Degasification of the outcropped epikarst water：A case study on the Baishuwan Spring in Nanchuan，Chongqing

HCO3- Concentration, pH, conductivity (EC) and dissolved oxygen are monitored with certain space along the downstream of the Baishuwan Spring—the Baizhi Stream, and a preliminary study on the degasification of the karst water is conducted in the case study. The results show that (1)there is a decreasing trend in HCO3- concentration along the flow path; (2) the decreasing speed of HCO3- concentration reflects the speed of degasification and the degassing speed in different season assumes “drought period ＞ normal period ＞ rainy period”; (3) dilution effect of the rain water makes the decreasing trend unobvious, but after the rainfall, it starts to present a decreasing trend again; (4) degasification also causes the conductivity (EC) decline along the flow path, but pH values increase; (5) diurnal variation in dissolved oxygen (DO) along the flow path shows that the aquatic organism may have some influences on the degasification, but the influencing mechanism still needs further study.