简介：Theeffectsofnitrogen,phosphorusandpotassiumapplicationlevel,seedrateandtransplantingdensityonthegrowthanddevelopmentofriceplantswerestudiedtofindoutnutrientstatusinhigh-yieldingriceplantsandtoincreasegrainyieldbyadequatefertilization.Therewasanequilibriumrelationshipamongnutrientelementsforhigh-yieldingriceplantpopulations.Theequilibriumindexofnutrientamount,contentanddistributioninhigh-yieldingriceplantsshouldbegenerallygreaterthan-2butlessthan2.Theoptimumnutritiveproportionofnitrogen:phosphorus:potassiumassimilatedbytheplantswasabout10:2:9attheripeningstage.Butthecontentandtheproportionvariedwiththegrowthstages,Therefore,thenutrientinriceplantpopulationsshouldbeinadynamicequilibrium.Soastoachievehighyield.

简介：Thechangesofclaymineralassociationafterhigh-gradientmagneticseparation(HGMS)treatment,andtheeffectsofchemicalandphysicaltechnologiesonconcentratingFeoxidesformiansoilsincentralandsouthernChinawereinvestigatedbymeansofX-raydiffraction(XRD)andchemicalanalysismethods.ResultsindicatedthattheconcentratingtimesofFeoxidesbyHGMStreatmentwerethelargestfor0.2-2μmsizefractionintheexaminedsoils.Forthesoilsinwhich2:1phyllosilicatesweredominant,concentratingtimesofironoxidesbyHGMStreatmentwerelargerthanby5molL^-1NaOHtreatment.Phyllosili-catesweredecreasedafterHGMStreatment;however,thedecreasewaslessthanthatofkaolinite,Thegoethite/(goethite+hematite)valuesinFeoxidesofthesoilskeptvirtuallyconstantafterHGMStreatment.

简介：TheverticaldistributionandmigrationofCu,Zn,Pb,andCdintwoforestsoilprofilesnearanindustrialemissionsourcewereinvestigatedusingahighresolutionsamplingmethodtogetherwithreferenceelementTi.One-metersoilprofilewassectionedhorizontallyat2cmintervalsinthefirst40cm,5cmintervalsinthenext40cm,and10cmintervalsinthelast20cm.Themigrationdistanceandrateofheavymetalsinthesoilprofileswerecalculatedaccordingtotheirrelativeconcentrationsintheprofiles,ascalibratedbythereferenceelementTi.Theenrichmentofheavymetalsappearedintheuppermostlayeroftheforestsoil,andthesoilheavymetalconcentrationsdecreaseddowntheprofileuntilreachingtheirbackgroundvalues.ThecalculatedaveragemigrationratesofCd,Cu,Pb,andZnwere0.70,0.33,0.37,and0.76cmyear-1,respectively,whichwerecomparabletoothermethods.Asimulationmodelwasproposed,whichcouldwelldescribethedistributionofCu,Zn,Pb,andCdinnaturalforestsoils.

简介：为简洁的原因，最通常使用的水文学模型基于土壤保存服务曲线数字(SCS-CN)当模特儿，它可能是为中国的黄土高原上的流量的评价的一种好选择；然而，高空间的异质，主要在土壤类型由碎裂的地形和变化引起了，可以限制它的适用性到这个区域。因此，到一个小分水岭的SCS-CN模型的适用性，高原上的Liudaogou，被评估，在模型的最适当的起始的抽象比率(Ia/S)价值被反的方法确定。结果证明标准SCS-CN模型对在Liudaogou分水岭的流量的评价适用，模型表演根据相对错误和Nash-Sutcliffe效率的价值是可接受的。因为，为分水岭的最适当的Ia/S值是0.22与这修改Ia/S值，模型性能稍微被改进。当一个重降雨事件(50.1公里)没被考虑时，模型表演不对Ia/S价值的修正敏感，它暗示模型用标准Ia/S价值，因为很少超过50公里的单个降雨事件发生在那个区域，能为Liudaogou分水岭被推荐。流量数量由SCS-CN模型为Liudaogou分水岭预言了，用修改Ia/S价值，当降雨价值比50公里低时，与增加降雨逐渐地增加了，而当降雨超过了50公里时，预言的数量很快增加了。这些调查结果可能在在中国的黄土高原上解决严肃的土壤和水损失的问题是有用的。

简介：Effectsofcolumntemperatureandflowrateonseparationoforganicacidswerestudiedbydeterminingninelow-molecular-weightorganicacidsonreversed-phaseC18columnusinghighperformaceliquidchromatography(HPLC)withawavelengthofUV(ultraviolet)214nmandamobilephaseof18mmolL^-1KH2PO4buffersolution(pH2.1).Thethermalstabiltiyoforganicacidswasdeterminedbycomparingtherecoveriesoforganicacidsindifferenttemperaturetreatments.Therelationshipsbetweencolumntemperature,flowrateorsolventpHandretentiontimewereanalyzed.AtlowsolventpH,separatioinefficiencyoforganicacidswasincreasedbyraisingtheflowrateofthesolventbecauseofloweringtheretentiontimeororganicacids.Highcolumntemperaturewasunfavorablefortheseparationoforganicacids.Theseparatingeffectcanbeenhancedthroughreducingcolumntemperatureinorganicaciddeterminationduetoincreasingretentiontime.Highthermalstabilityoforganicacidswithlowconcentrationswasobservedattemperatureof40℃-45℃,SensitivityandseparationeffectoforganicaciddeterminationbyHPLCwereclearlyimprovedbyacombinationofraisingflowrateandloweringcolumntemperatureatlowsolventpH.

简介：Methodsfordeterminingnienelowmolecular-weightoragnicacidsinrootexudatesweredevelopedbyusingreversed-phasehighperformanceliquiedchromatographywithUV(ultraviolet)detectionat214nm.Themobilephasewas18mmolL^-1kH2PO4adjustedtopH2.25withphosporicacidndtheflowratewas0.3mLmin^-1,Theanalyticalcolumnwasareversed-phasesilicabasedC-18column(shim-packCLC-ODS).Therootexudateswerecollectedthroughsubmergingthewholerootsystemintoaerateddeionizedwaterfor2hours,Thefilteredexudatesolutionswereconcentratedtodrynessbyrotaryevaporationat40℃,dissolvedin10mLmobilephase.Thechromatoraphicconditionsoforganicaciddeterminationwereanalyzed.Theresultsshowedthattherewasahighselectivityandsensitivityintheorganicaciddeterminationbyreversed-phasehighperformanceliquidchromatography.Coefficientsofvariationfororganicacieddeterminationwerelowerthan10%exceptlacticacid.Therecoverieswereconsistentlybetween80.1%to108.3%.Detectionlimitswereapproximately0.05to4.5mgL^-1fororganicacidsexceptsuccinicacidwiththedetectionlimitof7.0mgL^-1.Phosphorusdeficiencymaycontributetothereleaseoforganicacidsinsoybeanrootexudatesespeciallymalic,lacticandcitricacids.