Study area

ROLF TORE OTTESEN& MA RI A N N ELA N G ED A L NG U-BULL438,2001 - PA GE 63

Urban geochemistry in Trondheim, Norway

ROLFTOREOTIESEN &MARIANNELANGEDAL

Ottesen,R.T.&Langedal,M.2001:Urban geochemistryin Tro ndheim,Norway. Norges geologiske undersaketse 8ulletin 438,63-69.

The chemical com pos ition of urban surface soilin Trondheim, orway,has been mapped to serve a two-foldpur- pose.1)To assess whethe rstack-emissions from industrialsite s, inci nerato rs and crematoria,as well as road traffic.

have caused local elevated concentrationsof certain elements.2)To providea database forenvi ronm ental health risk evaluat ion.Surf ace soil samples were collectedfrom 314 sitesin gardens,parksandind ustri al areas.The samples were analysed forthe AquaRegia soluble fractionof 31 elements. aturalbackground concentrationswere deter- mined in thedeep er partsof overbanksedimentprofi les from theregio n.In general,the pollutionlevels were low.

However,Cd,Hg,Pband Zn pollute the surface soils in the central andolder part s ofthe cityand alongthe main roads.The mostdo minantsources are presumablyautomobileexhaust(Pbl,tyre wear(Zn and Cd),andemissions fro m a cremator iu m oraho sp ital incinerato r(Hgl. lnthe easternpart s ofTron d heim,indus tries burningcoalhave probably causedelevated As concentratio ns.

RolfTore Ottesen1& MarianneLangedal,Departmentof Environment,Cityof Trondheim,N-1004Trondheim,Norway1.

Present address:Geological Survey ofNorway,N-1491Trondheim,Norway.

E-mail:rolf.ottesen@ngu.no&marianne.langedal@trondheim.kommune.no

Introduction

Urbanenvironment s arepollutedby a num ber of diffe rent sources such as road traffic , indust ry,waste incinerat ion, waste sites,crematoria and incineration of coal, oil and wood (e.g.,Berglund et al. 1994, Birke&Rauch1994, Ahlgren1996, Chen et al. 1997,Mielke & Reagan 1998,Mielke et al.1999, and Ottesen et al. 2000a & b).Spills and deliberate disposal from point sources have caused extremely high levels of pol- lutants in soilsatindust rial sitesandwaste dumps(Ot tesen et al. 1989, Karlsaune 1995). Airborne pollutants are deposited on surface soils and often accumulated in the soil compartment. Lately,it has been observedthat general con- sumption and waste disposal have caused non-pointpollu- tion of urbansoils(Ot tesen et al. 2000a,Langedal & Ottesen 2001). Soils act as reservoirs for heavy metals and organic micro-pollutants. Human activity may create pathways from these reservoirsto the urban populations.Thus,the quality of urban soilscan influence human health(Mielke&Reagan 1998).

Only a few urban soilstudies haveso far beencarried out,compared wit h thenumberof studieson agricultura l and forest soils.Asur vey of the conte nt ofinorganic and orga nicpoll ut ant s in urban soil can serv eas a basisfor com- munityplanning and to assesstheneedfor emissionregula- tion.

In Trondheim ,the third largest city in Norway,concern about local airpollution was expressedin the early 1990s, and in 1994 the city administration decided to map the chemical compositionof urban surfacesoilsin order to eval- uate the stateof pollution.Thisgeochemical mapping had a two-foldpurpose:1)To assess whetherstack-emissionsfrom indust rialsites,incinerators and cremato riaas wellasroad

traffic had causedlocal,traceablepollution.2)To providea database for environmental health risk evaluation.In addi- tio n,thedatasetshould provid e backgroundknow ledge for further commu nity planning . In this article we present a brief overv iewof themethod s usedand the main resultsof themapping.

Study area

Geography

The cityofTrondheim liesincentral Norway,350 km south of the Arctic Circle (Fig.1). Theclimate is typically cool and humid.Trondheim was founded in997,andduring the first 900 years of its history the urban areawas concentra ted in the present city centre (Fig. 2).Durin g thethe 20'hcent ury, the urban area increased markedly and todaythe densely populated area covers 70 km'.Thecity nowhasa populat ion of 164,000.

Geology

Metamorp hosed volcanic and sedimentaryrocksequences ofmainly EarlyOrdovicianto Early Silurian age constitute a sign ifi cant part ofthe allochthonintheCaledo nides of cen- tral Norway (Wolff 1979).The Storen Nap pe of the Upper Allochthon dominates in the Trondheim region (Gale &

Roberts 1974, Roberts & Gee 1985).The main rocksin and around the city are MORB-type tholeiiticbasaltwith subor- dinate cherts and hemi-pelagic sedimentary rocks andalso bodies and dykes of trondhjemite,all metamorphosed at greenschist facies.These form part of the Bymarkaophiolite (Slagstad 1998).

Most of the city is situated on marine clay,deposited abou t 10, 000 years ago as the sea-level rose during

NGU-BULL 438.2001 - PAGE 64

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A \ Va te inc inerator B H o pital wa ste

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D Rock wool fa ct ory

Fig.1.The stu dy area smapling pointsfor surface soils(314 samples)

deglaciation.Later,isostatic forces caused a relative sea-level decrease leaving the marine clay onshore. Along the Nidelva river,the city rests on fluvial sediments (Reite 1983, Reite et al. 1999).lnthe city centre,the overburden has been used and recycled many times during historical times.It is therefore difficult to determine the original type of material (Reite et al. 1999).

The urban soil also contains building materials (bricks, paint,concrete,metal),waste,ash,slag,transported soils, organic materials and local original mineral matter(Ottesen et al. 1999a & b,Langedal & Ottesen 2001).

Methods

Sampling and sample preparation

Surface soil was selected asthe sampling medium sinceit is readily accessible and is knownto accumulate airborne pol- lutants. From gardens,parks,fields and industrial sites within

ROLF TORE OTTESEN&MARIANNE LA GED AL

1909 194 6 1982

~ 1987

Fig.2.Mapshowingthedevelopment of densely populated areasin Trondheimduringthe period1909-1987.

the populated parts of Trondheim,314 samples were col- lected at a density of 4.5 samples per km' (Fig. l).The sam- ples were collected from areas consistingof marineclay,flu- vialsediments or reworked urban soil.From each site,grass was removed before one half kilogramof material was col- lected at 0-2cm depth.The sampleswere packedin paper bags and air dried.

Overbank sediments of varying age from the Nidelva riverand from 55 other riversor streams in the area were also sampled and analysed to study the chemicalchanges through time (Hana 1996,Ottesen et al. 1989,2000c).The element concentrations in the deeper and older overbank sediments were interpreted as providing a reasonable indi- cation of pre-industrial,natural concentrations.

Chem ica l a nalysis, in o rg a n ic substances

The sampleswere sievedthrough a 2-mm nyloncloth.One gram of this< 2 mm sample materialwas digested in hot Aqua Regia(3ml 3:2:1HCI:HN0₃:H₂₀).The solutions were analysed for 31 elements by ICP-AES.In addit ion,the solu- tionswere analysed by GFAAS for As and Cd. Hgwas deter·

mined by AAS(cold vapour technique)after H 0₃diqes- tion.Sewas determined after HN0₃and H₂₀₂digestion .The analyticalwork was carriedout by the GeologicalSurvey of Finland,which is accredited after EN 45001.

Loss -o n-ig n it ion

Loss-on-ign it ionwas determined in allsamples by heating 2 grams of material of each sample to 200°Cfor 2 hours,fol- lowed by 20 hours at 430°C.

Statistica l methods

The analytical resultswere treated statistically by summary statisticsand factor analysis.

ROLFTOR E OTTESEN&MARIAN NE LANGEDAL NGU-BULL43 8,2001 - PAGE 65

Table 1.Co ntentsof aqua regiaext racta bleelementsin 314 sam plesof

Mineralogical analysis

surfacesoil from Tro nd heim,Norwa y.

Ele me nt Arithmet ric Media n Minimum Maximum Twelve sample sofsurfacesoil(6 sam ple sof marineclayand

mean 6 sam ples of fluvial sediments)were analysed by XRD^for

AI(%) 1.91 1.86 0.17 4.47 determina tionofth e main minerals present in thesamples.

As(mg/kg) 3.0 2.8 0.5 83

B_Ba(mg/_(mg/kg)_{kg) 77.4}5.8 _72.25.0 _18.03.0 28.0

Results and discussion

385

Ca(%) 0.68 0.54 0.06 10.60 Geochemistry of surface soil from Trondheim

Cd(mg/kgl 0.24 0.16 <0.01 11.3 Tab le 1 su m m a rize sth e resultsof thechemicalan a lys e s. The

Co(mg/kg) 14.4 13.5 1.6 45.0 ge ogra p hicaldist ribu t io ns of high and low con c entra tio ns

Cr(mg/kg) 73.3 69.3 7.9 199

varyfro m oneelement to anothe r(Fig.3).Co m p ariso n with

Cu(mg/kg) 42.3 34.5 1.7 706

Fe(%) 3.21 3.10 0.33 8.49 the regional and loca l geochemical background (Table 2)

Hg(mg/kgl 0.21 0.13 0.02 4.49 sh ows that Pb,Zn,Ba and Mg aresig ni fica n t ly enriched in K(%) 0.29 0.23 0.04 1.11 theurban surface soils. The enric h me nt of Cr,Cu,Fe,NiandV

La(mg/kg) 15.9 15.4 1.4 33.8

inthesame materi alis le ss sig nifica n t.

Li(mg/ kg) 18.5 17.8 0.9 39.3

Mg(%) 1.34 1.29 0.15 3.04

Mn(mg/kgl 479 442 43 4410 Table3 Principalcompo ne ntfactor analysisof the correlation matrix.

Mo(mg/ kgl <1.0 7.2 Rotatedfactorloadingand communalities. (Va rimax rotatio n).

Na(%) 0.02 0.02 0.007 0.76

Ni(mg/ kg) 47.8 45.0 6.0 231

P(mg/kg ) 848 794 50 2480 Variab le Factor1 Factor2Factor 3 Factor4 Factor5 Comm un alit)'

Pb(mg/kg ) 51.2 35 9.0 976 LogCo 0.964 0.080 0.033 0.035 -0.179 0.970

5(mg/ kg) 605 475 37 4813 LogCr 0.950 0.040 0.063 0.036 -0.086 0.934

5e(m g/kg) 3.6 3.3 0.1 9.2 Lo gv 0.935 0.205 0.037 0.183 0.058 0.953

5e(mg/kg) 0.27 0.20 0.04 3.69 LogFe 0.910 0.371 0.040 0.071 0.008 0.973

5r(mg/ kg) 30.8 27.0 5.8 255 LogNi 0.901 0.183 -0.026 -0.087 -0.262 0.922

Ti(mg/kg) 1171 1110 83.8 3170 LogMg 0.901 0.308 -0.012 -0.039 -0.19 7 0.947

V(mg/kg) 55.6 55.1 6.7 144 LogMn 0.853 0.061 0.102 0.107 -0.092 0.761

Y(mg/ kgl 8.4 8.0 0.6 17.5 LogTi 0.824 0.246 -0.176 -0.164 0.003 0.80 1

LOI(%) 13.7 10.9 0.4 91.5 LogAI 0.822 0.521 -0.036 0.123 0.093 0.972

La 0.099 0.941 -0. 120 0.083 -0.033 0.917 Y 0.230 0.882 -0. 150 -0.175 -0.153 0.907 LogNa 0.133 0.874 0.065 -0.2 11 -0.115 0.844 LogK 0.387 0.849 -0.116 -0.130 -0.097 0.911 Ba 0.403 0.728 0.319 0.026 -0.060 0.799 Table2..Medianvalues forthe contentsofacid-soluble ele mentsin Li 0.60 1 0.715 -0.028 0.059 0.111 0.889 overbanksed ime nts from the city ofTrondheimand theTro ndelag Log5c 0.644 0.677 -0.173 -0.15 1 -0.098 0.936

region, Norway. LogB 0.096 0.567 0.134 0.289 -0.421 0.609

LogPb -0.067 -0. 109 0.866 0.098 0.076 0.781 LogZn 0.183 0.018 0.822 -0.086 -0.304 0.809 Element Surface so il, Overbank sediments Overbanksediments LogCd 0.057 -0.038 0.736 0.007 -0.32 1 0.650

(m g/kg) Trondheim Tro ndelagregio n Nidelva river.Tro ndh eim LogHg -0.178 -0.183 0.607 0.366 0.310 0.664

(N=314) (N=55) (N=2S)

AI 18600 17 400 10000 LogpH -0.2 13 0.086 0.578 0.478 -0.124 0.630

As 2.8 2.8 <3 LogAs 0.055 0.189 0.394 0.127 -0.327 0.317

B 5.0 4.1 <3 Lo g LOI 0.05 1 -0.046 0.112 0.853 -0.048 0.747

Ba 72.2 43 46.8 LogS -0.105 -0.154 0.200 0.809 -0.354 0.854

Ca 5400 5000 2700 Log Se 0.260 -0.153 -0.026 0.743 -0.060 0.648

Co 13.5 15.7 8.5 LogCa 0.074 0.114 0.090 0.164 -0.906 0.873

Cu 34.5 27 28.9 LogCu 0.351 0.075 0.384 0.074 -0.640 0.691

Cr 69.3 53.6 43.4 Log5r 0.072 0.481 0.217 0.322 -0.529 0.667

Fe 31 000 25000 17 000

K 2300 1500 2500 Varia nce 8.7716 6.0 103 3.3380 2.7822 2.4769 23.3789

La 15.4 23 %Va r 0.302 0.207 0.115 0.096 0.085 0.806

8.3

Li 17.8 13.3 5.2

Mg 12900 9200 7100

Tabl e 4.Mineralsdet ect ed by X-raydiffraction (XRD) in surface soils

Mn 442 400 136 from Trondheim,Norway.

Na 20 30 40

Ni 45 35.6 32.9

A 794 900 771 Miner al Characte rist ic chemicaleleme nts

Pb 35 9.6 <3 Amphibole 5i,AI,Mg,Ca,Na,Ni,Co,Cr,Cu

Sc 3.3 5.2 2.7 Chlorite Si, Mg,Fe,AI,

u

Sr 27.0 28.1 17.5 Biotite Si

Ti 1110 1200 850 Muscovite Si,Fe,Mg,AI.K

V 55.1 40.4 30.5 Plag ioclase Si,AI,Fe, Ca,Na,Ba

Z n

NGU-BULL 43 8.2001 -PAGE 66 ROLF TORE

ot

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Fig.3.Conte ntofacid-soluble AS.Hg,Ni,and Pb(m ovingmedian)in surface soils from Trondheim.

ROLF TORE OTTESEN&MARIA N N ELA N GED A L

Factoranalysis of thedat aset indicates certain eleme nt associatio ns that point to partic ularsources. Factor 1(Table 3)explai ns a sig nifica nt part of the variance forAI,Co,Cr,Fe, U,Mg,Mn,Ni,Se,TiandV in the surfacesoil.Fortheseele- ments,the communali tiesare relativelyhigh(>0.8).

Factor2exp lainsa sig ni fican t part of thevarianc efo rAI, B,Ba,La,Li,Na,Se and Y.Excep t for B,allthe elementsof fac- to r2 have high communalities.The mineralogical analysis (Table4)shows that natural minerals cont ribute to theAI, Ba,Ca,Cr,Fe,K,La,Li,Mg,Mn,Na,Ni,Se,Si,Ti,andYconcent ra- tion s of the samples.Sincethese elements belon gto factors 1 and 2,local geology probably controls the covariation bet we en eleme ntswit hi n thesefact or s.As anexam p le,itcan be seen that the dist ribut ion of Ni inso il (Fig.3)is largely related to occurrences of basic volcanic rocks in the Trondheim region(Gale & Rober ts1974,Wolff1979).

Factor3includ es Pb,Zn,Cd,Hg and P.The communalit ies forCd,Hgand P are relativel ylow,andonly65%of the vari- ance for these elements is explai ned by the fact o r model.

However,Pb and Znare clearly enr iched in the surface soil comparedwiththe natural background represented by the deep erparts of overb ank sedi me nt profiles(Tab les1and2).

It isassumed that Pb,Zn,Cd and Hg mainly have anthro - pogenic sources.The highest concentrations of these ele- ments are found at someindu st rialsites and in the city cen- tre(Hg and Pb forexam plein Fig.3).Thispatternis common in several other cities around the world (Mo ir & Thornton 1989,Birke etal.1992,Kellyetal.1994,Viveretteetal.1996, Ottesen&Volden1999).

A large part ofthe variance for LOI,S and Se is explained byfact o r4.S and Se probably mainly reflect the contentof organic mat ter in the samples. Ca is described by factor5.

The model indicates a eo-variance wit h Srand Cu.

The variance of Asis not explainedby the factor model.

How ever, the geogra phical distribu tion of this element shows that As concentra tions are generally higher in the eastern part of Trondheim than in other parts of the city (Fig.3).The eastern part of Trondheim has hosted several ind ustries burningcoalsuchas a smelter,arockwool fact ory, and an abandoned gasworks.It is assumedthat these are theprobab le sources of the elevated As concentrations.

Evaluation of main pollution sources

Municipal waste incinerator

A mun icipal wast eincinerator, located approxi mate ly10 km so ut hof thecit ycentre,became ope rativein late 1985.The plant hastwo incinera to rs wit h a capacity of 13 tonnes waste/hour,The plant produ cesenergy for cent ral heat ing, covering 15per cent of the heating requireme ntsfor the cit y.The flue gas passes throu gh electrofilters fo r dust rem oval and then throug h a washing tower beforebeing released fro m a 70m-h igh chimneystack.

Meta l co ncentrations in samples collected within a radi usof 2.5 km around the municipal waste incinerato r

(m arked AinFig.1)are lower thanthe median concen tra-

NGU-BULL438 ,2001 - PAGE 67

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tions forthe wholedataset(Fig.4).Sofar,the incinerato r has not emitted sufficient quantitiesto pollutethenearb y soil.

Crematorium and hospitalincinerator

In the areaaround the main crem ato riu m and thehospit al wast e incinerator(marked Bin Fig .1)there is a clear Hghalo in the downw inddirect io n.The same areais also enrichedin Pb,Zn and Cd(Fig.5).How ever,a main roadpassing throug h the areais also likely to influencethechemistryof the sur- face soils.

Cremat orium and smelter

In the eastern part of the city,there is a crematorium,an abandoned gasworks,and someheavy ind ustry(marked C and D in Fig.1).Thereisalso a main road running through

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Fig.6.Enrichmentfactorsfor As,Pb,Cd, Cu, Cr..Hg, Niand Zn in thearea closeto thecrem atoriumandheavy industryintheeast ern part of the city ofTron dheim.

NGU-BULL 43 B, 2001- PAGE 68 ROLF TORE OT ESE N MAR/A N ELA GEDAL

Fig. 7.Enrichm entfact o rs for As,Pb,Cd,Cu,Cr..Hg.Niand Zninthe area closetothe main roads,Trondheim,Norway.

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Table6. Contents of As and heavy metals in surface soil s from Trondheimin relation to nationalacceptancelevels.

Element Guidancelevel %of samp lesabove

guida nce level

As 2 mg/ 9 83%

Pb 60 mg/kg 20%

Cd 3 mg/kg 0.3%

Cu 100 mg/kg 2.2 %

Cr 25 mg/kg 96%

Hg 1 mg/kg 1.6%

50mg/kg 40%

Zn loomg/kg 50%

toruralairbeforethe amountofleadin petrol wasreduced (Hagen etal. 1989).

the area.Inthispart ofthe city,the surfacesoils are enriched in As,Pb,Cd,Hgand Zn(Fig.6).

Road traffic

Samp les collectedcloseto themainroads areenriched in Pb,Hg,Zn and Cd(Fig. 7).Leaded petrolis the most probable source for thePbenrichment,whiletyre wear may bethe main source for Zn and Cd in these samples (Table S).

ElevatedPblevelswere measured in the urban aircompared

Table 5.Conten tsof Zn and CdintyresIDuu n-Moen 1996).

---.!yre Sample 1 Sample2 Sample3 Sam le4

Zn(mg~g,-) ---=-Cd=-m:..:..:g~g_ _

17450 0.4

193 50 5.9

14050 1.9

15050 0.7

Large areas of Trondheim exceed theselevels for As,Cr, i, Pb and Zn(Table 6).Levels of Pband Zn are mainlyexceeded in the cit y centre,while concentrations of Cr,As and i exceedthe nation alguidelinesthroughout the study area.

Theguidelines considerall routesof exposurefrom soilto man.Iftheguidelines are exceeded,a specific riskanalysis should be performed onthe site.

Conclusions and practical implications

Localgeology and rocktypes account forthe fundamental, background composition s ofurbansoilsinTrond heim,cen- tralNorway.However,concent rations of As,Cd,Hg,Pband Zn are influenced bypollutionsourcessuch asroadtraffi c, localindustry,crematoria anda hospitalwasteincinerator.

Concentration s of As,Cr, Ni,PbandZn exceed the nationa l guidance levelsfor sensitive land-use overlarge areas ofthe city.The data indicate that there is a definite need for a healthriskevaluation.

Ore mill

Severe As and heavy metal pollution (Fig. 8) has been report edfrom an abandone dore millin the westernpart of the harbour.

Results in relation to national guidance levels

In Norway,the nationalguidance levelsadvi se concentr a- tion sthat are generally safe for sensit ive land-usesuchas child ren'splaygroun ds and commercial market gardening.

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Fig.8.Enr ichm ent factorsfor As.Pb,Cd,Cu,Cr..Hg. iandZn at an aban- donedind ustrial site,Trondheirn,Norway.

Acknowledgem ent s

Theauthors wishestothank ProfessorsBjorn Bolviken andEiliv Steinnes for their helpful discussions and thorough reviews.which helped to im provethe paper.Assistancefrom the editor,DavidRoberts,during final revisionsof the manuscrip tareacknowledged with thanks.

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