非对称天然沸石陶瓷膜的制备及其性能表征

利用天然沸石为主要原料,制备出具有过滤功能和重金属离子吸附功能的天然沸石非对称陶瓷膜。非对称膜中支撑体、中间层膜和顶层膜的平均孔径分别为6.6μm、0.6μm和0.1μm。非对称膜单位压力降(1 MPa)下的氮气通量和水通量分别为:24.69×103m3/(m2h)和1.87×103m3/(m2h);对重金属离子(铅离子)吸附交换能力为7.13 mg/g。     

Factors influencing the release of dissolved organic carbon and dissolved forms of nitrogen from a small upland headwater during autumn runoff events

We identify and assess the relative importance of the principal factors influencing the release of dissolved organic carbon (DOC) and dissolved forms of nitrogen (N) from a small upland headwater dominated by podzolic soils during a sequence of autumn runoff events. We achieve this by subjecting high‐resolution hydrometeorological and hydrochemical data to an R‐mode principal component factor analysis and a stepwise multivariate regression analysis. We find that the release of DOC and N is influenced by four principal factors, namely event magnitude, soil water flow through the Bs horizon, the length of time since the soil profile was last flushed, and rewetting of the H horizon. The release of DOC and dissolved organic nitrogen (DON) is most strongly influenced by the combination of event magnitude and soil water flow through the Bs horizon, and to a lesser extent by the length of time since the soil profile was last flushed. Rewetting of the H horizon also influences the release of DOC, but this is not the case for DON. The release of nitrate (NO₃‐N) is most strongly influenced by the combination of the length of time since the soil profile was last flushed and rewetting of the H horizon, and to a lesser extent by event magnitude. Soil water flow through the Bs horizon does not influence the release of NO₃‐N. We argue that the mechanisms by which the above factors influence the release of DOC and N are probably strongly associated with moisture‐dependent biological activity, which governs the turnover of organic matter in the soil and limits the availability of NO₃‐N in the soil for leaching. We conclude that the release of DOC and N from upland headwaters dominated by podzolic soils is largely controlled by the variable interaction of hydrometeorological factors and moisture‐dependent biological processes, and that a shift in climate towards drier summers and wetter winters may result in the release of DOC and N becoming increasingly variable and more episodic in the future. Copyright © 2006 John Wiley & Sons, Ltd.     

颗粒态氮磷负荷模型研究

为研究妫水河流域的颗粒态氮磷非点源污染来源,以控制非点源污染,在官厅水库周围进行了野外人工降雨试验。试验数据表明,氮磷输移率与产沙率具有很好的相关性,颗粒态氮、磷的平均相关系数分别为0.9594和0.9772。建立了新的颗粒态氮磷负荷模型,其中富集系数等于泥沙中总氮总磷百分含量与土壤中百分含量之比。根据妫水河流域的土壤图、土地利用图及数字高程模型,应用新的模型研究了妫水河流域颗粒态氮磷污染负荷的空间分布。结果表明,颗粒态氮磷主要来自地表植被覆盖差的丘陵和山地。     

Nitrogen isotopic geochemical characteristics of crude oils in several basins of China

Nitrogen occupies a high content in crust and in atmospheric circle. It is one of the main elements in organism and an important element in sedimentary circle. Although nitrogen is little in crude oil, to a cer-tain degree, it influences the physical and chemical properties of oil, such as viscosity and density[1]. In reservoir the nitrogen-bearing compounds can form ion bonds or hydrogen bonds with substances on rock and form van der Vaals’ force among moleculae so they affect and alter the …     

Seasonal changes in the distribution and exchange of inorganic nitrogen between sediment and water in the Northern Baltic (Gulf of Bothnia)

The concentration profiles of nitrate plus nitrite, ammonium, and redox potential in sediment and water column were determined in late winter and summer at a sampling site off Norrbyn, northern Sweden, in the Gulf of Bothnia. The sediment had an oxidized surface layer during winter and spring, and nitrification occurred. Nitrate but not ammonium was present in the water column at this time. During summer a layer of planktonic detritus was deposited onto the sediment and led to its deoxygenation and reduction. Ammonium was then the predominant form of inorganic nitrogen in the water column.Laboratory experiments confirmed that nitrification in the surface layer of sediment prevented ammonium export during winter. Enhanced temperature or organic detritus deoxygenated the surface sediment and inhibited nitrification, and export of ammonium from the sediment increased. Although nitrification was important in determining the flow of nitrogen in the sediment it accounted for at most only 5% of the total oxygen uptake by the sediment.     

Ammonium Photoproduction from Aquatic Humic and Colloidal Matter

It has recently been shown thatnitrogen contained in humic substances can be releasedas low molecular weight species through photochemicalprocesses or reactions. Nitrogen released in thismanner may then become available for biological useand chemical reactivity. This report providesadditional kinetic data for nitrogen photochemistry oforganic matter in natural waters from Louisiana andfor Suwannee River humic and fulvic acids. Naturalwater samples were fractionated into colloidal(>0.2 m, <1000 Dalton) and dissolved (>1000Dalton) fractions and the kinetics of these fractionsas well as 0.2 m filtered water samples weremeasured. For irradiations of less than 10 hours ofsimulated noon-time sun, samples showed linearproduction of ammonium and first-order fading at350 nm. Ammonium photoproduction was enhanced asmuch as three-fold by lowering pH, but linear kineticswere maintained. Light-dark cycling showed continuedrelease of ammonium immediately after irradiation,followed by uptake at longer post irradiation times.A two step mechanism was proposed to explain theobserved kinetics. Calculated net daytime release ofammonium from natural surface waters ranged from 0.33to 1.9 M h^-1 in the samples studied,corresponding to a photic zone conversion rate of9–20% of the total organic nitrogen per day intoammonium.     

CO2-Laser Extraction-Static Mass Spectrometry Analysis of Ultra-Low Concentrations of Nitrogen in Silicates

A new installation for the analysis of picomole quantities of nitrogen has been designed and constructed. It permits the simultaneous analysis of N and rare gases extracted from silicates by heating. The extraction procedure involves the use of a CO₂ laser as a heater, and the analysis is made by static mass spectrometry using a high sensitivity, high resolution mass spectrometer. Procedural blanks of 2 picomoles N₂ (60 picogram N) allow us to analyse routinely N in mg-sized samples such as mantle-derived and meteoritic minerals, and Lunar soil grains.     

Are spatial patterns of soil moisture at plot scales generalisable across catchments,climates, and other characteristics? A synthesis of synoptic soil moisture across the Mid-Atlantic

The spatial variation of soil moisture over very small areas (<100 m²) can have nonlinear impacts on cycling and flux rates resulting in bias if it is not considered, but measuring this variation is difficult over extensive temporal and spatial scales. Most studies examining spatial variation of soil moisture were conducted at hillslope (0.01 km²) to multi-catchment spatial scales (1000 km²). They found the greatest variation at mid wetness levels and the smallest variation at wet and dry wetness levels forming a concave down relationship. There is growing evidence that concave down relationships formed between spatial variation of soil moisture and average soil moisture are consistent across spatial scales spanning several orders of magnitude, but more research is needed at very small, plot scales (<100 m²). The goal of this study was to characterise spatial variation in shallow soil moisture at the plot scale by relating the mean of measurements collected in a plot to the standard deviation (SD). We combined data from a previous study with thousands of new soil moisture measurements from 212 plots in eight catchments distributed across the US Mid-Atlantic Region to (1) test for a generalisable mean–SD relationship at plot scales, (2) characterise how landcover, land use, season, and hillslope position contribute to differences in mean–SD relationships, and (3) use these generalised mean–SD relationships to quantify their impacts on catchment scale nitrification and denitrification potential. Our study found that 98% of all measurements formed a generalised mean–SD relationship like those observed at hillslope and catchment spatial scales. The remaining 2% of data comprised a mean–SD relationship with greater spatial variation that originated from two riparian plots reported in a previous study. Incorporating the generalised mean–SD relationship into estimates of nitrification and denitrification potential revealed strong bias that was even greater when incorporating mean–SD observations from the two riparian plots with significantly greater spatial variation.