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Tomato Growth and Organic Acid Changes in Response to Partial Replacement of NO_3^--N by NH_4^+-N

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Pedosphere 2004年第2期14卷 159-164页

作者： DONGCai-Xia SHeNQi-Rong WANGGe CollegeofResourcesandenvironmentalSciences NanjingAgriculturalUniversityNanjing210095（China）／E-mail：cxdong@***

A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized design was established with three replications and five treatments, i.e., NO-3-N/NH4+-N of 100/0, 75/25, 50/50, 25/75 and 0/100. Results showed that 25% replacement of NO3--N by NH4+-N significantly (P = 0.05) improved fresh and dry weight, revealing that a proper percentage of NH4+-N was important for tomato nitrogen nutrition. This could increase the plant growth even though tomato was a crop that preferred nitrate nutrition. Also an increase in the proportion of NH4+-N in the nutrient solution led to a significant decrease (P = 0.05) in malate, citrate and fumarate. However, the 25% NH4+-N plus 75% NO3--N treatment had no significant effect (P = 0.05) on the 2-ketoglutarate, succinate or oxalic acid content, showing that only some organic acids in tomato plants were affected. Only pyruvate increased significantly (P = 0.05), and it only increased for 25% and 50% replacement of NO3--N by NH4+-N. Metabolism of these organic acids, especially malate, citrate and fumarate, should be further studied at the molecular level in vegetables applied with different nitrogen forms.

关键词： NH_4^+-N nitrogen forms NO_3^--N organic acid tomato (Lycopersiconesculentum Mill.)

Characteristics of the natural organic matter sorption affects of organic contaminants

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Journal of environmental Sciences 2002年第3期14卷 351-356页

作者： LiuXB SongCY HeilongjiangInstituteofAgriculturalModernization ChineseAcademyofSciencesHarbin150040China.e－mail：songli@*** HeilongjiangInstituteofAgriculturalModernization ChineseAcademyofSciences

Several soil samples were used to study how the characteristics of natural organic matter (NOM) affect sorption of organic compounds. These soils contains different amounts and types of NOM. Aromaticity of NOM (percentage of aromatic carbons) was determined from solid state CPMAS 13 C NMR spectra and the soil effective polarity was computed from the equation developed by Xing et al . Naphthalene was used to examine the sorption characteristics of NOM. Both aromaticity and polarity of NOM strongly affected sorption of naphthalene. Old NOM showed higher affinity than that in the surface, young soils. Sorption increased with increasing aromaticity and decreasing polarity. Thus, the sorption coefficients of organic contaminants cannot be accurately predicted without some consideration of NOM characteristics.

关键词： characteristics of natural organic matter sorption of organic compounds influence

Phytosynthetic bacteria (PSB) as a water quality improvement mechanism in saline-alkali wetland ponds

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Journal of environmental Sciences 2002年第3期14卷 339-344页

作者： LiuFJ HuWY KeyLaboratoryofecologyandPhysiologyinAquaculture MinistryofAgricultureShangHaiFisheriesUniversityShanghai200090China.E－mail：fjliu@*** NanjinInstituteofGeographyandLimnolo

The efficiency of phytosynthetic bacteria (PSB) to improve the water quality in saline alkali ponds was studied, the result showed that (1) PSB application could increase the content of DO, NO\+-\-3\|N and effective phosphorus (eP) in ponds; (2) the changes of COD were not evident, just effective in later period after PSB application; (3) PSB application could decrease the contents of NH\+-\-4\|N (NH\-3\|N), NO\+-\-2\|N ; (4) PSB application could improve the structure of the effective nitrogen (eN) and eP, stimulate the growth of phytoplankton, and increase primary productivity, and finally increase the commercial profits of ponds because of the increase of eP and the decrease of eN contents; (5) the effect exerting speed of PSB was slower, but the effect sustaining time was longer; (6) the appropriate concentration of PSB application in saline alkali wetland ponds was 10×10 -6 mg/L, one time effective period was more than 15 days. So PSB was an efficient water quality improver in saline alkali ponds.

关键词： phytosynthetic bacteria (PSB) saline alkali wetland fishpond water quality improving

Heavy Metals, Phosphorus and Some Other elements in Urban Soils of Hangzhou City, China

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Pedosphere 2004年第2期14卷 177-185页

作者： ZHANGMing-Kui KeZi-Xia DepartmentofNaturalResourceScience CollegeofNaturalResourceandEnvironmentalSciencesZhefiangUniversityHangzhou310029（China）.E-mail：mkzhang@***

Health implications of inhaling and/or ingesting dust particles with high concentrations of heavy metals from urban soils are a subject of intense concern. Understanding the geochemistry of these metals is key to their effective management. Total concentrations of heavy metals,phosphorus (P) and 8 other elements from topsoil samples collected at 82 locations in Hangzhou City were measured to:a) assess their distribution in urban environments; and b) understand their differentiation as related to land use. Metal mobility was also studied using a three-step sequential chemical fractionation procedure. About 8.5%,1.2%,3.6%,11.0% and 30.3% of the soil samples had Cd,Cr,Cu,Pb,and Zn concentrations,respectively,above their allowable limits for public and private green areas and residential use. However,in commercial and industrial areas,most samples had metal concentrations below their allowable limits. Statistical analyses revealed that the 16 measured elements in urban soils could be divided into four groups based on natural or anthropic sources using a hierarchical cluster analysis. Additionally,Cu,Pb,and P showed similar spatial distributions with significant pollution in commercial zones,suggesting vehicle traffic or commercial activities as dominant pollutant sources. Also,Cd,Co,Cr,Ni,Zn,Mn and Fe had the highest concentrations in industrial locations,signifying that industrial activities were the main sources of these seven metals. Moreover,the data highlighted land-use as a major influence on heavy metal concentrations and forms found in topsoils with large proportions of soil Cd,Co,Cr,and Ni found in residual fractions and soil Cu,Pb and Zn mainly as extractable fractions.

关键词： anthropogenic pollution heavy metals phosphorus urban soils

Cadmium Release in Contaminated Soils due to Organic Acids

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Pedosphere 2004年第2期14卷 223-228页

作者： LIAOMin XIeXiao-Mei DepartmentofResourcesScience CollegeofEnvironmentalandResourceSciencesZhejiangUniversityHangzhou310029（China）.E-mail：liaomin@***

There is limited information on the release behavior of heavy metals fromnatural soils by organic acids. Thus, cadmium release, due to two organic acids (tartrate andcitrate) that are common in the rhizosphere, from soils polluted by metal smeltersor tailings andsoils artificially contaminated by adding Cd were analyzed. The presence of tartrate or citrate at alow concentration (e and e) inhibited Cdrelease, whereas the presence of organic acids in high concentrations (>= 2 mmol L^(-1) for citrateand >= 15 mmol L^(-1) for tartrate) apparently promoted Cd release. Under the same conditions, theCd release in naturally polluted soils was less than that of artificially ***, as the initial pH rose from 2 to 8 in the presence of citrate, a sequentialvalley and then peak appeared in the Cd release curve, while in the presence of tartrate the Cdrelease steadily decreased. In addition, Cd release was clearly enhanced as the electrolyteconcentration of KNO_3 or KC1 increased in the presence of 2 mmol L^(-1) tartrate. Moreover, ahigher desorption of Cd was shown with the KCl electrolyte compared to KNO_3 for the sameconcentration levels. This implied that the bioavailability of heavy metals could be promoted withthe addition of suitable types and concentrations of organic acids as well as reasonable fieldconditions.

关键词： artificially contaminated soil cadmium organic acid polluted soil release

experimental analysis of a nitrogen removal process simulation of wastewater land treatment under three different wheat planting densities

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Journal of environmental Sciences 2002年第3期14卷 317-324页

作者： WangHQ ChenJJ StateKeyJointLaboratoryofenvironmentalSimulationandPollutionControl InstituteofEnvironmentalSciencesBeijinNormalUniversityBeijing100875China.E－mail：whongqi@*** StateKeyJointLaboratory

Nitrogen contaminant transport, transformation and uptake simulation experiments were conducted in green house under three different planting density of winter wheat. They were Group A, planting density of 0.0208 plants/cm 2, Group B, 0.1042 plants /cm 2, and Group C, 0.1415 plants/cm 2. The capacity and ratio of nitrogen removal were different on three kinds of conditions of wastewater land treatment. From analysis of wastewater treatment capacity, wastewater concentration and irrigation intensity for Group C were suitable and nitrogen quantity added was 2 times of that for Group B, 2.6 times for Group A while nitrogen residue was only 7.06%. Hence, wastewater irrigation and treatment design with purpose of waste water treatment should select the design with maximum capacity, optimal removal ratio and least residue in soil, which was closely related to crop planting density, crop growth status and also background nitrogen quantity in soil.

关键词： wastewater land treatment planting density winter wheat nitrogen removal soil

Chemical composition of aerosols in winter/spring in Beijing

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Journal of environmental Sciences 2002年第1期14卷 7-11页

作者： ZhangRJ WangMX StateKeyLaboratoryofAtmospohericBoundaryPhysicsandAtmosphericChemistry InstituteofAtmospherisPhysicsChineseAcademyofSciencesBeijing100029China.E－mail：zrj@*** StateKeyLaboratoryofAtmospo

In 1999 aerosol samples were collected by cascade at Meteorological Tower in Beijing. The 12 group aerosol samples obtained were analyzed using PIXe method, which resulted in 20 elemental concentrations and size distribution of elemental concentrations. From the observation, the elemental concentrations, size distribution of elemental concentrations and their variations are analyzed. It shows that concentrations of the most elements in aerosols increase greatly compared with those in the past except that the concentrations of V, K, Sr, and the source of aerosols has changed greatly in the past decade. Fine mode aerosols increase more rapidly in the past decade, which may be due to the contribution of coal combustion and automobile exhaust. Pb content in aerosol is much higher than that at the beginning of 1980s, and has a decreasing trend in recent years because of using non leaded gasoline.

关键词： aerosol PIXe size distribution of elemental concentrations

A Force-Based Grid Manipulator for ALe Calculations in a Lobe Pump

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Journal of Thermal Science 2003年第4期12卷 318-322,370页

作者： John Vande Voorde rug.ac.be Jan Vierendeels rug.ac.be erik Dick rug.ac.be Department of Flow Heat and Combustion Mechanics Ghent University Belgium E-mail: John.VandevoordeDepartment of Flow Heat and Combustion Mechanics Ghent University Belgium E-mail: John.VandevoordeDepartment of Flow Heat and Combustion Mechanics Ghent University Belgium E-mail: John.Vandevoorde

In this paper, a time-dependant calculation of flow in a lobe pump is presented. Calculations are performed using the arbitrary Lagrangean eulerean (ALe) method. A grid manipulator is needed to move the nodes between time steps. The used grid manipulator is based on the pseudo-force idea. This means that each node is fictitiously connected with its 8 neighbours via fictitious springs. The equilibrium of the resulting pseudo spring forces defines the altered position of the nodes. The grid manipulator was coupled with a commercial flow solver and the whole was tested on the flow through a three-lobe lobe pump. Results were obtained for a rotational speed of 460 rpm and incompressible silicon oil as fluid.

关键词： ALe arbitrary Lagrangean eulerean moving grids lobe pump.

ANALYSIS OF AN SI ePIDeMIC MODeL WITH NONLINeAR TRANSMISSION AND STAGe STRUCTURe

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Acta Mathematica Scientia 2003年第4期23卷 440-446页

作者：陆忠华 *** 高淑京 *** 陈兰荪 *** Supercomputing Center of Computer Network Information Center Chinese Academy of Sciences Beijing 100080 China E-mail:zhlu Department of Mathematics Guangzhou University Guangzhou 510405 China E-mail:gaosjmath Institute of Mathematics Academy of Mathematics & System Sciences Academia Sinica Beijing 100080 China E-mail:lschen

A disease transmission model of SI type with stage structure is formulated. The stability of disease free equilibrium, the existence and uniqueness of an endemic equilibrium, the existence of a global attractor are in... 详细信息

关键词： SI epidemic model threshold disease free equilibrium endemic equilibrium global attractor