Distinct patterns of chemical weathering in the drainage basins of the Huanghe and Xijiang River, China: Evidence from chemical and Sr-isotopic compositions

Aquatic geochemistry on watershed background helps elucidate the influence of natural processes and anthropogenic activities to the environment. The 87Sr/86Sr ratios and dissolved loads were measured in 35 water samples from the Huanghe and Xijiang River drainage basins. The dissolved loads and 87Sr/86Sr ratios differed considerably between the two drainage basins. The 87Sr/86Sr ratios of the Xijiang River are between 0.70856 and 0.70936, with an average of 0.70894, reflecting weathering of carbonate minerals as the dominant source and anthropogenic pollution as the secondary one, especially in the upper reach tributaries, while the Sr isotopic ratios in the Huanghe River range from 0.70986 to 0.71139 averaging 0.71118 that results primarily from evaporite dissolution. Precipitation contributes to 2.8% and 5.7% to the chemistry of the Xijiang and Huanghe River, respectively. Evaporite dissolution and silicate weathering account for 79.4% and 11.3%, respectively, in the Huanghe River while carbonate dissolution and silicate weathering account for 75.4% and 14.6%, respectively, in the Xijiang River. The chemical weathering rate is 107.6 t/km2/yr in the Xijiang River drainage basin, and 34.2 t/km2/yr in the Huanghe River drainage basin. The CO2 consumption budget is 305.2 × 109 mol/yr in the Xijiang River drainage basin, and 147.9 × 109 mol/yr in the Huanghe River drainage basin.

► Distinct patterns of chemical weathering were found in the drainage basins of the Huanghe and Xijiang River.
► Carbonate weathering is the dominant source of Sr in the Xijiang River drainage basin.
► Evaporite dissolution is the primary source of Sr in the Huanghe River drainage basin.
► The contributions of precipitation to the chemistry of the Huanghe and Xijiang River are relatively low.
► The chemical weathering rate is much higher in the Xijiang River drainage basin than the Huanghe River.