Hydrochemical patterns indicating hydrological processes with the background of changing climatic and environmental conditions in China: a review.

In the background of global climate and environmental change, the hydrochemical characteristics of water bodies present significant instability to all regions, including humid, arid, and alpine ones. There are two main reasons for this: (1) climate change has altered the temporal and spatial distribution of precipitation, and climate warming intensified the mutual transformation of water bodies. The temperature in China increased by 0.29 °C/10a from 1951 to 2018. For different regions, whether the alpine region (0.37 °C/10a, P < 0.05), the arid region (0.278 °C/10a, P < 0.05), or the humid region (0.168 °C/10a, P < 0.05), there was a significant increasing trend (P < 0.05) from 1951 to 2018. Thus, the characteristics of water recharge sources and the hydrological processes and hydrochemical characteristics of water bodies are affected. Increase in precipitation increases the input sources for water transformation, intensifying the transformation of water bodies. (2) In the context of climate and environmental change, human activities and the local environment are seriously affecting the transformation of various water bodies and hydrochemical ion sources. The comprehensive effects of various physical and geographical conditions, geological structure, lithology and transformation, and recharge of various water bodies affect the hydrochemical characteristics of water bodies in China. The differences in the type of water bodies showed that the hydrochemical process of water bodies was more complex, although there was a hydraulic connection between precipitation, river water, lake water, and groundwater. This provides a new idea for the future study of hydrochemical characteristics and hydrology.

Environment significance and hydrochemical characteristics of supra-permafrost water in the source region of the Yangtze River.

This paper analyzed the environment significance and hydrochemical characteristics of the main ions on the supra-permafrost water from the view of space-time and different ablations. The study is conducted through collected 330 samples from June to September in 2016 and 2017 in the Source Region of the Yangtze River (SRYR). The results showed the pattern of ionic dominance based on mean value was following as: Cl- > Na+ > SO42- > Ca2+ > Mg2+ > K+ > NO3- > NO2- > NH4+ > F- > Li+. Cl- alone contributed 40.57%, and Cl-, Na+, SO42- and Ca2+ accounted for 94.06% of the total ionic concentrations. The spatial variation of ionic concentration was larger at the initial stage of ablation, and more stable in strong ablation and the end of the ablation stage. The area with elevation of 4500 m was the region where the control source of ions was more sensitive to the hydrochemical characteristics of supra-permafrost water in the study area. Through the analysis of the sources of ions, the anions and cations in supra-permafrost water in the study area were mainly controlled by crustal sources including evaporates rocks and carbonate rocks. The recharge effect of precipitation and snow-melt water only affected the concentration of Cl-, NH4+, NO3-, F-, Li+ and K+, but did not affect NO2-, SO42-, Mg2+ and Ca2+. The hydrochemical type of supra-permafrost water was Ca2+-SO42- in high elevation (>4800 m). However, the hydrochemical type of middle elevation (from 4400 m to 4700 m) was Na+-Cl-. The type of hydrochemistry at low altitude was more complex than at high and middle elevation. This study provides insights on the construction of hydrological models in the cold regions and scientific basis for water resources management in the Tibet Plateaus.