based photocatalysts has been receiving increased attention due to the ability of TiO 2 to degrade a great variety of organic compounds upon UV-A irradiation. In order to evaluate the photocatalytic performance of the new synthesized materials, it is essential to follow specific procedures during the photocatalytic process. Special care should be given on light intensity, presence of oxygen, catalyst loading, initial concentration of substrate, adsorption, pH, different irradiation wavelength, mineralization, intermediate products and toxicity. In this study, catalysts such as commercially available materials (Degussa P25, Kronos vlp-7000) and home prepared materials (N-TiO 2 , GO–TiO 2 and Ref-TiO 2 ) have been tested for their photocatalytic ability on the degradation and mineralization of the cyanobacterial toxin microcystin-LR and off-odor causing compounds (geosmin, 2-methylisoborneol) under UV-A, solar and visible light irradiation. Also, the identification of intermediate products and their toxicity under different experimental conditions for microcystin-LR was studied. Our results showed that in all cases of the compounds Degussa P25 was the better performing catalyst under UV-A light irradiation. Under solar light, all compounds were effectively degraded with the doped materials (N-TiO 2 , GO–TiO 2 , Kronos vlp-7000) showing better photocatalytic performance than theirs undoped material (Ref-TiO 2 ). As far as concerning visible light irradiation, only the visible light activated materials showed some photocatalytic activity (N-TiO 2 , Kronos vlp-7000). It was also showed in order to have reproducible evaluation results on the photocatalytic performance of several catalysts (intra and inter-laboratory), a careful selection of experimental parameters is required. [ABSTRACT FROM AUTHOR]

Highlights: [•] Photocatalytic degradation of GSM and MIB in water, using POM and TiO2 with UV-A. [•] Almost complete mineralization of compounds was achieved under UV-A with POM and TiO2. [•] OH scavengers retard the degradation in accordance with their ability to scavenge OH radicals. [•] Possible photocatalytic degradation pathway for both GSM and MIB is suggested. [•] Identical intermediates with POM and TiO2, suggest mechanism via a common reagent ( OH radicals). [ABSTRACT FROM AUTHOR]

Highlights: [•] Method for the determination of MCs and NOD in water by SPE and LC–ESI-MS/MS. [•] New patterns of MC-LA fragmentation have been observed. [•] Method validation by assessment of specificity, linearity, accuracy and precision. [•] MCs monitoring in Lake Marathonas (July 07–December 10). [•] MC-LR, MC-RR and MC-YR were detected. [Copyright &y& Elsevier]

Microcystin-LR (MC-LR) is the mostcommon and toxic variant ofthe group of microcystins (MCs) produced during the formation of harmfulcyanobacterial blooms. Geosmin (GSM) and 2-methylisoborneol (MIB)may also be produced during cyanobacterial blooms and can taint watercausing undesirable taste and odor. The photocatalytic degradationof MC-LR, GSM, and MIB in water under both UV-A and solar light inthe presence of reduced graphene oxide–TiO2composite(GO–TiO2) was studied. Two commercially availableTiO2materials (Degussa P25 and Kronos) and a referenceTiO2material prepared in the laboratory (ref-TiO2) were used for comparison. Under UV-A irradiation, Degussa P25 wasthe most efficient photocatalyst for the degradation of all targetanalytes followed by GO–TiO2, ref-TiO2, and Kronos. Under solar light irradiation GO–TiO2presented similar photocatalytic activity to Degussa P25, followedby Kronos and ref-TiO2which were less efficient. Intermediateproducts formed during the photocatalytic process with GO–TiO2under solar light were identified and were found to be almostidentical to those observed by Degussa P25/UV-A. Assessment of theresidual toxicity of MC-LR during the course of treatment with GO–TiO2showed that toxicity is proportional only to the remainingMC-LR concentration. The photocatalytic performance of GO–TiO2was also evaluated under solar light illumination in realsurface water samples, and GO–TiO2proved to beeffective in the degradation of all target compounds. [ABSTRACT FROM AUTHOR]

Abstract: Cyanobacteria blooms pose an environmental hazard because of the release of water soluble toxic compounds, called cyanotoxins. Microcystins (MCs), hepatotoxic cyclic peptide toxins, are the most widespread cyanotoxins with microcystin-LR (MC-LR) the most common and toxic variant. Health effects of MCs have resulted in the need of using efficient treatment methods for the removal of this class of toxins in water supplies. While physical treatment methods can remove MCs at full or some extent from contaminated water, their function is primary separation of the whole toxins as intact molecules and further processing is required. On the other hand, chemical oxidation processes are a promising alternative treatment option due to the potential of complete destruction of the MCs, transformation to less toxic by-products, and even complete mineralization. MCs reactivity towards different conventional oxidants is strongly affected by water quality parameters like pH, DOC and oxidant dose. Although there is a general trend for MCs oxidation (ozone>permanganate>chlorine>>>chlorine-based oxidants), the selection of the appropriate oxidant for toxin elimination during water treatment should be assessed for each particular source of water. Although advanced oxidation processes are generally more effective on MCs degradation than conventional oxidation processes, scale-up studies are needed before these methods are considered as economically-feasible and practical sustainable alternatives in water treatment facilities. In this review, recent literature concerning treatment of MCs in water by conventional and advanced oxidation processes are reviewed and discussed in terms of the degree of degradation, reaction kinetics, identity and toxicity of oxidation by-products and possible degradation pathways. [Copyright &y& Elsevier]

Abstract: In an attempt to face serious environmental hazards, the degradation of microcystin-LR (MC-LR), one of the most common and more toxic water soluble cyanotoxin compounds released by cyanobacteria blooms, was investigated using nitrogen doped TiO2 (N-TiO2) photocatalyst, under UV-A, solar and visible light. Commercial Degussa P25 TiO2, Kronos and reference TiO2 nanopowders were used for comparison. It was found that under UV-A irradiation, all photocatalysts were effective in toxin elimination. The higher MC-LR degradation (99%) was observed with Degussa P25 TiO2 followed by N-TiO2 with 96% toxin destruction after 20min of illumination. Under solar light illumination, N-TiO2 nanocatalyst exhibits similar photocatalytic activity with that of commercially available materials such as Degussa P25 and Kronos TiO2 for the destruction of MC-LR. Upon irradiation with visible light Degussa P25 practically did not show any response, while the N-TiO2 displayed remarkable photocatalytic efficiency. In addition, it has been shown that photodegradation products did not present any significant protein phosphatase inhibition activity, proving that toxicity is proportional only to the remaining MC-LR in solution. Finally, total organic carbon (TOC) and inorganic ions (NO2 −, NO3 − and NH4 +) determinations confirmed that complete photocatalytic mineralization of MC-LR was achieved under both UV-A and solar light. [Copyright &y& Elsevier]

Abstract: The destruction of the commonly found cyanobacterial toxin, microcystin-LR (MC-LR), in surface waters by UV-C/H2O2 advanced oxidation process (AOP) was studied. Experiments were carried out in a bench scale photochemical apparatus with low pressure mercury vapor germicidal lamps emitting at 253.7 nm. The degradation of MC-LR was a function of UV fluence. A 93.9% removal with an initial MC-LR concentration of 1 μM was achieved with a UV fluence of 80 mJ/cm2 and an initial H2O2 concentration of 882 μM. When increasing the concentration of MC-LR only, the UV fluence-based pseudo-first order reaction rate constant generally decreased, which was probably due to the competition between by-products and MC-LR for hydroxyl radicals. An increase in H2O2 concentration led to higher removal efficiency; however, the effect of HOng by H2O2 became significant for high H2O2 concentrations. The impact of water quality parameters, such as pH, alkalinity and the presence of natural organic matter (NOM), was also studied. Field water samples from Lake Erie, Michigan and St. Johns River, Florida were employed to evaluate the potential application of this process for the degradation of MC-LR. Results showed that the presence of both alkalinity (as 89.6–117.8 mg CaCO3/L) and NOM (as ∼2 to ∼9.5 mg/L TOC) contributed to a significant decrease in the destruction rate of MC-LR. However, a final concentration of MC-LR bellow the guideline value of 1 μg/L was still achievable under current experimental conditions when an initial MC-LR concentration of 2.5 μg/L was spiked into those real water samples. [Copyright &y& Elsevier]

Abstract: A system of analytical processes has been developed in order to serve as a cost-effective scheme for the monitoring of cyanobacterial toxins on a quantitative basis, in surface and drinking waters. Five cyclic peptide hepatotoxins, microcystin-LR, -RR, -YR, -LA and nodularin were chosen as the target compounds. Two different enzyme-linked immunosorbent assays (ELISA) were validated in order to serve as primary quantitative screening tools. Validation results showed that the ELISA methods are sufficiently specific and sensitive with limits of detection (LODs) around 0.1μg/L, however, matrix effects should be considered, especially with surface water samples or bacterial mass methanolic extracts. A colorimetric protein phosphatase inhibition assay (PPIA) utilizing protein phosphatase 2A and p-nitrophenyl phosphate as substrate, was applied in microplate format in order to serve as a quantitative screening method for the detection of the toxic activity associated with cyclic peptide hepatotoxins, at concentration levels >0.2μg/L of MC-LR equivalents. A fast HPLC/PDA method has been developed for the determination of microcystins, by using a short, 50mm C18 column, with 1.8μm particle size. Using this method a 10-fold reduction of sample run time was achieved and sufficient separation of microcystins was accomplished in less than 3min. Finally, the analytical system includes an LC/MS/MS method that was developed for the determination of the 5 target compounds after SPE extraction. The method achieves extremely low limits of detection (<0.02μg/L), in both surface and drinking waters and it is used for identification and verification purposes as well as for determinations at the ppt level. An analytical protocol that includes the above methods has been designed and validated through the analysis of a number of real samples. [Copyright &y& Elsevier]

Abstract: The photocatalytic degradation of lindane (γ-1,2,3,4,5,6-hexachlorocyclohexane) has been studied in the presence of the polyoxometalate PW12O40 3− in aqueous solutions. Lindane is fully decomposed to CO2, Cl− and H2O, while a great variety of intermediates has been detected using GC–MS, including aromatic compounds (dichlorophenol, trichlorophenols, tetrachlorophenol, hexachlorobenzene, di- and trichloro-benzenodiol), non-aromatic cyclic compounds (penta-, tetrachlorocyclohexene, heptachlorocyclohexane), aliphatic compounds (tetrachloroethane) and condensation products (polychlorinated biphenyls). The number and nature of the intermediates implies that the mechanism of decomposition of lindane is based on both oxidative and reductive processes. Common intermediates have been reported during photolysis of lindane in the presence of titanium dioxide. A similar overall mechanism of polyoxometalates and TiO2 photocatalysis through the formation of common reactive species is suggested. [Copyright &y& Elsevier]

Abstract: Selenium nanoparticles are formed upon photolysis of solutions of (propan-2-ol/POM/Se(IV)), where polyoxometalate (POM) is either PW12O40 3− or SiW12O40 4−. Propan-2-ol serves as sacrificial reagent for the photoformation of 1-equivalent reduced blue polyoxometalate, POM(e), which further reacts with Se(IV) to produce selenium nanoparticles. POM serves both as relay for the transfer of electrons from propan-2-ol to Se(IV) and stabilizer for the nanoparticles. Changing the ionic strength from 0 to 0.025 and 0.05M, results in the formation of gradually larger nanoparticles 40, 60 and 90nm, respectively. Increase of the initial concentration of SiW12O40 4−, from 2 to 4 and 10×10−3 M, results in the formation of gradually smaller nanoparticles, 110, 80 and 60nm, respectively. [Copyright &y& Elsevier]

• The long-term effect of sublethal exposure to Microcystis aeruginosa extracts during the embryonic stage of zebrafish was examined. • Pre-exposed larvae at metamorphosis showed a significant reduction in swimming performance (RU crit). • Pre-exposed fish also presented rounder cardiac ventricles and a high vertebral abnormalities rate. In the last decades, cyanobacterial harmful algal blooms (CyanoHABs) pose an intensifying ecological threat. Microcystis aeruginosa is a common CyanoHAB species in freshwater ecosystems, with severe toxic effects in a wide range of organisms. In the present paper we examined whether transient and short (48 h) exposure of fish embryos to sublethal levels of M. aeruginosa crude extract (200 mg biomass dw L−1) affects swimming performance at later life stages (end of metamorphosis, ca 12 mm TL, 22,23 days post-fertilization). Pre-exposed metamorphosing larvae presented a significant decrease in swimming performance (9.7 ± 1.6 vs 11.4 ± 1.7 TL s−1 in the control group, p < 0.01), and a significant decrease in the ventricle length-to-depth ratio (1.23 ± 0.15 vs 1.42 ± 0.15 in control fish, p < 0.05). In addition, extract-exposed fish presented significantly elevated rates of vertebral abnormalities (82 ± 13% vs 7 ± 4% in the control group), mainly consisting of the presence of extra neural and haemal processes. No significant differences between groups were detected in survival and growth rates. Results are discussed in respect to the mechanisms that might mediate the detected cyanobacterial effects. This is the first evidence of a direct link between sublethal exposure to M. aeruginosa during the embryonic period and swimming performance at later life-stages. Decreased swimming performance, altered cardiac shape, and elevated vertebral abnormalities in response to early exposure to M. aeruginosa could have significant effects on fish populations in the wild. [ABSTRACT FROM AUTHOR]

Abstract: A series of polyoxometalates (POM) PW12O40 3−, SiW12O40 4−, P2W18O62 6− and P2Mo18O62 6− have been used as photocatalysts for the destruction of the azo dye Acid Orange 7 (AO). There are two ways to consider: reductive and oxidative decomposition. The reductive decomposition involves absorption of light by polyoxometalates, oxidation of an organic substrate, for instance propan-2-ol as sacrificial reducing reagent and reoxidation-recycling of the reduced polyoxometalates by the azo dye via a thermal (dark) reaction. AO is reduced to aromatic amine derivatives in a multi-electron process, as suggested by the analysis of the detected products and the obtained stoichiometry of the electron transfer process, following a first-order dependence for AO. This process takes place within a few minutes. On the other hand, photooxidative decomposition involves again absorption of light by POM followed by direct or OH-mediated oxidation of the dye. This process is an order of magnitude slower than reductive elimination, but leads to mineralization of AO. Several intermediates have been detected prior to evolution of CO2. The nature of the POM catalyst is decisive in the efficiency of reductive AO decoloration, following the order PW12O40 3− >SiW12O40 4− >P2W18O62 6− >P2Mo18O62 6−, that is their photooxidizing ability, in one-pot photolysis experiments. On the other hand the efficiency of thermal (dark) reaction between reduced POM and AO follows the reductive ability of POM, i.e., SiW12O40 5− >PW12O40 4− >P2W18O62 7− >P2Mo18O62 8−. The presence of electron scavengers suppresses the reductive degradation rate according to the trend Ag+ >O2 >Cu2+ >Ni2+, while increase of pH retards decoloration. Contrary to TiO2, sensitized photodecomposition, i.e., absorption of light by AO and electron injection to POM has not been observed. [Copyright &y& Elsevier]

Cyanobacteria are photosynthetic microorganisms that are able to produce a large number of secondary metabolites. In freshwaters, under favorable conditions, they can rapidly multiply, forming blooms, and can release their toxic/bioactive metabolites in water. Among them, anabaenopeptins (APs) are a less studied class of cyclic bioactive cyanopeptides. The occurrence and structural variety of APs in cyanobacterial blooms and cultured strains from Greek freshwaters were investigated. Cyanobacterial extracts were analyzed with LC–qTRAP MS/MS using information-dependent acquisition in enhanced ion product mode in order to obtain the fragmentation mass spectra of APs. Thirteen APs were detected, and their possible structures were annotated based on the elucidation of fragmentation spectra, including three novel ones. APs were present in the majority of bloom samples (91%) collected from nine Greek lakes during different time periods. A large variety of APs was observed, with up to eight congeners co-occurring in the same sample. AP F (87%), Oscillamide Y (87%) and AP B (65%) were the most frequently detected congeners. Thirty cyanobacterial strain cultures were also analyzed. APs were only detected in one strain (Microcystis ichtyoblabe). The results contribute to a better understanding of APs produced by freshwater cyanobacteria and expand the range of structurally characterized APs. [ABSTRACT FROM AUTHOR]

Abstract: A new method for the simultaneous determination of 1,4-dichlorobenzene (p-DCB), naphthalene and 1,2-dibromoethane (1,2-DBE) residues in honey has been developed. Analysis is carried out using gas chromatography–mass spectrometry (GC/MS) in selected ion monitoring mode (SIM), after extraction and preconcentration of target analytes by headspace solid-phase microextraction (HS-SPME), with a 100μm film thickness polydimethylsiloxane (PDMS) fiber. Several parameters affecting the extension of the adsorption process (i.e., addition of salt, extraction time, extraction temperature) were studied. The optimal conditions for the determination of these analytes were established. The proposed HS-SPME method showed good sensitivity, without carryover between the samples. Linearity was studied from 5 to 2500μgkg−1 for p-DCB, 0.5 to 500μgkg−1 for naphthalene and 5 to 500μgkg−1 honey for 1,2-DBE with correlation coefficients (r 2) ranging from 0.9901 to 0.9999. Precision was assessed and both intra and inter-day R.S.D.s (%) were below 6.3%. The detection limits were found to be 1, 0.1 and 2μgkg−1 honey for p-DCB, naphthalene and 1,2-DBE, respectively. The percentage recoveries that were evaluated with the proposed HS-SPME method and the standard addition calibration technique gave values among 72.8 and 104.3% for measurements in samples spiked with one target analyte or mixtures of the three. This method has been applied for the analysis of unknown honey samples. The results showed an excellent applicability of the proposed method for the determination of the target compounds in honey samples. [Copyright &y& Elsevier]

Abstract: Polyoxometallates (POMs) as a homogeneous photocatalyst and TiO2 as a heterogeneous photocatalyst seem to exhibit overall similar photocatalytic behavior. Both systems cause photodecomposition of a variety of organic pollutants via the formation and decay of several similar intermediates formed by OH addition (hydroxylation), dehalogenation, deamination, decarboxylation, etc. The final degradation products, for most organic substrates for both systems are CO2, H2O and inorganic anions. The similarity of behavior has been attributed to the formation of the common powerful oxidizing reagent, OH radical, from the reaction of the excited catalyst and water molecules. On the other hand, lately, various laboratories have pointed out differences in reactivity and degradation mechanism between the two photocatalysts. The results are interesting and to a great extent contradictory. This study compares the photodegradation of four substrates with diversified structures, namely, atrazine, fenitrothion, 4-chlorophenol (4-ClPh), and 2,4-dichlorophenoxyacetic acid (2,4-D) by both PW12O40 3− and TiO2 and how their photodegradation is affected by the presence of strong OH radical scavengers, i.e., Br− and isopropyl alcohol (i-prOH). The results provide substantial evidence that the literature data on the apparent photooxidation mechanism of these two categories of photocatalysts is circumstantial, depending on substrate and the mode of investigation. Overall, though, the action of OH radicals relative to h+ appears to be more pronounced with PW12O40 3− than TiO2. With respect to thermal (dark) reaction of photoreduced catalysts, both systems can deliver their electrons to a variety of oxidants including metal ions. The advantages of POM relative to TiO2 relates to the selective reduction precipitation of metal ions and to their unique ability to form metal nanoparticles in which POM serve both as reducing reagents and stabilizers. [Copyright &y& Elsevier]

Abstract: Various polyoxometallates (POM) PW12O40 3−, SiW12O40 4−, P2W18O62 6− and P2Mo18O62 6− have been used as photocatalysts for the reductive destruction of the azo dye naphthol blue black (NB). In the process POM absorb light and mediate the electron transfer from a sacrificial donor, propan-2-ol, to the azo dye. NB is rapidly destructed in the presence of POM, while toxic intermediate products, such as aromatic amine derivatives (aniline, p-nitro-aniline and p-phenylene-diamine) are observed in a multi-electron process. Increase of catalyst and/or propan-2-ol concentration accelerates the photodegradation of dye till a saturation value, while an optimum concentration of the added dye is required. The nature of the POM catalyst dictates the efficiency of the reductive decoloration of NB, following the order PW12O40 3− >SiW12O40 4− >P2W18O62 6− according to their photooxidizing ability. No reaction is noticed with the 2-e-reduced molybdate, P2Mo18O62 8−, which exhibits a more positive redox potential. [Copyright &y& Elsevier]