Gh. Oaieet al. - Poilutlonstate ol sedimenbdredged from the Sulinadistributary [nogo ceskii rmpul ie in POLLUTIONSTATE OF SEDIMENTSDREDGED FROM THE SULINA 127- DISTRIBUTARYAND THEIR INFLUENCE TO THEDANUBE DELTA 640 FRONTAREA ruka, GheorgheOArEl, Dan SecnteRul, Stefan SzoBorKAl, Adrian SrArurcA1, Romeo llca, SoARE' rkoe lNationaffnstitute of MarineGeology and Geoecology (GEoEcoMAR), Str. Dimitrie Onciul 23-25, R0-70318,Bucharest, Romania, e-mail: [email protected] 2LowerDanube Fluvial Administration-Giurgiu Branch, Str. Portului 1, Giurgiu, Romania Abstract:The Sulina Canal and mouth bar are dredged for betternavigation conditions. The dredged sediments contain important quantitiesof heavymetals (e.9. Pb, Cd, Cr).The sameheavy metals were found in lowerconcentrations in the sedimentsamples collectedfrom the geoecologicalmonitoring stations from the RomanianBlack Sea shelf. The dredgedsediments are discharged two nauticalmiles SE of the Sulinaprotection jetties. These contribute to the localpollution of the DanubeDelta Front area, thus showingthe important role of the DanubeRiver as pollutingagent. The presence of heavymetals ln highcontents in someareas of the RomanianBlack Sea shelf indicates a significantanthropic contribution that disturbed the marineecosystems. Keywords: Danube River, Sulina mouth bar, Black Sea, sediment fluxes, dredged sediments, heavy metals The multiannualmean water dischargeis about 1.INTRODUCTION 6000 m3s-1(Bondar ef a/., 1996).The lengthof the DanubeRomanian watershed is 1075Km. between the TheDanube is the secondEuropean river with a total confluenceof the riverwith the Neratributary and the lengthof 2850 Km. lts drainagebasin is extendedon BlackSea. 817.000Km.' on the territoriesof 15 Centraland The naturalflowing regime of the DanubeRiver has EasternEuropean countries (Fig. 1) beendisturbed by anthropicactivities (e.9. river . Hydrogrs,phlc stafrot e and ftain lowns r' Easin Limlt Fig. 1 Hydrographicbasin ofthe RiverDanube (km 1075. Black SeaRomanian section ofthe river) GEO-ECO-MAR|NA,4/1 999 JI Nationallnstitute of MarineGeology ancl ceo-ecology Proc.lntem. Workshop on "Modernand Ancient Sedimentary Envlronmenb and Processes" in Moeciu,Romania, Oct. 8-15, 1998 Gh.Oaie et al. - Pollutionstate of sedimentsdredged lrom the SulinaDistributary damming, embankments, dredging of the Sulina The cutting of the meandersof the Sulina Distributaryfor navigation,meandering cut-off works). Distributaryand the constructionof jettiesthat flankthe After the buildingof the dams from the lron Gates I and Sulinamouth for the protectionof the navigationcanal ll hydroelectricpower plants,the river sedimentload has haveinfluenced the natural equilibrium between the river decreasedby 50 - 70o/ocompared to the mean value of pre-dammingsediment flux regime(Fig. 2). 2500 6t 2000 -L,!-l--r-- v E i-532118t''f 1E+06x.i 7E+08 i o ct 6 1500 -L+i' g i, o ri, ./ :iqli o ' I, 1000 :- j- i-.i .,-i.-.-,, ' , I l$- i u,ct rv:stzP*-i1q610qiiii i i if il'l'?i i i i i i - _ - -a_l-T _ - w-r--i 500 r r_-r_ 1--r'__r-_r-r-l--r- r'fti 5R3b-61- iil I i i 0 "-_--, 1960 1965 1970 1975 1980 198s 1990 1995 2000 Fig. 2 DanubeSediment Discharge at VaduOii hydrographicstation 'Km,247 (1961-1996) (afterPanin & Jipa,1998) The sedimentdischarges of the Danube into the and the sea (Panin,1998). The breakingof the liftoral BlackSea are not biggerthan 20 - 30 milliontons/year longshoresediment drift altered the natural sediment (Paninef a/., 1996)"The sedimentsoriginating from the distributionalong the deltaic coast and created the three main distributariesof the Danubeare mainlysilts, conditionsfor the evolutionof the Sulina bar at 8 km mudsand fine sands. offshorethe coast.The Sulinacanal and mouth bar are Out of the Danubetotal water and sedimentinputs continuouslydredged for the maintainance of the into the Black Sea, 22o/oof the generaldischarges are navigationconditions. directedthrough the Sulina Distributary(Bondar ef a/., The quantitiesof sedimentsdredged for navigation 1996).The coarse sedimentsvolumes discharged into purposes from the Sulina Mouth Bar suffer important the Black Sea by the Sulina mouth have remained variationsin time. Between1992 and 1998the quantity relativelyconstant. Between 1990 and 2000, the highest of dredgedsediments decreased constantly from over sedimentdischarges were attainedin 1995 and 1999, 867,000cubic meters in 1992to lessthan 70,000cubic respectively(Bondar et a|.,2000)(Fig. 3) metersin 1998(Table 1, Fig.4). Table I Quantitiesof dredgedsediments from the SulinaMouth Bar dischargedinto the BlackSea Year 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 Quantity of dischargec 330343 1670s7710221633204 ;ediments(cubic meters) 502085 328800395844 56401 303990 277348 it National lnstituteof Maine Geology and Geo-ecology Proc. lntem. Workshop on "Modern and Ancient Sedimentary Environmentsand Processes"in Moeciu, Romania,OcL 8-15, 1998 L-- Gh.Oaie et al. - Po$utianstate of sedimentsdradged from the Sulinadistributary ulina r the anal 'iver Fig.3 Meancoarse bottom sediment inputs at the Sulinamouth 1993 1994 i99S 1996 1999 Fig. 4 Q|ranlily of sedimenls dregedfrom the Sulina mouth bar between1991-2000 2. RESULTS samplescollected from the geoecologicalmonitoring Alongthe SulinaDistributary the bottomsediments stationsfrom the BlackSea shelf in (e.9. frontof the Danube aremainly sandy, At themouth betweenthe Sulina Delta(Table 2). harbor and the end of protectionjetties) the the The Danube River sedimentand organic matter sedimentsare fine sand to mud. dischargesinto the BlackSea are of abourt11.000 Uday Heavy metals contentsin the superficialbottom (Gomoiuef a/., 1998).The Phyto- and zooplanKon sedimentsare higherfor Pb, Cd and Cr (Oaieef a/., represent8.9% and 0.2o/oof the solid suspension 1998).The values are similarto those from the discharge.Expanding the data for an entireyear, the sediments dredgedfrom the SulinaMouth Bar that are totalsuspended solids and biomassdischarges are of dischargedtwo NauticalMiles SE of the mouthof the about4000x10'Uyear, suspended solids, out^of which SulinaJetties (Fig. Thesevalues 5). are higherin 35x10" Uyear phytoplanktonand 7x10" tlyear comparisonwith those measured in the bottomsediment zooplankton(Gomoiu et a/., 1998).These compounds GEO.ECO-MARINA,UI999 National lnstituteof Maine Geology and Geo-ecology Proc.lntern. Workshop on "Modernand Ancient Sedlmentary Environments and Processes' in Moeciu,Ramania, Oct. 8-15, 1998 Gh.Oaie et al.- Pollutionstate of sedimentsdredged from the SulinaDistributary %oo- ar Sullna X Ganaft.llcuSonda \*"* X CasmVadanel \2a Y Sf. Gheoroho @ \%" e.Advaningdnehe @B ShUodrf,*p il Su[0nadf,sfirlbubry a $ror*noherqNi[r Dir€attonof ltr&onalcunsnb * dlschargearea of drcdgedeedinnenb B[aaSSe6 Fig.5 Sulina-Sf.Gheorghe littoral zone (Black Sea-Danube Delta front); evolution of beachsectors, positions of littoralcurrents, dischargearea of dredgedsediments. influencethe north-westernpart of the BlackSea shelf. than any ratio recordedin the DanubeDelta Front, Thestate of fluvialand marine ecosystems is affectedby indicatinggreater amounts of anthropicheavy metals in pollution,this fact being supportedby the low theirconstitution. For Pb and Cd the ditferencereaches biodiversityand predominance of a fewspecies. oneorder of magnitude, The sedimentcore from Hm 72 Sulina (GPS coordinates:450 08' 843" N lat.; 290 45' 761' E iong., coNcLUstoNs witha lengthof 91 cm.) containsintervals with high concentrationsof Cu, Pb andZn at 35 cm depthand Pb at 73.2cm. From top to bottom,the coresediments vary The pollutantsdischarged by the DanubeRiver into from medium to fine silts, the clayey fraction the BlackSea are adsorbed on the fine fraction.This is representing8.27 to 15.19%from fine silt 8.89 to transportedeither as suspendedor bed load and 13.56%from medium silt (R6dan in Paninef a/.,1996), redistributedon the Black Sea shelf by the normal The bottomlayers of the coreconsist of finesand. The littoral-marinecurrents (Fig. 5). Another means of heavymineral fraction from coarser sediments (garnets, transportationis also due to the stormsperiod, when opaques,amphiboles) vary between1 and 6 % (Fulga, finer sedimentsare redistributedby stormwaves and in Paninef a/., 1996),the mainsouree being the fossil currentsfrom the shallowerareas to deepersedimentary beach ridges. The heavy metals contentsvertical environments.Thus, the dredgedsediments contribute distributionis important,as the dredgingreach depths of to the localpollution of the DanubeDelta Front between 2 metersin the sedimentsfrom the Sulinamouth bar. At Sulinaand Sf. Gheorghe,supplying especially great the same time, the heavymetals to FezOoratios for quantitiesof Pb and Cd, two of the most toxic heavy dredgedsediments are, with a singleexception, higher metals. Table 2 Pollutantcontents in dredged sedimentsfrom Sulina mouth bar and from the geoecologicalmonitoring stationson the BlackSea shelfin front of the DanubeDelta Superficial Pollutantcontent {opml No. Location bottom Fe* Cu Pb Zn Ni cd Cr MnO' sediments lo/"1 lol"l v 1 Hm72 SulinaDistr. sitt 32 67.8 73.2 46,6 6.63 76.1 2.4 0.107 61.6 2 51 (marine Clayeysilt 79 21 123 u 0.41 112 5.50 0.138 u monitorino slatinn) 52 (marine silt 60 24 117 93 0.41 11 5.87 4.142 96 moniiorino stafion) 4 B53(marine Clayeysilt 48 E't I 37 1.24 16 2.05 0.060 12 monitorind slationI 40 GEAECO-MARINA,U1999 NationalInstitute of MarineGeology and Geo-ecology Proc.Intem. Workshop on "Modernand AncientSedimentary Environments and Processes" in Moeciu,Romania, Oct. &15, 1998 brr--