Alkyl Chain Oxidation Research Articles

The generation mechanism of CO and CO2 in coal spontaneous combustion by mathematical statistical and other methods

At present, the mechanism of CO and CO2 production in coal spontaneous combustion is controversial. With the hope of exploring the generation mechanism of CO and CO2 in the low-temperature oxidation of coal, in this study, the correlation between the relative contents of three active functional groups, –CH3/–CH2, -C = O, and –COOH and the generation law of CO and CO2 in the low-temperature oxidation of coal samples with different metamorphic degrees was explored by means of principal component analysis, Pearson linear analysis, and Fourier transform infrared spectroscopy. The results indicate that –CH3/–CH2, -C = O, and –COOH in low-rank lignite (HC) are significantly correlated with the concentrations of CO and CO2. The -C = O and –COOH in medium-rank bituminous coal (BC) are closely correlated with the concentrations of CO and CO2. The concentrations of CO and CO2 in high-rank anthracite (CQ) show the highest correlation with the relative content of –CH3/–CH2, followed by their correlation with the relative content of -C = O, and their correlation with the relative content of –COOH is relatively low. Thus, it can be concluded that the generation mechanism of CO and CO2 varies with the metamorphic degrees of coal in coal spontaneous combustion. CO and CO2 generated from low-rank HC mainly come from continuous generation and oxidation of inherent and secondary alkyl chains and those generated from medium-rank BC mainly come from the oxidation of oxygen-containing functional groups. Besides, for high-rank CQ, CO is mainly generated from the process in which alkyl chains in coal oxidize to form carbonyl groups which then break to form CO, and a small part of CO comes from the coal-oxygen free radical reaction. As for CO2, its sources are more complex. A big portion of CO2 comes from the free radical reaction and CO2 may also come from the direct conversion of CO at high temperature and in the presence of water. Finally, the reaction mechanism of C = O· and ·OH free radicals was studied by quantum chemical calculation. The calculation results reveal that the free radical reaction can occur spontaneously and release a certain amount of heat under certain conditions, thus playing a positive role in promoting coal spontaneous combustion.

Resolving the kinetic and intrinsic constraints of heat-activated peroxydisulfate oxidation of iopromide in aqueous solution

Iopromide (IOP) has been identified as one of the most persistent pharmaceuticals in wastewater treatment processes, however, kinetic and intrinsic factors constraining its fast removal in advanced oxidation processes (AOPs) are yet to be resolved. Here oxidation of IOP by heat-activated peroxydisulfate (PDS) was investigated both experimentally and theoretically. Rates of IOP degradation were enhanced by elevating solution temperature and acidity. An apparent kinetic rate equation was developed, based on the pseudo-first-order reaction model and assumption of steady state of SO4−. The common water constituents showed inhibitory effects on IOP decomposition to various extent. An insufficient supply of SO4− was considered as the major kinetic constraint. Eight byproducts were identified and most of which had intact triiodinated benzene ring. O-demethylation, oxidation of amino moiety and oxidation/elimination of alcohol groups are proposed as the primary degradation pathways, in accordance with the incomplete mineralization and non-detectable release of inorganic iodine. Quantum chemical calculations predict that oxidation of alkyl chains of IOP preferentially occurs and IOP byproducts with shorter side chains and intact triiodinated ring are more reactive than IOP. By virtue of the identified kinetic and intrinsic constraints, strategies to maximize degradation efficiency of IOP are proposed.

Biodegradation of the endocrine disrupter 4-t-octylphenol by the non-ligninolytic fungus Fusarium falciforme RRK20: Process optimization, estrogenicity assessment, metabolite identification and proposed pathways

4-t-octylphenol (4-t-OP), a well-known endocrine disrupting compound, is frequently found in various environmental compartments at levels that may cause adverse effects to the ecosystem and public health. To date, most of the studies that investigate microbial transformations of 4-t-OP have focused on the process mediated by bacteria, ligninolytic fungi, or microbial consortia. There is no report on the complete degradation mechanism of 4-t-OP by non-ligninolytic fungi. In this study, we conducted laboratory experiments to explore and characterize the non-ligninolytic fungal strain Fusarium falciforme RRK20 to degrade 4-t-OP. Using the response surface methodology, the initial biomass concentration and temperature were the factors identified to be more influential on the efficiency of the biodegradation process as compared with pH. Under the optimized conditions (i.e., 28 °C, pH 6.5 with an initial inoculum density of 0.6 g L−1), 25 mg L−1 4-t-OP served as sole carbon source was completely depleted within a 14-d incubation; addition of low dosage of glucose was shown to significantly accelerate 4-t-OP degradation. The yeast estrogenic screening assay further confirmed the loss of estrogenic activity during the biodegradation process, though a longer incubation period was required for complete removal of estrogenicity. Metabolites identified by LC-MS/MS revealed that strain RRK20 might degrade 4-t-OP as sole energy source via alkyl chain oxidation and aromatic ring hydroxylation pathways. Together, these results not only suggest the potential use of non-ligninolytic fungi like strain RRK20 in remediation of 4-t-OP contaminated environments but may also improve our understanding of the environmental fate of 4-t-OP.

Aerobic oxidation of alkyl chain in alkylphenols over combination of Pt and Pd catalysts

Oxidation of benzylic position in alkylphenols with molecular oxygen in acidic conditions, which is very difficult because of the intense dimerization or polymerization, was investigated with various combinations of noble metal catalysts. The combination of Pt/C and Pd(CH3COO)2 catalysts showed activity in the formation of p-hydroxybenzaldehyde formation from p-cresol. The best p-hydroxybenzaldehyde yield was 35%, which was obtained in 50 wt% aqueous acetic acid, Pt on carbon : Pd(CH3COO)2 weight ratio = 1 : 2, at 353 K. From XRD, TEM-EDX and XAFS characterizations, the Pt and Pd species were totally reduced to Pt and Pd metal particles, respectively, in spite of the oxidative reaction conditions. Polymerized products (“tar”) of p-cresol formed with Pt/C catalyst and air can be the reductants for Pd(CH3COO)2 into Pd metal. The catalysts or catalyst combinations without Pd metal showed no activity in the formation of p-hydroxybenzaldehyde, suggesting that Pd° is the active species. The effects of the air pressure and presence of radical scavenger were very small, suggesting that non-free-radical mechanism was involved.

Degradation of atrazine and structurally related s-triazine herbicides in soils by ferrous-activated persulfate: Kinetics, mechanisms and soil-types effects

The occurrence of s-triazine herbicides in soils and groundwaters has been reported globally and remediation of these contaminated sites are essentially imperative, especially at accidental spill sites. Present work investigated the feasibility of using Fe2+ catalyzed persulfate (PS) to effectively degrade s-triazine herbicides (e.g., atrazine (ATZ), terbuthylazine (TEA) and ametryn (AMT)) in soils. The degradation kinetics, mechanisms and soil-types effects were systematically investigated. For arable soil A1, extent of degradation reached 80% for 100 mg kg−1 ATZ contaminated soil after 600 min (PS/Fe2+ of 16.6 mM/16.6 mM) at 23 °C. Increasing PS and Fe2+ dosages could enhance ATZ degradation. Acidic condition was favorable for the degradation of ATZ with Fe2+/PS process and the contribution of SO4− to the overall degradation of ATZ decreased as initial pH increased. The ethyl group and chloride substituent on molecular structure of ATZ affected its degradation comparing to other two s-triazine herbicides. ATZ degradations in two arable soils and one paddy soil indicated that different soils with various physical-chemical properties, such as soil organic matter, available and total Fe contents, may influence the ATZ degradation. Moreover, a total of five degradation products of ATZ were identified in soil A1 by Fe2+/PS process. Three degradation pathways including alkyl chain oxidation, dealkylation and dechlorination-hydroxylation reactions with the underlying oxidation mechanisms were tentatively proposed.

Determination of Urinary Metabolites of the Emerging UV Filter Octocrylene by Online-SPE-LC-MS/MS.

Octocrylene (OC) is an emerging UV filter, which is used in the majority of sunscreens as well as other personal care products (PCP) and consumer products. Its presence in various environmental matrices has been reported. However, information on the internal OC exposure in humans is not available, due to the lack of appropriate biomarkers of exposure and analytical methods. Here, we describe a rugged, precise, and accurate analytical method for the determination of three OC metabolites (ester hydrolysis and alkyl chain oxidation products) in human urine by stable isotope dilution analysis. Urine samples are incubated with β-glucuronidase (E. coli K12) and then analyzed by liquid chromatography-electrospray ionization-triple quadrupole-tandem mass spectrometry with online turbulent flow chromatography for sample cleanup and analyte enrichment (online-SPE-LC-MS/MS). Syntheses of analytical standards, including deuterium-labeled internal standards, are also described. In a pilot study, we investigated the applicability of the metabolites as biomarkers of exposure in urine samples from the general population (n = 35). OC metabolites were detected in 91% of the samples, with the highest concentrations for three individuals having used sunscreen within 5 days prior to sample collection. We will apply the method in future human biomonitoring studies for OC exposure and risk assessment.

Activation of peroxymonosulfate using drinking water treatment residuals for the degradation of atrazine

Drinking water treatment residuals (WTRs) are safe byproducts of water treatment plants containing iron. This work studies the degradation of atrazine (ATZ) by WTR-catalyzed peroxymonosulfate (PMS) in aqueous solutions. Factors that affect the catalytic performance (the PMS concentration, catalyst dose, initial solution pH, reaction temperature and water matrix species) were investigated. The results show that the catalytic degradation efficiency of ATZ increases with the increase in PMS concentration and temperature, whereas a higher content of WTRs results in lower removal efficiency because of the quenching effect and negative effect of high pH. For an initial solution pH of 3 and 5, 94.1% and 87.4% of ATZ degradation can be achieved within 6h, whereas the value is only 26% for pH of 7. The production of sulfate radicals (SO4−) and hydroxyl radicals (OH) was confirmed by classic radical quenching and electron spin resonance (ESR) tests. Based on the GC–MS and LC–MS results, the main degradation pathways of ATZ may contain dealkylation, dechlorination-hydroxylation, and alkyl chain oxidation processes. In addition to the ATZ removal ability, the WTRs/PMS system can simultaneously remove phosphorus. This article provides a new idea for wastewater treatment and usage of WTRs as a resource.

Biodegradation of the endocrine disrupter 4-tert-octylphenol by the yeast strain Candida rugopelliculosa RRKY5 via phenolic ring hydroxylation and alkyl chain oxidation pathways

4-(1,1,3,3-tetramethylbutane)-phenol (4-tert-OP) is one of the most prevalent endocrine disrupting pollutants. Information about bioremediation of 4-tert-OP remains limited, and no study has been reported on the mechanism of 4-tert-OP degradation by yeasts. The yeast Candida rugopelliculosa RRKY5 was proved to be able to utilize 4-methylphenol, bisphenol A, 4-ethylphenol, 4-tert-butylphenol, 4-tert-OP, 4-tert-nonylphenol, isooctane, and phenol under aerobic conditions. The optimum conditions for 4-tert-OP degradation were 30°C, pH 5.0, and an initial 4-tert-OP concentration of 30mgL−1; the maximum biodegradation rate constant was 0.107d−1, equivalent to a minimum half-life of 9.6d. Scanning electron microscopy revealed formation of arthroconidia when cells were grown in the presence of 4-tert-OP, whereas the cells remained in the budding form without 4-tert-OP. Identification of the 4-tert-OP degradation metabolites using liquid chromatography–hybrid mass spectrometry revealed three different mechanisms via both branched alkyl side chain and aromatic ring cleavage pathways.

Aromatic hydroxylation using an oxo-bridged diiron(III) complex: a bio-inspired functional model of toluene monooxygenases.

In biology, aromatic hydroxylation is carried out using a family of heme and nonheme oxygenases, such as cytochrome P450, toluene monooxygenases (TMOs), and methane monooxygenase (MMO). In contrast, a vast majority of synthetic iron based catalysts employed so far in aromatic hydroxylation are monomeric in nature. Herein, we have employed a diferric complex of an aminopyridine ligand ([(bpmen)2Fe2O(μ-O)(μ-OH)](ClO4)3 (2), bpmen = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-diaminoethane) towards aromatic hydroxylation with H2O2 and acetic acid. The diiron(iii) complex shows promising reactivity in the hydroxylation of benzene and alkylbenzenes with a higher selectivity towards aromatic ring hydroxylation over alkyl chain oxidation. The μ-oxo diiron(iii) core has been shown to be regenerated at the end of catalytic turnover. However, mechanistic studies indicate that the diiron(iii) complex undergoes dissociation into its monomeric congener and the resulting iron(iii) complex mitigates aromatic hydroxylation.

New insights into atrazine degradation by cobalt catalyzed peroxymonosulfate oxidation: Kinetics, reaction products and transformation mechanisms

The widespread occurrence of atrazine in waters poses potential risk to ecosystem and human health. In this study, we investigated the underlying mechanisms and transformation pathways of atrazine degradation by cobalt catalyzed peroxymonosulfate (Co(II)/PMS). Co(II)/PMS was found to be more efficient for ATZ elimination in aqueous solution than Fe(II)/PMS process. ATZ oxidation by Co(II)/PMS followed pseudo-first-order kinetics, and the reaction rate constant (kobs) increased appreciably with increasing Co(II) concentration. Increasing initial PMS concentration favored the decomposition of ATZ, however, no linear relationship between kobs and PMS concentration was observed. Higher efficiency of ATZ oxidation was observed around neutral pH, implying the possibility of applying Co(II)/PMS process under environmental realistic conditions. Natural organic matter (NOM), chloride (Cl−) and bicarbonate (HCO3−) showed detrimental effects on ATZ degradation, particularly at higher concentrations. Eleven products were identified by applying solid phase extraction-liquid chromatography–mass spectrometry (SPE-LC/MS) techniques. Major transformation pathways of ATZ included dealkylation, dechlorination-hydroxylation, and alkyl chain oxidation. Detailed mechanisms responsible for these transformation pathways were discussed. Our results reveal that Co(II)/PMS process might be an efficient technique for remediation of groundwater contaminated by ATZ and structurally related s-triazine herbicides.

Heat-activated persulfate oxidation of atrazine: Implications for remediation of groundwater contaminated by herbicides

Contamination of herbicides such as atrazine (ATZ) poses a significant threat to human health and aquatic ecosystem. In this study, we demonstrated that heat-activated persulfate could effectively degrade ATZ in water. Complete disappearance of 50μM ATZ could be obtained after 2h reaction in the presence of 1mM persulfate under 60°C. Increasing the initial persulfate concentration or temperature significantly enhanced the degradation efficiency. Natural organic matter (NOM) decreased the degradation rate, but complete removal of ATZ could still be obtained. The presence of chloride (Cl−) and bicarbonate (HCO3−) had little effects on ATZ degradation at lower concentration (e.g., 5mM). However, inhibitory effects were observed when concentrations of Cl− and HCO3− increased (e.g., 100mM). Radical scavenging test revealed that sulfate radical (SO4−) was the predominant radical species at acidic to neutral pH, while hydroxyl radical (HO) was predominant at basic pH. Eight intermediates and products were identified by applying solid phase extraction and liquid chromatography–tandem mass spectrometry (SPE-LC–MS/MS) techniques. Transformation pathways including dealkylation, alkyl chain oxidation, and dechlorination–hydroxylation were proposed, and the underlying mechanisms for each pathway were systematically analyzed.

Photocatalytic removal of atrazine using N-doped TiO2 supported on phosphors

Visible light-active N-doped TiO2 (N-TiO2) was successfully immobilized on ZnS-based phosphors microparticles (ZSP) by a modified sol–gel method. Core-shell catalysts were prepared to serve as “photoactive support”, able to harvest the external irradiation and to emit a luminescence with wavelength suitable for activation of N-doped TiO2. The nominal loading of N-TiO2 on ZSP was in the range of 15–50wt% and the effect of the progressive increase in N-TiO2 loading on the coverage of phosphors particles was evaluated. The preparation method did not induce alterations of the initial ZSP crystallographic structure and allowed to obtain N-TiO2 dispersion on ZSP surface. By varying the N-TiO2 loadings on the surface of ZSP, its morphology gradually evolved from pseudo-spherical shape, until 30wt% N-TiO2 loading, to elongated shape for an N-TiO2 content of 50wt%. The photocatalytic activity of N-TiO2/ZSP was evaluated for the removal of atrazine under UVA light irradiation. Enhanced performance compared to either pure N-TiO2 nanoparticles or bare ZSP was observed. The photocatalyst N-TiO2/ZSP at 30wt% of N-TiO2 loading (30N-TiO2/ZSP) demonstrated the highest photocatalytic activity. Photocatalytic performances were strongly dependent on the concentration of catalyst and the initial pH of solution. The optimal catalyst concentration was 0.5gL−1 and the optimal initial pH was 5.8. A study of the reaction intermediates during the photocatalytic removal of atrazine was carried out, evidencing that the sequence of intermediates for 30N-TiO2/ZSP and for the phosphors ZSP alone included dealkylation reactions and alkyl chain oxidation.

Oxidizing octadecylphosphonic acid molecules without disrupting their self-assembled monolayers

In examination of oxidation of octadecylphosphonic acid (OPA) self-assembled monolayers (SAMs) prepared on the native oxide of a Si wafer upon exposure to UV/ozone (UVO) for up to 5 min, atomic force microscopy studies of the surface elucidated that there were no changes in morphology of the SAMs. Surprisingly, investigations on the same samples of OPA SAMs using time-of-flight secondary ion mass spectrometry revealed that the intensity of the deprotonated molecular ion fragment decreased exponentially to approximately one fourth of that of the control. We clarify that UVO-induced oxidation of alkyl chains of the OPA molecules in their SAMs precedes the disruption of the monolayer structure, which is the basis for controlling surface chemistry of SAMs with brief UVO exposure.

NP1EC Degradation Pathways Under Oxic and Microxic Conditions

The degradation pathway of nonylphenol ethoxyacetic acid (NP1EC) and the conditions favoring dicarboxylated alklyphenol ethoxyacetic acid (CAnP1EC; where n = the number of aliphatic carbon atoms) formation were studied in oxic microcosms constructed with organic carbon-poor soil from the Mesa soil aquifer treatment (SAT) facility (Arizona) and pristine organic carbon-rich sediments from Coyote Creek (California). Results suggest that the availability of dissolved oxygen determines the dominant biodegradation pathway; ether cleavage and the formation of NP is favored by oxic conditions, while alkyl chain oxidation and the formation of CAP1ECs is favored under microxic conditions. In the Mesa microcosms, para-NP1EC was transformed to para-nonylphenol (NP) before being rapidly transformed to nonyl alcohols via ipso-hydroxylation. In the Coyote Creek microcosms, large quantities of CAP1ECs were observed. Initially, CA8P1ECs were the dominant metabolites, but as biodegradation continued, CAP1ECs became the dominant metabolites. Compared to the CAsP1ECs, the number of CA6P1ECs peaks observed was small (< 6) even though their concentrations were high. Several novel metabolites, tentatively identified as 3-alkylchroman-4-carboxylic acids (with alkyl groups ranging from C2 to C5), were formed in the Coyote Creek microcosms. These metabolites are presumably formed from ortho-CAP1ECs by intramolecular ring closure.

Photolysis of nonylphenol ethoxylates: The determination of the degradation kinetics and the intermediate products

The photolysis of nonylphenol ethoxylates with an average oligomers length of ten ethoxylate units (NPEO(10)) in aqueous solution under UV, as well as the influence of humic acid (HA) on the photolysis was studied. A 125W high-pressure mercury lamp was employed as the light source. The intermediate products from the photolysis were determined by LC-MS. The results indicated that NPEO(10) underwent direct photolysis upon exposed to UV. The degradation pathway was complex. Besides the generally proposed degradation pathway of ethylene oxide (EO) side chains shortening, the oxidation of alkyl chain and EO chain led to intermediates having both a carboxylated (as well as carbonylated) ethoxylate and alkyl chain of varying lengths. The hydrogenation of benzene ring was also detected. The kinetics data showed that the first order reaction kinetics could be well used to describe the kinetics of NPEO(10) degradation. In the presence of dissolved organic matter by HA addition, the performance of NPEO(10) photodegradation was reduced. The photolysis rate decreased with increased HA concentration.

Fate of a 14C-Labeled Nonylphenol Isomer in a Laboratory-Scale Membrane Bioreactor

This study aimed at giving a better insight into the possible fate of nonylphenol (NP) during wastewater treatment by using a lab-scale membrane bioreactor (MBR) designed and optimized for fate studies carried out with radiolabeled compounds. After a single pulse of 14C-labeled-NP isomer (4-[1-ethyl-1,3-dimethylpentyl]phenol) as radiotracer, the applied radioactivity was monitored in the MBR system over 34 days. The mass balance of NP residues at the end of the study showed that 42% of the applied radioactivity was recovered in the effluent as degradation products of NP, 21% was removed with the daily excess sludge from the MBR, and 34% was recovered as adsorbed in the component parts of the MBR. A high amount of NP was associated to the sludge during the test period, while degradation compounds were mainly found in the effluent. Partial identification of these metabolites by means of HPLC-tandem mass spectrometry coupled to radio-detection showed they are alkyl-chain oxidation products of NP. The use of this MBR and a radiolabeled test compound was found suitable for demonstrating that under the applied conditions, the elimination of NP through mineralization and volatilization processes (both less than 1%) was negligible. However, the removal of NP via sorption and the continuous release of oxidation products of NP in permeate were of relevance.

Microbial degradation of nonylphenol and other alkylphenols—our evolving view

Because the endocrine disrupting effects of nonylphenol (NP) and octylphenol became evident, the degradation of long-chain alkylphenols (AP) by microorganisms was intensively studied. Most NP-degrading bacteria belong to the sphingomonads and closely related genera, while NP metabolism is not restricted to defined fungal taxa. Growth on NP and its mineralization was demonstrated for bacterial isolates, whereas ultimate degradation by fungi still remains unclear. While both bacterial and fungal degradation of short-chain AP, such as cresols, and the bacterial degradation of long-chain branched AP involves aromatic ring hydroxylation, alkyl chain oxidation and the formation of phenolic polymers seem to be preferential elimination pathways of long-chain branched AP in fungi, whereby both intracellular and extracellular oxidative enzymes may be involved. The degradation of NP by sphingomonads does not proceed via the common degradation mechanisms reported for short-chain AP, rather, via an unusual ipso-substitution mechanism. This fact underlies the peculiarity of long-chain AP such as NP isomers, which possess highly branched alkyl groups mostly containing a quaternary alpha-carbon. In addition to physicochemical parameters influencing degradation rates, this structural characteristic confers to branched isomers of NP a biodegradability different to that of the widely used linear isomer of NP. Potential biotechnological applications for the removal of AP from contaminated media and the difficulties of analysis and application inherent to the hydrophobic NP, in particular, are also discussed. The combination of bacteria and fungi, attacking NP at both the phenolic and alkylic moiety, represents a promising perspective.

Alkyl Chain Length Effect on Tribological Behavior of Alkanethiol Self-Assembled Monolayers on Au

We have investigated the frictional properties of alkanethiol self-assembled monolayers (SAMs) by pin-on-plate methods. SAMs made from octadecanethiol (C18) with a longer alkylchain exhibited lower friction coefficients (approximately 0.2), while the friction coefficients were higher (approximately 0.4) in the case of the SAMs made from other alkanethiols with short alkylchains. The reasons for the increase in friction were i) the distortion of SAM structures because of the penetration of pins into SAMs and ii) oxidation of molecules as a result of X-ray photoelectron spectroscopy (XPS) measurements. Further friction tests on C18 SAMs for 600 cycles of sliding (1 h) caused the higher friction coefficients (0.6–0.7) and oxidation of alkylchains. It was considered that repeating of slides led to the distortion of SAMs, the oxidation of alkylchains, or adsorption of water or oxygen. The total XPS peak ratios of C(1s)/Au(4f) hardly changed after 1800 cycles of sliding (3 h), indicating that C18 SAM remained even after many repetitions of sliding.

Residues of 14C-4n-nonylphenol in mosquitofish (Gambusia holbrooki) oocytes and embryos during dietary exposure of mature females to this xenohormone

In order to assess in fish the maternal transfer of alkylphenolic compounds to the progeny, the identification and quantification of the labelled compounds present in oocytes and embryos was conducted after dietary exposure of mature female mosquitofish to 14C-4n-nonylphenol during vitellogenesis and embryogenesis respectively. Radioactivity found in bile and liver extracts accounted for 0.9–0.6 and 0.2–0.1% of ingested radioactivity for females exposed during vitellogenesis and embryogenesis respectively. The amount of extractable radioactivity present in oocytes and embryos was 0.19 and 0.07% of the ingested dose respectively. The radio-HPLC profiles obtained from bile, liver, oocyte and embryo extracts were similar. They showed the presence of 4n-NP-glucuronide as the major metabolite and traces of unchanged 4n-NP. The other metabolites corresponded to 8-hydroxynonylphenol, 9-(4-hydroxyphenyl)-nonanoic acid and para-hydroxybenzoic acid which is the final product of the alkyl chain oxidation. Our results indicate that exposure of ovoviviparous female fish to 4-NP during vitellogenesis and embryogenesis leads to the contamination of the progeny by 4-NP and its metabolites.

Riboflavin-photosensitized degradation of atrazine in a freshwater environment

The effect of the photosensitizer riboflavin (0, 10, 50, 100 μM) on the fate of atrazine (10 mg/l) in a freshwater environment was studied. It was found that at 100 μM riboflavin significantly enhanced the degradation of atrazine and more than 80% of atrazine in a natural water environment was depleted in 72 h. The relative contribution of microbial assemblages and the freshwater matrix to the degradation of atrazine and the degradation kinetics of atrazine were compared under different experimental conditions. The products and pathways of atrazine transformation were studied with GC–MS and HPLC with a photodiode array detector. The results show that dealkylation and alkyl chain oxidation are involved in the degradation of atrazine.