WANG Jingliang, ZHANG Cheng, PEI Jianguo, MIAO Ying
Key Laboratory of Karst Dynamics, MLR/GZAR, Institute of Karst Geology, CAGS, Guilin, 541004, China

 

Abstract: Study on diel variation of dissolved inorganic carbon can help to estimate carbon flux in river water more precisely. Five-day monitoring with high resolution data logger and high frequency sampling with 1-hour interval were conducted in a typical karst spring-fed stream with abundant aquatic vegetation. Daily changes of hydrochemistry, especially diel cycling of calcium and dissolved inorganic carbon (DIC) were discussed and the influence of biogeochemical processes on diel cycling was analyzed. The diel fluxes of calcium and inorganic carbon were also estimated. Results show that the changes in aqueous chemistry are closely associated with biogeochemical processes and featured as diel cycling. During the daytime, pH value of water and the saturation index of calcite increase, thereby causing calcite to precipitate and removing Ca and HCO3- from water. During the nighttime, concentrations of Ca2+ and DIC gradually increase due to the input of Ca and HCO3- by groundwater exchange. The daily loss of Ca and DIC are estimated to be about 69.04 kg/d and 168.68 kg/d, respectively which represent about 51.14 g/(d·m) and 124.95 g/(d·m), respectively along the 1350m of the Guancun River. The study clearly shows that photosynthesis and calcite precipitation have strong influence on the chemistry of the spring-fed river. Diel DIC cycling downstream and their changes along the stream flow indicate that the river is losing inorganic carbon along its flowpath, and converting it into organic carbon, thus acts as an important DIC sink in small productive streams.

 

Key words：spring-fed river；dissolved inorganic carbon；diel change；calcite precipitation；Guancun River; Guangxi Province

 

EARTH AND ENVIRONMENT Vol. 43, No.4, Tot No.306, 2015, Page 395-402