Effects of heterogeneity of karst media on the hydrochemical parameters from vertical borehole logs

Karst media are highly heterogeneous, which has been manifested both on surface and subsurface.In general,the description of rock formation and the analyses of physical and chemical properties of a borehole groundwater may help to understand the structural features of an aquifer and associated ground water evolution. This study is conducted on the basis of groundwater vertical logging data derived from the boreholes situated on the border between peak cluster mountain area and peak forest-plain in the southwest of Guilin Karst Experimental Site. On this site, the influence of the heterogeneity of karst media on physical and chemical indexes of the aquifer by using portable multi-parameter device which basically logged pH, temperature (T), electrical conductivity (EC)at different holes. The results showed that in the small-scale karstic aquifer,the physical and chemical properties measured in-situ are different across the area; and these parameters obviously varied at depth in one borehole.Moreover, it is noted that the groundwater in the boreholes with analogously karstified conditions shows similar properties which suggests that the heterogeneity of the karst mediahas an influence on the groundwater occurrence and hydraulic connection. This should be fully taken into account during the research of karst groundwater and associated aquifer properties; and the groundwater sampling and monitoring can be focused on the conductive zones in the boreholes, in order to reflect flow dynamics and hydrogeological setting of karst aquifer.