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1、土壤化學題庫1.Explainhowlayerchargeinfluencesthefollowinglayersilicateproperties:(a)Interlayerbonds(b)Crystalsize(c)Swelling(d)Surfacearea(e)cspacing(f)Exchangeabilityofadsorbedcations2.Writethehalf-unit-cellformulaforamontmorillonitemineralwithalayerchargeof0.3,with90%ofthesubst
2、itutionintheoctahedrallayer(Mg2+forAl3+)and10%ofthesubstitutioninthetetrahedrallayer(Al3+forSi4+).ThesaturatingcationisNa+.Drawadiagramofthismineral,indicatingthepositionofMg2+,Al3+,Si4+andNa+?3.Whatismeantbythezeropointofcharge?WhatarethefunctionalgroupsresponsibleforpH-de
3、pendentchargeinsoil?4.AnacidicpesticideofpK5isbeingappliedtosoilsofagivenregion.Wouldleachingbegreatestforsoilsof(a)pH>5?(b)pH6to8?(c)pH<5?Why?5.AsoilofpH5.5retains60mmol(+)kg-1ofexchangeablebasesandhasaCECatpH7of80mmol(+)kg-1:(a)Whatisitspercentbasesolution?(b)Whatisitsapp
4、roximateCECatpH5.5?6.Anirrigationwatercontains750mgL-1solublesalts.Ifusedatanaverageleachingfractionof0.15,whatwouldbetheaverageECofthedrainagewaterleavingthebottomofthecroprootzone?7.A30-cmdepthofsurfacesoilcontains28%exchangeablesodiumandhasaCECof150mmol(+)kg-1.Howmanyton
5、nesperhectareofsulfurwillberequiredtoloweritsESPto5%?8.Avermiculitesurfacesoilhastheabilitytofix25mmolkg-1ofK+orNH4+.Whatrateof(NH4)2SO4orKClfertilizer(inkgha-1)wouldberequiretosaturatethisfixationcapacityfora30-cmdepthofsoil?9.ForaCECprocedurethatusesNa+astheindexcation,H2
6、O/ethanolasthewashsolvent,andMg2+asthedisplacingcation,discusstheeffectofeachofthefollowingonCECmeasurements:(a)Hydrolysisduetoexcesswashing(b)Presenceoflargeamountsoflimeorgypsuminthesoil(c)Incompleteindex-cationsaturation(d)PrecipitationofaninsolubleNa+saltintheethanol(e)
7、IncompleteremovaloftheindexcationbyMg2+10.Tocalculateb(maximumamountofadsorbate)andK(affinityconstant)ofapesticidewithLangmuirequationfromthedata:Each25mL20,40,60,80,100mg/Lrespectivelyaddtoeach0.5gmsoil,andfinalsolutioncocentrationrespectivelyis0.4,2,20,35,50mg/L.11.Whatki
8、ndsoffunctiongroupsorsegmentscontributetothehydrophobicityofsoilorganicmatters?Wha
