Trace element contamination in the arms of the Danube Delta (Romania/Ukraine): Current state of knowledge and future needs

摘要

This paper provides the first critical synopsis of contamination by selected trace elements in the wholeudDanube Delta (Romania/Ukraine) to: identify general patterns of contamination by trace elements acrossudthe Delta, provide recommendations to refine existing monitoring networks and discuss the potentialudtoxicity of trace elements in the whole Delta. Sediment samples were collected between 2004 and 2007udin the three main branches of the Delta (Chilia, Sulina and Sfantu Gheorghe) and in the secondary delta ofudthe Chilia branch. Samples were analyzed for trace elements (Cd, Co, Cr, Cu, Ni, Pb, V, and Zn) and TiO2,udFe2O3, MnO, CaCO3 and total organic carbon. Cluster analysis (CA) and Principal Component Analysisud(PCA) showed that levels of Cd, Cu, Pb, and Zn were influenced by anthropogenic activities. At theudopposite, concentrations of Cr and Ni largely originated from the weathering of rocks located in theudRomanian part of the Danube catchment and naturally rich in these elements. Data analysis using Self-udOrganizing Maps confirmed the conclusions of CA/PCA and further detected that the contaminationudtended to be higher in the Chilia and Sulina arms than in the Sfantu Gheorghe arm. The potentialudecological risks due to trace element contamination in the Danube Delta could be identified as moderateudand localized, provided that the presence of the natural sources of Cr and Ni was properly considered.udThe available results suggest that monitoring sediment quality at the mouths of Sulina and SfantuudGheorghe arms is probably enough to get a picture of the sediment quality along their entire lengths.udHowever, a larger network of monitoring points is necessary in the Chilia and secondary Chilia delta toudaccount for the presence of local point sources and for the more complex hydrodynamic of this part ofudthe Danube Delta.