Fenton (H2O2/Fe) reaction involved in Penicillium sp. culture for DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane)] degradation

The purpose of this work was to demonstrate that a Fenton (H₂O₂/Fe) reaction was involved in DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane)] degradation in a culture of Penicillium sp. spiked with FeSO₄. A commercial DDT mixture (10% DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], 30% o,p-DDT and 60% of p,p′ -DDT) of 10 mg L^{? 1} was used. Hydrogen peroxide (H₂O₂), tartaric acid and oxalic acid were identified at 18 h in culture media, with and without added DDT; this correlated positively with lowering of pH from 5.8 to 2.7. Lower concentrations of oxalic acid and H₂O₂ (7.9 and 52.6 mg L^{? 1}, respectively) occurred in media with DDT at 30 h, in comparison to that one without DDT mixture (27.9 and 65.3 mg L^{? 1}, respectively), at this time there was maximum degradation (87.7, 91.7 and 94.2%) for DDE, o,p-DDT and p,p′-DDT, respectively. We propose that the degradation of the DDT mixture by Penicillium sp. was through a Fenton reaction (H₂O₂/Fe) under acidic conditions produced in situ during the fungal culture amended with FeSO₄.     

The Cl-initiated oxidation of CH3C(O)OCH=CH2, CH3C(O)OCH2CH=CH2, and CH2=CHC(O)O(CH2)3CH3 in the troposphere

Background, aim, and scope  

Unsaturated esters are emitted to the atmosphere from biogenic and anthropogenic sources, including those from the polymer industry. Little information exists concerning the atmospheric degradation of unsaturated esters, which are mainly initiated by OH radicals. Limited information is available on the degradation of alkenes by Cl atoms and almost no data exists for the reactions of unsaturated esters with Cl atoms. This data is necessary to assess the impact of such reactions in maritime environments where, under circumstances, OH radical- and Cl atom-initiated oxidation of the compounds can be important. Rate coefficients for the reactions of chlorine atoms with vinyl acetate, allyl acetate, and n-butyl acrylate have been determined at 298 ± 3 K and atmospheric pressure. The kinetic data have been used in combination with that for structurally similar compounds to infer the kinetic contributions from the possible reaction channels to the overall reaction rate.     

Biliary PAH metabolites, EROD activity and DNA damage in dab (Limanda limanda) from Seine Estuary (France)

The Seine Estuary is well known to be widely contaminated by organic pollutants and especially by polycyclic aromatic hydrocarbons (PAHs). Fish are known to metabolize PAHs, leading to different toxic effects at both cellular and sub-cellular levels. In this work, we studied the relationships between the 7-ethoxyresorufin-O-deethylase (EROD) activity in the liver, the level of DNA strand breaks in blood cells and the concentration of PAH metabolites in the bile of the sentinel flatfish species Limanda limanda. Muscle and liver samples were analysed for parent PAH levels. Female and male dabs of two size classes (juveniles and adults) were collected by trawling in two sites with different degrees of pollution during March and September 2005 and 2006. Significant effects of sex, age, site and season were demonstrated on EROD activity and the level of strand breaks. Parent PAH concentrations in dabs did not allow discriminating of the two sampling sites. However, for PAH metabolites, significant differences were observed with sites and seasons. Dabs collected at the mouth of the estuary appeared to be the most impacted when looking at the results obtained with the three selected markers. The significant correlations observed between the level of PAH metabolites and the level of DNA lesions showed the importance of a combined analysis of chemical and biochemical markers to correctly assess the contribution of chemical contamination to the toxic effects measured in situ in fish.     

Comparative study of H(2)O(2) and O3 effects on radiation treatment of TCE and PCE

The effects of H(2)O(2) and O(3) on the decomposition of trichloroethylene (TCE) and perchloroethylene (PCE) by gamma-rays (gamma-rays) were investigated in this work. The combined gamma-rays/O(3) process showed a synergistic effect and enhanced the removal of TCE and PCE compared with gamma-rays alone, but, the gamma-rays/H(2)O(2) process did not increase the removal. This interesting result was successfully identified by an electron paramagnetic resonance spectroscopy/spin-trapping method that can quantify hydroxyl radicals, which is directly related to the efficiency of TCE and PCE decomposition. For gamma-rays/H(2)O(2) system, there was no difference of hydroxyl radical production between gamma-rays alone and gamma-rays/H(2)O(2). This indicates gamma-rays cannot activate H(2)O(2) to produce hydroxyl radicals and this causes no increase of TCE and PCE removals. To the contrary, the production of hydroxyl radicals was obviously increased in the case of gamma-rays/O(3) process. This suggests additional hydroxyl radicals are produced from the reaction of O(3) with the irradiation products of water such as hydrated electrons, hydrogen atoms, etc. and this accelerates the removal of TCE and PCE.     

Photooxidation of naphthalenesulfonic acids: comparison between processes based on O(3), O(3)/activated carbon and UV/H(2)O(2)

The aim of the present study was to analyze and compare the efficacy of UV photodegradation with that of different advanced oxidation processes (O(3), UV/H(2)O(2), O(3)/activated carbon) in the degradation of naphthalenesulfonic acids from aqueous solution and to investigate the kinetics and the mechanism involved in these processes. Results obtained showed that photodegradation with UV radiation (254 nm) of 1-naphthalenesulfonic, 1,5-naphthalendisulfonic and 1,3,6-naphthalentrisulfonic acids is not effective. Presence of duroquinone and 4-carboxybenzophenone during UV irradiation (308-410 nm) of the naphthalenesulfonic acids increased the photodegradation rate. Addition of H(2)O(2) during irradiation of naphthalenesulfonic acids accelerated their elimination, due to the generation of ()OH radicals in the medium. Comparison between UV photodegradation 254 m and the advanced oxidation processes (O(3), O(3)/activated carbon and UV/H(2)O(2)) showed the low-efficacy of the former in the degradation of these compounds from aqueous medium. Thus, among the systems studied, those based on the use of UV/H(2)O(2) and O(3)/activated carbon were the most effective in the oxidation of these contaminants from the medium. This is because of the high-reactivity of naphthalenesulfonic acids with the *OH radicals generated by these two systems. This was confirmed by the values of the reaction rate constant of *OH radicals with these compounds k(OH), obtained by competitive kinetics (5.7 x 10(9) M(-1) s(-1), 5.2 x 10(9) M(-1) s(-1) and 3.7 x 10(9) M(-1) s(-1) for NS, NDS and NTS, respectively).     

Hydroxyl (OH) radical production rates in snowpacks from photolysis of hydrogen peroxide (H2O2) and nitrate (NO3−)

Atmospheric chemistry directly above snowpacks is strongly influenced by ultraviolet (UV) radiation initiated emissions of chemicals from the snowpack. The emission of gases from the snowpack to the atmosphere is in part due to chemical reactions between hydroxyl radical, OH (produced from photolysis of hydrogen peroxide (H₂O₂) or nitrate (NO₃⁻)) and impurities in the snowpack. The work presented here is a radiative-transfer modelling study to calculate the depth-integrated production rates of hydroxyl radical from the photolysis of hydrogen peroxide and nitrate anion in snow for four different snowpacks and for solar zenith angles 30°–90°. This work also demonstrates the importance of hydrogen peroxide photolysis to produce hydroxyl radical relative to nitrate photolysis with (a) different snowpacks, (b) different ozone column depths, and (c) snowpack depths. The importance of hydrogen peroxide photolysis over nitrate photolysis for hydroxyl radical production increases with increasing depth in snowpack, column ozone depth, and solar zenith angle. With a solar zenith angle of 60° the production of hydroxyl radical from hydrogen peroxide photolysis accounts for 91–99% of all hydroxyl radical production from hydrogen peroxide and nitrate photolysis.     

Degradation of 2,7-dichlorodibenzo-p-dioxin by Fe(3+)-H(2)O(2) mixed reagent

Fe(3+)-H(2)O(2) mixed reagent, but not Fe(2+)-H(2)O(2), was found to be capable of degrading 2,7-dichlorodibenzo-p-dioxin (DCDD). A reaction mixture of FeCl(3) (8 mM) and H(2)O(2) (1%) caused approximately 50% degradation within 6 h and >90% degradation within 24 h at 27 degrees C. Increasing the temperature remarkably stimulated degradation: at 70 degrees C, approximately 100% degradation was achieved within 15 min. When DCDD-treated model soil (5 micrograms/g) was conducted, approximately 100% of the DCDD was degraded within 30 min at 70 degrees C (both reagents were added every 10 min). These results suggest that Fe(3+)-H(2)O(2) mixed reagent may be a new tool for combating persistent environmental pollutants such as dioxins and polychlorinated biphenyls.     

A novel application of H2O2-Fe(II) process for arsenate removal from synthetic acid mine drainage (AMD) water

Batch experiments were carried out to investigate the influences of H₂O₂/Fe(II) molar ratio, pH, sequence of pH adjustment, initial As(V) concentration, and interfering ions on As(V) removal in H₂O₂-Fe(II) process from synthetic acid mine drainage (AMD). The optimum H₂O₂/Fe(II) molar ratio was one for arsenate removal over the pH range of 4-7. Arsenate removal at pH 3 was poor even at high Fe(II) dosage due to the high solubility of Fe(III) formed in situ. With the increase of Fe(II) dosage, arsenate removal increased progressively before a plateau was reached at pH 5 as arsenate concentration varied from 0.05 to 2.0 mg L⁻¹. However, arsenate removal was negligible at Fe/As molar ratio <3 and then experienced a striking increase before a plateau was reached at pH 7 and arsenate concentration ≥1.0 mg L⁻¹. The co-occurring ions exerted no significant effect on arsenate removal at pH 5. The experimental results with synthetic AMD revealed that this method is highly selective for arsenate removal and the co-occurring ions either improved arsenate removal or slightly depressed arsenate removal at pH 5-7. The extended X-ray absorption fine structure (EXAFS) derived As-Fe length, 3.27-3.30 Å, indicated that arsenate was removed by forming bidentate-binuclear complexes with FeO(OH) octahydra. The economic analysis revealed that the cost of the H₂O₂-Fe(II) process was only 17-32% of that of conventional Fe(III) coagulation process to achieve arsenate concentration below 10 μg L⁻¹ in treated solution. The results suggested that the H₂O₂-Fe(II) process is an efficient, economical, selective and practical method for arsenate removal from AMD.     

Seasonal evolutions of ozone (O3) and its nitrogen precursors (NO, NO2) in urban Sfax (Tunisia)

Seasonal evolution of ozone (O3) and its nitrogen precursors (NO, NO2) in downtown Sfax (Tunisia) was monitored. Nitrogen oxides are shown to be closely related to local vehicle sources. Seasonal ozone levels, however, are shown to be dependent on regional meteorological conditions. High ozone levels are due to the effect of anticyclones and stratosphere intrusions (cut-off lows). Low levels are associated with cyclonic conditions of small vertical range of motion. Other than these particular conditions, ozone levels are shown to be relatively higher in fall and winter seasons, characterised by a very steady atmosphere. Overall, the examined meteorological conditions, the ozone concentrations observed in downtown Sfax are characterised by clear day/night cycles, which can be explained by the significant ventilation of the region.     

Simazine removal from water in a continuous bubble column by O3 and O3/H2O2.

Simazine, [2-chloro, 4,6-bis(ethylamino)-1,3,5-s-triazine], a common herbicide found in surface and ground water has been ozonized in continuous flow mode. Typical operating variables in ozonation processes have been investigated. Thus, the ozone dose fed to the system exerted a positive effect, while the gas flow rate did not influence the efficiency of the process provided ozone mass flow rate was kept constant. Increasing the pH led to a higher extension of the free radical degradation of simazine and, therefore, to a higher efficiency of the process. Also, addition of free radical promoters, i.e. hydrogen peroxide, did result in a significant improvement of the simazine removal rate. A first approach to process economy showed the system ozone/hydrogen peroxide as the most advantageous in terms of electrical energy requirements.     

Sulphur-containing metabolites of the fungicides pentachloronitrobenzene (PCNB) and hexachlorobenzene (HCB) I. Syntheses

Syntheses of sulphur-containing metabolites of the fungicides pentachloronitrobenzene and hexachlorobenzene are described.     

The photodecomposition of fenitrothion [0, 0-dimethyl-0-(3-methyl-4-nitrophenol) phosphorothioate]

The photolysis of fenitrothion in vapor and liquid phase has been examined, using radiation available in the solar spectrum, i.e., λ> 300 nm. In both the vapor phase and in ethanol solution, two primary products are produced, the major one being p-nitrocresol (4-nitro-3-methyl-phenol). Prolonged irradiation yields additional products probably due to secondary photolysis. The photodecomposition of fenitrothion may be one of the reasons for the rapid disappearance of this material when it is introduced into the environment.     

Estimation and projection of nitrous oxide (N2O) emissions from anthropogenic sources in Taiwan

Taiwan is a densely populated and developed country with more than 97% of energy consumption supplied by imported fuels. Greenhouse gas emissions are thus becoming significant environmental issues in the country. Using the Intergovernmental Panel on Climate Change (IPCC) recommended methodologies, anthropogenic emissions of nitrous oxide (N2O) in Taiwan during 2000-2003 were estimated to be around 41 thousand metric tons annually. About 87% of N2O emissions come from agriculture, 7% from the energy sector, 3% from industrial processes sector, 3% from waste sector. On the basis of N2O emissions in 2000, projections for the year 2010 show that emissions were estimated to decline by about 6% mainly due to agricultural changes in response to the entry of WTO in 2002. In contrast to projections for the year 2020, N2O emissions were projected to grow by about 17%. This is based on the reasonable scenario that a new adipic acid/nitric acid plant will be probably started after 2010.     

NiFe2O4/ZnAl-LDH吸附去除水中Cr(VI)

采用共沉淀法合成磁性复合材料NiFe2O4/ZnAl-LDH,通过静态吸附试验考察复合材料去除水中Cr（VI）的性能,系统地研究了溶液初始pH值、吸附剂投加量、吸附时间和温度等因素对Cr（VI）去除效果的影响。结果表明,当溶液初始pH值为2、初始Cr（VI）浓度为50 mg·L-1、吸附剂投加量为4 g·L-1时,吸附过程在240 min内达到平衡,此时Cr（VI）的去除率为89.5%。动力学和吸附等温式的研究表明：NiFe2O4/ZnAl-LDH吸附Cr（VI）的过程符合准二级动力学和Langmuir等温吸附模型。热力学参数表明该吸附过程为自发、放热的反应过程,低温有利于吸附剂对Cr（VI）的吸附。吸附剂经4次再生后对Cr（VI）仍有83.1%的去除率,且其在外加磁场的作用下能快速与水溶液分离,因此NiFe2O4/ZnAl-LDH可作为去除水中Cr（VI）的良好吸附剂。     

Spatiotemporal variations of nitrous oxide (N2O) emissions from two reservoirs in SW China

Greenhouse gas emissions from hydroelectric dams have recently given rise to controversies about whether hydropower still provides clean energy. China has a large number of dams used for energy supply and irrigation, but few studies have been carried out on aquatic nitrous oxide (N₂O) variation and its emissions in Chinese river-reservoir systems. In this study, N₂O spatiotemporal variations were investigated monthly in two reservoirs along the Wujiang River, Southwest China, and the emission fluxes of N₂O were estimated. N₂O production in the reservoirs tended to be dominated by nitrification, according to the correlation between N₂O and other parameters. N₂O saturation in the surface water of the Wujiangdu reservoir ranged from 214% to 662%, with an average fluctuation of 388%, while in the Hongjiadu reservoir, it ranged from 201% to 484%, with an average fluctuation of 312%. The dissolved N₂O in both reservoirs was over-saturated with respect to atmospheric equilibrium levels, suggesting that the reservoirs were net sources of N₂O emissions to the atmosphere. The averaged N₂O emission flux in the Wujiangdu reservoir was 0.64 μmol m^?2 h^?1, while it was 0.45 μmol m^?2 h^?1 in the Hongjiadu reservoir, indicating that these two reservoirs had moderate N₂O emission fluxes as compared to other lakes in the world. Downstream water of the dams had quite high levels of N₂O saturation, and the estimated annual N₂O emissions from hydropower generation were 3.60 × 10⁵ and 2.15 × 10⁵ mol N₂O for the Wujiangdu and the Hongjiadu reservoir, respectively. These fluxes were similar to the total N₂O emissions from the reservoir surfaces, suggesting that water released from reservoirs would be another important way for N₂O to diffuse into the atmosphere. It can be concluded that dam construction significantly changes the water environment, especially in terms of nutrient status and physicochemical conditions, which have obvious influences on the N₂O spatiotemporal variations and emissions.