Analysis of break through curve in groundwater tracer test——Taking the underground karst system of Pingnan red mud yard in Pingguo County as an example
Interpreting breakthrough curves in groundwater tracer tests is an important technique for obtaining crucial infor-mation about underground karst conduit systems,such as conduit dimensions,connectivity,distribution,and direction.How-ever,several challenges still exist in practical applications,which need to be addressed to enhance the accuracy and reliability of breakthrough curve interpretation.In this study,we utilized fluorescence measurements and QTRACER2 software to calcu-late parameters such as tracer recovery,average residence time,dispersion coefficient,and average groundwater velocity in the karst system underneath the Pingguo County landfill in Pingnan.We also analyzed phenomena observed in the breakthrough curves,including multi-peak and abnormal fluctuations,in accordance with widely accepted theories.Given the relatively small scale of the karst conduits in the study area,the complexity of the conduit system was reduced to a computable level,and an approximate value for the length of the parallel conduits was calculated.Finally,the peak at the tail of the curve was attributed to solute storage,confirming the presence of a multi-conduit karst system in the study area,where groundwater pri-marily exhibits the characteristics of"karst water diffusion flow".This study provides a basis for groundwater numerical model-ing and serves as a reference for analyzing transport characteristics in complex karst media.
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