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Physical mechanisms of plant roots affecting weathering and leaching of loess soil

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Science China Earth sciences 2006年第9期49卷 1002-1008页

作者： LI Yong1,2. ZHANG Qingwen1,2. WAN Guojiang3. HUANG Ronggui3. PIAO Hechun3. BAI Lingyu2.& LI Lu2.1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, institute of Soil and Water Conservation, chinese academy of sciences, Yangling 712.00, China 2. institute of Agro-Environment and Sustainable Development, {3. academy of Agricultural sciences, Beijing 100081, China 3. institute of geochemistry, chinese academy of sciences, guiyang {12. China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water Conservation Chinese Academy of Sciences Yangling China institute of Agro-Environment and Sustainable Development Chinese Academy of Agricultural Sciences Beijing China institute of geochemistry Chinese Academy of Sciences Guiyang China

Plant roots have potential impacts on soil mineral weathering and leaching. Our objective is to understand the physical mechanisms of plant roots affecting weathering and leaching of loess soil. Root densities were measured through the method of a large-size dug profile, and transport fluxes of soil elements were determined using an undisturbed monolith soil infiltration device on the hilly and gully regions of the chinese Loess Plateau. The results show that the improvement effects of soil environment by plant roots are mainly controlled by the density and weight of the fibrous roots with the diameters less than 1 mm. Plant roots have the stronger effects on soil physical properties than chemical properties. The principal components analysis (PCA) indicates that soil physical properties by plant roots account for 56.7% of variations in soil environment whereas soil chemical properties and pH contribute about 2..2. of the soil variations. The roles of plant roots in controlling soil weathering and leaching increased in the following order: infiltration enhancement > increase of bio- active substance > stabilization of soil structure. The effects of plant roots on soil mineral weathering and leaching can be quantified using the multiple regression models with the high prediction accura- cies developed in this study.

关键词： plant roots, soil weathering and leaching rates, soil environment field, principal components analysis (PCA), chinese Loess Plateau.

Population information extraction in Chaohu watershed based on RS and GIS

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chinese Science Bulletin 2003年第2期48卷 181-183页

作者： LIU Jianjun1,2.& LI Chunlai3.1. institute of {2., chinese academy of sciences, {3. 550002. China 2. Graduate School, chinese academy of sciences, Beijing 10003., China 3. National Astronomical Observatories, chinese academy of sciences, Beijing 100012. China Correspondence should be addressed to Liu Jianjun (e-mail: dhsliujj@ ***) institute of geochemistry Chinese Academy of Sciences Guiyang China Graduate School Chinese Academy of Sciences Beijing China National Astronomical Observatories Chinese Academy of Sciences Beijing China

It is always difficult to extract population in-formation of small watershed during the region environment assessment. The report adopted compound areal interpola-tion to study the population in Chaohu watershed with the GIS technique and landuse interpretation data from remote sensing. The result indicated that the method is effective to extract population information of small watershed.

关键词：巢湖流域人口分布信息提取 RS GIS 小流域生态环境评价

Evidence of acid nature of ore-forming solutions

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chinese Science Bulletin 1999年第S2期44卷 199-201页

作者： CHEN Fu institute of geochemistry,{2., {3. 550002. China institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

THE author thinks that the ore-forming solution is formed not by the near-neutral brine but by the strongacid solutions. Some evidence are the following: （i） The simulating experiments showed that, all near-neutral supergenic water as volcanic hotspring water of Tengchong, K-brine of Mengyejing, seawater of Qingdao, oil-gasses-bearing water of Chitianhua, rain water of guiyang and CO2./sub>-bearing rain cannot form metal-bearing solutions by heating mixedabove-mentioned supergenic water with ore-source rocks as basalt, ore-bearing carbonate, sandstone andshale. The most content of Cu, Pb, Zn, Hg, Sb, As, Ag in solutions is only （0.3.0.5）×10-6.They cannot form any ore deposit. Oppositely, the acid solution of pH=1.0 is easy to form metal-bearingsolutions with every ore-source rocks. The most content of metal in solution is n×10-n×1000 × 10-6i.e. rose in 3.5 grades. The content of metals in humic acid-bearing solutions is variable, perhaps dueto the changes of humic components and content and due to easy-decomposition by oxidation or *** the best one in solutions to form ore-forming solution is only the acidic water.

关键词： ore-forming solution acid solution in nature genesis of brine.

Mantle-derived sulfur and its time constraints on gold mineralization of Ailaoshan gold belt, China

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chinese Science Bulletin 1999年第S2期44卷 242-244页

作者： BI Xianwu institute of geochemistry,{2., {3. 550002. China institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

IN the previous studies of hydrothermal deposits much attention was paid to their material sources ratherthan the mechanisms of dynamic association of ore-forming fluids. In recent years many studies haveshown that ore-forming elements were transferred into ore-forming solutions after some suitable mineralizerwas incorporated into hydrothermal solutions. Therefore, the time at which the mineralizer is incorporated into hydrothermal solutions could, to a great extent, reflect the time of ore deposition. In the dynamic study of the origin of ore deposits on a trial basis the author took the Ailaoshan gold belt in YunnanProvince as an example and carried out investigations into the sources of mineralizers (the anion coordinates of stable complexes of gold in hydrothermal solutions) in ore-forming hydrothermal solutions and theconstraints of relevant geological events on gold mineralization.

关键词： sulfur isotope mantle-derived sulfur dating gold mineralization Ailaoshan gold belt.

Epithermal gold deposits in China and potential assessment

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chinese Science Bulletin 1999年第S2期44卷 164-166页

作者： QIU Yuzhuo institute of geochemistry,{2., {3. 550002. China institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

THE epithermal gold deposit (epi-gold) is one of the most important types in various gold deposits all overthe world. The discovery of several superlarge deposits of this type around the circum-Pacific Rim duringthe 1980s, greatly stimulated the interest in searching for epi-golds in the world as well as in China. Theepi-gold has become a major target in gold exploration in China during last two-decade "Golden *** discovery of the Zijinshan Cu (Au) deposit in SE China and the Axi and other Au deposits in NWChina is the significant success in gold prospecting in this field. The author suggested that it is the timeto do an overview and the potential assessment of epi-golds in China Some people are holding an optimistic idea on this topic mainly based on the following considerations: (i) as a host rock, the subaerial volcanic rocks of Mesozoic are widespread in East China; (ii)

关键词： epithermal gold deposit China potential assessment.

ANNUAL LAMINATIONS IN THE SEDIMENTS OF HONGFENG LAKE, CHINA

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chinese Geographical Science 1996年第4期6卷 375-382页

作者： Wu Fengchang Wan Guojiang(State Key Laboratory of Environmental geochemistry, institute of geochemistry, the{3., guiyang 550002. PRC) State Key Laboratory of Environmental geochemistry Institute of Geochemistry the Chinese Academy of Sciences Guiyang PRC

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关键词： annual laminations Hongfeng Lake carbonate geochemistry

Experimental measurement of the electrical conductivity of single crystal olivine at high temperature and high pressure under different oxygen fugacities

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Progress in Natural Science:Materials International 2006年第4期16卷 387-393页

作者： DAI Lidong, LI Heping, LIU Congqiang, CUI Tongdi, SHAN Shuangming, YANG Changjun, LIU Qingyou and DENG Heming Laboratory of the Earth’s Interior Materials and Fluid geochemistry, institute of geochemistry,{3., guiyang 550002. China Graduate School of the{3., Beijing 10003., China institute of geochemistry,{3., guiyang 550002. China Guizhou University, guiyang 550004, China Laboratory of the Earth's Interior Materials and Fluid geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China Graduate School of the chinese academy of sciences Beijing 100039 China institute of geochemistry{2. Guiyang 550002 China Guizhou University Guiyang 550004 China

At 1.0-4.0 GPa and 112.0}1473.K and under oxygen fugacity-controlled conditions (Ni + NiO, Fe + Fe3.4, Fe + FeO and Mo+ M0O2.buffers), a YJ-3.00t Model six-anvil solid high-pressure apparatus and a Sarltron-12.0 Impedance/Gain-Phase analyzer were employed to conduct an in situ measurement of the electrical conductivity of single crystal olivine. Experimental results showed that: (1) within the range of experimentally selected frequencies (103.106 Hz), the electrical conductivity of the sample is of great dependence on the frequency; (2. with the rise of temperature ( T), the electrical conductivity (σ) will increase, and the Arrenhius linear relationship is established between lgσ and 1/T; (3. under the control of oxygen buffer Fe+ Fe3.4, with the rise of pressure, the electrical conductivity tends to decrease whereas the activation enthalpy and independent-of-temperature preexponential factor tend to increase, with the activation energy and activation volume of the sample estimated at (1. 2. ± 0.08) eV and (0.105 ±0.02.) cm3.mol, respectively; (4) under given pressure and temperature conditions, the electrical conductivity tends to increase whereas the activation energy tends to decrease with increasing oxygen fugacity; and ( 5) the mechanism of electrical conduction of small polarons can provide insight into the behavior of electrical conduction of olivine under high pressure and high temperature.

关键词： olivine high temperature and high pressure electrical conductivity oxygen fugacity small polaron.

Geological setting of some classical selenium-bearing formations in China

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chinese Science Bulletin 1999年第S2期44卷 185-186页

作者： WEN Hanjie and QIU Yuzhuo institute of geochemistry,{2., {3. 550002. China institute of geochemistry Chinese Academy of Sciences Guiyang 550002 China

SELENIUM is a highly dispersed element with a lower Clarke of 0.05×10-6 and rarely forms its own independent deposits in the crust. In recent years by the discovery of a series of selenium-bearing deposits（such as Laerma selenium-gold deposit and Yutangba selenium deposit） and selenium-rich strata （westHubei, Laerma, Ziyang, Langao, northwest Hunan, etc.）, the character and genesis of the seleniumbearing formation （SBF） have been noted by many researchers. 1 Some classical SBF in China In China the classical SBFs include: （i） The Lower Cambrian SBF in Laerma, west Qinling: Thebackground value of selenium is 5.47×10-6, and the selenium content of the sillcalite and slate （mainrock type） averages 8.70×10-6 and 3.05×10-6 respectively. （ii） The Lower Cambrian SBF inZiyang and Langao, east Qinling: Selenium is present in relatively high abundance in the SBF, averaging3.89×10-6 in the slate, 2.86×10-6 in the sillcalite. （iii） The Lower Cambrian SBF in northwest Hu-

关键词： selenium selenium-bearing formation geological setting.

Oxygen isotopic (^(17)O-^(18)O) heterogeneity in Archaean continental nucleus, North China Craton

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chinese Science Bulletin 1999年第24期44卷 2267-2269页

作者： LIU Jianzhong, ZHANG Fuqin, LI Chunlai and WANG Shijie institute of geochemistry ,{2. , {3. 550002., China institute of Geophysics ,{2. , Beijing 100101 , China institute of geochemistry Chinese Academy of Sciences Guiyang China institute of Geophysics Chinese Academy of Sciences Beijing China

The oxygen isotopic data for amphibolites from Archaean continental nucleus, North China Craton indicate that ( i ) the evolving lines structured by the data are parallel to the geoselenic evolving line, which means that the parent materials of these continental nucleus o-riginated from solar matter; ( ii ) different intercepts for these evolving lines manifest that oxy-

关键词： North China Craton oxygen isotope (I7O-18O ) heterogeneity.