Species and distribution of rare earth elements in the Baotou section of the Yellow River in China.

This paper analyses the contents and species distributions of rare earth elements (REEs) in the water-suspended particulate-sediment system of the Baotou section of the Yellow River, China, with known anthropogenic REE input from industrial discharges. The major forms of REEs were suspended and dissolved in the mainstream and the tributaries of the Baotou section, respectively. The concentrations of the dissolved and suspended REEs had the same trends in the overlying water along the mainstream, which increased from the Seqi section (site A) to the mouth of the Sidaosha River (site D), reaching a maximum value at site D, and tending to decrease thereafter. The contents of REEs in sediment cores showed enrichment with light rare earth elements (LREEs). The bound to carbonates and to Fe-Mn oxides are the major forms of REE in the secondary phase and the REE exhibited LREE enrichment pattern and moderate Eu depletion in suspended particulates and surface sediments. The contents and species distributions of REEs in the water-suspended particulate-sediment system of the Baotou section suggest that the anthropogenic source of REEs from Baotou city have enhanced REE accumulation to the Baotou section. This information is important for predicting possible pollution resulting from anthropogenic REE input into rivers.

[Heavy metal adsorption research on different size fractions of sediment in the Baotou section of the Yellow River by using modified fractal dimension model].

The expression of surface fractal dimension (SFD) for size fractions of the Yellow River sediment was deduced. Based on the expression, the SFD value of different size fractions of the sediment was calculated. The SFD value of the sediment in the Baotou section of the Yellow River is 1.91, and the SFD value of the sediment smaller than 63 microm is 1.36, indicating strong ablation and separating ability of the Yellow River water. Using the modified fractal model, Freundlich model and Langmuir model to fit the data of heavy metal (Cu, Pb, Zn and Cd) adsorption, it is found that the modified fractal model is more available. And the adsorptive thermodynamics is better described by combining the modified fractal model and metastable equilibrium adsorption (MEA) theory. The variation extents of equilibrium adsorption capacity influenced by different grain size are ranked as Cu > Pb > Zn approximately equal to Cd. For each selected heavy metal, the higher initial concentration is, the stronger variation of adsorption capacity will be. The adsorptions of Cu and Pb are mainly associated with mineral composition of the sediment, while the adsorptions of Zn and Cd are mainly associated with physical characteristics of the sediment surface.