Tropical Geography ›› 2020, Vol. 40 ›› Issue (2): 335-345.

### Diel Variations of Hydrochemistry and Influencing Factors in the Surface Water of the Yelanghu Reservoir in Puding, Guizhou Province

Wang Jialu1,2, Ren Juan1, Wang Yong1(), Li Weijie1, Lou Zhao2, Chen Jia3

1. 1.Chongqing Key Laboratory of Karst Environment//School of Geographical Sciences, Southwest University, Chongqing 400715, China
2.School of Resources and Environmental Engineering, Anshun University, Anshun 561000, China
3.Puding Karst Ecosystem Observation and Research Station, Chinese Academy of Sciences, Puding 562100, China
• Received:2019-10-18 Revised:2019-12-12 Online:2020-03-10 Published:2020-05-15
• Contact: Wang Yong E-mail:190966549@qq.com

Abstract:

A karst reservoir is a type of semi-natural and semi-artificial water body. Owing to the dual regulation of fragile geological background of the karst and human activities, the geochemical indexes of karst water body differ considerably. To understand the variation processes of hydrochemistry of the Yelanghu karst reservoirs, which are located in Puding in Guizhou Province, the diel cycles of geochemistry of their surface water were measured for three days and nights. The results indicate that: 1) the ion indices of the reservoir water did not exhibit obvious diel variations due to variable weather and hydrological conditions, whereas regular indices of water temperature, Dissolved Oxygen (DO), pH, and partial pressure of CO2 exhibited apparent diurnal fluctuations. Under the control of water-rock interactions and the effect of the coal-bearing bedrock, the water chemical type of the Yelanghu Reservoir is Ca-HCO3·SO4. 2) By calculating the thermodynamic parameters and analyzing the principal components, it is found that these parameters are controlled by temperature, biological effects, and human activities, as well as storage and discharge of the reservoir, of which their contribution rates are 21.66%, 17.28%, 14.08%, and 10.22%, respectively, indicating that the influencing factors of hydrochemistry of the reservoirs are multivariate. 3) During the study period, the variation ranges of the Yelanghu Reservoir water’s δD and δ 18O values were -60.61‰~-57.17‰ and -8.11‰~-8.85‰, respectively, and the mean values were -59.44‰ and -8.46‰, respectively. The δD and δ 18O values were smaller during the day and larger at night. During the day, the biological activity in the reservoir is primarily photosynthesis with weak respiration; whereas at night, it is primarily respiration, which consumes a large amount of O2 to obtain more light isotope 16O, thereby resulting in a decrease in DO concentration in the water at night and a negative 18O. However, a comparison of the d-excess value of the reservoir water with the local atmospheric precipitation shows that the d-excess value of the former (8.21‰) is significantly lower than that of the latter (9.64‰), indicating the main effect of unbalanced fractionation caused by evaporation over a long period of time.

CLC Number:

• P342