KINEMATIC WAVE APPROXIMATION TO THE TRANSPORT OF ESCHERICHIA-COLI IN THE VADOSE ZONE

Threshold values for macropore flow parameters that are thought to be critical in the transport of microbial suspensions through macroporous soils were established through the application of a kinematic wave approach to bacterial breakthrough curves. According to the presented examples, moisture content omega and conductance b in the macropore systems of four different soils had simultaneously to exceed 0. 015 (m**3/m**3) and 0. 1 (m/s), respectively, before substantial microbial breakthrough was observed at the bottom of undisturbed columns of macroporous soils. The application of these thresholds in a modeling approach to large-scale flow revealed that hardly any microbes can be transported deeper than 2-3 m in soils when durations and intensities of naturally occurring precipitation events were entered into the model.