Contribution of winter fluxes to the annual CH4, CO2 and N2O emissions from freshwater marshes in the Sanjiang Plain

Introduction C arbon dioxide, m ethane and nitrous oxide play im portant roles in the radiation balance of the earth contributing to the greenhouse effect (Rodhe, 1990). N 2O also takes part in the destruction of stratospheric ozone (W ang, 1999). N atura…     

膜—生物反应器特性影响因素研究

通过对外压管式膜组件与曝气池构成的好氧膜生物反应器的研究，分别考究膜组件的操作压力，膜面流速以及活性污泥混合液的污泥浓度，溶解性有机特的含量和温度等对膜通量的影响。     

辽东湾海冰生消的热力要素分析

利用辽海湾ＪＺ２０－２海域冰斯气象、水文和海泳的测量资料，对冰面太阳辐射、长波辐射、盛热、潜热、冰内热传导和泳下海洋热通量等热力要素的计算方法进行了讨论，并对其中的部分参数进行了确定；对１９９７～１９９８年度不同天气条件和不同泳期的海８泳热力要素进行了对比分析，发展太阳辐射的主要影响因素为云层，冰面感热主要受控于风速和和气温，而长波辐射变化量不大，不同风向时的相对湿度差别很大，疳直接影响到冰面潜热     

Nitrous oxide emission from an agricultural field: Comparison between measurements by flux chamber and micrometerological techniques

The soil in a drained fjord area, reclaimed for arable farming, produced N₂O mainly at 75–105 cm depth, just above the ground water level. Surface emissions of N₂O were measured from discrete small areas by closed and open-flow chamber methods, using gas chromatographic analysis and over larger areas by integrative methods: flux gradient (analysis by FTIR), conditional sampling (analysis by TDLAS), and eddy covariance (analysis by TDLAS). The mean emission of N₂O as determined by chamber procedures during a 9-day campaign was 162–202 μg N₂ONm⁻²h⁻¹ from a wheat stubble and 328–467 μg N₂ONm⁻² h⁻¹ from a carrot field. The integrative approaches gave N₂O emissions of 149–495 μg N₂ONm⁻² h⁻¹, i.e. a range similar to those determined with the chamber methods. Wind direction affected the comparison of chamber and integrative methods because of patchiness of the N₂O emission over the area. When a uniform area with a single type of vegetation had a dominant effect on the N₂O gradient at the sampling mast, the temporal variation in N₂O emission determined by the flux gradient/FTIR method and chamber methods was very similar, with differences of only 18% or less in mean N₂O emission, well below the variation encountered with the chamber methods themselves. A detailed comparison of FTIR gradient and chamber data taking into account the precise emission footprint showed good agreement. It is concluded that there was no bias between the different approaches used to measure the N₂O emission and that the precision of the measurements was determined by the spatial variability of the N₂O emission at the site and the variability inherent in the individual techniques. These results confirm that measurements of N₂O emissions from different ecosystems obtained by the different methods can be meaningfully compared.     

PCDDs and PCDFs in water, sludge and air samples from various levels in a waste water treatment plant with respect to composition changes and total flux

A flux estimate of PCDDs and PCDFs through a waste water treatment plant has been made on an annual basis. The samples were collected from different steps in the treatment procedure within the plant i.e. inlet and outlet water, different sludge types and air samples. From the surroundings of the plant were collected samples of urban air, storm sewer water (urban runoff), plant discharge water and settling particulates from a sediment trap downstream the plant discharge. Differences in congener profiles were found between the samples taken within the plant compared to those collected outside. The flux of PCDD and PCDF equivalents through the plant was found to be approximately 0.4 – 0.5 g/year and the major part was taken away as digested sludge.     

液体旋流分离器内部流场分布的测试与研究

改变传统的利用皮托管插入法对流场分布的测试方法 ,利用激光流速计分别对两种具有代表性的液体旋流分离器的切线方向和轴线方向的流场分布进行了测试 ,得到了精确的结果。为分析、研究和提高旋流分离器的性能 ,提供了最基本的和最有效的数据     

无机微滤膜过滤阻力的研究

本文采用孔径为 0 .8μm、0 .2 μm和 5 0nm的无机微滤膜 ,考察了不同情况下膜的过滤阻力分布情况。对于造纸黑液 ,当浓度较低时 ,过滤阻力由膜阻力、吸附阻力、堵孔阻力和浓差极化阻力共同控制 ;当浓度较高时 ,吸附阻力起主要作用。过滤 1g/L聚乙二醇溶液的试验结果表明 ,不同孔径膜的过滤阻力构成是不同的 ,孔径越小则吸附阻力越小 ,但浓差极化阻力会显著增加     

平板膜生物反应器中临界通量问题研究

通过小试试验,探讨了平板膜生物反应器中临界通量问题。在试验中发现,平板膜生物反应器运行过程中,存在临界通量值,本试验中污泥质量浓度为10 g/L,临界通量值为4.86×10-6m/s;在该通量值以下运行时,膜污染速度比较缓慢,在该通量值以上运行时,膜污染比较迅速。通过对膜运行过程阻力的分析发现,随着通量的提高,内部污染阻力增加速度大于膜泥饼污染阻力增加速度。膜片在恒流下运行一段时间后,压力会突然上升,其主要原因是由于膜面泥饼的聚集。     

膜生物反应器处理高氨氮废水

试验采用MBR处理高氨氮废水,重点分析了氨氮、有机物的去除以及膜比通量变化等。结果表明,工艺运行稳定,出水氨氮平均浓度低于3mg/L,MBR能够抵抗有机物冲击负荷,氨氮容积负荷可以达到1.11kgNH3-N/(m3·d)。在整个运行期间膜比通量下降比较缓慢,分析认为是高曝气量、低碳氮比以及自养菌的优势生长起了主要作用。     

Principal Biogeochemical Factors Affecting the Speciation And Transport of Mercury through the terrestrial environment

It is increasingly becoming known that mercury transport and speciation in the terrestrial environment play major roles in methyl-mercury bioaccumulation potential in surface water. This review discusses the principal biogeochemical reactions affecting the transport and speciation of mercury in the terrestrial watershed. The issues presented are mercury-ligand formation, mercury adsorption/desorption, and elemental mercury reduction and volatilization. In terrestrial environments, OH^–, Cl^– and S^– ions have the largest influence on ligand formation. Under oxidized surface soil conditions Hg(OH)₂, HgCl₂, HgOH⁺, HgS, and Hg⁰ are the predominant inorganic mercury forms. In reduced environments, common mercury forms are HgSH⁺, HgOHSH, and HgClSH. Many of these mercury forms are further bound to organic and inorganic ligands. Mercury adsorption to mineral and organic surfaces is mainly dictated by two factors: pH and dissolved ions. An increase in Cl^– concentration and a decrease in pH can, together or separately, decrease mercury adsorption. Clay and organic soils have the highest capability of adsorbing mercury. Important parameters that increase abiotic inorganic mercury reduction are availability of electron donors, low redox potential, and sunlight intensity. Primary factors that increase volatilization are soil permeability and temperature. A decrease in mercury adsorption and an increase in soil moisture will also increase volatilization. The effect of climate on biogeochemical reactions in the terrestrial watershed indicates mercury speciation and transport to receiving water will vary on a regional basis.