煤的受热升温过程及厚度与粒度的影响

为了解煤在中等温度(150～400℃)下氧化的特点,对贫煤和褐煤进行了系列恒温加热.重点考察在超过加热温度后煤的升温速率,以分析其氧化放热反应的特点.不同条件实验中,贫煤的升温速率曲线都在相同的一些温度点附近出现峰值;褐煤也有相同的规律.这表明在特定温度附近氧化反应加强是由煤自身的特性决定的.另一方面煤样的厚度越小、粒度越大都使得升温速率数值增大,说明厚度小、粒度大有利于氧气的输运,而导致氧化反应加快.     

Nitrogen loss through lateral seepage in near-trench paddy fields

A near-trench paddy field experiment with five urea application rates (0-360 kg N ha(-1) in 90-kg increments) was conducted on a paddy soil in the Taihu Lake Region of China to elucidate N losses through lateral seepage during three rice (Oryza sativa L.) growing seasons. The total N (Nt), NH4(+) -N, and NO3(-) -N concentrations in the lateral seepage water increased with increasing N rates. The seasonal Nt fluxes by lateral seepage varied from 6.8 to 25.6 kg N ha(-1) for urea application rates of 90 to 360 kg N ha(-1). Lateral seepage accounted for 4.7 to 6.6% of the Nt applied, implying that lateral seepage was an important pathway of N loss from near-trench paddy fields. The cumulative N loss via lateral seepage was significantly related to N fertilization rate (P = 0.05). Floodwater level was also identified as a main factor affecting N losses via lateral seepage from paddy fields, as indicated by a positive linear relationship (R2 = 0.43) between floodwater level and daily lateral flow during the flooded period (P = 0.05). Under the conditions of these experiments, a shallow floodwater depth of 50 mm, urea application rates of 90 kg N ha(-1) or less, and no rainfall within 1 wk after N application reduced N losses by lateral seepage from paddy fields.     

Adsorption of Pb and Cd on the natural surface coatings (NSCs) in the presence of organochlorine pesticides: a preliminary investigation

Adsorption of Pb and Cd in the presence and absence of organochlorine pesticides (OCPs) on natural surface coatings (NSCs), which were collected in the Nanhu Lake in Changchun, China, was measured in order to investigate the effect of the OCPs on the adsorption of heavy metals on the NSCs. Adsorption of Pb/Cd was carried out under controlled laboratory conditions (mineral salt solution with defined species, ionic strength 0.05 mol/l, 25 degrees C and pH 6.0) with initial Pb and Cd concentrations ranging from 0.2 to 2.5 mol/l. The classical Langmuir adsorption isotherm was applied to estimate the equilibrium coefficients of the adsorption of Pb and Cd on the NSCs. Adsorption interference between Pb/Cd and the OCPs on the NSCs indicated that the adsorption of Pb/Cd on the NSCs was influenced by the OCPs, and competitive adsorption between Pb and the OCPs was observed while adsorption of Cd was enhanced by addition of the OCPs. Adsorption data fit the Langmuir isotherm well for the NSCs treated with the OCPs at different equilibrium concentrations. The results showed that the amount of adsorbed Pb decreased by more than 40% while the amount of adsorbed Cd increased by over 60% with an increase in the initial concentrations of the OCPs ranging from 0 to 5.0 microg/l and that adsorption of Pb/Cd on the NSCs was strongly affected by the OCPs. This preliminary study highlights the importance of the OCPs on the NSCs in controlling the transport, fate, biogeochemistry, bioavailability and toxicity of trace metals in aquatic environments.     

关于不确定度评定中两个问题的讨论

通过对环境监测仪器分析不确定度评定中,标准不确定度和相对标准不确定度的单位来源以及关于相对标准不确定度两种计算方法的讨论,得出标准不确定度是有量纲的、相对标准不确定度是无量纲的;最大允许误差较易获得,用这种方法计算不确定度有很好的可靠性。相对标准偏差计算不确定度则结果更好。     

巧用Premiere Pro 2.0 制作艺术倒计时片头

Premiere Pro 2.0 是用于编辑影视作品的专业软件,可以编辑和制作电影、DV、栏目包装、字幕、网络视频、电子相册等.本文介绍了其自带的制作倒计时片头效果模板的使用方法,提出了利用Premiere Pro 2.0视频转场特效结合专业制图软件制作艺术倒计时效果的具体方法.     

论大学生职业生涯教育的现状及其对策

目前,高校对开展大学生职业生涯教育的重要性尚未有足够认识,职业生涯教育和辅导的保障机制也还不够完善,高校课程、专业设置等还不能为职业生涯教育提供有效支持。因此,要不断建立、完善职业生涯教育和辅导体系,推动高校招生教育体制改革,完善大学生职业生涯教育配套机制,以提高高校人才培养质量,促进大学生就业质量和水平,推动高校健康发展。     

NaNO(2)/FeCl(3) catalyzed wet oxidation of the azo dye Acid Orange 7

A combination of ferric chloride and sodium nitrite significantly improved the wet oxidation of the azo dye Acid Orange 7 (AO7) in acid aqueous media (pH 2.6) under moderate conditions (T=150 degrees C; oxygen pressure=0.5 MPa). To evaluate the catalytic system, wet oxidation of AO7 was carried out at temperatures between 90 and 150 degrees C and oxygen pressures ranging from 0.1 to 0.5 MPa. The effect of initial solution pH from 2.6 to 11.4 and the amount of catalyst on the degradation of AO7 were also investigated. AO7 initial concentration was kept 200 mg L(-1). The degradation process was monitored by UV-visible spectroscopy, HPLC, IC (ion chromatography), GC-MS and TOC analysis. At 150 degrees C and 0.5 MPa oxygen pressure, 56% TOC was removed after 4h of treatment, while no obvious TOC removal were achieved without catalyst at the same experimental condition. The main degradation products were some small organic acids: formic acid, acetic acid, pyruvic acid, oxalic acid, succinic acid (identified and quantified by IC) and phthalic acid (identified by GC-MS).     

Decomposition of nitrotoluenes from trinitrotoluene manufacturing process by Electro-Fenton oxidation

Oxidative degradation of dinitrotoluene (DNT) isomers and 2,4,6-trinitrotoluene (TNT) in spent acid was conducted by Electro-Fenton's reagents. The electrolytic experiments were carried out to elucidate the influence of various operating parameters on the performance of mineralization of total organic compounds (TOC) in spent acid, including reaction temperature, dosage of oxygen, sulfuric acid concentration and dosage of ferrous ions. It deserves to note that organic compounds could be completely destructed by Electro-Fenton's reagent with in situ electrogenerated hydrogen peroxide obtained from cathodic reduction of oxygen, which was mainly supplied by anodic oxidation of water. Based on the spectra analyzed by gas chromatograph/mass spectrometer, it is proposed that initial denitration of 2,4,6-TNT gives rise to formation of 2,4-DNT and/or 2,6-DNT, which undergo the cleavage of nitro group into o-mononitrotoluene, followed by denitration to toluene and subsequent oxidation of the methyl group. Owing to the removal of both TOC and partial amounts of water simultaneously, the electrolytic method established is potentially applied to regenerate spent acid from toluene nitration processes in practice.     

Mechanisms of silicon-mediated alleviation of abiotic stresses in higher plants: a review

Although silicon (Si) is the second most abundant element both on the surface of the Earth's crust and in soils, it has not yet been listed among the essential elements for higher plants. However, the beneficial role of Si in stimulating the growth and development of many plant species has been generally recognized. Silicon is known to effectively mitigate various abiotic stresses such as manganese, aluminum and heavy metal toxicities, and salinity, drought, chilling and freezing stresses. However, mechanisms of Si-mediated alleviation of abiotic stresses remain poorly understood. The key mechanisms of Si-mediated alleviation of abiotic stresses in higher plants include: (1) stimulation of antioxidant systems in plants, (2) complexation or co-precipitation of toxic metal ions with Si, (3) immobilization of toxic metal ions in growth media, (4) uptake processes, and (5) compartmentation of metal ions within plants. Future research needs for Si-mediated alleviation of abiotic stresses are also discussed.     

Co-cropping for phyto-separation of zinc and potassium from sewage sludge

The use of sewage sludge as a fertilizer and soil amendment has resulted in high concentrations of heavy metals in the soil limiting its use. The present study was carried out to find the possibility of phyto-separating toxic and beneficial elements from the sludge using suitable plants. Of the five plants tested the hyperaccumulator Sedum alfredii H achieved the greatest removal of Zn, while shoots of Alocasia marorrhiza accumulated high content of K. Co-cropping these two plants on the sludge verified the previous observations on A. marorrhiza and the shoots of this plant could accumulate more than 120 g K kg(-1) dry matter in the median growth stage. Zn hyperaccumulated in Sedum's shoots to an extent more than 10 g kg(-1) dry matter; K concentrated five to ten times in the Alocasia's shoots which could be used as a good organic-K-fertilizer. Hence, the two elements were simultaneously phytoseparated and could be recycled. Furthermore, cultivation of plants in the sludge resulted in significant decreases in total Zn but kept the favorable agronomic characteristics of the sludge material, such as pH, organic matter content, and NPK concentrations and ameliorated its biological stability. These results suggest that simultaneous phyto-separation of toxic and beneficial elements from sewage sludge are possible by co-cropping using specific plants without the input of any chemicals.