Chemical and Isotopic Characters of the Water and Suspended Particulate Materials in the Yellow River and Their Geological and Environmental Implications

The chemical and isotopic characteristics of the water and suspended particulate materials (SPM) in the Yellow River were investigated on the samples collected from 29 hydrological monitoring stations in the mainstem and several major tributaries during 2004 to 2007. The δD and δ¹⁸O values of the Yellow River water vary in large ranges from ?32‰ to ?91‰ and from ?3.1‰ to ?12.5‰, respectively. The characters of H and O isotope variations indicate that the major sources of the Yellow River water are meteoric water and snow melting water, and water cycle in the Yellow River basin is affected strongly by evaporation process and human activity. The average SPM content (9.635 g/L) of the Yellow River is the highest among the world large rivers. Compared with the Yangtze River, the Yellow River SPM has much lower clay content and significantly higher contents of clastic silicates and carbonates. In comparison to the upper crust rocks, the Yellow River SPM contains less SiO₂, CaO, K₂O and Na₂O, but more TFe₂O₃, Co, Ni, Cu, Zn, Pb and Cd. The abnormal high Cd contents found in some sample may be related to local industrial activity. The REE contents and distribution pattern of the Yellow River SPM are very close to the average value of the global shale. The average δ³⁰Si_SPM in the Yellow River (–0.11‰) is slightly higher than the average value (–0.22‰) of the Yangtze River SPM. The major factors controlling the δ³⁰Si_spm of the Yellow River are the soil supply, the isotopic composition of the soil and the climate conditions. The TDS in the Yellow River are the highest among those of world large rivers. Fair correlations are observed among CI^?, Na⁺, K⁺, and Mg²⁺ contents of the Yellow River water, indicating the effect of evaporation. The Ca²⁺ and Sr²⁺ concentrations show good correlation to the SO₄^2– concentration rather than HCO₃^? concentration, reflecting its origin from evaporates. The NO₃^? contents are affected by farmland fertilization. The Cu, Zn and Cd contents in dissolved load of the Yellow River water are all higher than those of average world large rivers, reflecting the effect of human activity. The dissolved load in the Yellow River water generally shows a REE distribution pattern parallel to those for the Yangtze River and the Xijiang River. The δ³⁰Si values of the dissolved silicon vary in a range from 0.4‰ to 2.9‰, averaging 1.34‰. The major processes controlling the D_Si and δ³⁰Si_diss of the Yellow River water are the weathering process of silicate rocks, growth of phytolith in plants, evaporation, dissolution of phytolith in soil, growth of fresh water diatom, adsorption and desorption of aqueous monosilicic acid on iron oxide and human activities. The average δ³⁰Si_Diss value of the Yellow River is significantly lower than that of the Nile River, Yangtze River and Siberia rivers, but higher than those of other rivers, reflecting their differences in chemical weathering and biological activity. The δ³⁴S_SO4 values of the Yellow River water range from ?3.8‰ to 14.1‰, averaging 7.97‰. There is some correlation between SO₄^2– content and δ³⁴S_so4. The factors controlling the δ³⁴S_SO4 of the Yellow River water are the SO₄ in the meteoric water, the SO₄ from gypsum or anhydrite in evaporite rocks, oxidation and dissolution of sulfides in the mineral deposits, magmatic rocks and sedimentary rocks, the sulfate reduction and precipitation process and the sulfate from fertilizer. The ⁸⁷Sr/⁸⁶Sr ratios of all samples range from 0.71041 to 0.71237, averaging 0.71128. The variations in the ⁸⁷Sr/⁸⁶Sr ratio and Sr concentration of river water are primarily caused by mixing of waters of various origins with different ⁸⁷Sr/⁸⁶Sr ratios and Sr contents resulting from water‐rock interaction with different rock types.