Effects of fluoride on growth and reproduction of the army worm, Mythimna separata (Walker)

This paper deals with effects of airborne fluorine on the army worm, Mythimna separata (Walker), by rearing the larvae on the wheat foliage exposed to HF or fumigating the larvae on the artificial diet with the pollutant. Larval relative growth rate (GR) and index of population trend of the insect reduced by 5% and 11%, respectively, when the larvae were reared on the foliage taken from the wheat plants exposed to 0.87 g·dm^-2·day^-1 of fluorine compared with those of the control. An extra instar appeared in a majority of the larvae treated. Survival rate and GR of the larvae on the wheat plant being exposure to the same concentration of fluorine in field open-top fumigation device were 40% and 15% lower than that of the control, respectively. Similar experiment with the insect on the artificial diet also showed that direct impact of the pollutant on the army worm was greater than its indirect effect via their host plant.     

自动固相微萃取-毛细管气相色谱法检测环境水中苯系物的研究

对自动固相微萃取(SPME)-毛细管气相色谱法测定环境水中苯系物的方法进行了研究。通过对环境水中苯系物在不同SPME条件的优化、筛选实验，建立了苯系物的自动固相微萃取-气相色谱的检测方法，该方法简便、灵敏、快捷、可靠，分离度高，准确性好。在0．001mg／L～1．00mg／L范围内有良好的线性关系，最低检测浓度为0．1lμg／L～0．41μg／L。样品测定的相对标准偏差为1．8％～3．5％，回收率为88％～108％，精密度和准确度均较好。     

Assessment of global industrial-age anthropogenic arsenic contamination

Arsenic, a carcinogenic trace element, threatens not only the health of millions of humans and other living organisms, but also global sustainability. We present here, for the first time, the global industrial-age cumulative anthropogenic arsenic production and its potential accumulation and risks in the environment. In 2000, the world cumulative industrial-age anthropogenic arsenic production was 4.53 million tonnes. The world-wide coal and petroleum industries accounted for 46% of global annual gross arsenic production, and their overall contribution to industrial-age gross arsenic production was 27% in 2000. Global industrial-age anthropogenic As sources (as As cumulative production) follow the order: As mining production >As generated from coal >As generated from petroleum. The potential industrial-age anthropogenic arsenic input in world arable surface in 2000 was 2.18 mg arsenic kg^–1, which is 1.2 times that in the lithosphere. The development of substitute materials for arsenic applications in the agricultural and forestry industries and controls of arsenic emissions from the coal industry may be possible strategies to significantly decrease arsenic pollution sources and dissipation rates into the environment.     

Replacement of H2O2 by O2 in Fenton and photo-Fenton reactions

The consumption of oxygen during the degradation of aniline by Fenton and photo-Fenton reactions is studied. The effect that parameters like aniline, Fe(II) and H2O2 initial concentration, pH, temperature and O2 flow rate have on the ratio O2 consumed/H2O2 consumed is examined. The determination of those combinations of experimental conditions for which an effective partial replacement of H2O2 by O2 as electron acceptor takes place is investigated. The results show that this replacement takes place in a variable extent, but the presence of H2O2 is necessary along the reaction, and the maximum consumption of O2 only takes place when the ratio amount of aniline mineralized vs. initial aniline concentration is minimal.     

Effects of butachlor on microbial populations and enzyme activities in paddy soil

This paper reports the influences of the herbicide butachlor (n-butoxymethlchloro -2', 6'-diethylacetnilide) on microbial populations, respiration, nitrogen fixation and nitrification, and on the activities of dehydrogenase and hydrogen peroxidase in paddy soil. The results showed that the number of actinomycetes declined significantly after the application of butachlor at different concentrations ranging from 5.5 microg g(-1) to 22.0 microg g(-1) dried soil, while that of bacteria and fungi increased. Fungi were easily affected by butachlor compared to the bacteria. The growth of fungi was retarded by butachlor at higher concentrations. Butachlor however, stimulated the growth of anaerobic hydrolytic fermentative bacteria, sulfate-reducing bacteria (SRB) and denitrifying bacteria. The increased concentration of butachlor applied resulted in the higher number of SRB. Butachlor inhibited the growth of hydrogen-producing acetogenic bacteria. The effect of butachlor varied on methane-producing bacteria (MPB) at different concentrations. Butachlor at the concentration of 1.0 microg g(-1) dried soil or less than this concentration accelerated the growth of MPB, while at 22.0 microg g(-1) dried soil showed an inhibition. Butachlor enhanced the activity of dehydrogenase at increasing concentrations. The soil dehydrogenase showed the highest activity on the 16th day after application of 22.0 microg g(-1) dried soil of butachlor. The hydrogen peroxidase could be stimulated by butachlor. The soil respiration was depressed during the period from several days to more than 20 days, depending on concentrations of butachlor applied. Both the nitrogen fixation and nitrification were stimulated in the beginning but reduced greatly afterwards in paddy soil.     

Photocatalytic degradation of azo dyes by nitrogen-doped TiO2 nanocatalysts

This study examined the photocatalytic degradation of three azo dyes, acid orange 7 (AO7), procion red MX-5B (MX-5B) and reactive black 5 (RB5) using a new type of nitrogen-doped TiO2 nanocrystals. These newly developed doped titania nanocatalysts demonstrated high reactivity under visible light (lambda>390 nm), allowing more efficient usage of solar light. The doped titania were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Experiments were conducted to compare the photocatalytic activities of nitrogen-doped TiO2 nanocatalysts and commercially available Degussa P25 powder using both UV illumination and solar light. It is shown that nitrogen-doped TiO2 after calcination had the highest photocatalytic activity among all three catalysts tested, with 95% of AO7 decolorized in 1 h under UV illumination. The doped TiO2 also exhibited substantial photocatalytic activity under direct sunlight irradiation, with 70% of the dye color removed in 1h and complete decolorization within 3 h. Degussa P25 did not cause detectable dye decolorization under identical experimental conditions using solar light. The decrease of total organic carbon (TOC) and evolution of inorganic sulfate (SO4(2-)) ions in dye solutions were measured to monitor the dye mineralization process.     

汽车尾气催化转化器模型研究进展

本文主要介绍汽车尾气催化转化器模型的研究进展 ,包括反应器内气体流动特性、单通道反应器内的传递现象和反应动力学、通道间的热传递和反应行为的模拟 ;并指出认识反应器内的各种特性和规律对设计汽车尾气催化转化器的必要性和意义     

Synergetic effects of anodic-cathodic electrocatalysis for phenol degradation in the presence of iron(II)

A novel electrocatalysis method for phenol degradation was described using a β-PbO₂ anode modified with fluorine resin and a Ni–Cr–Ti alloy cathode. In case of air sparging at the cathodic zone, the techniques of anodic–cathodic electrocatalysis (ACEC) and ferrous ion catalyzed anodic–cathodic electrocatalysis (FACEC) in the presence of iron(II) were developed. Both of ACEC and FACEC were more effective than anodic electrocatalysis (AEC). The percentage of phenol eliminated by FACEC could increase by nearly 30% compared with that of AEC, and the current efficiency could reach to 70%. Important operating factors such as ferrous ion concentration, air-sparging rate and applied current were investigated and it was found that such beneficial effects could be achieved at a suitable current and ratio of the concentration of ferrous ion to the air sparged. The mechanism of phenol degradation is proposed to be the generation of hydroxyl radicals concerned with the two electrodes. Results also indicated that the process provided an efficient way to regenerate ferrous ion compared with the conventional Fenton's system.     

Abatement of sulfur hexafluoride emissions from the semiconductor manufacturing process by atmospheric-pressure plasmas

Sulfur hexafluoride (SF6) is an important gas for plasma etching processes in the semiconductor industry. SF6 intensely absorbs infrared radiation and, consequently, aggravates global warming. This study investigates SF6 abatement by nonthermal plasma technologies under atmospheric pressure. Two kinds of nonthermal plasma processes--dielectric barrier discharge (DBD) and combined plasma catalysis (CPC)--were employed and evaluated. Experimental results indicated that as much as 91% of SF6 was removed with DBDs at 20 kV of applied voltage and 150 Hz of discharge frequency for the gas stream containing 300 ppm SF6, 12% oxygen (O2), and 40% argon (Ar), with nitrogen (N2) as the carrier gas. Four additives, including Ar, O2, ethylene (C2H4), and H2O(g), are effective in enhancing SF6 abatement in the range of conditions studied. DBD achieves a higher SF6 removal efficiency than does CPC at the same operation condition. But CPC achieves a higher electrical energy utilization compared with DBD. However, poisoning of catalysts by sulfur (S)-containing species needs further investigation. SF6 is mainly converted to SOF2, SO2F4, sulfur dioxide (SO2), oxygen difluoride (OF2), and fluoride (F2). They do not cause global warming and can be captured by either wet scrubbing or adsorption. This study indicates that DBD and CPC are feasible control technologies for reducing SF6 emissions.