SOIL AND ENVIRONMENTAL CHEMISTRY SOIL AND ENVIRONMENTAL CHEMISTRY SECOND EDITION William Bleam UW-Madison,DepartmentofSoilScience Madison,WI,UnitedStates AMSTERDAM (cid:129) BOSTON (cid:129) HEIDELBERG (cid:129) LONDON NEW YORK (cid:129) OXFORD (cid:129) PARIS (cid:129) SAN DIEGO SAN FRANCISCO (cid:129) SINGAPORE (cid:129) SYDNEY (cid:129) TOKYO Academic Press is an imprint of Elsevier AcademicPressisanimprintofElsevier 125LondonWall,LondonEC2Y5AS,UnitedKingdom 525BStreet,Suite1800,SanDiego,CA92101-4495,UnitedStates 50HampshireStreet,5thFloor,Cambridge,MA02139,UnitedStates TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UnitedKingdom ©2017,2011ElsevierInc.Allrightsreserved. Nopartofthispublicationmaybereproducedortransmittedinanyformorbyanymeans,electronic ormechanical,includingphotocopying,recording,oranyinformationstorageandretrievalsystem, withoutpermissioninwritingfromthepublisher.Detailsonhowtoseekpermission,further informationaboutthePublisher’spermissionspoliciesandourarrangementswithorganizationssuch astheCopyrightClearanceCenterandtheCopyrightLicensingAgency,canbefoundatourwebsite: www.elsevier.com/permissions. Thisbookandtheindividualcontributionscontainedinitareprotectedundercopyrightbythe Publisher(otherthanasmaybenotedherein). Notices Knowledgeandbestpracticeinthisfieldareconstantlychanging.Asnewresearchandexperience broadenourunderstanding,changesinresearchmethods,professionalpractices,ormedicaltreatment maybecomenecessary. Practitionersandresearchersmustalwaysrelyontheirownexperienceandknowledgeinevaluating andusinganyinformation,methods,compounds,orexperimentsdescribedherein.Inusingsuch informationormethodstheyshouldbemindfuloftheirownsafetyandthesafetyofothers,including partiesforwhomtheyhaveaprofessionalresponsibility. Tothefullestextentofthelaw,neitherthePublishernortheauthors,contributors,oreditors,assume anyliabilityforanyinjuryand/ordamagetopersonsorpropertyasamatterofproductsliability, negligenceorotherwise,orfromanyuseoroperationofanymethods,products,instructions,orideas containedinthematerialherein. LibraryofCongressCataloging-in-PublicationData AcatalogrecordforthisbookisavailablefromtheLibraryofCongress BritishLibraryCataloguing-in-PublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary ISBN:978-0-12-804178-9 ForinformationonallAcademicPresspublications visitourwebsiteathttps://www.elsevier.com/ Publisher:CandiceJanco AcquisitionEditor:CandiceJanco EditorialProjectManager:EmilyThomson ProductionProjectManager:PaulPrasadChandramohan CoverDesigner:GregHarris TypesetbySPiGlobal,India Dedication ToSharon,mywife v Second Edition Preface I made numerous major changes in this The biochemistry community often uses the second edition of Soil and Environmental a pH 7 standard state that differs from Chemistry. One that will be immediately the pH 0 standard state used by the pure apparent was a decision to adopt insofar chemistrycommunity.Assuch,IUPACdoes as possible the notation and nomenclature not endorse a special notation for reduction recommended by the International Union of half-reactions under biochemical standard Pure and Applied Chemistry IUPAC. This was stateconditions.InthesecondeditionIhave motivated,inpart,toclarifytherootsofsoil adoptedthenotationusedbyAtkinsandde chemistry, geochemistry, and environmental Paula (2005) in Physical Chemistry for the Life chemistry in pure chemistry and, in part, Sciences. to make this particular field of applied Finally,thehydrologyandsoilphysicsno- chemistry more immediately accessible to tationusedinChapter2(ChemicalHydrology) studentstrainedinpurechemistry. and elsewhere follow Hillel (2004) in Intro- There are a few exceptions, the first ductiontoEnvironmentalSoilPhysics. relating to partition constant notation. The Water residence time and water budgets environmental science community uses haveimportantimplicationsforenvironmen- a special notation for the octanol-water talchemistry.Chapter2(ChemicalHydrology) partition constant that explicitly identifies now includes a discussion of elementary octanol as the organic phase involved in potential evapotranspiration models that al- physisorption by partition. Identifying the lowscientiststocomputeapproximatewater adsorbent is essential for the environmen- budgets and estimate soil water residence tal science community because the same timeusingreadilyavailabletemperatureand adsorptive will yield different partition precipitationdatafromthousandsofweather constants for partitioning into octanol, the stationsworldwide.Therearealsosignificant fattytissueoflivingorganisms(inthecaseof revisionsoftheplate-theorytransportmodel bioconcentration factors), adsorption by the that will hopefully make the discussion of solid phase soils, sediments or aquifers, and thismodelmoretransparent. adsorptionbytheorganiccarboncomponent Reviewers requested further details on in the same. IUPAC does not identify the mechanisms of silicate mineral chemical the organic phase in their recommended weathering. Chapter 3 (Clay Mineralogy and partition constant (Kφ) and, hence, the Chemistry) now includes a discussion of the D A IUPAC recommended partition constant solid-state transformation and surface-site symbol is unable to represent legitimate limited reactions that many mineralogists distinctionsrecognizedbytheenvironmental believe explain the formation of low- sciencecommunity. temperaturelayersilicatesthroughchemical xiii xiv SECONDEDITIONPREFACE weathering. This chapter also discusses the and Adsorption) by drawing distinctions origins of silicate mineral alkalinity that between physisorption and chemisorption, is essential for the later chapter on acid- and importance of molecular association base chemistry. Finally, the discussion of in organic matter extracts. The associative clay swelling was completely rewritten to behavior of extracted organic matter is a provideamoresoundfoundationtothisvery key factor in the physisorption of organic importantphenomenon. substances by dissolved and adsorbed Chapter 4 (Ion Exchange) immediately organicmatter.Chapter8nowincludesadis- follows the chapter on clay chemistry. cussionofadsorptionedgefittingandanex- This chapter now includes a thorough panded evaluation of surface-complexation discussion of the Vanselow mole-fraction models. and the Gaines-Thomas equivalent-fraction Reconciling the pure chemistry perspec- conventions,demonstratingboththedistinc- tive of reduction-oxidation chemistry with tions between the two equilibrium quotient thebiologicalanaerobiosisdrivingreduction expressionsandtheirunderlyingunity.More in soils and sediments is an important advancedtopics,suchastheroleofrealand addition to Chapter 9 (Reduction-Oxidation ideal mixtures in the ion exchange process Chemistry). This discussion provides a andthefatalflawsoftheGaponconvention, rational basis for the relative efficiency of appearinappendixes. ferricironrespirationandsulfaterespiration Chapter 5 (Water Chemistry) places less and allows a deeper understanding of emphasis on R.I.C.E. tables, scaling back the restrictionsoncarbon-useefficiencyimposed discussion and moving it to an appendix. byanaerobicrespiration. This edition discusses the steps students Chapter 10 (Human Health and Ecological can take to design input files that will Risk Analysis) now includes a more sound faithfully simulate the chemistry of the justification for the profoundly different component species and the importance of treatmentofcarcinogensandnoncarcinogens evaluating water analyses for reliability, a in risk analysis: the irreversible adverse theme continued in Chapter 6 (Acid-Base effect of carcinogen intoxication and the Chemistry). Chapter 6 includes an expanded presumedreversibleeffectsofnoncarcinogen discussion of alkalinity and methods for intoxication. A brief discussion of ecotox- incorporating alkalinity in water chemistry icity risk assessment reveals the parallels simulations. between human health and ecological risk Chapter7(NaturalOrganicMatter)isnow assessment. positionedbeforethechapteronadsorption, The number of chapter exercises is followingthelogicofpositioningclaychem- expanded by about half to more than one istry before ion exchange. This chapter be- hundred exercises. None of the chapter gins with a brief review of natural organic exercisesincludesolutions;exercisesolutions matter research for the past 100 years. The appear in the Instructor’s Manual (http:// secondeditionexpandsthediscussionofbe- booksite.elsevier.com/9780128041789/) that low ground carbon cycle models and now accompanies thesecond edition.Thesecond includes a discussion linking carbon-use ef- edition also attempts to strike a balance ficiencytothemeancarbonreductioninnat- between topics appropriate for undergrad- uralorganicmatter. uates with limited chemistry experience Some of the topics raised in Chapter 7 and more advanced topics intended for areexpandedinChapter8(SurfaceChemistry moreadvancedundergraduatestudentsand xv SECONDEDITIONPREFACE graduatestudentswhoarenotspecializingin “Bill” Hickey, Robert W. Taylor, Beat Müller, chemistry.Advancedtopicsgenerallyappear Francisco Arriaga, Birl Lowery, and Alfred inappendixesattheendofeachchapter. Hartimink. Iwishtothankthefollowingcolleaguesfor WilliamF.Bleam their assistance and encouragement: Willim Madison,Wisconsin C H A P T E R 1 Element Abundance O U T L I N E 1.1 Introduction 1 1.7 Element Abundance Frequency Distributions 20 1.2 ABriefHistoryoftheSolarSystem andPlanetEarth 3 1.8 Estimating the Central Tendency of Logarithmic-Normal 1.3 Elemental Composition of Earth’s Distributions 25 LithosphereandSoils 4 1.3.1 RelativeElementalAbundance 4 1.9 Summary 32 1.3.2 ElementsandIsotopes 6 Appendices 32 1.3.3 NuclearBindingEnergy 7 1.AFactorsGoverningNuclearStability 1.4 Enrichment and Depletion During andNuclideAbundance 32 PlanetaryFormation 12 1.A.1 TheTableofNuclides 32 1.4.1 PlanetaryAccretion 12 1.A.2 NuclearMagicNumbers 34 1.4.2 PlanetaryStratification 13 1.B RandomSequentialDilutionandthe 1.5 TheRockCycle 17 LawofProportionateEffect 35 1.6 SoilFormation 19 References 37 1.1 INTRODUCTION StudentsencounterthePeriodicTableoftheElementsasearlyashighschoolandbycollege have come to understand the periodicity underlying its design, to associate letter symbols with atomic numbers, and how to find the atomic mass and electron configuration of each element.Whileitislikelystudentswillbefamiliarwiththeisotopeconceptandunderstand 1 SoilandEnvironmentalChemistry ©2017ElsevierInc.Allrightsreserved. http://dx.doi.org/10.1016/B978-0-12-804178-9.00001-X 2 1.ELEMENTABUNDANCE TABLE1.1 IntegerAtomicMassesforElementsThatHaveNoStable Nuclides AtomicNumber(Z) ElementSymbol ElementName AtomicMass 43 Tc Technetium 98 61 Pm Promethium 145 84 Po Polonium 209 85 At Astatine 210 86 Rn Radon 222 87 Fr Francium 223 88 Ra Radium 226 89 Ac Actinium 227 what determines atomic mass of an element,1 it is unlikely they are familiar with the Table ofNuclides. Theofficialatomicmasses,appearinginareportreleasedbyInternationalUnionofPureand AppliedChemistry(IUPAC)(Wieser,2007),arebasedonisotopicabundancescompiledbyan- otherIUPACcommission(Bohlkeetal.,2005).Carefulinspectionoftheatomicmasseslistedin thePeriodicTableoftheElementsrevealsthat,forsomeelements,theatomicmassisassigned integer atomic mass rather than adecimal atomic mass. These elements appear inTable 1.1. Severalotheractinideelements(thoriumTh,protactiniumPa,anduraniumU)areidentifiedas havingnostableisotopesyetIUPACquotesdecimalatomicmasses.Acompleteunderstanding ofatomicmassandisotopestabilityrequiresinformationcompiledintheTableofNuclides. ThePeriodicTableoftheElementsimpliestheexistenceofallnaturallyoccurringelements from hydrogen to uranium and it is reasonable to assume these elements exist on planet Earth. In fact, every sample of water, rock, sediment, and soil contains every stable element and many of the unstable elements. The Periodic Table of the Elements, however, fails to provide sufficient information to understand natural abundance in the Universe, the Solar System,andplanetEarth. Naturalelementalabundancehasotherimplicationsbesidescosmologicalandgeological chemistry. The Environmental Working Group published an article in October 2008 entitled “Bottledwaterqualityinvestigation:10majorbrands,38pollutants”(Naidenkoetal.,2008). AmongthepollutantsfoundinbottledwatersoldintheUnitedStateswasradioactiveSr-90 (0.02 Bqdm−3),2 radioactive radium3 (0.02 Bq dm−3), boron (60–90 mg dm−3), and arsenic 1Theatomicmassofanelement,asitismostcommonlyreported,isaweightedaverage.Itmultipliesthemass ofeachstableisotopetimesitsrelativeabundance(Bohlkeetal.,2005). 2StrontiumisthenamegiventotheelementwithatomicnumberZ=38.Strontium-90(9308Sr52)istheunstable (i.e.,radioactive)nuclidewithatomicnumberZ=38,massnumberA=90,andneutronnumberN=52. StrontiumisotopesincludeallnuclideswithatomicnumberZ=38. 3Radioactiveradiumisreportedasthecombinedactivityoftwounstableradiumisotopes:22868Ra138and 28288Ra140. 3 1.2 ABRIEFHISTORYOFTHESOLARSYSTEMANDPLANETEARTH (1mgdm−3).Thereportedconcentrations,combinedwithacommentarylistingthepotential andactualtoxicityofthesesubstances,canbealarming.Theimportantquestionisnotwhether drinking water, food, air, soil, or dust contains toxic elements; it most certainly does! The importantquestionsare:Istheconcentrationofatoxicelementindrinkingwater,food,orsoils elevatedrelativetonaturalabundanceorisitsufficienttoproduceanadversehealtheffect? The US Environmental Protection Agency (USEPA) has established a maximum contam- inant level (MCL) for beta emitters—such as strontium-90 or radium-228/radium-226—in public drinking water: 0.296Bq dm−3, which is tenfold higher than the single detection reportedbyNaidenkoetal.(2008).TheUSEPAdoesnothaveadrinkingwaterstandardfor boron, but the World Health Organization recommends boron levels in drinking water less than 500mg dm−3, and in 1998 the European Union adopted a drinking water standard of 100mgdm−3.TypicalboronconcentrationsinUSgroundwaterfallbelow100 mgdm−3 and 90%below40mgdm−3. Of the contaminants featured by Naidenko et al. (2008), arsenic is the most troubling. Naidenko et al. (2008) reported a single case of 1 ppb arsenic4 in bottled water; however, the mean arsenic concentration in US groundwater5 is 13.9 μgdm−3 with a median arsenic concentrationof1.4μgdm−3.TheoriginalUSEPAarsenicdrinkingwaterMCLof50μgdm−3 was lowered to the current MCL of 10 μgdm−3 in 2001.6 Natural arsenic abundance in US groundwater means over 10% of the population is potentially exposed to arsenic at levels exceedingthecurrentarsenicMCL. Understandingtheprocessesthatdeterminerelativeelementalabundanceandthestatisti- calmethodsneededtoestimatetheelementalcompositionofrocks,sediments,andsoilsare themajorthemesofthischapter. 1.2 A BRIEF HISTORY OF THE SOLAR SYSTEM AND PLANET EARTH Gravitationalcollapseofaprimordialgasanddustcloudgavebirthtothepresent-daySolar System.Conservationofangularmomentumintheprimordialcloudexplainstherotationof theSunandtheprimordialaccretiondiskthatspawnedtheplanetsandotherbodiesthatorbit theSun. AccretionandradioactivedecayreleasedsufficientheattomelttheprimordialEarth,lead- ingitsstratificationintoasolidmetalliccore,amoltenmantle,andacrystallinelithosphere. PlanetaryaccretionandstratificationalteredthecompositionofEarth’slithosphererelativeto theprimordialcloudandimposedvariabilityinthecompositionofeachelementasadirect consequenceofeachdifferentiationprocess. Throughout its entire history, planet Earth has experienced continual transformation as plate tectonics generate new oceanic lithosphere and shift continental lithosphere plates aroundlikejigsawpuzzlepieces.Platetectonicsandthehydrologiccycledrivearockcyclethat 41ppb=1μgdm−3. 5Geometricmeanbasedonover7199samples(NewcombandRimstidt,2002). 6http://water.epa.gov/lawsregs/rulesregs/sdwa/arsenic/regulations.cfm(September17,2015).