Metolachlor and TCE Plume Characteristics in a Dolostone Aquifer Using a Transect
Matrix diffusion and strong temporal variability of the groundwater flow system caused by pumping of nearby municipal wells have likely caused strong natural attenuation of metolachlor and TCE and degradation has likely contributed to even stronger TCE attenuation. The transect shows rock core concentrations much higher than the groundwater concentrations in the multilevel systems at the same locations and in the conventional monitoring wells, which indicates that plume persistence is likely maintained by back diffusion from the rock matrix, which has very low hydraulic conductivity but substantial porosity, into the active groundwater flow in the fractures.
Metolachlor has been observed at very low concentrations and has persisted at these concentrations in the nearest municipal pumping well located approximately 780 m downgradient of the transect, however this well shows no detectable TCE. The relatively low concentrations along the transect and the replenishment of the plume by back diffusion suggests that a substantial increase of metolachlor or TCE in the municipal well is unlikely.
School:University of Waterloo
School Location:Canada - Ontario
Source Type:Master's Thesis
Keywords:earth sciences fractured rock metolachlor tce transect groundwater contamination natural attenuation
Date of Publication:01/01/2006