『Abstract
This study focuses on the chemical and Sr isotopic compositions
of the dissolved load of the rivers of the Changjiang Basin, one
of the largest riverine systems in the world. Water samples were
collected in August 2006 from the main tributaries and the main
Changjiang channel. The chemical and isotopic analyses indicated
that four major reservoirs (carbonates, silicates, evaporites
and agriculture/urban effluents) contribute to the total dissolved
solutes. The overall chemical weathering (carbonate and silicate)
rate for the Changjiang is approximately 40 ton/km2/year
or 19 mm/kyr, similar to that of the Ganges-Brahmaputra system,
and the basin is characterized by carbonate and silicate weathering
rates ranging from 17 to 56 ton/km2/year and from 0.7
to 7.1 ton/km2/year, respectively. In the lower reach
of the Changjiang main channel, the weathering rates are estimated
to be 36 and 2.2 ton/km2/year for carbonates and silicates,
respectively. It appears that sulphuric acid may dominate chemical
weathering reactions for some sub-basins. The budgets of CO2 consumption are estimated to be 646×109
and 191×109 mol/year by carbonate and silicate weathering,
respectively. The contribution of the anthropogenic inputs to
the cationic TDS of the Changjiang is estimated to be 15-20％ for
the most downstream stations. Our study suggested that the Changjiang
is strongly impacted by human activities and is very sensitive
to the change of land use.』
1. Introduction
2. Natural setting of the Changjiang drainage basin
2.1. Topography and geology
2.2. Hydrology and land cover
3. Sampling and analytical methods
4. Results
4.1. Major elements
4.2. Strontium isotopes
4.3. Long-term evolution of the solute concentrations in the
rivers of the Changjiang basin
5. Discussion
5.1. Sources of solute and characterization of the end-members
5.1.1. Atmospheric inputs
5.1.2. Anthropogenic inputs
5.1.3. Weathering component
5.1.3.1. Evaporites dissolution
5.1.3.2. Silicate weathering
5.1.3.3. Carbonate weathering
5.1.3.4. Sulphide oxidation
5.2. Chemical mass balance for the rivers of the Changjiang basin
5.3. Results of the calculations
5.4. Chemical weathering in the Changjiang basin
5.5. Sources of protons as weathering agent and CO2
consumption rates
6. Conclusions
Acknowledgments
Appendix A. Inversion model
Appendix B
Appendix C
References