CHARACTERISTICS OF REE AND HEAVY METALS IN THE SURFICIAL SEDIMENTS OF LAIZHOU BAY, BOHAI SEA AND THEIR IMPLICATIONS FOR PROVENANCE

With the surface sediment samples collected from the 32 stations of Laizhou Bay, some critical environment problems, such as the composition and distribution patterns of rare earth elements (REE) and heavy metals, heavy metal pollution degree and the sources of pollutants are studied in this paper. Upon the basis, we made discussion on such environmental factors as the distribution of heavy metals and rare earth elements by means of heavy metal provenance, chemical alteration index (CIA) and REE characteristics. The results show that the total amount of rare earth elements increases from southeast to north in the bay, and the contents of some rare earth elements, such as Eu, Gd and Tb, are obviously related to fine grained clay minerals and organic carbon, and little affected by chemical weathering. Some stations in the study area are polluted by Cd and Hg obviously enriched by human activities; Cu, Pb and Zn might be the products of natural weathering of the earth crust; and Cu and Zn are also closely related to human activities; while Cr is influenced by both natural weathering and human activities; the accumulation of most heavy metals is affected by the hydrodynamic forces of the bay. Provenance discrimination results suggest that the average value of CIA in the study area is 50.83, close to the value of the Yellow River sediments (50.9～59.7), but lower than the value of the Chinese loess; the REE distribution pattern and characteristic parameters of the study area are also very close to the Yellow River, which indicates that the Yellow River is the most important source of surface sediments of Laizhou Bay; The Guangli River and Weihe-Mihe delta only contribute some sediments in the south and southwest, while the contribution of the Chinese Loess and the local soil in Shandong Province is relatively little.