大气环境化学-挥发性有机物研究

中国城市大气污染与VOCs研究的需求邵敏北京大学环境学院BackgroundVOCsstudiesRecentworkO3levelsinsummerofBeijing,2000Therelativeincrementalreactivities(RIR)areexpressedasozonereductionin%whenitsprecursorsreducedin%1950sPresent1980sNMVOCs+NOx

+CH4??OzoneabatementstrategiesevolveasourunderstandingoftheO3problemimprovesAbatement

Strategy:O3smogrecognizedasanURBANproblem:

LosAngeles,Haagen-SmitidentifieschemicalmechanismSmogconsideredREGIONALproblem;roleofbiogenicVOCsdiscoveredAGLOBALperspective:roleofintercontinentaltransport,background

Focus:heterogeneousprocess

Oxidants(O3,OH)SO2,NOxFineparticlesVOC、NOxVehicleexhuast,Coalburningetc.hvMajorconcerns:PhotochemicalsmoghasbeenaseriousprobleminmegacitiesFineparticlespresentathighlevelSecondarypollutionextendsregionallyBackgroundVOCsstudiesRecentwork大气挥发性有机物(VOCs)VolatileOrganicCompoundsVeryOftenConfusedproblems（浓度变化，反应性和源特征等非常复杂）Very-wellOrganizedCompetitions（国际上在外场观测、反应机理、来源研究等方面具有公认的优势单位，分别为加州大学Irvine的Blake,Riverside的Atkinson,以及NCAR的A.Guenther)大气挥发性有机物(VOCs)可能的有毒有害物质，室内室外的暴露均很重要；大气臭氧的前体物之一，种类繁多，浓度和化学活性差异巨大细粒子的前体物CompetitionsMeasurementtechnique(on-line,continuous,ChemicalionizationMS)Photochemistry(Atkinson)MappingofNaturalEmissions(A.Guenther,NCAR)Secondaryaerosols(RKamens,NCarolina)

VOCs的分析技术VOCs的来源研究化学活性分析NMHC卤代烃CarbonylNMOGHeavyHCVOC挥发性有机物（VOCs）半挥发性有机物（Semi-volatile）颗粒有机物

(POM，Particulateorganicmatters)VOCs的测量方法离线在线GC-MS离线分析AnalyticalSystem典型的离线分析系统典型的在线分析系统PTR-MS北京市大气VOCs分析共测量108种VOCs组分：饱和烷烃： 32 种烯烃： 26 种单环芳香烃： 20 种卤代烷烃： 18 种卤代烯烃： 9 种氯苯： 3 种

GeneralaspectsofambientVOCsinBeijingSeasonalvariationsofVOCgroupsAlkenesandalkanesappearedhigherinNov.,lowerinMarch,muchlowerinJuly;Theconcentrationsofaromaticsinsummerwerehigherthanspring.（张靖等，环境科学研究，2003）来源研究源清单

(sourceinventory)简单直接，误差较大，难以反映变化受体模式（Receptormodel)依赖源特征，能反应变化因素，但不能给出分布ChemicalMassBalance(CMB)ApproachMassbalanceequationsinCMBmodel:TheambientconcentrationCimeasuredatreceptorsite,equalsthesumoftheproductofrelativeabundanceFijofcomponentiinsourcejandcontributionofsourcej.CMBisappliedtoassesstheconcentrationsofeachVOCssources.源成分谱（sourceprofiles)机动车排放的比较——隧道实验（付琳琳等，环境科学学报，2005）

VOCsSourceInventoryofBeijingcity,1999VOCsemissions:245Gg/yrCMBmodelperformanceGoodagreementbetweenthemeasuredandcalculatedconcentrationsVOCsSourceapportionmentbyCMB（wt%）

SummaryUncertaintiesofinventory&sourceapportoinmentEmissionfactorbasedonUSandEuropeLackofstationarysourceprofilesSeasonalvariationofsourcecontributionstoambientVOCs

VehicleexhaustisthelargestcontributorineveryseasonThecontributionofpaintsandgasolineevaporationincreasefromwintertosummerDiurnalvariationsofsourcecontributionstoambientVOCs（LiuYingetal.,JESH,2005)VOCs的化学活性OHLossRate15％的烯烃贡献了大约75％的化学活性；VOCs整体的化学活性相当于乙烯。烯烃组分化学活性的相对贡献(邵敏等，中国科学，2005，accepted)VOCs控制对策建议确定优先控制物种；加快机动车排放控制（新车，在用车）石油精炼的全加氢工艺通过管理措施减少泄漏Emissions/DepositionsofplantsNO2Deposition

StomotacontroledprocessNOdeposition/emission

CompensationeffectVOCsemissions

Isoprene,terpene,alkanes,alkenes,aromatics,aldehydes,ketones,alkohols,etc..O3

Deposition/precursorofcarbonylsAlgorithmtodescribeVOCsemissionsTingeyetal,1991Guentheretal,1993Schuhetal.,1997BiosynthesisPoolFvocBiosynthesisFvocBiosynthesisPoolFPFBVOCemissionrates:NetphotosynthesisStomataconductivityVOCisemissionratesatleaftemperatureTandlightintensityL(LisidenticaltoPAR);PandBisthefirstandsecondtermoftheequation,isstandardemissionrateindarknessatstandardtemperatureTS(here25oC);isstandardemissionratefromprocessinparallelwithphotosynthesisactivity.TM:enzymeoptimaltemperature.CTP,CT1andCT2areempiricalparametersfortemperaturedependence;aisparametertodescribelightintensitydependence.SeveralDays?However……VOCsNOxOzonePositivefeedbackofbiogenicVOCemissions?InsectseffectBiogenicSourceinventoryofVOCsinBeijingBiogenic:11km2,1htimeresolutionGuentheralgorithm;Digitalland-usefromremotesensing;NDVI,TemperatureandPARfromrealtimemeasurement;Emissionratesmeasuredfor23kindsof39typesofvegetationTVOCIsopreneMonoterpeneOVOCAnnualemission167.93.54.8(unit:109gC)(Source:Wangetal.,Atmos.Environ,2003)Furtherresearchneedsparisontounderstandsources;RoleofVOCsinground-levelozone;