Présentations Colloques

Oral Presentation
8.05
Session 8.05: Karst aquifers
Shi Yu
Water chemistry and carbon flux in a storm event in a karst river
Rainfall (P), discharge (Q), water temperature, pH, and specific electrical conductivity (EC) of the karst surface river(Li river) in Yangshuo transect(surface layer), and Fuli transect (surface layer and -2m layer) in Guangxi Province, Southwest China were continuously monitored during a period 50 hours from 7 to 9 in April, 2015 using high-resolution data loggers. Water samples were collected at 2-h sampling interval, which were analyzed in the laboratory for major parameters. Continuous karst-related carbon sink fluxes (CSFs) were also estimated through continuous Q and HCO3- concentrations in each site. The primary goal of this study is to assess the intensity of chemical weathering at the storm event, and estimate end-member contribution to geological carbon flux in study catchment. Results show that 1) The EC and pH in Yangshuo transect increased before peak flow, indicating the weathering was enhanced by the quick water-rock interaction in storm event while it was diluted during peak flowperiod. Meanwhile, the EC in two Fuli transects both increased while the pH decreased, which suggested the continuously precipitation was beyond the maximum capacity of water-rock interaction or the rain flowed into river through the surface flow+ 2) The variation of HCO3- indicated that the weathering which was predominant during the peak flow instead of dilution. Furthermore, the increase of Ca2+ and the decrease of Mg2+ indicated the limestone weathering was the main type of weathering+ 3) The CSFs of Yangshuo, Fuli and Fuli(-2m) was 4122.29 tCO2, 4322.14 tCO2, and 4324.91 tCO2, respectively in monitoring time. The proportion of carbonate weathering were account for 75.23%, 71.42% and 72.72%, respectively, of the 3 sites while the portion of silicate weathering were 3.2%, 3.06% and 3.11%, respectively. The proportion of weathering with the allogenic acid taking part in were 21.58%, 25.52% and 24.18%, respectively, which caused the distinctly carbon loss.
China