腐植酸研究历史.docx
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腐植酸研究历史.docx
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腐植酸研究历史
AHISTORYOFHUMICACID RESEARCH
MORETHANTWOCENTURIESOF HUMICACIDRESEARCH
—WHY SOLONG?
BYMICHAELSUSIC
RESEARCHSCIENTIST
2FEBRUARY2001
(Revised10June2008)
ABSTRACT
Eventhoughhumuswasnamedin1761andtheextractionof humicacidswasreportedin1786,humicacidstructureand originhasonlyrecentlybeendetermined.Suchatimespanfromthediscoveryofasubstancetotheelucidation ofitsoriginandstructureisindeedrare,perhapsunique. Yethumicacidsareextremelycommon,andalsoareprecursorstosuchimportantnaturalresourcesascoaland petroleum.Thepressuretoimproveagricultureinthe18thand19thcenturieswastheimpetusbehindtheeffort tounderstandhumicacidchemistry,andthegrowingimportanceofcoalandpetroleuminthe20thcentury furtherincreasedthispressure.Therehasbeennoshortage ofresearcheffort,withabout10,000reportsinthescientificliterature.Despitethis,theworkhasbeen conflictingandconfused.Therearetwoprincipalreasons whyprogresshasbeensoslow.First,humicacidchemistrywasdifficulttounravelwiththetechnologythatwasavailablebeforeWWII.Second,asaconsequenceofthis,researchersbecamestubbornlypolarizedintheirinterpretationofdataandrefusedtoacknowledgevalidresultsthatweredifferenttotheirown.WhenadequatetechnologyforthestudyofhumicacidsbecameavailableafterWWII,thepreviousunhealthyattitudeswerecontinuedandmajorerrorswentunchallengedforlongperiodsoftime.Itishopedthatwiththelatesthumic aciddiscoveriesamoresensibleapproachwillprevail, andthatfutureprogresswillbemuchmorerapid.
Introduction
Withinthepast150yearsorso,thestructuresof naturally-occurringorganiccompoundshavegenerallybeen elucidatedwithindecadesoftheirdiscovery.Aclassic exampleisthestructureelucidationofDNA.Evenifthe exactsequenceofaminoacidsandsugarsinforexample,a glycoprotein,hasnotbeendetermined,thenumberandtypes ofaminoacidsandsugarsiswell-known.Incontrast,the situationforhumicacidshasbeenverydifferent.Humicacids*arebrown-blackpolymericacidsofplantoriginthatareubiquitousattheEarth’ssurface.Theycontributetosoilfertility,afactthathasbeenrecognizedsinceancient times.Asthestudyofhumicacidsprogressedfrom1786when theywerefirstextractedfrompeatbogsinGermany,their importancehasbecomeclearer.Notonlyaretheyimportant forsoilfertility,buttheyarealsoprecursorsofkerogens,peat,asphalt,bitumen,petroleum,andcoal.Buttheyalso havedeleteriouseffects,andinmorerecenttimesithasbeendiscoveredthathumicacidsaffecttheenvironmentby complexingwithmetalsandorganics,whichcanmodifythe toxicityofheavymetals,pesticides,andherbicides.They canalsointerferewiththeefficiencyofindustrial processessuchasaluminaextractionfrombauxite,adversely affectwaterpurification,andformcarcinogensduringraw waterdisinfection.
Alongwithagoodclimate,fertilesoilsareanecessityforhumanexistence,survival,andenjoymentoflife.Theculturesofmanyancientpeoplewerebasedonan agriculturalexistence.Tothemfertilesoilswerethe responsibilityofthegods,whomtheyfrequentlyimplored forgoodcrops.AsknowledgeofMan’senvironmentslowly grew,especiallyintheMiddleAges,humansturnedtheir mindstomoreconcretereasonsforgoodcropyields,rather thanthemerewhimsofmythicalgods.Differencesinplant litterwereafairlyobviouscandidateforstudy,apartfromthenon-descriptentitiessuchas wind,earth, and fire whichwereinvogueatthetime.Hence,thelinkingofsoil fertilitywithplantlitterwasnosurprise.Butthe complexnatureofthiscouldnothavebeenforeseen.After all,itisnowknownthatplantsarecomposedofaplethora ofchemicalcompounds,andevenmoreareproducedinthe soilduetomicrobialalterationofthem.Knowledgeabout thisinaneraof wind,earth, and fire thinkinghadtocomeslowlybyobservation,experiment,andrecordingofresults.Man’sobviousneedforandconcernaboutfood,orthescarcityofit,broughthumus,andlater,humicacids,intosharpfocus.
Thepressuretoimproveagricultureinthe18thand19thcenturieswastheimpetusbehindtheefforttounderstandhumicacidchemistry.Then,thegrowingimportanceofcoalandpetroleuminthe20thcenturyfurtherincreasedthepressure.However,fromthelate1700stothemid1800s researcherswereonlyjustdiscoveringsuchsimplethings asoxygen,hydrogen,carbondioxide,andthenoblegases, yetthequestionwasbeingasked:
Whatarehumicacids?
Thequestioncamefartooearly,andwiththeinadequateknowledgeandtechnologyofthetime,incorrectviewpoints becamestubbornlyentrenched.Thisattitudethenpersisted evenwhenadequatetechnologybecameavailableafter WWII.
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