Twentieth century overview of heavy metals in the Galician Rias (NW Iberian Peninsula) R. Prego*, A. Cobelo-Garcı ´ a Marine Biogeochemistry Research Group, Instituto de Investigaciones Marinas (CSIC) C/ Eduardo Cabello, n  6. E-36208 Vigo, Spain Received 7 September 2001; accepted 26 April 2002 ‘‘Capsule’’: All information published on metals in this region up to the year 2000 is reviewed from a biogeochemical viewpoint. Abstract The 18 Galician Rias, comprising 25% of the Iberian Peninsula coastline, form a unique system within the European continental Atlanticcoastandprovideausefulreferenceareaforstudiesofmetals.Theseriasaresensitivetoanthropogenicinfluenceduetothe socioeconomicimportancegeneratedintheseareasbyindustry,aquaculture,portactivities,fishing,tourismand,accordingly,several islandslyingwithincloseproximitytotheriashaverecentlybeendeclarednaturalparks.AquacultureintheGalicianRiasisagrowth industry and in 2000 the rias supported 3386 mussel rafts producing 2.510 8 kg year 1 , i.e. 40% of European Union total seafood production.TheGalicianRiasarepartiallystratifiedestuarieswithpositiveresidualcirculationwithfresh(runofflowerthan100m 3 s 1 )andsaltwatermixinginsidethebasins.Thisbehaviourhasdirectconsequencesonmetalfluxeswherebytheriasbehaveasabarrier andaccumulatemetalsinthesediments.Metalstendtodepositclosetopointsourcesandremobilizationoccursinsidetheria,leading toaseawarddecreaseinmetalconcentration.WiththeexceptionoftheUlla(ArosaRia)andEume(Ares-BetanzosRia)headrivers andtheLagaresriver(VigoRia)theavailabledatasuggestthatriverinefreshwaterinputsarenotthemainsourceofcontamination. MetalstudiesreportedintheliteraturemainlyrelatetoCd,Co,Cr,Cu,Fe,Mn,Ni,PbandZn,andtoalesserextentHgandSn. Studies of other harmful metals such as Ag, Se and As are notably lacking. In addition, the studies have been localized and mainly restricted to the surface sediment. Data of heavy metals in the dissolved phase, suspended particulate matter and biota is scarce in the mainstream literature and should be considered in the future research. From the entire Galician coast, data from seven rias of socio-economicimportanceformthebulkofthepublishedwork.Thereisanurgentneedtostandardizeprocedures,employ‘clean’ procedurestoavoidcontaminationofsamplesandregularassessmentofanalyticalaccuracywithCRMsinorderthatresultscanbe comparedamongthescientificcommunityandproducereliableresults.Thecontinuationofcoastalenvironmentalstudiesrequiresan enlargementofthesamplinglocationsaswellassystematicandperiodicanalysisofknownpollutionsourcesinordertodecidewhether coastalregenerationactionisneeded.Studiesdedicatedtometalsinthewatercolumnarelackingandneedmoreattentioninfuture research.Themajorityoftheavailabledatacorrespondtothefluvialfront(30%)atriaheadand,toalesserextent,totheoceanicfront (3%),undersummerupwellingevents. Current awareness of the rias suggests that they are not contaminated although there is some evidence of important localized anthropogenicallyinducedenrichmentsattheoutflowoftheLagaresRiver(Pb,Zn),theSanSimo´ninlet(Pb)andneartotheharbor (Pb,Zn,Cu)intheVigoRia,theinnerpart(Cu,Zn,Hg,Pb)ofthePontevedraRia,theUllaRiverestuary(Cu,Cr,Mn,Ni;Zn)inthe ArosaRia,theinnerzone(Cu,Pb,Zn)oftheCorun˜aRia,theFerrolRia(Zn)andtheEumeEstuary(Zn,Mn,Ni,Co)intheAres- BetanzosRia.Inaddition,TBTenrichmenthasbeenfoundalongtheGaliciancoast,beinghighestintheindustrialbays(Vigo,Corun˜a andFerrol).Nevertheless,itisimportanttopointoutthelackofinformationconcerningtherelationshipbetweenmetalconcentrations indifferentfractionsofsedimentsand/orwaterandtheirbioavailabilityandtoxicityonbiotainordertoconfirmmetalcontamination dangers. The present paper reviews all the information published on metals in the rias up to the year 2000 and takes a biogeochemical standpoint, i.e. metal presence in the ria reservoirs: water column, suspended particulate matter, sediments and biota, as well as the fluvialandoceanicfrontiers. # 2002ElsevierScienceLtd.Allrightsreserved. Keywords: Metals; Sediments; Water; Biota; Review; Rias; Galicia 0269-7491/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(02)00231-2 Environmental Pollution 121 (2003) 425–452 www.elsevier.com/locate/envpol * Corresponding author. Fax: +34-986-292-762. E-mail address: prego@iim.csic.es (R. Prego).