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Spatialseasonal

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SpatialseasonalSpatia

AtmosphericEnvironment36200234033411SpatialandseasonalvariationofPM10masscon

    centrationsinTaiwanKuang-LingYangInstituteofEarthSciencesAcademiaSinicaTaiwanROCReceived1September2000receivedinrevisedform10April2002accepted19April2002AbstractHourlydataofPM10concentrationcollectedfromanairquality-monitoringnetworkhasbeenanalyzedoverTaiwanfrom1994to1999.Fourteensitesfrom72monitoringstationswereselectedtoevaluatethespatialandseasonalvariationsintheregionsofnorthsouthwestsoutheastandNationalPark.TheselectedmonitoringsitesarelocatedinasuburbanenvironmentexceptNantzandLinyuanthatarelocatedinindustrialareas.MoreoverYangmingandHengchuenarelocatedinNationalPark.SpatialandseasonalvariationsofPM10concentrationsareratherlargeoverTaiwan.AnnualaverageinsouthisapproximatelysixtimeshigherthaninNationalparks.InnorthernsitesthehighestconcentrationoccursinMarchMaywhichisattributedtotheoccurrenceofduststorm

    sinaridregionsofcentralAsiaandthetransportofdustbynortheasterlymonsoon.AmarkedseasonalvariationofPM10concentrationscanbeobservedbothinsouthwesternandsouthernregions.Thepatternischaracterizedbyhighconcentrationsinwinterandlowinsummer.AppearanceofthehighestmonthlyPM10concentrationinwinterofsouthmaybeinpartduetothelowestnumberofmonthlyprecipitationdaysandlowtemperaturebothofwhichoccurredinwinter.ThefrequencyofPM10dailymeanconcentrationforexceeded150mgm??3is15duringwinterinsouthwhichreectstheseriouspollutionproblemthere.MonitoringsitesinNationalParkarerepresentativesofremoteenvironmentsbutthePM10concentrationsarestillaffectedbytheduststormsandhumanactivities.r2002ElsevierScienceLtd.Allrightsreserved.Keywords:PM10Airquality-monitoringnetworkTaiwanDuststormsPrecipitationdays1.IntroductionDuetotherapidgrowthofindustrialactivitiespopulationandtrafcdensitypeopleinTaiwanarefacingseriousairpollutionproblems.Insomesoutherncitieswherethehighestindustrialactivitye.g.petro-leumreneryplantspowerplantsandpetro-chemicalplantsislocatedairpollutionproblemsareespeciallysevere.AccordingtoTaiwanEnvironmentalProtectionAdministration’sreportthefrequencyofairpollution

    standardindexPSIvaluesgt100wereapproximately6.2intheperiodfrom1994to1996andtheitemsofexceededPSIvalueswereO3andPM10.ConcernedaboutthehealtheffectmanyepidemiologicalstudiespointoutthatsomediseasesoccurredevenatlevelsbelowthepresentPSIstandards150mgm??3at24-haverageforPM10and120ppbinmax.hourvalueforO3Popeetal.1995.InadditionthereisstrongevidencethatsomeaerosolshavegreenhousepropertiesandcontributetothechangeofglobalclimatePreining1991.InrecentyearssincethegreateffortsmadebyTaiwangovernmenttowardsthereductionofO3andPM10concentrationsbycontrollingtheemissionratesoflocalpollutantssourcesthefrequencyofexceededPSIhasgraduallydecreasedtothevalueof4.9in1999TaiwanEPA2000.DespitetheseeffortsinpollutionSendcorrespondenceto:InstituteofBotanyR410AcademiaSinicaNankangTaipei115TaiwanROC.Fax:886-2-27827954.E-mailaddress:irisyanggate.sinica.edu.twK.-L.Yang.1352-2310/02/-seefrontmatterr2002ElsevierScienceLtd.Allrightsreserved.PII:S1352-23100200312-6reductionPM10massconcentrationsarestillelevatedinwintertimeinsomesouthernareasandPSIvaluesgt100arestilloftenfoundduringthattime.Further-morearegularseasonalvariationisfoundwhichdisplayhighconcentrationinwinterandlowconcentra-tionsinsummer.InamonthlyorseasonaltimeperiodwecanassumethattheamountfromanthropogenicemissionsourcesisalmostconstantinalimitedregionsotheseasonalvariationinPM10concentrationsshouldbepartiallycausedbychangesinthemeteorologicalconditions.VariationsinPM10concentrationsattrib-utedtochangesinmeteorologicalconditionwerealsofoundinothercountries.TemperatureandwinddirectionweretwomainfactorsInNetherlandsvanderWalandJanssen19962000monsoonandraineffectsinHongKongChengetal.2000Qinetal.1997windspeedanddirectioninSingaporeOrlicetal.1999.InJapanthehighP

    M10concentrationinwinterwasattributedtothepresenceofduststormsthatoccurredincentralAsiaandthehighstabilityofmeteorologicalconditionsVaretal.2000.ThevariationofPM10concentrationsisnotonlycontrolledbytherateemissioninPM10sourcesbutalsobythemeteorologicalconditions.TheaimofthisstudyistoshowtheseasonalvariationofPM10concentrationsindifferentregionsofTaiwanandtherelationshipsbetweenPM10massconcentra-tionsandmeteorologicalconditions.WehavecollectedthedataofPM10hourlyconcentrationsfromselectedEPAsamplingsitesaswellasthemeteorologicalconditionsfromCentralWeatherBureauCWBfrom1994to1999acrossTaiwan.2.Studymethods2.1.Dataresources2.1.1.EnvironmentalProtectionAdministrationEPAInordertounderstandandpredictthepresentandfuturestatusoftheairqualityinTaiwanawell-organizedairquality-monitoringnetworkwasoperatedformallyfromOctober1993byTaiwanEnvironmentalProtectionAdministrationandsixcriteriaairpollutantssuchasO3CONO2HCSO2andPM10wereobservedautomatically.SincethePM2.5fractionaccountedfor5467ofthePM10massinurbanareasChenetal.1999PM2.5measurementwasalsoaddedinsomesitestoevaluatethehealthriskofthehumanrespiratorysystemHeyderetal.1986about3yrago.Currently72monitoringsiteshavebeensetupincludingvetrafcintheroadswithhighdensityofvehiclesthreeindustrydownwindofindustrialareasfourbackgroundupwindofbackgroundenvironmenttwoNationalParkinsideofNationalparkand58ambientareaairquality-monitoringstationsdownwindorupwindofhighdensityofpopulation.DatacollectedfromEPA’sairqualitynetworkisforthepurposeoflegislatingcontrollingandpreventingairpollution.InTaiwan’sairqualitymonitoringnetworkPM10concentrationsareroutinelymeasuredbytheautomaticWeddingb-gaugemonitorswhichisoneoftheUSEPA-designatedequivalentmethodsNo.EQPM-0391-081.ThePM10inletisacycloneoperatedat18.9lmin??1.Particlesarecontinuouslycollectedontheltertapeanddetectedonceeveryhourandthedailyaverageiscalculatedforatleast16effectivehourseachday.AccordingtoSeinfeldandPandis1998particlesontheltertapemayabsorbwaterwhenthedeliques-cencepointisexceededwhichmayleadtoover-estimationofPM10concentrations.DuetothefrequentoccurrenceofhighhumidityintheambientairofTaiwanacomparisonexperimentwasmadewithWeddingb-gaugemonitorsandthemanualsamplersbyTaiwanEPA.ResultsshowthatPM10concentrationsfromautomaticWeddingb-gaugemonitorareclosetothosefromthemanualsamplersChangetal.2001.AnorthsouthalignedmountainrangecoversTaiwanI

    slandthehighestpeakisat3997m.ThishypsographynotonlymakesforcomplexterrainbutalsoaffectsthemeteorologicalconditionssuchasprecipitationandprevailingwindinmanylocationsthroughoutTaiwanChenandLin1997.AccordingtothedifferencesingeographicalandmeteorologicalconditionsTaiwanIslandcanbedividedintovegeographicregionsi.e.northsouthwestsoutheastandremoteenvironmentstodiscussthespatialandseasonalvariationofPM10concentrationandrelationshipwithmeteorologicalconditions.Fourteenmonitoringsiteshavebeenchosenfromthe72stationstorepresentthesevegeographicregions.Thelocationsofthese14samplingsitesandtheclassicationofvegeographicregionsareshowninFig.1.Sites1and112and346710an

    d1214representNationalParknorthsouthwestsouthandeastrespectively.RelatedinformationforthesamplingsitesincludinglongitudelatitudetypesamplingheightanddistancefrommainroadisgiveninTable1.2.1.2.CentralWeatherBureauCWBAllthemeteorologicaldataincludingwindspeedanddirectionprecipitationamountthenumberofprecipi-tationdaysandtemperaturewereacquiredfromthereportsofCWBClimatological19931999.Althoughthesemeteorologi

    calstationsdonotexactlycorrespondtotheairquality-measuringsitesthemeteorologicaldataaregatheredfromCWBstationclosetosamplingsitesasnearaspossible.MostoftheCWBstationsundertakeeightsynopticweatherobservationsdailyincludingwindspeedanddirectionprecipitationamountthenumberofprecipitationdaysandtempera-tureetc.Precipitationdayisdenedasad

ayinwhichK.-L.Yang/AtmosphericEnvironment362002340334113404thereisprecipitatio

    nof0.1mmormoremeasuredfrommidnighttomidnight.AccordingtoCWBreportmonthlyaveragetempera-tureinTaiwanshowsaregularpatternwiththelowesttemperatureinJanuaryorFebruaryandthehighesttemperatureinJulyorAugust.Themaximummonthlyaveragetemperatureis301Cbothinnorthernandsouthernregionbutthelowesttemperatureinnorthisapproximately51Clowerthanthatinsouth.Othermeteorologicalconditionssuchaswinddirectionandspeedaswellasprecipitationamountanddaysarehighlyvariablewithdifferentregionsorseasons.Themainwinddirectioninnorthisnortheasterlywindinwhichlaststhewholeyearbutturnsweakinsummer.Themainwinddirectionsinsouthwestisnortherlyandnortheasterlywindoverthewholeyearexceptinsummerwhenitcoincideswithsoutherlyorsouth-westerlywindandinsouththewholeyearwinddirectionsarealmostwesterlyturntonorthwesterly.Innorthandeastthemonthlyaveragewindspeedisbelow3ms1.Duetothepreventionofcentralmountainsmonsoonbecomesweakw

    ithwindspeedbelow1ms1anductuationsofwindspeedareratherlessinsouth.ThereareexceptionsfortheTaishiandHengchueofsouthernregionbecausetheyareclosetotheseashoreandthetrendofwindspeedislowinsummerandhighinwinterthere.Thewindspeedsareintherangeof29a

    nd26ms1forTaishiandHengchuerespectively.3.Resultsanddiscussion3.1.AveragePM10concentrationsAnnualarithmeticmeanconcentrationsandstandarddeviationsofPM10ineachobservedyearsfrom1994to1999andoverall6yraverageatthe14sitesareshowninTable2.AscanbeseeninTable2thehighestannualaverageconcentrationisobservedinLinyuanwhichhasthehighestdensityofchemicalandpetroleumplantsinTaiwan.RankedsecondthirdandfourthareChanjouMeinungandNantzrespectively.Allofthemareinthesouthernregion.NantzisalsoanindustrialcitysoitisreasonabletoexpecthighPM10concentrations.Chan-jouandMeinungshowthesecondandthirdhighPM10concentrationssurprisingusdespitebeingsmallagriculturaltowns.InitiallythesetwositeswereselectedbyEPAforthepurposeofobservingtheinuenceofpollutiontransportfromhighlypollutedareassuchasTable1Relatedinformationfor14monitoringsitesNumberNameLocationLongitudeLatitudeTypeSamplingheightmDistancefrommainroadm1YangmingNorth1211300251110NationalPark4.665002DanshueiNorth1211250251100Ambient15.42303GuanjinNorth12114025120Ambient12.542504TaishiSouthwest1201120231420Ambient13.232505ChiaiSouthwest1201250231280Ambient15.47606ShinyingSouth1201180231180Ambient11.532007NantzSouth1201190221440Industrial14.5508MeinungSouth1201310221530Ambient13.731209LinyuanSouth1201240221280Industrial11.4320010ChanjouSouth1201310221300Ambient8.2520011HengchuenSouth1201460211570NationalPark4.5100012TaitungEast121180221450Ambient12.452013HualienEast1211350231580Ambient9.61514IlanEast1211440241450Ambient15.5120Fig.1.Mapof14monitoringsitesofEPAinTaiwan.K.-L.Yang/AtmosphericEnvironment362002340334113405Linyuant

    oitsdownwindplaces.ThelowestannualaverageconcentrationoccurredwithinthetwoNationalParksYangmingandHengchueandrangedfrom16.9to22.5mgm??3.Theannualaverageconcentrationsinsoutharealmost2timeshigherthanthatinnorth1.5timesthansouthwest3timesthaneastand6timesthantheNationalParks.Thereisadecliningtrendinannualaverageconcen-trationsofPM10aftertheyearof1997insouthespeciallyintheseriouslypollutedareassuchasLinyuan.Thevalueofannualaverageconcentrationdecreasesfrom110to76mgm??3whichshowstheeffortsofTaiwan’sEPAinthereductionofemissionrates.ManyprojectshavebeencarriedoutbyEPAsuchasminimizingthefactoriesoperationtimeinwinterplantingtreesorgrassinwildlandsencouragingpeopletotakepublictransportationinsteadofprivatecarsetc.ComparedtoothermetropolitanareaslocatedinEastAsiathePM10concentrationobservedinsomesouth-erncitiesinTaiwanwerehigher.ForexamplesPM10concentrationinSeoulKoreawasabout75mgm??3betwe

    en1987and1991Hashimotoetal.1994andinHongKongwasanaverageof55.3mgm??3between1990and1994Qinetal.1997.3.2.SpatialandseasonalvariationofPM10concentrationsAspreviouslymentionedTaiwan’snorth–southalignedmountainsformacomplexterrainanditchang

    estheprevailingwinddirectionandprecipitationdaysindifferentregions.InadditiontheindustrialactivitiesaredistributedextremelyunequallyacrossTaiwan.Mostoftheindustrialplantsareconcentratedinthesouthernregion.FromTable2thelargeststandarddeviationvalueoftheannualaverageuptohalfofthemeanvalueisfoundinsouthwhichindicatestheespeciallylargeseasonalvariationofPM10concentrationinthisregion.InordertopresenttheseriesspatialandseasonalvariationwiththemonthlyPM10concentrationtimeseries1993/101999/12plotsofPM10monthlya

    verageconcentrationat14sitesinveregionsareshowninFig.2.AregularpatternofseasonalvariationofPM10concentrationwereformedbothinsouthwesternandsouthernregionsespeciallyinsouthwhichischaracterizedbyhighwinterNovemberDecemberandJanuaryandlowsummerJuneJulyandAugustmodiedbyasecondhighpeakinMarch.ThePM10monthlyconcentrationsareintherangeof100200mgm??3inhighwinterand2050mgm??3inlowsummer.Thehighestmo

    nthlyconcentrationupto200mgm??3appearedinwinterinLinyuan.Althoughhighmonthlyconcentrationsap-pearedindifferentseasonsandhaddifferentvaluesthelowestmonthlyconcentrationalwaysappearedinsummerandhadsimilarconcentrationrangeo50mgm??3intheveregions.InnorthernareasincludingDanshueiGuanjinandNationalParkYangmingthehighestconcentrationappearsintheseasonofspringMarchMayandthelowestconcen-trationappearsinsumme

    r.Theconcentrationisca.Table2AnnualaveragevaluesofPM10concentrationsateachobservedyearandtotal6yraveragefor14sitesinveregionsSites199419951996199719981999199419

    99NationalPark1.Yangming22.476.518.573.618.777.719.274.616.974.516.773.618.775.6North2.Danshuei52.0719.350.5712.748.0713.750.278.653.1712.841.4710.049.2713.63.Guanjin53.4713.655.3716.855.0713.453.8711.848.9712.344.1713.351.7714.0Southwest4.Taishi73.0721.973.7724.974.4726.167.4723.163.6717.061.7721.568.9722.85.Chiai79.5729.862.4727.386.1728.579.1730.073.7730.679.8729.576.8729.76.Shinying72.6728.673.6726.873.9726.165.8725.752.9723.955.9723.265.8726.7South7.Nantz84.7729.181.1733.889.5735.077.9726.265.9728.878.9733.079.7731.48.Meinung91.6744.590.1742.085.2735.579.2731.069.3736.771.5730.481.2736.79.Linyuan110.1750.0110.9747.8110.8750.183.8737.075.5735.076.1738.694.5745.810.Chanjou95.7745.3103.4743.489.5739.279.7732.774.5741.390.6745.388.9742.0NationalPark11.Hengchue22.374.319.075.522.575.022.374.421.674.420.674.921.474.8East14.Ilan39.975.942.976.738.977.239.276.633.975.034.576.138.277.513.Hualien46.077.341.3711.337.978.440.575.937.476.933.4710.439.479.312.Taitung44.2710.435.575.633.375.528.773.532.276.735.275.834.978.0K.-L.Yang/AtmosphericEnvironment362002340334113406100mgm??3insummerand30mgm??3inspring.T

    hereisnoobviousseasonalvariationofPM10concentrationobservedintheeastandthetwoNationalParks.InordertoknowthefrequencydistributionofdailyPM10concentrationsfrom1993to1999whichwasdividedintofourrangesi.e.030306060150andexceeded150mgm??3byfour

    seasonsat14sitesofveregionsseeFig.3.AccordingtotheclassicationofPSItherangeofPM10concentrationfarexceeding150mgm??3representstheseriousPM10pollutanteventsresultinginhealthdamage.OccurrencefrequencyofPM10concentrationfarexceeding150mgm??3isseeninallseasonsexceptsummerwhichmeansthatthesummeristhecleanestseasoninTaiwan.InthesiteofLinyuanfrequencyofPM10concentrationforexceeded150mgm??3isapproximately15duringwinter.ThisFig.2.Timeseries1993/101999/12plotsofPM10monthlyaverageconcentrat

    ionsmgm??3at14selectedsitesrepresentingveregionsofTaiwan.K.-L.Yang/AtmosphericEnvironment362002340334113407phenomenonreectstheseriouspollutionprobleminthesout

hernregion.Duetotheinuenceofduststormsinnorththehighconcentration60150voccurredin

    springandoccurrencefrequencyisapproxi-mately40.InNationalParkover80oftheyearPM10isintherangeof030mgm??3whichshowsthattheNationalParkscanbeseenasabackgroundenvironment.3.3.RelationshipsbetweenPM10concentrationsandmeteorologicalconditionsThespatialandseasonalvariationofPM10massconcentrationinTaiwancanbeexplainedbymeteor-ologicalconditionssuchaswinddirectionandspeedprecipitationdaysandamountsaswellastemperature.ThehighPM10concentrationsobservedinnorthintheFig.3.FrequencydistributionofdailyPM10concentrationdividedintofourconcentrationrangesforfourseasonsintheyearperiod19931999at14monitoringsitesofveregions.K.-L.Yang/AtmosphericEnvironment362002340334113408timeperiodofMarchMayisattributedtothepresenceofduststormsthatoccurre

    dinthearidregionsincentralAsiaandtransportedtoTaiwanbythenorth-easterlymonsoonfromMarchtoMayHung1997Zhouetal.1992Changetal.2000Lin2001.AtthesametimeitwasalsofoundinJapan’s‘‘Kosa’’periodthedustseasonfromMarch–MaybroughtbywesterlywindFaneta

    l.1996Varetal.2000.ThemonthlyPM10c.

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