Seasonal variations of CH(4) and N(2)O emissions in response to water management of paddy fields located in Southeast China

Water management is one of the most important practices that affect methane (CH₄) and nitrous oxide (N₂O) emissions from paddy fields. A field experiment was designed to study the effects of controlled irrigation (CI) on CH₄ and N₂O emissions from paddy fields, with traditional irrigation (TI) as the control. The effects of CI on CH₄ and N₂O emissions from paddy fields were very clear. The peaks of CH₄ emissions from the CI paddies were observed 1-2 d after the water layer disappeared. Afterward, the emissions reduced rapidly and remained low until the soil was re-flooded. A slight increase of CH₄ emission was observed in a short period after re-flooding. N₂O emissions peaks from CI paddies were all observed 8-10 d after the fertilization at the WFPS ranging from 78.1% to 85.3%. Soil drying caused substantial N₂O emissions, whereas no substantial N₂O emissions were observed when the soil was re-wetted after the dry phase. Compared with TI, the cumulative CH₄ emissions from the CI fields were reduced by 81.8% on the average, whereas the cumulative N₂O emissions were increased by 135.4% on the average. The integrative global warming potential of CH₄ and N₂O on a 100-year horizon decreased by 27.3% in the CI paddy fields, whereas no significant difference in the rice yield was observed between the CI and TI fields. These results suggest that CI can effectively mitigate the integrative greenhouse effect caused by CH₄ and N₂O emissions from paddy fields while ensuring the rice yield.     

An experimental investigation of an inertization effectiveness of fluorinated hydrocarbons in relation to premixed H2–N2O and CH4–N2O flames

An experimental investigation of an influence of trifluoromethane CHF_3, pentafluoroethane C₂HF₅ and perfluorobutane C₄F₁₀ on near-limit hydrogen-nitrous oxide and methane-nitrous oxide premixed flames was performed. Flammability limits, a maximum explosion pressure ΔP_max, maximum rate of pressure rise (dP/dt)_max, and a laminar burning velocity S_u were determined. The flammability area in the case of N₂O as an oxidizer is substantially wider than for the case of the oxidizer which is the mixture of oxygen and nitrogen with the O₂ content 25% (vol.). The dependences of S_u, ΔP_max and (dP/dt)_max on concentration of the fluorinated hydrocarbons are characterizing by an availability of maxima which positions are close to the peak concentrations of the flammability regions. A qualitative interpretation of the results obtained is given.     

Some Physical Properties of CdO Thin Films Used as Window Material in Photovoltaic Solar Cells

Abstract

CdO thin films which can be used in photovoltaic solar cells as window material were obtained on glass substrates at 250°C and 300°C substrate temperatures using Ultrasonic Spray Pyrolysis (USP) technique. The electrical, optical, structural, and surface properties of the films were investigated for two different substrate temperatures. After all investigations, it is concluded that, the CdO thin films can be used in photovoltaic solar cells as window materials and cell efficiencies can be increased using different growth parameters.     

催化法脱除NO_x的研究进展

如何有效地脱除氮氧化物是目前空气污染治理的一个重点和难点 ,催化还原和催化分解是目前研究得较多的脱除氮氧化物方法。本文从催化剂创新和催化反应体系的发展等方面对上述过程研究、应用情况进行了总结 ,并根据作者的认识进行了适当的评述。     

电收尘技术在氧化铝熟料烧结中的应用

氧化铝熟料烧结生产中产生大量高温、高湿、高浓度含尘气体,利用电收尘技术可使粉尘排放浓度达到国家标准。回收大量碱性物料,降低生产消耗。介绍了电除尘技术的基本原理及在氧化铝生产中的应用、常见的现象和故障及解决办法,提出了今后改造的方向。     

燃煤电站锅炉技改中控制氮氧化物的效果

原锅炉热损失较大,NOx排放超标,改造后的锅炉增加了新型燃烧器,既减少了热损,又能减少NOx排放量,使NOx排放浓度达到国家规定标准。     

沸腾炉大气污染物的生成与排放特征分析

以20台沸腾炉(功率小于等于60 MW)的燃料特性分析数据和大气污染物的排放实测数据为基础,利用统计分析方法,研究了燃烧过程中排放的颗粒物(PM)、SO_2和NO_x初始排放浓度的影响因素,分析了沸腾炉PM、SO_2和NO_x排放现状,探讨了我国中小型沸腾炉PM、SO_2和NO_x排放管理控制的潜力和可行性.实验结果表明:在锅炉运行负荷大于等于80%的条件下,中小型沸腾炉PM的初始排放浓度基本上不受锅炉出力、过量空气系数和燃煤灰分含量的影响;燃煤的硫含量越高,SO_2初始排放浓度越高;过量空气系数越大,燃煤挥发分越低,NO_x初始排放浓度越高.     

Allium cepa root tip assay in assessment of toxicity of magnesium oxide nanoparticles and microparticles

Allium cepa bioassay had been used from decades for the assessment of toxicants and their harmful effects on environment as well as human health. Magnesium oxide(MgO) particles are being utilized in different fields. However, reports on the adverse effects of MgO nanoparticles on the environment and mankind are scarce. Hence, the toxicity of MgO particles is of concern because of their increased utilization. In the current study, A. cepa was used as an indicator to assess the toxicological efficiency of MgO nano-and microparticles(NPs and MPs) at a range of exposure concentrations(12.5, 25, 50, and100 μg/m L). The toxicity was evaluated by using various bioassays on A. cepa root tip cells such as comet assay, oxidative stress and their uptake/internalization profile. Results indicated a dose dependent increase in chromosomal aberrations and decrease in mitotic index(MI) when compared to control cells and the effect was more significant for NPs than MPs(at p 0.05). Comet analysis revealed that the Deoxyribonucleic acid(DNA) damage in terms of percent tail DNA ranged from 6.8–30.1 over 12.5–100 μg/m L concentrations of MgO NPs and was found to be significant at the exposed concentrations. A significant increase in generation of hydrogen peroxide and superoxide radicals was observed in accordance with the lipid peroxidation profile in both MgO NPs and MPs treated plants when compared with control. In conclusion, this investigation revealed that MgO NPs exposure exhibited greater toxicity on A. cepa than MPs.     

Production and Consumption of NO in Forest and Pasture Soils from the Amazon Basin

NO production and the rate constant of NO consumptionin soil samples from Amazonian forest and pasturesites were determined in the laboratory. The purposewas to study NO production and consumption in soilsfrom both types of land use as functions of soiltemperature and soil moisture. NO productionincreased exponentially with soil temperature. Thedegree of increase depended on soil moisture,indicating that the response of NO production to achange in soil temperature is most pronounced at acertain intermediate soil moisture. NO productionpeaked at a soil moisture of 0.10 g g^-1, correspondingto 0.27 and 0.38 water-filled pore space for forestand pasture soils, respectively. The optimum soilmoisture for which maximum NO release was observedwas independent of soil temperature. NO consumptionwas most efficient at high soil temperatures andunder dry soil conditions. NO release wasapproximately 10 times larger for forest than pasturesoil. The difference may be related to the higherNO₃ ^- content in forest soil.