Background
The pollution of the second-longest European river (the river Danube) has been under monitoring and focused on various contaminants including metals/metalloids (Hg, As, Ni, Zn, Cu, Cr, Pb, and Cd), personal care products, technical additives, pesticides, pharmaceuticals, etc. Recent studies show that technology critical elements (TCE) – elements with a high supply risk and economic importance – are becoming emerging pollutants due to their wide application in new technologies. According to the European Union Water Framework Directive, sediments are one of the three major sources of river pollution. This study aims to determine major and trace elements including some TCEs in the Danube River sediment. The concentrations of the targeted elements in the surface sediments were discussed in the sense of the effect of building hydropower dam Iron Gate I and increasing the quantity of sediments in the Iron Gate gorge.
Results
The surface sediments were collected on the Danube River-km 1141 to 864 and three tributaries along this waterway. Two samples of deep sediments were used for comparison. Instrumental Neutron Activation Analysis was applied for quantification of 36 elements, with special attention to selected TCE belonging to lanthanides (La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Tm, and Yb). Spatial distribution is discussed (i) in the total pool of all analyzed elements and (ii) only lanthanides. For better understanding and to highlight a hidden relationship between targeted elements, multivariate statistical techniques (cluster analysis and principal component analysis) were applied to analyze the analytical data and to identify possible pollution sources. The obtained results of the targeted elements in the surface sediments were discussed in relation to the influence of hydropower dam Iron Gates I and the increasing quantity of sediments.
Conclusion
Overall results show increasing concentration of almost all investigated elements in the surface sediments from the Danube River-km 1112 to the dam. Sediment od the River Pek was separated as a location with extreme anthropogenic influence due to close vicinity of the copper mining site.