Photochemical transformation of azoxystrobin in aqueous solutions

The photochemical behaviour of azoxystrobin fungicide (AZX) in water was studied under laboratory conditions. Photodegradation was initiated using a solar simulator (xenon arc lamp) or a jacketed Pyrex reaction cell equipped with a 125 W, high-pressure mercury lamp. HPLC/MS analysis (APCI and ESI in positive and negative modes) was used to identify AZX photoproducts. The calculated polychromatic quantum efficiencies (phi) of AZX at pH 4.5, 7 and 9 were 5.42 x 10(-3), 3.47 x 10(-3) and 3.06 x 10(-3) (degraded molecules per absorbed photon), respectively. The relatively narrow range of values indicates the stability of AZX with respect to photodegradation in the studied pH range. Results from the HPLC/MS analysis suggest that the phototransformation of AZX proceeds via multiple, parallel reaction pathways including: (1) photo-isomerization (E-->Z), (2) photo-hydrolysis of the methyl ester and of the nitrile group, (3) cleavage of the acrylate double bond, (4) photohydrolytic ether cleavage between the aromatic ring giving phenol, and (5) oxidative cleavage of the acrylate double bond.     

Fate and transformation of naphthylaminesulfonic azo dye Reactive Black 5 during wastewater treatment process

Certain aromatic amines generated by the decolorization of some azo dyes are not removed substantially by conventional anaerobic–aerobic biotreatment. These aromatic amines are potentially toxic and often released in the wastewater of industrial plants. In this study, the fate and transformation of the naphthylaminesulfonic azo dye Reactive Black 5 (RB5) during different phases of a sequencing batch reactor were investigated. The major products of RB5 decolorization during the anaerobic phase include 2-[(4-aminophenyl)sulfonyl]ethyl hydrogen sulfate (APSEHS) and 1-2-7-triamino-8-hydroxy-3-6-naphthalinedisulfate (TAHNDS). During the aerobic phase, APSEHS was hydrolyzed and produced 4-aminobenzenesulfonic acid, which was further degraded via dearomatization. TAHNDS was transformed rapidly via auto-oxidation into TAHNDS_DP-1 and TAHNDS_DP-2, which were not further removed by the activated sludge during the entire 30-day aerobic phase. In contrast, different behaviors of TAHNDS were observed during the anoxic phase. The transformation of TAHNDS was initiated either by deamination or desulfonation reaction. TAHNDS was then converted into 3,5-diamino-4-hydroxynaphthalene-2-sulfonic acid, which was subsequently removed via ring cleavage reaction under aerobic condition. In conclusion, complete degradation of TAHNDS by activated sludge occurs only during anoxic/aerobic processes instead of the conventional anaerobic/aerobic processes.     

Oxidative ring cleavage of low chlorinated biphenyl derivatives by fungi leads to the formation of chlorinated lactone derivatives

The yeast Trichosporon mucoides and the filamentous fungus Paecilomyces lilacinus as biphenyl oxidizing organisms are able to oxidize chlorinated biphenyl derivatives. Initial oxidation of derivatives chlorinated at C4 position started at the non-halogenated ring and went on up to ring cleavage. The products formed were mono- and dihydroxylated 4-chlorobiphenyls, muconic acid derivatives 2-hydroxy-4-(4-chlorophenyl)-muconic acid and 2-hydroxy-5-(4-chlorophenyl)-muconic acid as well as the corresponding lactones 4-(4-chlorophenyl)-2-pyrone-6-carboxylic acid and 3-(4-chlorophenyl)-2-pyrone-6-carboxylic acid. Altogether T. mucoides formed 12 products and P. lilacinus accumulated five products. Whereas the rate of the first oxidation step at 4-chlorobiphenyl seems to be diminished by the decreased bioavailability of the compound, no considerable differences were observed between the degradation of 4-chloro-4'-hydroxybiphenyl and 4-hydroxybiphenyl. Twofold chlorinated biphenyl derivatives did not serve as substrates for oxidation by either organism with the exception of 2,2'-dichlorobiphenyl, transformed by the yeast Trichosporon mucoides to two monohydroxylated derivatives. The results show, that soil fungi may contribute to the aerobic degradation of low chlorinated biphenyls accumulating from anaerobic dehalogenation of PCB by bacteria.     

Titanium dioxide mediated photocatalytic degradation of 17beta-estradiol in aqueous solution

Photocatalytic degradation of 17beta-estradiol (E2) in aqueous medium mediated with titanium dioxide (TiO(2)) was studied. Moreover, effect of TiO(2) dosage on the degradation efficiency was investigated. Particular attention was paid to the identification of intermediates and analysis of photocatalytic degradation mechanism of E2 under neutral and alkaline conditions. The degradation efficiency of E2 increased with increasing concentration of TiO(2) but decreased due to light scattering as TiO(2) concentration was greater than 0.5mgml(-1). Several intermediates were formed during photocatalytic degradation of E2. However, only a few of the compounds could be identified and confirmed by LC-MS and LC-MS/MS. Six intermediates were observed by photocatalytic oxidation under alkaline conditions, namely 2-hydroxyestradiol, 10epsilon-17beta-dihydroxy-1,4-estradien-3-one (DEO), 10epsilon-hydroperoxide-17beta-hydroxy-1,4-estradien-3-one and three kinds of dicarboxylic acids formed by the opening of aromatic ring. In addition to the six intermediates mentioned above, 17beta-hydroxy-1,4-estradien-3-one (EO) was observed under neutral conditions and in the presence of methanol. Based on these intermediates, which were hardly degraded even after E2 was fully degraded, the mechanism of E2 degradation by TiO(2) photocatalysis was elucidated.     

Enzymatic degradation of anthracene, dibenzothiophene and pyrene by manganese peroxidase in media containing acetone

The high hydrophobicity of polycyclic aromatic hydrocarbons (PAHs) greatly hamper their degradation in liquid media. The use of an organic solvent can assist the degradative action of ligninolytic enzymes from white rot fungi. The enzymatic action of the enzyme manganese peroxidase (MnP) in media containing a miscible organic solvent, acetone (36% v/v), was evaluated as a feasible system for the in vitro degradation of three PAHs: anthracene, dibenzothiophene and pyrene. These compounds were degraded to a large extent after a short period of time (7, 24 and 24h, respectively), at conditions maximizing the MnP-oxidative system. The initial amount of enzyme present in the reaction medium was determinant for the kinetics of the process. The order of degradability, in terms of degradation rates was as follows: anthracene>dibenzothiophene>pyrene. The intermediate compounds were determined using gas chromatography-mass spectrometry and the degradation mechanisms were proposed. Anthracene was degraded to phthalic acid. A ring cleavage product of the oxidation of dibenzothiophene, 4-methoxybenzoic acid, was also observed.     

Identification of 2,6-diisopropylnaphthalene metabolites in carp part 1. In vivo experiment

The metabolism of diisopropylnaphthalene (DIPN) in fish was studied from an ecotoxicological viewpoint to clarify the environmental fate of DIPN, a solvent of carbonless paper which is widely used as a substitute for PCB. This study identified the following metabolites in carp by in vivo experiment; 2-(1-hydroxy-1-methyl) ethyl-6-isopropylnaphthalene, 2-(1-methyl-2-hydroxyethyl)-6-isopropyl-naphthalene, 2,6-(1-hydroxy-1-methyl) ethyl-naphthalene, 2-(1-hydroxy-1-hydroxymethyl) ethyl-6-isopropylnaphthalene and α-[2-(6-isopropylnaphthyl)] propionic acid. Identification was based on UV, IR, MS, and NMR analyses. The metabolism of 2,6-DIPN in carp was concluded to mainly through oxidation of the isopropyl chain.     

Products and mechanisms of the gas-phase reactions of OH radicals and O3 with 2-methyl-3-buten-2-ol

Products of the gas-phase reactions of OH radicals (in the presence of NO) and O₃ with the biogenic organic compound 2-methyl-3-buten-2-ol have been investigated using gas chromatography with flame ionization detection (GC-FID), combined gas chromatography–mass spectrometry (GC-MS), gas chromatography with Fourier transform infrared detection (GC-FTIR), in situ FT-IR spectroscopy and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS/MS). Formaldehyde, 2-hydroxy-2-methylpropanal and acetone were identified from both the OH radical and O₃ reactions, glycolaldehyde and organic nitrate (s) were also observed from the OH radical reaction, and the OH radical formation yield from the O₃ reaction was measured. The formaldehyde, 2-hydroxy-2-methylpropanal, glycolaldehyde, acetone and organic nitrate yields from the OH radical reaction were 0.29±0.03, 0.19±0.07, 0.61±0.09, 0.58±0.04 and 0.05±0.02, respectively, and the formaldehyde, 2-hydroxy-2-methylpropanal and OH radical formation yields from the O₃ reaction were 0.29±0.03, 0.30±0.06 (0.47 from FT-IR measurements) and 0.19 (uncertain to a factor of 1.5), respectively. Acetone was also observed from the O₃ reaction, but appeared to be formed from secondary reactions. Reaction mechanisms are presented and discussed.     

Photolysis of the herbicide bispyribac sodium in aqueous medium under the influence of UV and sunlight in presence or absence of sensitizers

The photolysis of a rice herbicide Bispyribac sodium (Sodium 2, 6-bis [(4, 6-dimethoxypyrimidin-2-yl) oxy] benzoate) has been studied in different aqueous medium (distilled water, pond water and Irrigation water) under the influence of UV (λ max ≥ 250 nm) and sunlight in presence or absence of sensitizers (TiO₂ and KNO₃). The study was conducted under laboratory simulated condition which made it possible to evaluate the contribution of different factors viz. source of irradiation, solvent and sensitizers towards the photolysis of bispyribac sodium. The photodegradation proceeds via first order reaction Kinetics in all the cases. Five photo metabolites (M₁-M₅) were isolated in pure form by column chromatographic method from the irradiation system under UV influenced and TiO₂ as sensitizer. From the different spectral data (IR, NMR, UV-VIS, Mass) the structure of these five metabolites were assigned as M₁ (Phenol), M₂ [2, 6-Dihydroxy benzoic acid], M₃ [2, 6-bis [(4, 6 dimethoxypyrimidin-2yl) oxy] benzoic acid], M₄ [2-(3-Hydroxy-phenoxy)-pyrimidine-4, 6-diol] and M₅ as [2,4-Dihydroxy-3, 5-dimethoxy-6-(4-methoxy pyrimidine-2-yloxy)-benzoic acid]. Moreover, another six photometabolites (M₆-M₁₁) were identified from the different irradiation system on the basis of Micromass analysis. On the basis of MS/MS data analysis, the structure of these six photometabolites were assigned as M₆ [2-(4, 6-Dimethoxy-pyrimidin-2-yloxy)-6-hydroxy-benzoic acid], M₇ [2-Hydroxy-6-(4-hydroxy-6-methoxy-pyrimidin-2-yloxy)-benzoic acid], M₈ [4, 6-Dimethoxy-pyrimidin-2-ol], M₉ [6-Methoxy-pyrimidine-2, 4-diol], M₁₀ [2-Hydroxy-6-(pyrimidin-2-yloxy)-benzoic acid] and M₁₁ [2, 4, 6-Trimethoxy-pyrimidine]. The plausible Photodegradation pathways of bispyribac sodium in the present investigation were portrayed which proceeds via hydrolysis, hydrolytic cleavage, O-dealkylation, decarboxylation, dehydroxylation, O-alkylation and hydroxylation.     

Phylogenetic and degradation characterization of Burkholderia cepacia WZ1 degrading herbicide quinclorac

Strain WZI capable of degrading quinclorac was isolated from a pesticide manufactory soil and considered to be Burkholderia cepacia, belonged to bacteria, Proteobacteria, beta-Proteobacteria, based on morphology, physio-biochemical properties, whole cell fatty acid analysis and a partial sequencing of 16S rDNA. Strain WZ1 decomposed 90% of quinclorac at original concentration of 1000 mg L(-1) within 11 days. GC/MS analysis showed that the strain degraded quinclorac to 3,7-dichloro-8-quinoline and the cracked residue 2-chloro, 1,4-benzenedicarboxylic acid, indicating that the metabolic pathway was initiated by process of decarboxylation followed by cleavage of the aromatic ring. Stain WZ1 was also able to degrade some other herbicides and aromatic compounds, including 2,4,5-T, phenol, naphthalene and hydrochinone etc. This paper describes for the first time Phylogenetic and degradation characterization of a pure bacterium which, is able to mineralize quinclorac.     

Determination of polycyclic aromatic ketones in particulate emissions of internal combustion engines

Benzanthrone (7-H-benz(de)anthracene-7-one, MW 230) and another polycyclic aromatic ketone (6-H-benzo(cd)pyrene-6-one, MW 254) are identified in particulate emissions from both air-cooled and water-cooled automobile engines operating on gasoline. The concentrations of these compounds are roughly equal to [Formula: see text] in these sources. Determination is carried out by capillary gas chromatography using glass and fused silica columns coated with SE-54, OV-1 or Dexsil 300. Results are confirmed by GC/MS. GC/MS data indicate that other polycyclic aromatic ketones are present at much lower concentrations than the two compounds described above. This is different from PAHs, where a large number of isomeric compounds are present at similar concentrations.     

Degradation characteristics and metabolic pathway of 17alpha-ethynylestradiol by Sphingobacterium sp. JCR5

A 17alpha-ethynylestradiol (EE2)-degrading bacterium was isolated from the activated sludge of the wastewater treatment plant (WWTP) of an oral contraceptives producing factory in Beijing, China. On the basis of its morphology, biochemical properties and the 16S rDNA sequence analysis, this strain was identified as Sphingobacterium sp. JCR5. This strain grew on EE2 as sole source of carbon and energy, and metabolized up to 87% of the substrate added (30 mgl-1) within 10 d at 30 degrees C. In addition to EE2 the strain could be cultivated on steroidal estrogens like estrone (E1), 17beta-estradiol (E2), estriol (E3) and mestranol (MeEE2), the intermediates of contraceptive medicine processing and on some aromatic compounds. Mass spectrum analysis of the EE2 degradation showed that in the first step it is oxygenized to E1, 2-hydroxy-2,4-dienevaleric acid and 2-hydroxy-2,4-diene-1,6-dioic acid, which are the main catabolic intermediates. The former was analogous to the pathway of a previously reported testosterone-degrading bacterium Comamonas testosteroni TA441 and the latter is a metabolite with a different cleavage position of 3-hydroxy-4,5-9,10-disecoestrane-1(10),2-diene-5,9,17-trione-4-oic acid from the former.     

Hydrolytic degradation of azimsulfuron, a sulfonylurea herbicide

The chemical degradation of the herbicide azimsulfuron was investigated in aqueous solutions at different pH values. The hydrolysis rate, determined by HPLC analyses, was pH dependent and was much faster in acidic than in neutral or weakly basic conditions. The metabolites formed at different pH values were compared with standards when possible or isolated and identified using ESI-LC-MS/MS, (1)H NMR and (13)C NMR. The two main products of hydrolysis in mild acidic solution were identified as 2-amino-4,6-dimethoxy-pyrimidine and 2-methyl-4-(2-methyl-2H-tetrazol-5-yl)-2H-pyrazole-3-sulfonamide, both produced as a result of the sulfonylurea bridge cleavage. Under basic conditions, a new product, a substituted 2-pyrimidinamine, deriving from the contraction of the sulfonylurea bridge, was isolated and completely characterized for the first time.     

Phototransformation of methabenthiazuron in the presence of nitrate and nitrite ions

The influence of nitrate and nitrite ions on the degradation of methabenzthiazuron upon irradiation using artificial solar light has been investigated. The rate of degradation of methabenzthiazuron (1 microM) was accelerated by NO3- (0.1 mM) by a factor of 10. The irradiation of methabenzthiazuron (0.1 mM) in the presence of NO3- (1 mM) or NO2- (0.1 mM) yielded numerous intermediary photoproducts. Mineralization was achieved after prolonged exposure. Some were identified with the help of LC-ESI-MS and flow injection APCI-MS techniques. Both oxidations of the aromatic ring and of the urea chain were observed. The former started by hydroxylation of the ring. Further oxidation of the ring led to cleavage of the benzenic ring with formation of dialdehydic, diacidic and anhydric compounds. Complete removal of the lateral urea chain took place subsequently to demethylation of the terminal methyl group and loss of the CO-NH2 group. Nitration was a minor process. This work shows that the photodegradation of methabenzthiazuron in the presence of nitrate or nitrite ions is highly non-specific.     

Hydroxycinnamic acid derivatives in an aquatic liverwort as possible bioindicators of enhanced UV radiation

We examined, under laboratory conditions, the physiological responses of the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia to artificially enhanced ultraviolet (UV) radiation for 82 days, especially considering the responses of five hydroxycinnamic acid derivatives. This species lives in mountain streams, where it is exposed to low temperatures and high UV levels, and this combination is believed to increase the adverse effects of UV. Enhanced UV radiation hardly caused any change in several physiological variables indicative of vitality, such as Fv/Fm and chlorophylls/phaeopigments ratio (OD430/OD410). Thus, this liverwort seemed to be tolerant to UV radiation, probably due to the accumulation of three UV-absorbing hydroxycinnamic acid derivatives: p-coumaroylmalic acid, 5'-(7',8'-dihydroxycoumaroyl)-2-caffeoylmalic acid, and 5'-(7',8'-dihydroxy-7-O-beta-glucosyl-coumaroyl)-2-caffeoylmalic acid. These compounds might serve as bioindicators of enhanced UV radiation.     

Rat intestinal metabolism of crufomate (4-tert-butyl-2-chlorophenyl methyl methylphosphoramidate).

Everted sacs of rat small intestine metabolized crufomate (4-tert-butyl-2-chlorophenyl methyl methylphosphoramidate) under in vitro conditions to form six 14C-labeled metabolites in quantities sufficient for isolation and identification. These metabolites were 4-tert-butyl-2-chlorophenyl methyl phosphoramidate (25%), 2-chloro-4(2-hydroxy-1,1-dimethylethyl)phenyl methyl methylphosphoramidate (19%), 2-[3-chloro-4-[[(methoxy) (methyl-amino)phosphoinyl]oxy]phenyl]-2-methylpropionic acid (2%), 4-tert-butyl-2-chlorophenol (0.8%) and its glucuronide (6%), and the aromatic glucuronide of 2-chloro-4(2-hydroxy-1,1-dimethylethyl)phenol (1%). These intestinal metabolites may represent precursory stages in the overall metabolism of crufomate.     

Phototransformation of clodinafop-propargyl

Photodegradation of the herbicide clodinafop-propargyl was investigated on glass surface under sunlight and UV light. Four photoproducts were identified by NMR, IR, and MS. Major photolysis products were 2-[(5-chloro-3-fluoro-2-pyridyloxy) phenoxy] propanoic acid and prop-2-ynyl-2-[(5-chloro-3-hydroxy-2-pyridyloxy) phenoxy] propanoate, while minor were ethyl 2-[(5-chloro-3-fluoro-2-pyridyloxy) phenoxy] propanoate and 1-hydroxypropanyl-2-[(5-chloro-3-fluoro-2-pyridyloxy) phenoxy] propanoate. Rate of photodegradation followed first-order kinetics with significant correlation coefficient. The major photoproducts were observed in maximum quantity on the 7th and 10th day and further degraded within 15-20 days.     

Anaerobic testosterone degradation in Steroidobacter denitrificans - Identification of transformation products

The transformation of the androgenic steroid testosterone by gammaproteobacterium Steroidobacter denitrificans was studied under denitrifying conditions. For the first time, growth experiments showed that testosterone was mineralized under consumption of nitrate and concurrent biomass production. Experiments with cell suspensions using [4-¹⁴C]-testosterone revealed the intermediate production of several transformation products (TPs). Characterisation of ten TPs was carried out by means of HPLC coupled to high resolution mass spectrometry with atmospheric pressure chemical ionization as well as ¹H and ¹³C NMR spectroscopy. 3β-hydroxy-5α-androstan-17-one (trans-androsterone) was formed in the highest amount followed by 5α-androstan-3,17-dione. The data suggests that several dehydrogenation and hydrogenation processes take place concurrently in ring A and D because no consistent time-resolved pattern of TP peaks was observed and assays using 2 TPs as substrates resulted in essentially the same TPs. The further transformation of testosterone in S. denitrificans seems to be very efficient and fast without formation of detectable intermediates.     

Benzo[a]pyrene degradation by Sphingomonas yanoikuyae JAR02

Batch experiments were conducted to characterize the degradation of benzo[a]pyrene, a representative high molecular weight (HMW) polycyclic aromatic hydrocarbon (PAH), by Sphingomonas yanoikuyae JAR02. Concentrations up to the solubility limit (1.2 microg l(-1)) of benzo[a]pyrene were completely removed from solution within 20 h when the bacterium was grown on salicylate. Additional experiments with [(14)C]7-benzo[a]pyrene demonstrated 3.8% mineralization over 7 days when salicylate was present is solution, and one major radio-labeled metabolite was observed that accounted for approximately 10% of the initial radio-label. Further characterization of the radio-labeled metabolite using HPLC/MS and HPLC/MS/MS identified radio-labeled pyrene-8-hydroxy-7-carboxylic acid and unlabeled pyrene-7-hydroxy-8-carboxylic acid as novel ring-cleavage metabolites, and a benzo[a]pyrene degradation pathway was proposed. Results indicate that biostimulation of HMW PAH degradation by salicylate, a water-soluble, non-toxic substrate, has significant potential for in situ bioremediation.     

Effects of sensitizers on the photodegradation of the systemic fungicide triadimenol

The photochemical behaviour of triadimenol (1) under various conditions has been examined. Significant degradation is obtained only in the presence of electron-acceptor sensitizers as 9,10-dicyanoanthracene or 2,4,6-triphenylpyrylium tetrafluoroborate, and long irradiation times are required. 1H-1,2,4-Triazole (2), 4-chlorophenyl formate (3), 4-chlorophenol (4), 1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)butan-2-one (5), 4-chlorophenyl 2,2-dimethylpropanoate (6) and 4-chlorobenzoic acid (7) were identified as photoproducts by NMR and GC-MS.     

Phototransformation of Clodinafop-Propargyl

Abstract

Photodegradation of the herbicide clodinafop-propargyl was investigated on glass surface under sunlight and UV light. Four photoproducts were identified by NMR, IR, and MS. Major photolysis products were 2-[(5-chloro-3-fluoro-2-pyridyloxy) phenoxy] propanoic acid and prop-2-ynyl-2-[(5-chloro-3-hydroxy-2-pyridyloxy) phenoxy] propanoate, while minor were ethyl 2-[(5-chloro-3-fluoro-2-pyridyloxy) phenoxy] propanoate and 1-hydroxypropanyl-2-[(5-chloro-3-fluoro-2-pyridyloxy) phenoxy] propanoate. Rate of photodegradation followed first-order kinetics with significant correlation coefficient. The major photoproducts were observed in maximum quantity on the 7th and 10th day and further degraded within 15–20 days.