Impurities in Winter precipitation on the Japan Sea Side of Japan

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Impurities in Winter precipitation on the Japan Sea Side of Japan

著者 Ecker Franz‑Josef journal or

publication title

博士学位論文要旨論文内容の要旨および論文審査結果の要旨／金沢大学大学院自然科学研究科

number 平成2年6月

page range 87‑93

year 1990‑02‑01

URL http://hdl.handle.net/2297/33159

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氏名ECKERFranzJosef

学位の種類学位記番号学位授与の日付学位授与の要件学位授与の題目

論文審査委員

学術博士学博甲第25号平成2年3月25日

博士課程終了（学位規則第5条第1項）

ImpuritiesinWinterPrecipitationontheJapan SeaSideofJapan

(冬季の日本海側地域における大気汚染降下物に関する研究）

( 主査）平井英二 ( 副査）山本善一 ( 副査）林良茂 ( 副査）寺田喜久雄 ( 副査）宮崎元一

学位論文要旨

ABSTRACT

Dailysnowfallwascollectedonpolyethylenesheetsatsixsitesalongthecoast, incityareasandintheinlandmountains.ThesampleswereanalyzedfOrEC, pH,solubleandinsolubleamountsofAl,Cd,Cr,Cu,Fe,Mn,Pb,andZn;Cl‑, NO3‑,SO42‑,Ca2+,K+,Mg2+,andNH4+.Experimentswereconductedtoestimate thebelow‑cloudscavenging,thewetanddrydeposition,thepropagationof impuritiesinasnowpack,andtheirfinalreleaseinmeltwater.

Contrarytocoastalsnowpackswhichreleasedmeltwateralmostdaily,most oftheimpuritiesinmountainsnowpackswereretaineduntilspring;thefirst fractionofmeltwaterreleasedbetween50and90percentofthetotalamount ofwater‑dissolvedimpurities・Thelastmeltwaterfractioncontainedthe maximumofwater‑undissolvedmetals.

1．INTRODUCTION

InJapan,numerousfieldsurveyshavestudiedtheioniccompositionofwet

‑

depositionintensiveiy.However,fewinfOrmationisavailableonthedeposition oftracemetals.Dataconcerningtheirdepositionandreleaseinandfrom snowpacksarelacking;suchdataareespeciallyimportantfortheestimateof

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long‑rangetransportfromtheAsiancontinenttothesnow‑richHokurikuarea alongtheJapanSeasideofcentralJapan.

Thisthesispresentsananalysisoftheconcentrationoftracemetals,anions andcationsinwetdepositionandmeltwaterreleasedfromsnowpackinthe areaduringthewintersofl986‑1988.

2.METHODS

Dailysnowfallwascollectedonpolyethylenefoils(50×50cm)atsixsitesalong thecoast,incityareas,andintheinlandmountains(Fig.1).Experimentswere conductedtoestimatewetanddrydeposition,Iocalbackgroundconcentrations, andthefinalreleaseinnaturalmeltwater・Meltwaterwascollectedinlysimeters embeddedinthegroundbeforethefirstsnowfallaccumulatedtoasnowpack.

SampleswereanalyzedfOrEC,pH,andsolubleandinsolubleamountsofFe, Mn,Pb,Cd,Cr,Cu,Zn,andAl;Cl‑,NO3‑,SO42‑,Ca2+,K+,Mg2+,Na+,and NH4+.

3．RESULTS

3．1．MeanMetalConcentration

Thechemophysicalpropertiesofvarious metalsinfreshlyfallensnowwereofthesame orderofmagnitudeatallsixsamplingstations fromthecoasttotheinlandmountains.

Tablelshowstheaverageconcentrationsin

Ｎ︲１１１十Ｉ︲助)i四

晩

wet‑depositedsnowofcon‑

currentsnowfallatthesix sites.Itshouldbenotedthat theaveragevalueS,cal‑

culatedasarithmeticmeans, areoverestimates,consider‑

ingthemostfrequentlyoc‑

curring(median)valuesat aparticularsite.

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3 ． 2 ． M e t a l S o l u b i l i t y ! o o Allexaminedelementsoccurredinboth2 solubleandinsolublefractions.Fig.2show"

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theaveragesolublefractionsofthemetals35o whichwereobtainedbytheratiosof2

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(solublefraction)/(totalamount)ofeach('' metal.GiventhepHvaluesinvolved,the o

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3．3．LocalDistributionofpH｡

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Fig.3showstheaverageandstandard deviationsinpHofmelted,wet‑deposited 3

Fig.2Averagepercentsolubility andstandarddeviation(1)in depositedsnow.

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snowsamplesateachsamplingsite．c…Cc yき,…Hou…,n患

AveragepHvalueswerelowestattheurbao「喝3Aver拳話賦Ggtandantde.

andsuburbansitesandgenerallyhigherviation(D)andextrema(1)inwet‑

attheremotesites.Itisinterestingtonotedepositedsnow

thatstandarddeviationsoccurredwithinanarrowrangefrompH4.2topH5.2 ateverysite,especiallyasthepHvaluesofrainwateratthesamesitesoccurred withinawiderrangeduringotherseasonsoftheyear.Investigationofthis phenomenonincludedtheanalysisofarangeofanionsandcationsandfinally ledtotheconclusionthatlocalwashoutofacidicionsexceededthatofalkaline

ions2).WeeklydepositionsampleswithhighpHvaluesappearedtobeinflated byexcessCa2+,whichwasemittedfromroaddust.Exceptforthesesamples contaminatedbyroaddust,pHvaluesofweeklydepositionwereconfonnwith thedailywetdepositionsamples.

TheaverageannualpHremainednearlyconstantduringthefivewintersof thestudy.

3．4．RegionalBackgroundConcentrationsofTraceMetals

Allconcentrationsofairborneimpuritiesexhibitedfairlysimilardistributions.

Relativelyhighconcentrationsatthebeginingofasnowfalleventdeclinedto nearlyconstant,lowvalueswithincreasingsnowquantitiesandsnowfalldura‑

tion.Theselowervalueswereacceptedasthelocalbackgroundconcentra‑

tion.Absoluteregionalbackgroundconcentrations(thesumoftheinsoluble andsoluble)fortracemetalswerederiveedforeachelement(Table2).

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Tablel AverageConcentrationsofTraceMetalsinWet‑DepositedSnow attheVariousSitesandNumber(#)ofSamples(1986‑1988)

qncentrationIIlg/1l MeasuringsiteF℃M1

一一ー −

OKodatsuno 77．12．9 (suburb)

IUchinada 72．94．9 (ocean)

2Honda面Bchi82．63.1 (city)

3KoITBtsu 85．22．4

(city)

4Tbrigoe ^68．73．0 (mountain)

5 S h i r a m i n e 6 3 . 2 2 ． 1 (mountain)

P b m C r Q l Z n A l #

−

3 ． 5 0 ． 1 7 5 ． 9 1 ． 9 4 ． 3 2 0 . 5 3 1 3 ． 7 0 ． 1 7 8 . 5 2 . 1 4 ． 6 9 ． 6 1 9 3 . 4 0 . 1 9 4 ． 7 2 ． 3 5 . 7 1 7 . 7 2 4 4 ． l O . 1 8 6 ． 8 2 ． 0 5 ． 2 2 5 ． 8 2 0 3 . 1 0 ． 1 5 1 1 . 0 1 ． 8 3 . 1 1 1 ． 3 2 3 2 . 6 0 . 1 5 8 . 7 1 . 9 2 ． 7 1 7 ． 3 2 2

Table2RegionalBackground 3．5．Long‑rangeTransport ConcentrationsinWet‑DepositedSnow Tounderstandlong‑rangetrans‑

α：0．02‑O.0411g/lportmechanisms,itisimportant

todetenninelocalandregional Cr,Ql,M1,Pb:0.1‑0.5Ug/1 sourceswhichmightcontributeto Zn,AI:0.5‑2．Ollg/lthebackground・Besideslocal anthropogenicemissionsources, F e : 1 0 ． O P g / l

theanalysisofbackgroundvalues

一ー

ontheJapanSeasideofJapan mustaccountfOrnaturalsourcessuchasseaspraycomponentsandtheso‑

called{lKosa"(Ioessaerosol)fromtheAsiancontinent.

Results,however,indicatethatneitherKosanorseaspraycontribute significantlytothelocaltracemetalbackgroundinwinter・AIso,theimmission patternsofthesolubleandinsolublefractionsofthevariousmetalsatsixsites demonstratedthattheconcentrationlevelsweredirectlyrelatedtolocalsources.

ThecitiesofKanazawaandKomatsurepresentmajorsourcesofinsoluble metalcompounds.InthecaseofCr,amajorsourcecanbeassumedinthe vicinityofTorigoe(Fig.1).

3．6．ReleaseofMeltwater

Theconcentrationsofthe@soluble/insoluble'fractionsfOundinwetdeposition samplesweredistributedaroundanarithmeticmean(Fig.2).Themeltwater samplesduringwinter,however,revealedseparatereleasesofsolubleand insolublecomponents.(Fig.4).Atthecoastalsites,lysimetersamplesshowed areleaseofmeltwaterfromthesnow‑packtothegroundallwinter.The

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Fig.4Concentrationoftracemetalsinlysimeter samplesatShiramineinl988

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concentrationsoftheinsolubleandsolublefractions,theECandpHvalues ofconsequentsamples,thoughtheyexhibitedapreferentialreleaseofdissoIved impurities,wereintheorderofmagnitudeofwetdepositionsamples・Atthe remotemountainsite,however,meltwaterbreakthroughwasdelaydintolate Marchandwasrestrictedtoarelativelyshortperiod.Thefirstmeltwaterfraction carriedanenriched(50‑90%ofthetotalmeltwaterconcentration)loadofwater‑

solublematerialandwascharacterizedbylowpH(3.97)andhighEC(420"S/

cm)values,amagnitudenevermeasuredduringanyother,priorsnowfallevent.

Comparedtothesolubleconcentrations,theinsolublefractionofalltracemetals wasnegligibleinthefirstmeltwatersamples.Duringthelatermeltwater discharges,thesolublefractionrapidlyfelloffwhiletheinsolublequantities increasedtoamaximuminthelastsample.Thehighionicstrength(EC,pH) andtheenrichmentofbio‑available(i.e､,water‑soluble)heavymetalsinthis firstmeltwaterbreakthroughwascausedbypreferentialelution;thisimpurity‑

ladenfirstreleaseundoubtedlyreachesaquaticsystemsandmayaffectaquatic biota.

Onthecoastalplain,impuritieswerereleasedduringseveralmidwintermelts inamountSwhichdidnotshowanysignificantenrichmentscomparedwithother

localrainorsnowdata=

TheseasaltaerosolcomponentsNaClandMgCl2couldbewelltracedfrom theirdepositiontothefinalrun‑off.

4．FINALCONSIDERATIONS

Inordertodeepentheunderstandingoflong‑rangetransportacrosstheJapan Sea,locatesourcesoftracemetals,andfollowtheirpathinwinter,themeasuring netanddata‑collectionprogramneedtobeextended.Tracerexperimentsand casestudiesneedtobeperfonnednotonlyontherathersmallcoastalline ofJapan,butinallcountriesborderingtheJapanSea.

Furtherstudiesalsocanassessthesignificanceofthesequentialsnowpack releasedatainregionalecologicalmodels.

5.ACKNOWLEDGMENTS

TheacademicsupportgrantedbyProf.EijiHiraiandDr・TetsujiChohji deserveshighestappreciation.ThefinancialsupportoftheToyotaFoundation isgratefullyacknowledged.

6.REFERENCES

1)Rohbock,E.(1987)．Bemerkungenuberdieltislichenundunl6s‑lichen SchwermetallverbindungenimNiederschlagswasser.StaubReinhaltungderLuft

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47,Nr.9/10,pp.244‑248

2)Hirai,E.Miyazaki,M.,Chohji,T.,Kitamura,M.,Okubo,N.,Nakagawa,C.

andEcker,F.‑J.(1989).AcidityinwintertimedepositionontheJapanSeaside ofJapan.submittedto:EnvironmentalTechnologyLetters,London

論文審査の結果の要旨

Ecker学位論文審査委員会は，平成2年2月1日と2月9日に第1,第2回論文審査委員会を開催して本学位論文を検討し，2月15日に口頭発表，最終審査会を開催し，意見交換の後に協議の結果，下記の通り判定した。

大気汚染物質は自然界や人為的発生源から大気に放出され，それらは大気循環に伴った輸送や拡散過程をへて，結果として雨及び雪に取り込まれる。よって本論で日本海側における大気汚染物質についての測定と解析を行った。主な内容は下記の通りである。

1）サンプリングの場所について，内灘町から白峰までの間にほぼ南北に6地点を観測点として，降雪のサンプリングを行い，積雪のコアーは白峰と工学部を中心にサンフ・

リングを行った｡これらの結果からpHの平均値は都市部が最も低く，海岸や山間部では平均値はやや高いデータが得られた。また，鉄，マンガン，鉛，カドミウム，クロム等の金属濃度として，山間部の鳥越村観測点ではクロムの濃度ｶ都市部より高いこ

とが明かとなった。

2）降雪量が少ないときは，金属濃度は降雪毎に異なっているが，積雪量が多い程，比較的低い濃度を示し，一定濃度に収束している。

3）積雪中からの融雪水の濃度であるが，マンガン，亜鉛，カドミウムなどは最初の分画部で高い溶解度を示しているが，その他の不溶解性成分は最終的な分画部でまとめて検出され，溶解成分と不溶解成分とが明確に分離される現象を示している。その他にもpH,EC等についても有益なデータが得られている。

石川県で代表される日本海側は成果でも有名な豪雪地方でもあり，冬季の雨及び雪中の大気汚染物質の定量的評価は環境問題として重要である。この研究によって新しい知見を多く得られている。

本委員会は以上を総合して，提出された本論文が学術博士に値すると判定した。

Impurities in Winter precipitation on the Japan Sea Side of Japan

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