『Abstract
　The silicon isotopic composition of dissolved silicon and suspended particulate matter (SPM) were systematically investigated in water samples from the mainstem of the Yellow River and 4 major tributaries. The SPM content of the Yellow River varied from 1.4 to 38,560 mg/L, averaging 3568 mg/L, and the δ³⁰Si of suspended particulate matter (δ³⁰SiSPM) varied from 0.3‰ to -0.4‰, averaging -0.02‰. The major factors affecting the SPM content and the δ³⁰SiSPM values in the Yellow River were inferred to be the mineralogical, chemical and isotopic characteristics of the sediments from the Loess Plateau and a combination of the climate and the flow discharge of the river.
　The major ions in the Yellow River water were Na⁺, Ca²⁺, Mg²⁺, HCO3^-, SO4^2- and Cl^-. high salt concentration was observed in samples from the middle and lower reaches, likely reflecting the effects of evaporation and irrigation because the Na⁺, Mg²⁺, SO4^2- and K⁺ concentrations were correlated with the Cl^- concentration. The dissolved Si connection (DSi) increased downstream, varying from 0.016 to 0.323 nM. The δ³⁰Si of dissolved Si (δ³⁰SiDiss) varied from 0.4‰ to 2.5‰, averaging 1.28‰. The major processes controlling the DSi and δ³⁰SiDiss of the Yellow River are (a) the weathering of silicate rocks, (b) the formation of phytoliths in plants, (c) the evaporation of water from and the addition of meteoric water to the river system, which only affects concentrations, (d) the adsorption and desorption of aqueous monosilicic acid on iron oxide, and (e) the dissolution of phytoliths in soils.
　The DSi and δ³⁰SiDiss values of global rivers vary spatially and temporally in response to changes in climate, chemical weathering intensity and biological activity. The moderately positive δ³⁰SiDiss values observed in the Yellow River may be attributed to the higher rates of chemical weathering and biological activities that have been observed in this catchment in comparison with those of other previously studied catchments, excluding the Yangtze River. Human activities may also potentially influence chemical weathering and biological activities and affect the DSi and δ³⁰SiDiss values of the major rivers of the world. Further river studies should be performed to gain a better understanding of the global Si isotope budget.』

1. Introduction
2. Geographic, geological and hydrological background of the Yellow River
3. Samples and experiments
4. Results
　4.1. The concentrations, mineral composition and SiO2 content of the SPM and the δ³⁰SiSPM values of the Yellow River
　4.2. The ion concentrations, DSi and δ³⁰SiDiss values of Yellow River water
5. Discussion
　5.1. The major factors controlling the SPM content and δ³⁰SiSPM of the Yellow River
　5.2. The major processes controlling the DSi and δ³⁰SiDiss values of Yellow River water
　　5.2.1. The weathering process of silicate rocks
　　5.2.2. Growth of phytoliths in plants
　　5.2.3. Evaporation of water from the river system and addition of meteoric water into the river system
　　5.2.4. Dissolution of phytoliths in soil
　　5.2.5. Growth of freshwater diatom
　　5.2.6. adsorption and desorption of aqueous monosilicic acid on iron oxide
　　5.2.7. Precipitation of silcretes and formation of clays coating in aquifers
　　5.2.8. Human activities
　5.3. A comparison of the DSi and δ³⁰SiDiss values for several river systems of the world and implications for the global silicon cycle
6. Conclusion
Acknowledgements
References