『Abstract
Water and sediment samples were collected from the headwaters
of the Yangtze River, Tongtian He and Jinsha Jiang (upstream of
the Yangtze River which flows on the eastern Qinghai-Tibet Plateau).
A detailed geochemical study of the river system was carried out
to determine: (i) temporal and spatial variations of the major
ions and their implications; (ii) contribution of carbonate, silicate
and evaporite to the river dissolved load and (iii) CO2
consumption via silicate weathering. Results show that cations
derived from evaporite dissolution account for 44.7-82.8％ of the
total cations in the headwaters of the Yangtze River and increasing
from SE to NW of the drainage basin. The contribution from silicate
weathering gradually increases from the headwaters due to exposure
of intrusive rocks and volcanic rocks in the Jinsha Jiang suture
belt. Proportion of cations derived from silicate weathering to
the total cations in river waters reaches a maximum at Panzhihua
City, which is consistent with the abundant exposure of Cenozoic
granitoids and Precambrian high-grade metamorphic rocks around
Panzhihua. The Jinsha Jiang basin has higher silicate weathering
rates but lower carbonate weathering rates than the middle and
lower reaches of the Yangtze River. The calculated enrichment
factors of potentially harmful metals in the river sediments are
within the range of 0.33-2.59, indicative of level 1 or 2 contamination.
The highest enrichment factor for Co, Cr and V is found in Panzhihua
City, indicating that it has been influenced by anthropogenic
sources.』
1. Introduction
2. Study area
2.1. Geography and hydrology
2.2. Geology
3. Sampling and analysis
4. Results and discussion
4.1. Characteristics of the total dissolved solids in rivers
4.2. Major ion composition
4.3. Characteristics of heavy metals in the riverbed sediments
4.4. Sources of major ions in the rivers
4.4.1. Contribution from anthropogenic activities
4.4.2. Atmospheric input
4.4.3. Silicate weathering
4.4.4. Carbonate weathering
4.5. The weathering rates and CO2 consumption
flux in basins
4.6. Physical weathering and chemical weathering
4.7. Temporal variations of chemical composition in the Jinsha
Jiang
5. Conclusions
Acknowledgements
References