Distribution, Enrichment and Transport of Trace Metals in Sediments from the Dagu River Estuary in the Jiaozhou Bay, Qingdao, China

26 river bank sediments and 15 estuary seafloor sediments were sampled from the Dagu River and the estuary of Northwestern Jiaozhou Bay to determine contaminations of heavy metals and metalloids (Cu, Pb, Zn, Cr, Cd, Hg and As). The trace metal contents in sediment from the estuary area were much higher than those of the river. Correlation analysis showed that except for Pb, the metals were mainly controlled by the grain size, and enriched by adsorption of aluminosilicate minerals, Fe/Mn oxides and organic matter in river and estuary sediments. In addition to Cu in some stations, the metals met the requirements of the marine organism and humans for the quality of the marine environment. The concentrations of Cu, Pb, Cr, Hg and As were between the threshold effect level (TEL) and probable effect level (PEL), indicating those metals might have occasional adverse effects. Results of Enrichment Factor values revealed that the entire study area was enriched in Pb and Hg, at moderate environmental risk, but the estuary was more significant. Pb and Hg contaminations in this area were mainly from coal combustion and automobile emissions. River runoff and atmospheric deposition dominated the metals distribution and enrichment in the study area. Contaminants in sediments entering the estuary were further transported to the south and east under the river runoff and reciprocating current in the Jiaozhou Bay.