Seasonal and interannual changes of river chemistry in the source region of Yellow River, Tibetan Plateau

摘要

The seasonal and annual processes of river chemistry as well as chemical weathering and controlling factors were examined in the source region of Yellow River (SRYE) during 2013-2015. River discharge exhibited strong seasonality and was dominated by precipitation and/or groundwater. Sediment concentrations were positively related to discharge, and the dominant sediment-producing area was this area from JM to JG owing to large precipitation and strong erosion. The dominant cations and anions were Na+, Ca2+ and HCO3-, and concentrations of most ions displayed obvious seasonality with a negative relationship with discharge, suggesting a hydrological control on river chemistry. Comparison of ion concentrations suggest that the regional climate and land surface affect the soil/rock erosion and solute release. River chemistry was dominated by the weathering of carbonate and silicate. HCO3-, Ca2+ and Mg2+ were primarily derived from calcite and dolomite weathering, and Na+ and K+ mainly came from silicate weathering. CWR and CatWR showed strong seasonality and were closely related to discharge, air temperature, precipitation and PER, suggesting that chemical weathering rates are dominated by lithology, discharge and precipitation. The sediment and solute yields ranged from 25,110 to 97,270 t km(-2) a(-1) and 22,610 to 27,800 t km(-2) a(-1) respectively in the SRYE (at TNH), where CWR and CatWR were 5.42-7.63 t km(-2) a(-1) and 1.20-2.62 t km(-2) a(-1) respectively. Higher CatWR in the SRYE than those in other basins with higher specific discharge implies that silicate weathering is more sensitive to permafrost degradation.