Cosmicexergybasedecologicalassessmentforawetlandin

EcologicalModelling222(2011)322–329ContentslistsavailableatScienceDirectEcologicalModellingjournalhomepage:∗,G.Q.Chena,∗aStateKeyLaboratoryofTurbulenceandComplexSystems,CollegeofEngineering,PekingUniversity,Beijing100871,ChinabStateKeyJointLaboratoryofEnvironmentalSimulationandPollutionControl,SchoolofEnvironment,No.19,XinjiekouwaiStreet,BeijingNormalUniversity,Beijing100875,ChinaarticleinfoArticlehistory:Availableonline11October2010Keywords:CosmicexergyWetlandecosystemEcologicalassessmentExergeticecologyabstractWetlandsresearchandrestorationhasbecomeoneofthecriticalconcernduetotheirimportanceinprovidingecosystemservices.Thisstudyproposesaholisticmethodologytoassessthewetlandecosys-tembasedoncosmicexergyasathermodynamicorientor.Thisnewapproachisappliedtotwotypicalwastewatertreatmentfacilities(anactivatedsludgesystemandacyclicactivatedsludgesystem)andtoaconstructedwetlandecosysteminBeijingforcomparison.ResultsshowthattheBeijingwetlandecosys-temgainspositivenetpresentecologicalvalueof3.08E+14Jcregardingitstotallifecycle.Comparisonwiththeactivatedsludgesystemandcyclicactivatedsludgesystem,showsthatthewetlandecosystemhasgreaterdependenciesonlocalresources(22%vs.0%vs.0%)andrenewableresources(67%vs.38%vs.31%)aswellasalargerecologicalsustainabilityindex(0.64157vs.0.00005vs.0.00008).Thisimpliesthatthewetlandecosystemismoreenvironmentallyfriendlyandsustainablemethodforwatertreatment.©2010ElsevierB.V.Allrightsreserved.1.IntroductionThermodynamicsanditsincorporationwitheconomicshaveobtainedinsightstotheconceptualizationofecologicalendow-mentsbasedonbiophysicalconsiderations(Clevelandetal.,1984;Cleveland,1987;Georgescu-Roegen,1971;Martinez-Alier,1987;Odum,1983).Withrespecttothebiophysicalconstraintsonthematerialuniverse,somethermodynamicmetricsareproposedtosimulatetheproceduresandassessthefunctionsofecosystems,e.g.,embodiedenergy(Costanza,1980),emergy(JuandChen,2010;Odum,1983,1988,1996a,b;UlgiatiandBrown,2009),exergy(Dincer,2002;GongandWall,2001;JørgensenandMejer,1977;Valero,2006;Wall,1977,1986,1990;WallandGong,2001;Zaleta-Aguilaretal.,1998;ChenandChen,2006;ZhangandChen,2010),cumulativeexergy(Szargutetal.,1988),eco-exergy(Jørgensen,2000,2001,2006a,2007a,b;Xuetal.,1999),extendedexergy(Sciubba,2001,2003;ChenandChen,2009),andcosmicexergy(Chen,2005,2006;H.Chenetal.,2010;Chenetal.,2010a,b;Ji,2010;Jiangetal.,2010).Amongthesecases,exergy,athermodynamicconceptassoci-atedwiththemaximumamountofworkthatcanbeperformedbyasysteminitsprocessofreachingequilibriumwiththereferenceenvironment,isoftenchosenasaunifiedmeasureandusefulindi-catorforaholisticdescriptionofthecomplexecosystems.Unlikeenergy,exergyisnotconserved,whosedestructioncanprovidea∗Correspondingauthors.Tel.:[phone].E-mailaddresses:[e-mail],[e-mail](B.Chen),[e-mail](G.Q.Chen).usefulmeasureoftheirreversibilityofnaturalprocesses(Sciubba,2008).Wall(1977,1986)pioneeredtheresourceexergyaccountingframeworkforcountriesandcomputedtheexergeticconsump-tionasecologicalcostforsystemsandprocesses.SciubbaandWall(2007)madefurthercontributionsbyevaluatingthecurrentexergy-basedresourceconsumptionsmethodologiesandrevealingtheutilityofexergyasasuitablemetricforresourceaccount-ing.Moreover,extendedexergy,proposedbySciubba,hasalsobeenrecommendedasapotentialsustainabilitymetriccoveringthebasicproductionfactorsthatareunderestimatedbytraditionalexergyanalysis,i.e.,labor,capital,andenvironmentalimpact,atthesocio-economicscale(ChenandChen,2009).Specifically,incomparisonwiththetechnologicalexergy,Jørgensenproposedeco-exergy,definedthereferenceenvironmentas‘inorganicsoup’,andcalculatedtheexergycontentofecosystemfarawayfromther-modynamicequilibriumwithbiochemicalcomponents.Sofar,asmentionedbyJørgensen(2006b)andJørgensenandFath(2006),eco-exergyandspecificeco-exergyhavebeenappliedasgeneralecologicalindicatorstovariousecosystems(e.g.,eutrophiedlakes,coastalzones,coastallagoons,andfarmingsystems)todescribetheirdevelopment,healthstatusandgrowthforms.Chen(2005,2006)developedthecosmicexergy,onthebasisofwhichcosmicbackgroundisappliedastheuniformther-modynamicequilibriumenvironmentofeachecologicalprocess.Referringtothebiophysicalunderstandingofcumulativeexergyandemergy,apathrelevantconceptofcosmicexergywasfurtherbroughtforwardasthetotalrequirementofexergyinvolvedintheoverallprocesstoobtainaproductorserviceinordertoreflecttheembeddedresourceconsumptionwithhistoricalinformation.Whenthethermodynamiceffectsassociatedwiththeplanetary0304-3800/$–seefrontmatter©2010ElsevierB.V.Allrightsreserved.doi:10.1016/j.ecolmodel.2010.09.023Z.M.Chenetal./EcologicalModelling222(2011)322–329323motionbrakedbyenergyandmaterialflowsfrominsidetheeartharegrantedtobenegligible,thematerialearthasaconcernedthermodynamicsystemhasadirectbearingonthecosmoscor-respondingtothesingularityofthesunandsurroundingcosmicbackground.Itisappropriatetoconsiderthattheearthsystemhasrelationsopentoenergyexchangebutclosedtomass