中国南方80个地表水体的酸沉降临界负荷计算

研究了酸沉降对中国南方地表水体的影响。应用动态酸化模型 MAGIC,计算了中国南方 80个地表水体的酸沉降临界负荷。结果表明 :大部分水体的酸沉降临界负荷较高 ,大于 2 kmol.hm- 2 .a- 1 ,呈现地带性分布。西南地区的地表水酸沉降临界负荷高于华东和华南地区 ,这主要是因为南方土壤的酸化敏感性由东南向西北减弱。临界负荷较高 ,表明这些水体对酸化不敏感。地表水酸化不太可能成为中国严重的区域环境问题。但是少数山地水体的酸化趋势值得关注。     

中国大气Ca2+传输和沉降模拟

盐基阳离子(Ca2 ,Mg2 ,K ,Na )在缓解土壤和水体酸化中起着重要作用。为了满足中国酸沉降控制的需要,该研究利用建立的多层动态Euler模型模拟中国大气Ca2 传输和沉降。结果表明:2000年中国的Ca2 总沉降量为5.29 Mt,其中湿沉降1.45 Mt,干沉降3.84 Mt。人为源排放对全国总沉降、湿沉降和干沉降的贡献率分别为67.1%、92.4%和57.6%,对东南部地区的贡献率更大,而自然源仅对西北地区的沉降起重要作用。中国酸沉降较为严重的东南部地区,Ca2 沉降量普遍大于0.10 kmol.hm-2.a-1,甚至超过0.25 kmol.hm-2.a-1,能够中和大部分的SO42-沉降。     

中国大气Ca~(2 )传输和沉降模拟

盐基阳离子(Ca2 ,Mg2 ,K ,Na )在缓解土壤和水体酸化中起着重要作用。为了满足中国酸沉降控制的需要,该研究利用建立的多层动态Euler模型,模拟了中国大气Ca2 传输和沉降。结果表明,2000年中国的Ca2 总沉降量为5.29Mt,其中湿沉降1.45Mt,干沉降3.84Mt。人为源排放对全国总沉降、湿沉降和干沉降的贡献率分别为67.1%、92.4%和57.6%,对东南部地区的贡献率更大;而自然源仅对西北地区的沉降起重要作用。中国酸沉降较为严重的东南部地区,Ca2 沉降量普遍大于0.10kmol.hm-2.a-1,甚至超过0.25kmol.hm-2.a-1,能够中和大部分的SO42-沉降。     

土壤速效钾对模拟氮沉降增加的响应

通过野外模拟试验,研究氮沉降增加对土壤速效钾的影响。试验设计为5种处理,分别为N0(0kg.hm-2.a-1)、N1(60kg.hm-2.a-1)、N2(120kg.hm-2.a-1)、N3(240kg.hm-2.a-1)、Nr(氮沉降恢复),每个处理重复3次。以尿素[CO(NH2)2]作为氮源,每月以溶液方式对林地进行喷施。通过3年的处理后发现,氮沉降导致土壤速效元素总量的淋失,0～20cm土层中的速效元素对氮沉降的反应要比20～60cm土层更为敏感,且其速效元素的淋失与沉降时间呈正相关,而20～60cm土层还未出现一致的变化规律。     

模拟大气氮沉降及短期氮沉降恢复对森林土壤酸化及养分的影响

通过野外模拟试验,研究氮沉降增加以及短期氮沉降恢复对杉木人工林土壤物理性质、pH值、NH4+-N、NO3--N、交换性钙、镁的影响。试验设计为5种处理,分别为N0(0kg·hm-2·a-1)、N1(60kg·hm-2·a-1)、N2(120kg·hm-2·a-1)、N3(240kg·hm-2·a-1)、Nr(氮沉降恢复),每个处理重复3次。以尿素[CO(NH2)2]作为氮源,每月以溶液方式对林地进行喷施。通过3年的处理后发现,氮沉降使土壤容重降低;0-20cm土层pH值出现短期的突增,而20-60cm则随氮沉降量的增大其酸化程度也越大;0-40cm土层中土壤NH4+-N含量从高到低的顺序比较为:N3>N2>N0>N1;40-60cm土层为:N3>N2>N1>N0,;土层中NO3--N含量从高到低的顺序为:N3>N2>N0>N1。氮沉降促进了土壤交换性钙和镁的增加。短期的氮沉降恢复过程中,土壤NH4+-N和NO3—N出现了显著的恢复特征;而土壤容重、pH值、交换性钙、镁也出现了一些恢复现象,但其特征并不显著。     

高寒草甸土壤微生物量及酶活性的研究

为揭示高寒草甸土壤微生物量和土壤酶活性特征,以青藏高原金露梅(Potentilla frutisosa)丛间草地和矮嵩草(Kobresia humilis)草甸为研究对象,分析了其土壤理化性质、土壤微生物量、微生物贡献率、土壤酶活性特征.结果表明:矮嵩草草甸土壤全氮、全磷、微生物碳(氮、磷)、微生物氮(磷)贡献率、土壤脲酶、过氧化氢酶、多酚氧化酶活性均显著大于金露梅丛间草地;而土壤有效磷、磷酸酶活性均显著小于金露梅丛间草甸;2种类型草甸的土壤有机质、微生物碳贡献率没有显著差异;2种类型草甸的土壤微生物量对土壤营养库的贡献率均在较低水平.说明高寒草甸在植被生长旺季土壤微生物量呈现较高的水平;而微生物量对土壤营养库比值略偏低.矮嵩草草甸比金露梅丛间草地更有利于土壤养分的提高以及土壤微生物的生长和繁殖.     

伊犁河上游典型草地生态系统氮磷含量及化学计量特征

【目的】了解伊犁河上游典型草地养分限制状况,为不同草地类型群落营养循环及植物-土壤养分管理提供理论依据,也为该区域生态环境的改善提供科学依据。【方法】通过野外调查采样和室内分析测定,采用相关性分析方法,分析了不同类型草地群落植物-土壤氮、磷、钾含量及化学计量学特征。【结果】研究区不同草地类型植物群落植物地上部分和地下部分根系的氮、磷、钾含量变异较大,山地草甸草原和高寒草甸植物地上部分氮含量荒漠草原、半荒漠草原和高寒草甸的氮含量;荒漠草原和半荒漠草原植物地下部分根系的氮含量山地草甸草原、山地草甸和高寒草甸的氮含量;不同草地群落类型植物地上部分的P含量与植物N/P比值呈显著负相关,土壤N与土壤P含量、土壤P含量与土壤N/P比值分别呈显著正相关,土壤N和土壤N/P比值极显著相关,其相关系数为0.983。【结论】研究区土壤氮素缺乏,可以考虑在草地生长过程中适当添加氮肥。     

模拟大气氮沉降对萍乡土壤酸化的初探

通过野外模拟试验,研究氮沉降增加对萍乡土壤酸化的影响。以尿素[CO(NH2)2]作为外加氮源,设置4种处理,分别为N0(对照,0g·m-2·a-1,以N计,下同)、N1(6g·m-2·a-1)、N2(12g·m-2·a-1)和N3(24g·m-2·a-1),每处理重复两次。结果显示,氮沉降引起土壤pH值下降;表层土壤比下层土壤更敏感;pH值的下降程度与氮沉降量及沉降时间呈正相关。     

N沉降增加对森林生态系统地表=土壤动物群落的影响

在3种南亚热地带代表性森林(季风常绿阔叶林、针阔混交林和马尾松林)中,历经16个月,通过5次取样,对模拟氮沉降增加条件下地表土壤动物群落的响应特征进行了比较研究.试验采用模拟的方法,人为构建了一个氮沉降增加梯度系列,即对照、低氮处理(50 kg·hm-2·a-1)、中氮处理(100 kg·hm-2·a-1)和高氮处理(150 kg·hm-2·a-1).结果表明,N处理水平整体上并未造成土壤动物群落的显著差异.但是,N沉降增加的处理效应在时间尺度上的动态变化中,也即,其在与不同植被演替类型、同一植被内不同取样期的交互作用中可以清楚地表现出来. 在演替尺度上,季风林和针叶林对N处理的反应都很灵敏,前者负效应明显,后者则正效应明显,并因此最终改变了土壤动物群落在不同林分内的分布格局;同时,不同林分对各N处理水平的反应也不同.季风林内,只有低N处理显示了利好效应;混交林内,N处理的利好作用有一个从较高浓度的中N处理向较低浓度低N处理转移的过程;针叶林内,中N处理自始至终都表现了正向作用.N处理效应的表现也有一个年变化的动态过程.在持续的施N处理过程中,各林分中表现良好的处理效应最后都有减弱的趋势,甚至发展到负向效应或转移至更低的N处理水平中.N处理效应的年动态变化过程表明N沉降的累积效应是存在的.与区内的人工苗圃地试验结果进行了比较,并对产生以上响应的内在机制进行了初步探讨.     

大气氮沉降对森林生态系统影响的研究进展

近几十年来,由于化石燃料和农牧业含氮化肥饲料的广泛使用,全球大气氮沉降量明显增加,一些地区已经达到饱和甚至超过了生态系统所能承受的临界负荷.过量氮沉降会对森林生态系统产生负效应.本文概述了全球氮沉降的现状,介绍了氮沉降增加对森林土壤和植物的影响机制,从而说明了我国开展氮沉降研究的必要性和紧迫性.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that