[Substances transport in an underground river of typical karst watershed during storm events].

Hydrologic process, turbidity, suspended particles matters (SPM), major cations and TOC concentrations during two storm events in late April 2008 were monitored at Jiangjia Spring which is the outlet of Qingmu Guan underground river system. Scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) analyses of SPM were also performed in order to investigate the transport characteristics of substances, such as SPM, turbidity and major cations in the underground river of typical karst watershed. The results show that at a single and well-developed karst conduit of Jiangjia Spring, discharge, turbidity, and concentrations of SPM, major cations and TOC respond promptly to the rainfall. The carbonate-derived cations including Ca2+, Mg2+ and Sr2+ are subject to dilution effect during the rising limb of discharge. The elevation in turbidity and SPM concentration is a result of the gradual increase of allochthonous substances (soil) flux input from the surface. Al3+, Fe, Mn, Ba2+ and TOC are concomitant substances of SPM. And their concentrations are ascending with turbid rise. The flux of SPM in diameter > 0.45 microm in the underground river is about 9.7 tons during the events. The bad water quality suggests us that the spring water is unfit to drink without purification during the period of rising and recession time of discharge at Jiangjia Spring. Thus, soil erosion and nutrient losing not only strongly destroy the fragile karst ecological environment, but also lead to non-point source pollution, and seriously threaten the drinking water safety of locals.