Calculation Of The Atmospheric CO₂ Consumption By Chemical Weathering In The Huanghe River Basin Considering The Contribution Of Water Consumption

The chemical weathering of continental rocks constitutes an important carbon sink for atmospheric CO₂, which is the same magnitude as the air-water CO₂ flux or flux that is caused by burning of fossil fuels. Because of the dominant role of river basins in the global chemical weathering, accurate quantification for the consumption flux of CO₂ by chemical weathering in river basins is essential for studying the global carbon cycle. With the increasing of agricultural-dominated water consumption, the discharges of rivers to the ocean have declined in recent years. If calculated with the actual discharge to the ocean by ignoring the contribution of water consumption, the consumption flux of CO₂ by chemical weathering in river basin will be underestimated.With the survey on inorganic carbonate and chemical characteristics of water from the main tributaries and main stream of the Huanghe River basin in summer 2009, this paper studies the transport characteristics of inorganic carbon and the main weathering reactions. The calculation of the CO₂ consumption flux by chemical weathering in the Huanghe River basin with the consideration of the contribution of water consumption is also discussed. In addition to the calculation of DIC fluxes from water consumed and to the sea and that of the air-water carbon flux in the Huanghe River basin, a model is established on the balance of DIC transportation. The Resluts are as follows:1. DIC/PIC is mainly attributed to the total suspended solids in the Huanghe River basin in summer. DIC is the major carbon form transported in the Huanghe River and PIC becomes the dominant content when TSS value increases to more than 3104mg/l.2. Due to abundant carbonate rock and heavy physical erosion and chemical weathering, annual DIC flux from erosion in the Yellow River basin surpasses that of PIC in an order of magnitude. Annual DIC and PIC flux of water consumed in the Huanghe River basin are 1.68 and 2.97 times of that discharged to sea, respectively.3. The flux and rate of CO₂ consumption by chemical weathering are 92.84×109mol/a and 123.49×10³mol/ (km²·a) in the Huanghe River basin, respectively. By considering the contributions of the water consumption in each stream, the fluxes of CO₂ consumption by chemical weathering in the upper, middle and lower reaches of the Huanghe River basin accounted for 63.3%, 35.5% and 1.2% of that in the whole basin, respectively. Hence, most CO₂ is consumed in the upper reach of the Huanghe River basin. In contrast, due to abundant evaporate the CO₂ consumption in the middle reach of the river is less. Ignoring the contribution of water consumption may cause a underestimation of the CO₂ flux by chemical weathering to 58%～69% in the Huanghe River basin.4. The main controlling factors of pCO₂ are the carbonate system with high carbonate content induced by the strong mechanical erosion and chemical weathering in the Huanghe River basin. The water of the Huanghe River basin is a source of CO₂ to the atmosphere, and the efflux is about 0.78×10¹¹gC/a.The calculation of CO₂ consumption by chemical weathering in the Huanghe River basin is significant to recognize the importance of chemical weathering on carbonate transportation in river systems, and also gives clues to the flux calculations of other substance.