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1.
Rates of CO 2 production in the reaction CO + OH and CO + OH + halocarbon have been used to determine rate constants for some OH + halocarbon reactions at 29.5°C relative to that of k(CO + OH) = 2.69 × 10 ?13 cm 3 molecule ?1 sec ?1. The following rate constants were obtained: k(OH + CH 3Cl) = 3.1 ± 0.8, k(OH + CH 2Cl 2) = 2.7 ± 1.0, k(OH + C 2H 5Cl) = 44.0 ± 25, k(OH + CICH 2CH 2CI) = 6.5, (<29) and k(OH + CH 3CCl 3) = 2.1 (<5.7) cm 3 molecule ?1 sec ?1 × 10 ?14. The k values, CH 2Cl 2 excepted, are in substantial agreement with determinations made in nonoxygen environments. The present results for CH 2Cl 2 are almost certainly in error due to difficulties with the competitive approach used. 相似文献
2.
The microstructure of 1/10 and 1/20 atmosphere, lean H 2S—O 2—N 2 flames is developed using the mass-spectrometric flame-sampling technique. The flame mechanism developed is in agreement with that determined from an earlier study on 1-atm H 2S flames. The formation of SO 2 appears to be primarily related to the production of SH and the ensuing oxidation steps SH + O 2 = SO + OH and SO + O 2 = SO 2 + O. While there is some question whether SO 2 formation occurs via an SO or an S 2O intermediate, the present study does not give direct support to the role of S 2O in the oxidation mechanism. However, the presence of significant quantities of free sulfur in the pre-flame zone may be indicative of S 2O formation via SO + S → S 2O, and, possibly, via the disproportionation of SO, 3SO → S 2O + SO 2. Kinetic analyses of some of the pre-flame reactions indicate an apparent activation energy of 17,300 calories/mole for the decomposition of H 2S. The actual initiation process in the flame mechanism requires further examination. The specific rate for the reaction step H 2S + O = OH + SH is given by k 6 = 1.45 × 10 15 exp ( – 6600/RT) cm 3 mole –1 sec –1, and the specific rate for the oxidation of SO, SO + O 2 = SO 2 + O, is given by k 5 = 5.2 × 10 14 exp (—19,300/RT) cm 3 mole –1 sec –1. 相似文献
3.
Using the relative rate technique, rate constants for the gas-phase reactions of hydroxyl radicals with 2-chloroethyl methyl ether ( k1), 2-chloroethyl ethyl ether ( k2) and bis(2-chloroethyl) ether ( k3) have been measured. Experiments were carried out at (298 ± 2) K and atmospheric pressure using synthetic air as bath gas. Using n-pentane and n-heptane as reference compounds, the following rate constants were derived: k1 = (5.2 ± 1.2) × 10 ?12, k2 = (8.3 ± 1.9) × 10 ?12 and k3 = (7.6 ± 1.9) × 10 ?12, in units of cm 3 molecule ?1 s ?1. This is the first experimental determination of k2 and k3 under atmospheric pressure. The rate constants obtained are compared with previous literature data and the observed trends in the relative rates of reaction of hydroxyl radicals with the ethers studied are discussed. The atmospheric implications of the results are considered in terms of lifetimes and fates of the hydrochloroethers studied. 相似文献
4.
A novel dual coagulant system of polyaluminum chloride sulfate (PACS) and polydiallyldimethylammonium chloride (PDADMAC) was used to treat natural algae-laden water from Meiliang Gulf, Lake Taihu. PACS (Al n(OH) mCl 3n-m-2k(SO 4) k) has a mass ratio of 10 %, a SO 4 2?/Al 3 + mole ratio of 0.0664, and an OH/Al mole ratio of 2. The PDADMAC ([C 8H 16NCl] m) has a MW which ranges from 5?×?10 5 to 20?×?10 5 Da. The variations of contaminants in water samples during treatments were estimated in the form of principal component analysis (PCA) factor scores and conventional variables (turbidity, DOC, etc.). Parallel factor analysis determined four chromophoric dissolved organic matters (CDOM) components, and PCA identified four integrated principle factors. PCA factor 1 had significant correlations with chlorophyll-a ( r?=?0.718), protein-like CDOM C1 (0.689), and C2 (0.756). Factor 2 correlated with UV 254 (0.672), humic-like CDOM component C3 (0.716), and C4 (0.758). Factors 3 and 4 had correlations with NH 3-N (0.748) and T-P (0.769), respectively. The variations of PCA factors scores revealed that PACS contributed less aluminum dissolution than PAC to obtain equivalent removal efficiency of contaminants. This might be due to the high cationic charge and pre-hydrolyzation of PACS. Compared with PACS coagulation (20 mg L ?1), the removal of PCA factors 1, 2, and 4 increased 45, 33, and 12 %, respectively, in combined PACS–PDADMAC treatment (0.8 mg L ?1?+?20 mg L ?1). Since PAC contained more Al (0.053 g/1 g) than PACS (0.028 g/1 g), the results indicated that PACS contributed less Al dissolution into the water to obtain equivalent removal efficiency. 相似文献
5.
The gas phase thermal decomposition rates of the C 1 and C 2-substituted peroxyacyl nitrates (RC(O)OONO 2), PAN (R = CH 3), PPN (R = C 2H 5) and vinyl-PAN (R = CH 2 = CH-) have been measured at ambient temperature (288 - 299 K) and 1 atm. of air. Our results for PAN (k = A exp (-E a/RT), log 10 (A, s -1) = 16.2 ± 1.6, E a = 26.9 ± 2.1 kcal / mol, k 298 = 3.0 × 10 ?4S ?1) are consistent with literature data. Thermal decomposition rates for PPN and vinyl-PAN are similar to that for PAN, with k 298 = 3.0 × 10 ?4S ?1 for PAN, 3.4 × 10 ?4S ?1 for PPN and 3.0 × 10 ?4S ?1 for vinyl-PAN. Implications for the atmospheric persistence of PPN and vinyl-PAN as compared to that of PAN are briefly discussed. 相似文献
6.
Acrylate esters are α,β-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon. These compounds are widely used in the production of plastics and resins. Atmospheric degradation processes of these compounds are currently not well understood. The kinetics of the gas phase reactions of OH radicals with methyl 3-methylacrylate and methyl 3,3-dimethylacrylate were determined using the relative rate technique in a 50 L Pyrex photoreactor using in situ FTIR spectroscopy at room temperature (298?±?2 K) and atmospheric pressure (708?±?8 Torr) with air as the bath gas. Rate coefficients obtained were (in units cm 3 molecule ?1 s ?1): (3.27?±?0.33)?×?10 ?11 and (4.43?±?0.42)?×?10 ?11, for CH 3CH═CHC(O)OCH 3 and (CH 3) 2CH═CHC(O)OCH 3, respectively. The same technique was used to study the gas phase reactions of hexyl acrylate and ethyl hexyl acrylate with OH radicals and Cl atoms. In the experiments with Cl, N 2 and air were used as the bath gases. The following rate coefficients were obtained (in cm 3 molecule ?1 s ?1): k 3 (CH 2═CHC(O)O(CH 2) 5CH 3?+?Cl)?=?(3.31?±?0.31)?×?10 ?10, k 4(CH 2═CHC(O)OCH 2CH(CH 2CH 3)(CH 2) 3CH 3?+?Cl)?=?(3.46?±?0.31)?×?10 ?10, k 5(CH 2═CHC(O)O(CH 2) 5CH 3?+?OH)?=?(2.28?±?0.23)?×?10 ?11, and k 6(CH 2═CHC(O)OCH 2CH(CH 2CH 3)(CH 2) 3CH 3?+?OH)?=?(2.74?±?0.26)?×?10 ?11. The reactivity increased with the number of methyl substituents on the double bond and with the chain length of the alkyl group in –C(O)OR. Estimations of the atmospheric lifetimes clearly indicate that the dominant atmospheric loss process for these compounds is their daytime reaction with the hydroxyl radical. In coastal areas and in some polluted environments, Cl atom-initiated degradation of these compounds can be significant, if not dominant. Maximum Incremental Reactivity (MIR) index and global warming potential (GWP) were also calculated, and it was concluded that these compounds have significant MIR values, but they do not influence global warming. 相似文献
7.
Rate coefficients for the gas-phase reactions of Cl atoms with a series of unsaturated esters CH 2C(CH 3)C(O)OCH 3 (MMA), CH 2CHC(O)OCH 3 (MAC) and CH 2C(CH 3)C(O)O(CH 2) 3CH 3 (BMA) have been measured as a function of temperature by the relative technique in an environmental chamber with in situ FTIR detection of reactants. The rate coefficients obtained at 298 K in one atmosphere of nitrogen or synthetic air using propene, isobutene and 1,3-butadiene as reference hydrocarbons were (in units of 10 ?10 cm 3 molecule ?1 s ?1) as follows: k(Cl+MMA) = 2.82 ± 0.93, k(Cl+MAC) = 2.04 ± 0.54 and k(Cl+BMA) = 3.60 ± 0.87. The kinetic data obtained over the temperature range 287–313 K were used to derive the following Arrhenius expressions (in units of cm 3 molecule ?1 s ?1): k(Cl+MMA) = (13.9 ± 7.8) × 10 ?15 exp[(2904 ± 420)/ T], k(Cl+MAC) = (0.4 ± 0.2) × 10 ?15 exp[(3884 ± 879)/ T], k(Cl+BMA) = (0.98 ± 0.42) × 10 ?15 exp[(3779 ± 850)/ T]. All the rate coefficients display a slight negative temperature dependence which points to the importance of the reversibility of the addition mechanism for these reactions. This work constitutes the first kinetic and temperature dependence study of the reactions cited above.An analysis of the available rates of addition of Cl atoms and OH radicals to the double bond of alkenes and unsaturated and oxygenated volatile organic compounds (VOCs) at 298 K has shown that they can be related by the expression: log kOH = 1.09 log kCl ? 0.10. In addition, a correlation between the reactivity of unsaturated VOCs toward OH radicals and Cl atoms and the HOMO of the unsaturated VOC is presented. Tropospheric implications of the results are also discussed. 相似文献
8.
Particulate matter, including coarse particles (PM 2.5–10, aerodynamic diameter of particle between 2.5 and 10 μm) and fine particles (PM 2.5, aerodynamic diameter of particle lower than 2.5 μm) and their compositions, including elemental carbon, organic carbon, and 11 water-soluble ionic species, and elements, were measured in a tunnel study. A comparison of the six-hour average of light-duty vehicle (LDV) flow of the two sampling periods showed that the peak hours over the weekend were higher than those on weekdays. However, the flow of heavy-duty vehicles (HDVs) on the weekdays was significant higher than that during the weekend in this study. EC and OC content were 49% for PM 2.5–10 and 47% for PM 2.5 in the tunnel center. EC content was higher than OC content in PM 2.5–10, but EC was about 2.3 times OC for PM 2.5. Sulfate, nitrate, ammonium were the main species for PM 2.5–10 and PM 2.5. The element contents of Na, Al, Ca, Fe and K were over 0.8 μg m ?3 in PM 2.5–10 and PM 2.5. In addition, the concentrations of S, Ba, Pb, and Zn were higher than 0.1 μg m ?3 for PM 2.5–10 and PM 2.5. The emission factors of PM 2.5–10 and PM 2.5 were 18 ± 6.5 and 39 ± 11 mg km ?1-vehicle, respectively. The emission factors of EC/OC were 3.6/2.7 mg km ?1-vehicle for PM 2.5–10 and 15/4.7 mg km ?1-vehicle for PM 2.5 Furthermore, the emission factors of water-soluble ions were 0.028(Mg 2+)–0.81(SO 42?) and 0.027(NO 2?)–0.97(SO 42?) mg km ?1-vehicle for PM 2.5–10 and PM 2.5, respectively. Elemental emission factors were 0.003(V)–1.6(Fe) and 0.001(Cd)–1.05(Na) mg km ?1-vehicle for PM 2.5–10 and PM 2.5, respectively. 相似文献
9.
The purpose of this study was to examine the kinetics and equilibrium properties of freshwater algae with Cu 2+. This was a model system to explore using algae as biosensors for water quality. Methods included making luminescence measurements (fluorescence) and copper ion-selective electrode (CuISE) measurements vs. time to obtain kinetic data. Results were analyzed using a pseudo-first-order model to calculate the rate constants of Cu 2+ uptake by algae: k p(Cu?Calgae)?=?0.0025?±?0.0006?s ?1 by CuISE and k p(Cu?Calgae)?=?0.0034?±?0.0011?s ?1 by luminescence. The binding constant of Cu?Calgae, K Cu?Calgae, was 1.62?±?0.07?×?10 7?M ?1. Fluorescence results analyzed using the Stern?CVolmer relationship indicate that algae have two types of binding sites of which only one appears to affect quenching. The fluorescence-based method was found to be able to detect the reaction of algae with Cu 2+ quickly and at a detection limit of 0.1?mg?L ?1. 相似文献
10.
Absolute rate coefficients for the gas-phase reactions of OH radical with 3-methylbutanal ( k1), trans-2-methyl-2-butenal ( k2), and 3-methyl-2-butenal ( k3) have been obtained with the pulsed laser photolysis/laser-induced fluorescence technique. Gas-phase concentration of aldehydes was measured by UV absorption spectroscopy at 185 nm. Experiments were performed over the temperature range of 263–353 K at total pressures of helium between 46.2 and 100 Torr. No pressure dependence of all ki ( i = 1–3) was observed at all temperatures. In contrast, a negative temperature dependence of ki ( i.e., ki increases when temperature decreases) was observed in that T range. The resulting Arrhenius expressions (±2 σ) are: k1( T) = (5.8 ± 1.7)×10 ?12 exp{(499 ± 94)/ T} cm 3 molecule ?1 s ?1, k2( T)=(6.9 ± 0.9)×10 ?12 exp{(526 ± 42)/ T} cm 3 molecule ?1 s ?1, k3( T)=(5.6 ± 1.2)×10 ?12 exp{(666 ± 54)/ T} cm 3 molecule ?1 s ?1.The tropospheric lifetimes derived from the above OH-reactivity trend are estimated to be higher for 3-methylbutanal than those for the unsaturated aldehydes. A comparison of the tropospheric removal of these aldehydes by OH radicals with other homogeneous degradation routes leads to the conclusion that this reaction can be the main homogeneous removal pathway. However, photolysis of these aldehydes in the actinic region ( λ > 290 nm) could play an important role along the troposphere, particularly for 3-methyl-2-butenal. This process could compete with the OH reaction for 3-methylbutanal or be negligible for trans-2-methyl-2-butenal in the troposphere. 相似文献
11.
Understanding the removal mechanisms and kinetics of trace tetracycline by activated sludge is critical to both evaluation of tetracycline elimination in sewage treatment plants and risk assessment/management of tetracycline released to soil environment due to the application of biosolids as fertilizer. Adsorption is found to be the primary removal mechanism while biodegradation, volatilization, and hydrolysis can be ignored in this study. Adsorption kinetics was well described by pseudo-second-order model. Faster adsorption rate ( k 2?=?2.04?×?10 ?2?g?min ?1?μg ?1) and greater adsorption capacity ( q e?=?38.8 μg?g ?1) were found in activated sludge treating freshwater sewage. Different adsorption rate and adsorption capacity resulted from chemical properties of sewage matrix rather than activated sludge surface characteristics. The decrease of tetracycline adsorption in saline sewage was mainly due to Mg 2+ which significantly reduced adsorption distribution coefficient ( K d) from 12,990?±?260 to 4,690?±?180 L?kg ?1. Species-specific adsorption distribution coefficients followed the order of $ K_{\mathrm{d}}^{{ + 00}} \gg K_{\mathrm{d}}^{{ + - 0}} > K_{\mathrm{d}}^{{ + - - }} $ . Contribution of zwitterionic tetracycline to the overall adsorption was >90 % in the actual pH range in aeration tank. Adsorption of tetracycline in a wide range of temperature (10 to 35 °C) followed the Freundlich adsorption isotherm well. 相似文献
12.
TSP and PM 2.5 samples were collected at Xi'an, China during dust storms (DSs) and several types of pollution events, including haze, biomass burning, and firework displays. Aerosol mass concentrations were up to 2 times higher during the particulate matter (PM) events than on normal days (NDs), and all types of PM led to decreased visibility. Water-soluble ions (Na +, NH 4+, K +, Mg 2+, Ca 2+, F ?, Cl ?, NO 3?, and SO 42?). were major aerosol components during the pollution episodes, but their concentrations were lower during DSs. NH 4+, K +, F ?, Cl ?, NO 3?, and SO 42? were more abundant in PM 2.5 than TSP but the opposite was true for Mg 2+ and Ca 2+. PM collected on hazy days was enriched with secondary species (NH 4+, NO 3?, and SO 42) while PM from straw combustion showed high K + and Cl ?. Firework displays caused increases in K + and also enrichments of NO 3? relative to SO 42?. During DSs, the concentrations of secondary aerosol components were low, but Ca 2+ was abundant. Ion balance calculations indicate that PM from haze and straw combustion was acidic while the DSs samples were alkaline and the fireworks' PM was close to neutral. Ion ratios (SO 42?/K +, NO 3?/SO 42?, and Cl ?/K +) proved effective as indicators for different pollution episodes. 相似文献
13.
In addition to direct photolysis studies, in this work the second-order reaction rate constants of pesticides imidacloprid (IMD) and ametryn (AMT) with hydroxyl radicals (HO●), singlet oxygen (1O2), and triplet excited states of chromophoric dissolved organic matter (3CDOM*) were determined by kinetic competition under sunlight. IMD and AMT exhibited low photolysis quantum yields: (1.23?±?0.07)?×?10–2 and (7.99?±?1.61)?×?10–3 mol Einstein?1, respectively. In contrast, reactions with HO● radicals and 3CDOM* dominate their degradation, with 1O2 exhibiting rates three to five orders of magnitude lower. The values of kIMD,HO● and kAMT,HO● were (3.51?±?0.06)?×?109 and (4.97?±?0.37)?×?109 L mol?1 s?1, respectively, while different rate constants were obtained using anthraquinone-2-sulfonate (AQ2S) or 4-carboxybenzophenone (CBBP) as CDOM proxies. For IMD this difference was significant, with kIMD,3AQ2S*?=?(1.02?±?0.08)?×?109 L mol?1 s?1 and kIMD,3CBBP*?=?(3.17?±?0.14)?×?108 L mol?1 s?1; on the contrary, the values found for AMT are close, kAMT,3AQ2S*?=?(8.13?±?0.35)?×?108 L mol?1 s?1 and kAMT,3CBBP*?=?(7.75?±?0.80)?×?108 L mol?1 s?1. Based on these results, mathematical simulations performed with the APEX model for typical levels of water constituents (NO3?, NO2?, CO32?, TOC, pH) indicate that the half-lives of these pesticides should vary between 24.1 and 18.8 days in the waters of the Paranapanema River (São Paulo, Brazil), which can therefore be impacted by intensive agricultural activity in the region. 相似文献
14.
In August 2012, eight rainwater samples were collected and analyzed for pH and metal ions, viz., iron, copper, and manganese. The pH was within the range 6.84–7.65. The rate of oxidation of dissolved sulfur dioxide was determined using these rainwater samples as reaction medium. Kinetics was defined by the rate law: ? d[S(IV)]/ dt = R o = k o[S(IV)]], where k o is the first-order rate constant and R o is the rate of the reaction. The effect of two volatile organic compounds—ethanol and 2-butanol—was examined and found to inhibit the oxidation as defined by the rate law: k obs = k o/(1 + B [Inh]), where k obs is the first-order rate constant in the presence of the inhibitor, [Inh] is the concentration of the inhibitor, and B is the inhibitor parameter—an empirical constant. In the pH range of collected rainwater samples, the values of first-order rate constants ranged from 3.1?×?10 ?5 to 1.5?×?10 ?4 s ?1 at 25 °C. The values of inhibition parameter were found to be (5.99?±?3.91?×?10 4) (ethanol) and (3.95?±?2.36)?×?10 4 (2-butanol) at 25 °C. 相似文献
15.
Smog chamber/FTIR techniques were used to study the relative reactivity of OH radicals with methanol, ethanol, phenol, C 2H 4, C 2H 2, and p-xylene in 750 Torr of air diluent at 296±2 K. Experiments were performed with, and without, 500–8000 μg m −3 (4000–50 000 μm 2 cm −3 surface area per volume) of NaCl, (NH 4) 2SO 4 or NH 4NO 3 aerosol. In contrast to the recent findings of Oh and Andino (Atmospheric Environment 34 (2000) 2901, 36 (2002) 149; International Journal of Chemical Kinetics 33 (2001) 422) there was no discernable effect of aerosol on the rate of loss of the organic compounds via reaction with OH radicals. Gas kinetic theory arguments cast doubt upon the findings of Oh and Andino. The available data suggest that the answer to the title question is “No”. As part of this work the rate constants for reactions of OH radicals with methanol, ethanol, and phenol in 750 Torr of air at 296 K were determined to be: kOH+CH3OH=(8.12±0.54)×10 −13, kOH+C2H5OH=(3.47±0.32)×10 −12 and kOH+phenol=(3.27±0.31)×10 −11 cm 3 molecule −1 s −1. 相似文献
16.
To further understand the role of substrates on the heterogeneous reactions of polycyclic aromatic hydrocarbons, the reactions of ozone with anthracene adsorbed on different mineral oxides (SiO 2, α-Al 2O 3 and α-Fe 2O 3) and on Teflon disc were investigated in dark at 20 °C. No reaction between ozone and anthracene on Teflon disc was observed when the ozone concentration was ~1.18 × 10 14 molecules cm ?3. The reactions on mineral oxides exhibited pseudo-first-order kinetics for anthracene loss, and the pseudo-first-order rate constant ( k1,obs) displayed a Langmuir–Hinshelwood dependence on the gas-phase ozone concentration. The adsorption equilibrium constants for ozone ( KO3) on SiO 2-1, SiO 2-2, α-Al 2O 3 and α-Fe 2O 3 were (0.81 ± 0.26) × 10 ?15 cm 3, (2.83 ± 1.17) × 10 ?15 cm 3, (2.48 ± 0.77) × 10 ?15 cm 3 and (1.66 ± 0.45) × 10 ?15 cm 3, respectively; and the maximum pseudo-first-order rate constant ( k1,max) on these oxides were (0.385 ± 0.058) s ?1, (0.101 ± 0.0138) s ?1, (0.0676 ± 0.0086) s ?1 and (0.0457 ± 0.004) s ?1, respectively. Anthraquinone was identified as the main surface product of anthracene reacted with ozone. Comparison with previous research and the results obtained in this study suggest that the reactivity of anthracene with ozone and the lifetimes of anthracene adsorbed on mineral dust in the atmosphere are determined by the nature of the substrate. 相似文献
17.
The homogeneous gas phase hydrolysis kinetics of the above compounds has been investigated in the 470° to 620°K temperature range. The following biomolecular rate constants were obtained: k(CCl 3COCl) = 2.54 × 10 6 exp (?18,350 ± 1750)/RT, k(CClH 2COCl) = 1.14 × 10 8 exp (?22,630 ± 780)/RT, and fr(COCl 2) = 9192 exp (?14,200 ± 2100)/RT liter mole ?1 sec ?1. Experimental difficulties prevented data being obtained for CHCl 2COCl. The half lives of these species with respect to homogeneous gas phase hydrolysis in the atmosphere have been estimated and it is concluded that this is not an efficient conversion process. Heterogeneous hydrolysis by water droplets may be a more efficient atmospheric scavenging process for these compounds. 相似文献
18.
Sulfur dioxide (SO 2) is considered as a main air pollutant in industrialized areas that can damage vegetation. In the present study, we investigated how exposure to SO 2 and foliar application of iron (Fe) would affect certain physiological characteristics of Plantago major. The plant seedlings exposed or unexposed to SO 2 (3900 μg m ?3) were non-supplemented or supplemented with Fe (3 g L ?1) as foliar spray. Plants were exposed to SO 2 for 6 weeks in 100 × 70 × 70 cm chambers. Fumigation of plants with SO 2 was performed for 3 h daily for 3 days per week (alternate day). Lower leaf Fe concentration in the plants exposed to SO 2 at no added Fe treatment was accompanied with incidence of chlorosis symptoms and reduced chlorophyll concentration. No visible chlorotic symptoms were observed on the SO 2-exposed plants supplied with Fe that accumulated higher Fe in their leaves. Both at with and without added Fe treatments, catalase (CAT) and peroxidase (POD) activity was higher in the plants fumigated with SO 2 in comparison with those non-fumigated with SO 2. Foliar application of Fe was also effective in increasing activity of antioxidant enzymes CAT and POD. Exposure to SO 2 led to reduced cellulose but enhanced lignin content of plant leaf cell wall. The results obtained showed that foliar application of Fe was effective in reducing the effects of exposure to SO 2 on cell wall composition. In contrast to SO 2, application of Fe increased cellulose while decreased lignin content of the leaf cell wall. This might be due to reduced oxidative stress induced by SO 2 in plants supplied with Fe compared with those unsupplied with Fe. 相似文献
19.
The increasing use of nanoparticles (NPs) worldwide has raised some concerns about their impact on the environment. The aim of the study was to assess the toxicity of metal oxide nanoparticles, singly or combined, in a freshwater fish ( Carassius auratus). The fish were exposed for 7, 14, and 21 days to different concentrations of NPs (10 μg Al 2O 3.L ?1, 10 μg ZnO.L ?1, 10 μg Al 2O 3.L ?1 plus 10 μg ZnO.L ?1, 100 μg Al 2O 3.L ?1, 100 μg ZnO.L ?1, and 100 μg Al 2O 3.L ?1 plus 100 μg ZnO.L ?1). At the end of each exposure period, antioxidant enzyme activity (catalase, glutathione-S-transferase, and superoxide dismutase), lipid peroxidation, and histopathology were assessed in the gills and livers of C. auratus. The results show an increase in catalase (CAT) and superoxide dismutase (SOD) activity in the gills and livers of fish, especially after 14 days of exposure to single and combined NPs, followed by a reduction at 21 days. An increase in glutathione S-transferase (GST) was observed in gills after 7 days for all tested NP concentrations (single and combined); while in livers, a significant increase was determined after 14 days of exposure to 100 μg.L ?1 of both single ZnO and Al 2O 3 NPs. Lipid peroxidation (LPO) significantly increased in gills after 7 days of exposure to 100 μg.L ?1 Al 2O 3 NPs (single or combined). In livers, LPO increased significantly after 7 days of exposure to all tested concentrations of both single ZnO and Al 2O 3 (except for 10 μg Al 2O 3.L ?1), and after 14 days of exposure to ZnO (10 and 100 μg.L ?1) and Al 2O 3 (100 μg.L ?1) . The results from histological observations suggest that exposure to metal oxide NPs affected both livers and gills, presenting alterations such as gill hyperplasia and liver degeneration. However, the most pronounced effects were found in gills. In general, this study shows that the tested NPs, single or combined, are capable of causing sub-lethal effects on C. auratus, but when combined, NPs seem to be slightly more toxic than when added alone. 相似文献
20.
In recent decades, biodegradation has been considered a promising and eco-friendly way to eliminate organophosphorus pesticides (OPs) from the environment. To enrich current biodegrading-enzyme resources, an alkaline phosphatase (AP3) from Bacillus amyloliquefaciens YP6 was characterized and utilized to test the potential for new applications in the biodegradation of five broad-spectrum OPs. Characterization of AP3 demonstrated that activity was optimal at 40?°C and pH 10.3. The activity of AP3 was enhanced by Mg 2+, Ca 2+, and Cu 2+, and strongly inhibited by Mn 2+, EDTA, and L-Cys. Compared to disodium phenyl phosphate, p-nitrophenyl phosphate (pNPP) was more suitable to AP3, and the Vm, Km, kcat, kcat/ Km values of AP3 for pNPP were 4,033?U mg ?1, 12.2?mmol L ?1, 3.3?×?10 6 s ?1, and 2.7?×?10 8 s ?1mol ?1L, respectively. Degradation of the five OPs, which included chlorpyrifos, dichlorvos, dipterex, phoxim, and triazophos, was 18.7%, 53.0%, 5.5%, 68.3%, and 96.3%, respectively, after treatment with AP3 for 1?h. After treatment of the OP for 8?h, AP3 activities remained more than 80%, with the exception of phoxim. It can be postulated that AP3 may have a broad OP-degradation ability and could possibly provide excellent potential for biodegradation and bioremediation in polluted ecosystems. 相似文献
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