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.

[Speciation and distribution characters of rare earth elements in the Baotou Section of the Yellow River].

As a whole of water column, suspended matter and surface sediment in the mainstream and the branch taking up industry wastewater, speciation and distribution characters of rare earth elements (REEs) were investigated systemically in the Baotou section of the Yellow River. This study shows that rare earth elements in the mainstream of the Baotou section of the Yellow River mainly exist in suspended particles, and the dissolved contents are in extremely minute quantities. REEs mainly exist in dissolved particles in the branch taking up industry wastewater, and suspended sigma REE and dissolved sigma REE are obviously higher than those in the mainstream. The change of sigma REE of dissolved particles in water phase along the Baotou section of the Yellow River is very similar to that of sigma REE of suspended particles, and consistent along the main river, it is that sigma REE increase appreciably from the control profile to the keystone discharged section, come to a head in the D site and reduce in the E site. This distribution pattern indicates pile industry wastewater of Baotou to rare earth elements in the mainstream of the Yellow River, particularly LREE. The REE distribution in the mainstream of the Baotou section of the Yellow River is the same, with LREE enrichment and Eu depletion. But LREE origin of D site is different from the other sites by excursion of LREE distribution curve and other geochemical parameters, they are origin of industry wastewater piled, otherwise the other four sites are origin of loess altiplano. And HREE are origin of loess altiplano in all the sites. The speciation characteristics of REE in the sediments and suspended matter are quite similar with the amount in as follows: residual >> bound to carbonates, bound to Fe-Mn oxides > bound to organic matter >> exchangeable. REEs exchangeable in surface sediment and suspended matter in the branch taking up industry wastewater are higher than those in the mainstream, it confirms that REEs in the mainstream mainly exist in suspended particles, and mainly exist in dissolved particles in the branch.