Heterogeneous reactions of ozone with pyrene, 1-hydroxypyrene and 1-nitropyrene adsorbed on particles

This work deals with the kinetic study of the reactions of ozone with pyrene, 1-hydroxypyrene and 1-nitropyrene, adsorbed on model particles. Experiments were performed at room temperature and atmospheric pressure, using a quasi-static flow reactor in the absence of light. Compounds were extracted from particles using pressurized fluid extraction (PFE) and concentration measurements were performed using gas chromatography/mass spectrometry (GC/MS). The pseudo-first order rate constants were obtained from the fit of the experimental decay of particulate polycyclic compound concentrations versus reaction time. Experiments were performed at three different O₃ concentrations from which second order rate constants were calculated. The following rate constant values were obtained at 293 K: k(O₃ + Pyrene) = (3.2 ± 0.7) × 10^?16 cm³ molecule^?1 s^?1; k(O₃ + 1OHP) = (7.7 ± 1.4) ×10 ^?16 cm³ molecule^?1 s^?1; and k(O₃ + 1NP) = (2.2 ± 0.5) × 10^?17 cm³ molecule^?1 s^?1, for pyrene, 1-hydroxypyrene and 1-nitropyrene adsorbed on silica particles. The variation in the rate constants demonstrates the strong influence of the substituent (OH or NO₂) on the heterogeneous reactivity of pyrene. The pyrene particulate concentration was also varied in order to check how this parameter may influence the experiments. Finally, oxidation products were investigated for all reactions and some were detected and identified for the first time for ozone heterogeneous reaction with pyrene adsorbed on particles.     

Heterogeneous reaction of NO2 with soot at different relative humidity

The influences of relative humidity (RH) on the heterogeneous reaction of NO₂ with soot were investigated by a coated wall flow tube reactor at ambient pressure. The initial uptake coefficient (γ _initial) of NO₂ showed a significant decrease with increasing RH from 7 to 70%. The γ _initial on “fuel-rich” and “fuel-lean” soot at RH = 7% was (2.59 ± 0.20) × 10^?5 and (5.92 ± 0.34) × 10^?6, respectively, and it decreased to (5.49 ± 0.83) × 10^?6 and (7.16 ± 0.73) × 10^?7 at RH = 70%, respectively. Nevertheless, the HONO yields were almost independent of RH, with average values of (72 ± 3)% for the fuel-rich soot and (60 ± 2)% for the fuel-lean soot. The Langmuir-Hinshelwood mechanism was used to demonstrate the negative role of RH in the heterogeneous uptake of NO₂ on soot. The species containing nitrogen formed on soot can undergo hydrolysis to produce carboxylic species or alcohols at high RH, accompanied by the release of little gas-phase HONO and NO.

     

Heterogeneous reactions of suspended parathion, malathion, and fenthion particles with NO(3) radicals

Organophosphorus pesticides (OPPs) emit into the atmosphere in both gas and particulate phases via spray drift from treatments and post-application emission, but most of their degradations in the atmosphere are not well known. In this study, the heterogeneous reactions of nitrate (NO₃) radicals with three typical OPPs (parathion, malathion, and fenthion) absorbed on azelaic acid particles are investigated using an online vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The reaction products observed with the VUV-ATOFMS are identified on the basis of GC/MS analysis of the products in the reaction between NO₃ radicals and the coating of the pesticide. Paraoxon is identified as the only product of parathion; malaoxon and bis(1,2-bis-ethoxycarbonylethyl)disulfide as the products of malathion; fenoxon, fenoxon sulfoxide, fenthion sulfoxide, fenoxon sulfone, and fenthion sulfone as the products of fenthion. The degradation rates of parathion, malathion, and fenthion under the experimental conditions are 5.5 × 10⁻³, 5.6 × 10⁻², and 3.3 × 10⁻² s⁻¹, respectively. The pathways of the heterogeneous reactions between the three OPPs and NO₃ radicals are proposed. The experimental results reveal the possible transformations of these OPPs through the oxidation of NO₃ radicals in the atmosphere.     

Mutagenic nitrated benzo[a]pyrene derivatives in the reaction product of benzo[a]pyrene in NO2-air in the presence of O3 or under photoirradiation

In order to clarify the contribution of nitrated products to the direct-mutagenic activity of products of the reactions of benzo[a]pyrene in NO2-air under various conditions, heterogeneous reactions of BaP deposited on filter in the air containing 10 ppm of NO2 have been conducted in dark or under photoirradiation. The reaction products have been analyzed by gas chromatography and mutagenicity of the products fractionated by preparative HPLC was assayed for Salmonella typhimurium strains TA98 and YG1024 in the absence of S9 mix. 3,6-dinitrobenzo[a]pyrene and 1,3-dinitrobenzo[a]pyrene, which are strong direct-acting mutagens, largely contributed to the total direct-acting mutagenicity of the dark reaction products in NO2-air. On the other hand, both the dark reaction in the presence of O3 and the photoreaction in NO2-air resulted in the formation of much smaller amounts of nitrobenzo[a]pyrenes than that observed in the dark reaction in the absence of O3. These results show that the contribution of other direct-acting mutagens to the total direct-acting mutagenicity of the products in these reactions should be considered. Benzo[a]pyrene lactones were identified in a highly mutagenic fraction of the products of the dark reaction in the presence of O3 and photoreaction and a nitrobenzo[a]pyrene lactone was also identified in a highly mutagenic fraction of the dark reaction products in the presence of O3. Nitrated oxygenated benzo[a]pyrene derivatives such as nitrobenzo[a]pyrene lactone were considered to largely contribute to direct-acting mutagenicity of the products of the dark reaction in the presence of O3 and photoreaction.     

Kinetics and mechanism of TNT degradation in TiO2 photocatalysis

The photocatalytic degradation of TNT in a circular photocatalytic reactor, using a UV lamp as a light source and TiO(2) as a photocatalyst, was investigated. The effects of various parameters such as the initial TNT concentration, and the initial pH on the TNT degradation rate of TiO(2) photocatalysis were examined. In the presence of both UV light illumination and TiO(2) catalyst, TNT was more effectively degraded than with either UV or TiO(2) alone. The reaction rate was found to obey pseudo first-order kinetics represented by the Langmuir-Hinshelwood model. In the mineralization study, TNT (30 mg/l) photocatalytic degradation resulted in an approximately 80% TOC decrease after 150 min, and 10% of acetate and 57% of formate were produced as the organic intermediates, and were further degraded. NO(-)(3) NO(-)(2), and NH(+)(4) were detected as the nitrogen byproducts from photocatalysis and photolysis, and more than 50% of the total nitrogen was converted mainly to NO(-)(3)in the photocatalysis. However, NO(-)(3) did not adsorbed on the TiO(2) surface. TNT showed higher photocatalytic degradation efficiency at neutral and basic pH.     

Kinetics and mechanism of oxidation of tetrachloroethylene with permanganate

The kinetics, reaction pathways and product distribution of oxidation of tetrachloroethylene (PCE) by potassium permanganate (KMnO4) were studied in phosphate-buffered solutions under constant pH, isothermal, completely mixed and zero headspace conditions. Experimental results indicate that the reaction is first-order with respect to both PCE and KMnO4 and has an activation energy of 9.3+/-0.9 kcal/mol. The second-order rate constant at 20 degrees C is 0.035+/-0.004 M(-1) s(-1), and is independent of pH and ionic strength (I) over a range of pH 3-10 and I approximately 0-0.2 M, respectively. The PCE-KMnO4 reaction may proceed through further oxidation and/or hydrolysis reaction pathways, greatly influenced by the acidity of the solution, to yield CO2(g), oxalic acid, formic acid and glycolic acid. Under acidic conditions (e.g., pH 3), the further oxidation pathway will dominate and PCE tends to be directly mineralized into CO2 and chloride. Under neutral (e.g., pH 7) and alkaline conditions (e.g., pH 10), the hydroxylation pathway dominates the reaction and PCE is primarily transformed into oxalic acid prior to complete PCE mineralization. Moreover, all chlorine atoms in PCE are rapidly liberated during the reaction and the rate of chloride production is very close to the rate of PCE degradation.     

Absorption cross-sections of atmospheric constituents: NO2, O2, and H2O

Absorption spectroscopy, which is widely used for concentration measurements of tropospheric and stratospheric compounds, requires precise values of the absorption cross-sections of the measured species. NO₂, O₂ and its collision-induced absorption spectrum, and H₂O absorption cross-sections have been measured at temperature and pressure conditions prevailing in the Earth’s atmosphere. Corrections to the generally accepted analysis procedures used to resolve the convolution problem are also proposed.     

Kinetics of the gas-phase reactions of NO3 radicals with ethyl acrylate,n-butyl acrylate,methyl methacrylate and ethyl methacrylate

The relative rate method has been used to determine the rate constants for the gas-phase reactions of NO₃ radicals with a series of acrylate esters: ethyl acrylate (k₁), n-butyl acrylate (k₂), methyl methacrylate (k₃) and ethyl methacrylate (k₄) at 298 ± 1 K and 760 Torr. The obtained rate constants are k₁ = (1.8 ± 0.25) × 10^?16 cm³ molecule^?1 s^?1, k₂ = (2.1 ± 0.33) × 10^?16 cm³ molecule^?1 s^?1, k₃ = (3.6 ± 1.2) × 10^?15 cm³ molecule^?1 s^?1, k₄ = (4.9 ± 1.7) × 10^?15 cm³ molecule^?1 s^?1. The experimental rate constants are in good agreement with theoretical rate constants calculated by an algorithm of the correlation between the rate constants and the orbital energies for the reactions of unsaturated VOCs with NO₃ radicals. In addition, the atmospheric lifetimes of the compound against NO₃ attack are estimated and the results show that NO₃ reactions contribute little to the atmospheric losses of acrylate esters except in polluted regions.     

Kinetics of IO radicals with C1, C2 aliphatic alcohols in tropospherically relevant conditions

Environmental Science and Pollution Research - Kinetics of the reaction of IO radicals with methanol (MeOH) and ethanol (EtOH) were experimentally studied in the gas phase using pulsed laser...     

Kinetics and mechanism of the hydrolysis of thiamethoxam

The degradation of thiamethoxam [(EZ)-3-(2-chloro-1,3-thiazol-5-yl-methyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene (nitro) amine] insecticide in buffers at different pH and temperature levels was investigated in laboratory studies. Acidic hydrolysis under conventional heating conditions and alkaline hydrolysis under both conventional heating and microwave conditions were carried out. Different hydrolysis products were found to form under alkaline and acidic conditions. Hydrolysis of thiamethoxam in acidic, neutral and alkaline buffers followed first-order reaction rate kinetics at pH 4, 7 and 9.2, respectively. Thiamethoxam readily hydrolyzed in alkaline buffer but was comparatively stable in neutral buffer solution. The main products formed under different conditions were characterized on the basis of infrared (IR), ¹H-NMR and Mass spectroscopy. The possible mechanisms for the formation of these hydrolysis products have also been proposed.     

Air pollution and agricultural aphid pests. I: Fumigation experiments with SO2 and NO2

A wide range of aphid/host-crop systems was surveyed by means of fumigation experiments in closed chambers for sensitivity to SO(2) and NO(2) at a concentration of 100 nl litre(-1). Aphid performance was measured by the mean relative growth rate (MRGR) of individual aphids. In all cases, except for Acrythosiphon pisum (Harris) on Vicia fabaL., there were increases in the MRGR of the aphids feeding on fumigated plants as compared to clean air controls, both during and post fumigation. The increases in MRGR ranged from 6 to 75%, with the majority falling between 25 and 40%. A. pisum on V. faba showed a consistent negative response, with decreases in MRGR between -9 and -12%. The changes in aohid MRGR were not due to direct effects, as no significant differences in MRGR were observed between fumigated and clean air chambers when aphids were fed on artificial diet sachets during fumigation.     

Short-term, real-time forecasting of hourly ozone, NO2 and NO levels by means of multiple linear regression modelling

Conclusions  The results are at least as good as those obtained with much more sophisticated models. Furthermore, the models can be easily run on a simple PC. This approach may provide a good diagnostic network (as seen in Bilbao) with real-time, short-term prognostic capabilities for a given location. The models have been built for Bilbao and are applicable only in this location. However, using the same methodology, similar results could be obtained in other environments if a good diagnostic network is available. The full paper is published in the Internet journal ‘Gate to EHS (Environmental and Health Science)’, in June 2001, and can be called up and cited by way of the DOI:http://dx.doi.org/10.1065/ehs2001.06.009     

New cytochrome P450 1B1, 1C1, 2Aa, 2Y3, and 2K genes from Chinese rare minnow (Gobiocypris rarus): Molecular characterization,basal expression and response of rare minnow CYP1s and CYP2s mRNA exposed to the AHR agonist benzo[a]pyrene

Cytochrome P450 (CYP450) genes play an important role in catalyzing oxidative metabolism of toxicants. Recently, CYP1 subfamily were discovered and reported in fish, however, little is known regarding the CYP2 isoforms in fish. In the present study, the cDNA fragments of CYP 1B1 and 1C1 and CYP2Aa, 2Y3, and 2K of rare minnow were cloned and exhibited a high amino acid sequence identity compared with their zebrafish orthologs. Basal expression showed CYP1C1 and CYP 2Aa expression were observed in all eight tissues analyzed (liver, gill, intestine, kidney, spleen, brain, skin, and muscle). CYP 1A, and 1B1 expression was found in all tissues except for muscle and skin. However, CYP 2Y3 was expressed in liver, spleen, intestine and muscle whereas CYP 2 K in liver, kidney and intestine. 4 and 100 μg L⁻¹ Benzo[a]pyrene (BaP) induced patterns showed that CYP 1A, 1B1 and 1C1 expression in liver, gill, and intestine was strongly up-regulated (p < 0.05). Furthermore, CYP 2Y3 was strongly induced in liver from BaP treatments (p < 0.05). The high induction on mRNA level of CYP1s and CYP 2Y3 by BaP could be associated with catalyzing detoxification and indicated that CYP2s may also be potential biomarker to screen AHR agonist. The high responsiveness of CYP1 and 2 genes suggested Chinese rare minnow is feasible to screen and assess pollution with AHR agonist.     

Photolysis of Enrofloxacin in aqueous systems under simulated sunlight irradiation: Kinetics, mechanism and toxicity of photolysis products

Photolysis of Enro in water was investigated under simulated sunlight irradiation using a Xenon lamp. The results showed that Enro photolysis followed apparent first-order kinetics. Increasing Enro concentration from 5.0 to 40.0 mg L⁻¹ led to the decrease of the photolysis rate constant from 1.6 × 10⁻² to 3.0 × 10⁻³ min⁻¹. Compared with the acidic and basic conditions, the photolysis rate was faster at neutral condition. Both of nitrate and humic acid can markedly decrease the photolysis rate of Enro because they can competitively absorb photons with Enro. The electron spin resonance and reactive oxygen species scavenging experiments indicated that Enro underwent self-sensitized photooxidation via OH and ¹O₂. After irradiation for 90 min, only 13.1% reduction of TOC occurred in spite of fast photolysis of 58.9% of Enro, indicating that Enro was transformed into intermediates without complete mineralization. The photolysis of Enro involved three main pathways: decarboxylation, defluorination, and piperazinyl N⁴-dealkylation. The bioluminescence inhibition rate using Vibrio fischeri increased to 67.2% at 60 min and then decreased to 56.9% at 90 min, indicative of the generation of some more toxic intermediates than Enro and then the degradation of the intermediates. The results will help us understand fundamental mechanisms of Enro photolysis and provide insight into the potential fate and transformation of Enro in surface waters.     

Mild hydrolysis of 2-trifluoromethylphenol: kinetics, mechanism and environmental relevance

2-Trifluoromethylphenol was hydrolysed in a phosphate buffer at neutral pH. At mild temperatures ranging from 34 degrees C to 69 degrees C this compound liberates consecutively fluorine anions to form salicylic acid. This process is energetically driven by the hydration of the fluorine anions. No intermediates have been detected by HPLC and (19)F-NMR and this was confirmed by computer calculations which favor the first step in the whole reaction sequence being rate-limiting. Accordingly, the reaction energy of the first dehalogenation of the trifluoromethyl anion is 28.4 kcal mol(-1) higher than for the second dehalogenation. The pseudo-first-order kinetic was determined and from an Arrhenius diagram an activation energy of E(a)=25.1 kcal mol(-1) has been estimated. At 37 degrees C and a pH of 7.4 the half-life was 6.9 h. The rate of hydrolysis was favored at higher pH and it was not influenced by oxygen, sunlight or trace elements found in natural water. The latter was shown by incubations with lake water instead of distilled water.     

UV Fourier transform measurements of tropospheric O3, NO2, SO2, benzene, and toluene.

Using the differential optical absorption spectroscopy (DOAS) technique and a Fourier transform spectrometer, NO2, SO2, O3, benzene. and toluene were measured during three measurement campaigns held in Brussels in 1995, 1996, and 1997. The O3 concentrations could be explained as the results of the local photochemistry and the dynamical properties of the mixing layer. NO2 concentrations were anti-correlated to the O3 concentrations, as expected. SO2 also showed a pronounced dependence on car traffic. Average benzene and toluene concentrations were, respectively 1.7 ppb and between 4.4 and 6.6 pbb, but high values of toluene up to 98.8 ppb were observed. SO2 concentrations and to a lesser extent, those of NO2 and 03, were dependent on the wind direction. Ozone in Brussels has been found to be influenced by the meteorological conditions prevailing in central Europe. Comparisons with other measurements have shown that 03 and SO2 data are in general in good agreement, but our NO2 concentrations seem to be generally higher.     

Absorption of NO and NO2 in caprolactam tetrabutyl ammonium halide ionic liquids

To explore environmentally benign solvents for the absorption of NO and NO2, a series of caprolactam tetrabutyl ammonium halide ionic liquids were synthesized. The solubility of NO and NO2 was measured at temperatures ranging from 298.2 to 363.2 K and atmospheric pressure, and the following trend in the solubility of NO and NO2 in ionic liquids with various halide anions was observed, respectively: F > Br > Cl and Br > Cl > F. Moreover, as the temperature increased from 308.15 to 363.15 K and the mole ratio of caprolactam increased from 2:1 to 6:1, the solubility of NO increased. Alternatively, the solubility of NO2 decreased as the temperature increased from 298.15 to 363.15 K, and the mole ratio of caprolactam increased from 2:1 to 6:1. The absorption and desorption of NO and NO2 was practically reversible in the ionic liquids, which was characterized by nuclear magnetic resonance. The method, which is at least partially reversible, offers interesting possibilities for the removal of NO and NO2.     

Absorption of NO and NO2 in Caprolactam Tetrabutyl Ammonium Halide Ionic Liquids

ABSTRACT

To explore environmentally benign solvents for the absorption of NO and NO₂, a series of caprolactam tetrabutyl ammonium halide ionic liquids were synthesized. The solubility of NO and NO₂ was measured at temperatures ranging from 298.2 to 363.2 K and atmospheric pressure, and the following trend in the solubility of NO and NO₂ in ionic liquids with various halide anions was observed, respectively: F > Br > Cl and Br > Cl > F. Moreover, as the temperature increased from 308.15 to 363.15 K and the mole ratio of caprolactam increased from 2:1 to 6:1, the solubility of NO increased. Alternatively, the solubility of NO₂ decreased as the temperature increased from 298.15 to 363.15 K, and the mole ratio of caprolactam increased from 2:1 to 6:1. The absorption and desorption of NO and NO₂ was practically reversible in the ionic liquids, which was characterized by nuclear magnetic resonance. The method, which is at least partially reversible, offers interesting possibilities for the removal of NO and NO₂.

IMPLICATIONS Basic ionic liquids with amino groups were synthesized and used to capture CO₂, SO₂, and H₂S, and to promote hydrogenation of CO₂. In this paper, the authors used caprolactam tetrabutyl ammonium halide ionic liquid (IL) as absorbing medium in which NO_x could be absorbed. NO_x desorbed from the absorbent could be efficiently reduced by right catalysts at high temperature. The absorbed NO and NO₂ gas could be desorbed at higher temperature, allowing the ionic liquids to be reused several times without loss of capability. It was believed that caprolactam tetrabutyl ammonium bromide (CPL-TBAB) ILs may be useful for NO_x removal reagent for pollution control.     

Comparison of microbial pyrene and benzo[a]pyrene mineralization in liquid medium, soil slurry, and soil

The microbial degradation of 14C-pyrene and 14C-benzo[a]pyrene by a bacterial mixed culture was studied within a mixture of the PAHs phenanthrene, anthracene, pyrene, fluoranthene, and benzo[a]pyrene as sole carbon source in the different culture systems: (i) liquid medium, (ii) soil slurry (surface and grinding influence), and (iii) soil. The fate of these two labeled compounds was followed in these systems with an emphasis on mineralization to carbon dioxide, extractability, and adsorption to humic materials and formation of unextractable residual. Mineralization showed the most obvious differences: soil slurries achieved the best results both concerning the extent of mineralization and the time required. The highest extent of pyrene mineralization (54% within 21 days) was observed in soil slurries; in liquid media, pyrene mineralization was slower, but reached approximately the same extent (54% in 150 days); in soils, mineralization reached only 36% of added pyrene after 160 days. Benzo[a]pyrene was mineralized in a mixture of PAHs in soil slurries to an extent of 34% within 70 days, whereas mineralization in liquid medium and soil occurred in the range of 5% (70 days). Mineralization of benzo[a]pyrene in sand slurries was lower compared to soil slurries (19% in sand slurries vs. 32% in soil slurries within 50 days).     

Heterogeneous Fenton degradation of persistent organic pollutants using natural chalcopyrite: effect of water matrix and catalytic mechanism

Environmental Science and Pollution Research - Natural chalcopyrite was evaluated as heterogeneous Fenton catalyst. Catalytic performance was evaluated considering different systems, catalyst...