Water chemistry of the headwaters of the Yangtze River

A total of 31 river water samples were collected from the headwater of the Yangtze River and its tributaries across Shigu Town to Mt. Tangula region. Water chemistry analysis was carried out to investigate water quality in the upstream Yangtze River. The results show that the headwaters of Yangtze River are turbid and have an alkaline environment with pH ranges from 8.3 to 9.3. The oxidation reduction potential (ORP) of the water varies from −77.1 to −134.2 mv with an average of −88.8 mv, indicating an anoxic water surface. Based on the ions analysis, the water chemistry of headwaters of the Yangtze River is affected by mineral (magnesium and calcium sulfate) weathering, evaporation–crystallization processes and ground water discharge. Concentrations of ions and elements except Hg in the headwaters of Yangtze River presented a trend of decreasing with the downward of altitude. All heavy metals and other toxic elements concentrations in this study were under the WHO and GB (China national standards) guidelines. But attention should be given to Hg because the concentration of Hg (2.6 ng/l) was much higher than the world average (0.07 ng/l) and it increased as the river flows down, which may become a threat to the inhabitants in the downstream area of the river.