Rare earth elements in surface sediments of a marine coast under heavy anthropogenic influence: The Bohai Bay, China

Abstract

Surface sediments along four river-to-sea transects from the coastal Bohai Bay were assessed using a four-step sequential extraction procedure to determine the concentrations of rare earth elements (REEs) and the geochemical fractions in which those elements were present. The concentrations of light REEs were slightly depleted than those of the middle REEs and the heavy REEs. No significant Ce anomaly was observed whereas slight Eu-positive anomaly was found. The sequential extraction results revealed that the geochemical fractions of REEs followed the order of residual > reducible > oxidizable > acid soluble. The residual fraction accounted for the majority of the total concentrations of REEs. Middle REEs were more easily leached than other REEs. No obvious river-to-sea transportation was observed and the concentrations of REEs in surface sediments of the coastal Bohai Sea were consistent with the data from the Post-Archean Australian Shale. This study further demonstrated on the basis of our previous inference that the geochemical features of REEs in coastal sediments were generally unaffected by heavy anthropogenic effects.